Quinoxolinol based Ligand for Molecular Recognition and Selective Extraction by Michael Alan DeVore II A disertation submited to the Graduate Faculty of Auburn University in partial fulfilment of the requirements for the Degree of Doctor of Philosophy in Chemistry Auburn, Alabama May 4, 2014 Keywords: Sensing, Actinides, Nuclear Chemistry, Extractions Copyright 2014 by Michael DeVore II Approved by Anne Gorden, Chair, Asociate Profesor, Department of Chemistry and Biochemistry Rik Blumenthal, Asociate Profesor, Department of Chemistry and Biochemistry Christopher Easley, Knowles Asociate Profesor, Department of Chemistry and Biochemistry Christian Goldsmith, Asociate Profesor, Department of Chemistry and Biochemistry ii Abstract As the current age of nuclear reactors gets older, more waste and a greater possibility of leaks can occur. There is a need for an on-site real time ability to be able to detect actinides in the environment to prevent a greater problem, or to help remedy clean up. Due to competing metals such as copper or iron, designing a ligand to selectively detect actinides is often very dificult. 2-quinoxolinol backbone was synthesized and two 3,5-di-t-butylsalicylaldehydes were atached as imines to provide a 2N-2O donor system as a binding pocket. This ligand by itself gave a signal in the UV-Vis at ~389 nm. When bound to uranyl, the peak shifted to higher energies to ~367 nm with a shoulder at 450 nm. When bound to copper, the peak was lower energy shifted to 450 nm. The detection limits were ~25 ppm for uranyl and ~1 ppm for copper. This became the starting point for designing a beter sensor using computational chemistry. What was found was that changing from a salicylaldehyde to a 2-aminobenzaldehyde should give greater selectivity in the UV-Vis spectrum. Much needs to be investigated to increase the signal to noise and lower the detection limit. Finaly, extractions were performed to determine the ligands ability to separate actinides from lanthanides. Typical of mixed N,O-donor ligands, the Salqu ligand decomposed at >1 M HNO 3 and would only have eficient extractions betwen 1x10 -1 ? 1x10 -3 M HNO 3 with distribution for uranyl ~3 and separation factors ~5. iii Acknowledgments The author would like to foremost thank my parents, Mike and Avalyn DeVore, and family for their support and any help I needed. I would like to thank my commite members, Dr. Rik Blumenthal, Dr. Christopher Easley, Dr. Christian Goldsmith, and outside reader Dr. Paul Cobine, for leting me get out alive. I would like to thank my boss Dr. Anne Gorden for the years of helpful advice, discussion, and learning that took place under your tutelage. I would like to thank my best friend and former roommate Dr. Kennon Deal for being there for me and geting me out of the house enough times not to go crazy, I mis you buddy. I would like to thank my lab mates, Dr. Kushan Werasiri, Dr. Branson Maynard, Dr. Mohan Bharrara, Dr. Yuanchen Li, Charmaine Tutson, and Nick Klann, for al the help with any questions about reactions, synthesis, and techniques. Good luck to new graduate students Chasity Ward, Maya West, and Emily Hardy. I have to thank Dr. Cobine again for use of his ICP-OES for much of this research on extractions. I would like to thank Dr. Enrique Batista for alowing me to intern at LANL for the summer and pick up new skils in computational chemistry that wil hopefully be worthwhile. Perhaps my second best friend Dr. Leah Godwin. I stil talk to you on a wekly basis about BBT and HIMYM. The conversations are hilarious. This is the culmination of a very long 6 years and I am happy that I got to spend it at Auburn University and make a number of new friends both in and out of the department. And finaly Auburn University Department of Chemistry and Biochemistry, Thank You! iv Table of Contents Abstract ................................................................................................................................ ii Acknowledgments ............................................................................................................. iii List of Tables .................................................................................................................... viii List of Illustrations ............................................................................................................. ix List of Schemes ............................................................................................................... xvii List of Abbreviations ...................................................................................................... xvii Chapter 1 Introduction ....................................................................................................... 1 1.1 Coordination Chemistry of the Actinides and Lanthanides ............................ 2 1.2 5f Coordination Compounds ............................................................................ 3 1.3 Sensing of Actinides in the Environment ........................................................ 4 1.4 Methods for Detection of Actinides ................................................................ 5 1.41 Alpha Spectroscopy ........................................................................... 5 1.42 Gama Spectroscopy ........................................................................ 6 1.43 Atomic Absorption Techniques ......................................................... 7 1.44 Inductively Coupled Plasma .............................................................. 7 1.45 Laser Induced Kinetic Phosphorimetry ............................................. 8 1.46 Ultra-Violet Visible Spectroscopy .................................................... 9 1.5 Background for Nuclear Fuel Recycling ....................................................... 11 1.6 Extraction Proceses ...................................................................................... 13 v 1.61 PUREX ............................................................................................ 13 1.62 DIAMEX ......................................................................................... 14 1.63 TRUEX ............................................................................................ 15 1.64 Cyanex ............................................................................................. 16 1.65 TALSPEAK ..................................................................................... 18 1.66 SANEX ............................................................................................ 19 1.7 References ..................................................................................................... 22 Chapter 2 Bis-Dithiophosphonates ................................................................................... 26 2.1 Introduction ................................................................................................... 26 2.2 Experimental .................................................................................................. 28 2.3 Synthesis of the Ligands ................................................................................ 28 2.4 Extraction and Hydrolysis Studies ................................................................ 29 2.5 Results and Discussion .................................................................................. 30 2.6 Conclusions ................................................................................................... 38 2.7 References ..................................................................................................... 40 Chapter 3 Quinoxalinol Salen Ligands for Colorimetric Sensors .................................... 41 3.1 Introduction .................................................................................................... 41 3.2 Experimental ................................................................................................... 42 3.21 General Procedure ........................................................................... 42 3.22 Synthesis of Ligands ........................................................................ 43 3.23 Metal titration and K b Studies ......................................................... 43 3.3 Results ........................................................................................................... 45 3.4 Fluorescence .................................................................................................. 64 vi 3.5 Calculations ................................................................................................... 66 3.6 Binding Constants ......................................................................................... 70 3.7 Colorimetry .................................................................................................... 71 3.8 Conclusion ..................................................................................................... 72 3.9 References ..................................................................................................... 74 Chapter 4 Quinoxolinol Ligands for Molecular Recognition: A Computational Study ..76 4.1 Introduction ................................................................................................... 76 4.2 Methods ......................................................................................................... 77 4.3 Results ........................................................................................................... 78 4.31 Salicylaldehydes .............................................................................. 80 4.32 Schif Bases ..................................................................................... 83 4.33 Triazine ............................................................................................ 86 4.34 Pyridine Amides .............................................................................. 89 4.35 Isopththaldehyde .............................................................................. 93 4.4 Conclusion ..................................................................................................... 94 4.5 References ..................................................................................................... 96 Chapter 5 Quinoxolinol Salen Ligand for Nuclear Waste Extractions ........................... 99 5.1 Introduction ..................................................................................................... 99 5.2 Experimental .................................................................................................. 101 5.3 Results ........................................................................................................... 103 5.31 0.5 mM ............................................................................................ 106 5.32 0.75 mM .......................................................................................... 109 5.33 1.0 mM ............................................................................................ 112 vii 5.4 Conclusion ..................................................................................................... 116 5.5 References ..................................................................................................... 117 Chapter 6 Conclusions and Future Work ........................................................................ 118 6.1 Future Work ................................................................................................... 123 Appendix 1 .................................................................................................................... 126 Appendix 2 .................................................................................................................... 148 vii List of Tables Table 2.1 Distribution of metal ions by SH 2 L1 .......................................................................... 35 Table 2.2 Distribution of metal ions by SH 2 L2 .......................................................................... 38 Table 2.3 Separation factor of copper over uranyl for SH 2 L2 .................................................... 38 Table 3.1 Batch Titration set-up to control water content .......................................................... 47 Table 3.2 H 2 L1 wavelength and extinction coeficient .............................................................. 54 Table 3.3 H 3 L3 wavelength and extinction coeficient .............................................................. 62 Table 3.4 Binding constants and extinction coeficients for H 2 L1 ........................................... 70 Table 3.5 Binding constants and extinction coeficients for H 3 L3 ........................................... 70 Table 4.1 Salicylaldehyde derivatives with maximum absorbencies ........................................ 82 Table 4.2 Schif base derivatives with maximum absorbencies ................................................ 84 Table 4.3 Di-ketones to complete triazine maximum absorbencies ........................................... 88 ix List of Figures Figure 1.1 Isoamethyrin .............................................................................................................. 10 Figure 1.2 Fuel Cycle Decay ...................................................................................................... 12 Figure 1.3 tri-n-butyl phosphate (TBP) ...................................................................................... 14 Figure 1.4 DMDBTDMA and DMDOHEMA .......................................................................... 15 Figure 1.5 CMPO ...................................................................................................................... 16 Figure 1.6 Cyanex 301 .............................................................................................................. 17 Figure 1.7 HDEHP and DTPA .................................................................................................. 19 Figure 1.8 BTP .......................................................................................................................... 19 Figure 1.9 CyMe 4 -BTP .............................................................................................................. 21 Figure 1.10 BTBP ...................................................................................................................... 21 Figure 2.1 Organophosphorous Reagents .................................................................................. 27 Figure 2.2 Hydrolysis of SH 2 L1 ................................................................................................ 32 Figure 2.3 Hydrolysis of SH 2 L2 ................................................................................................ 32 Figure 2.4 Percent extraction for SH 2 L1 .................................................................................... 34 Figure 2.5 Percent extraction for SH 2 L2 .................................................................................... 36 Figure 2.6 Copper % extraction at shorter time lengths ............................................................. 37 Figure 3.1 Example of batch titration ......................................................................................... 47 Figure 3.2 Example of serial titration ........................................................................................ 48 Figure 3.3 Combined UV-Vis spectra of H 2 L1 with copper and uranyl .................................... 50 x Figure 3.4 Combined metal titration with H 2 L1 in 5% water/DMF .......................................... 51 Figure 3.5 Combined metal titration with H 2 L1 in 10% water/DMF ......................................... 52 Figure 3.6 Combined metal titration with H 2 L1 in 15% water/DMF ......................................... 53 Figure 3.7 Combined metal titration with H 2 L1 in 20% water/DMF ......................................... 54 Figure 3.8 Combined metal titration with H 2 L1 in 20% water/Acetone .................................... 55 Figure 3.9 Combined metal titration with H 2 L2 in 20% water/DMF ......................................... 56 Figure 3.10 Combined metal titration with H 3 L3 in <1% water/DMF ...................................... 57 Figure 3.11 Combined metal titration with H 3 L3 in 10% water/DMF ....................................... 58 Figure 3.12 Combined metal titration with H 3 L3 in 20% water/DMF ....................................... 60 Figure 3.13 Combined metal titration with H 3 L3 in 30% water/DMF ....................................... 61 Figure 3.14 Combined metal titration with H 3 L3 in 40% water/DMF ....................................... 62 Figure 3.15 Combined metal titration with H 2 L1 in 20% water/DMF HEPES ......................... 64 Figure 3.16 Combined metal fluorescence spectra H 2 L1 20% water/DMF .............................. 65 Figure 3.17 Combined metal fluorescence spectra H 3 L3 40% water/DMF .............................. 66 Figure 3.18 Optimized structures and crystal structure bond lengths ....................................... 67 Figure 3.19 Combined experimental and calculated UV-Vis spectra for H 2 L1 ......................... 68 Figure 3.20 Hole and Particle NTO of uranyl complex of H 2 L1 .............................................. 69 Figure 3.21 Hole and Particle NTO of copper complex of H 2 L1 .............................................. 69 Figure 3.22 H 3 L3 colorimetry ................................................................................................... 71 Figure 3.23 H 2 L1 colorimetry ................................................................................................... 71 Figure 4.1 Experimental Salqu UV-Vis spectra ........................................................................ 79 Figure 4.2 Salicylaldehyde representation ................................................................................ 81 Figure 4.3 Calculated Salicylaldehyde spectra with copper and uranyl complex ..................... 82 xi Figure 4.4 Schif base representation ........................................................................................ 83 Figure 4.5 2-aminobenzaldehyde .............................................................................................. 85 Figure 4.6 Calculated 2-aminobenzaldehyde spectra with copper and uranyl complex ........... 85 Figure 4.7 Optimized uranyl binding structure for triazines ..................................................... 88 Figure 4.8 Calculated di-acetyl spectra with copper and uranyl complex ................................. 89 Figure 4.9 Pyridine amide ligand designs ................................................................................. 89 Figure 4.10 Optimized geometry of uranyl complex of pyridine amide macrocycle ................ 91 Figure 4.11 Optimized geometry of copper complex of pyridine amide macrocycle ............... 92 Figure 4.12 Calculated amide pyridine macrocycle spectra with copper and uranyl complex ......................................................................................................................... 92 Figure 4.13 Optimized geometry of uranyl complex of isophthaldehyde macrocycle .............. 93 Figure 5.1 Three ligands used in the extractions study ........................................................... 103 Figure 5.2 a Distribution of H 2 L1 at 1 to 1 molar concentration ............................................ 104 Figure 5.2 b Distribution of Salen at 1 to 1 molar concentration ............................................ 105 Figure 5.2 c Distribution of quinoxolinol at 1 to 1 molar concentration ................................. 105 Figure 5.3 Separation factor of the three ligands at 1 to 1 molar concentration ..................... 106 Figure 5.4 a Distribution of H 2 L1 at 0.5 mM .......................................................................... 107 Figure 5.4 b Distribution of Salen at 0.5 mM .......................................................................... 108 Figure 5.4 c Distribution of quinoxolinol at 0.5 mM .............................................................. 108 Figure 5.5 Separation factor of the three ligands at 0.5 mM ................................................... 109 Figure 5.6 a Distribution of H 2 L1 at 0.75 mM ........................................................................ 110 Figure 5.6 b Distribution of Salen at 0.75 mM ......................................................................... 111 Figure 5.6 c Distribution of quinoxolinol at 0.75 mM ............................................................. 111 xii Figure 5.7 Separation factor of the three ligands at 0.75 mM .................................................. 112 Figure 5.8 a Distribution of H 2 L1 at 1.0 mM .......................................................................... 113 Figure 5.8 b Distribution of Salen at 1.0 mM ........................................................................... 114 Figure 5.8 c Distribution of quinoxolinol at 1.0 mM ............................................................... 114 Figure 5.9 Separation factor of the three ligands at 1.0 mM .................................................... 115 Figure 6.1 Best ligands by calculations ................................................................................... 122 Figure 6.2 Salazine with 3,5-di-t-butylsalicylaldehyde ........................................................... 124 Figure 6.2 Salazine with pyridine amides ............................................................................... 125 Figure A3.1 Batch copper titration with H 2 L1 in 5% water/DMF ........................................... 126 Figure A3.2 Batch uranyl titration with H 2 L1 in 5% water/DMF ............................................ 127 Figure A3.3 Batch cobalt titration with H 2 L1 in 5% water/DMF ............................................ 127 Figure A3.4 Batch copper titration with H 2 L1 in 10% water/DMF ......................................... 128 Figure A3.5 Batch uranyl titration with H 2 L1 in 10% water/DMF .......................................... 128 Figure A3.6 Batch cobalt titration with H 2 L1 in 10% water/DMF .......................................... 129 Figure A3.7 Batch copper titration with H 2 L1 in 15% water/DMF ......................................... 129 Figure A3.8 Batch uranyl titration with H 2 L1 in 15% water/DMF .......................................... 130 Figure A3.9 Batch cobalt titration with H 2 L1 in 15% water/DMF .......................................... 130 Figure A3.10 Batch copper titration with H 2 L1 in 20% water/DMF ....................................... 131 Figure A3.11 Batch uranyl titration with H 2 L1 in 20% water/DMF ........................................ 131 Figure A3.12 Batch cobalt titration with H 2 L1 in 20% water/DMF ........................................ 132 Figure A3.13 Batch cerium titration with H 2 L1 in 20% water/DMF ....................................... 132 Figure A3.14 Batch nickel titration with H 2 L1 in 20% water/DMF ........................................ 133 Figure A3.15 Batch gadolinium titration with H 2 L1 in 20% water/DMF ................................ 133 xii Figure A3.16 Batch copper titration with H 2 L1 in 20% water/Acetone .................................. 134 Figure A3.17 Batch uranyl titration with H 2 L1 in 20% water/Acetone ................................... 134 Figure A3.18 Batch cobalt titration with H 2 L1 in 20% water/Acetone.................................... 135 Figure A3.19 Batch copper titration with H 2 L2 in 20% water/DMF ....................................... 135 Figure A3.20 Batch uranyl titration with H 2 L2 in 20% water/DMF ........................................ 136 Figure A3.21 Batch cobalt titration with H 2 L2 in 20% water/DMF ........................................ 136 Figure A3.22 Batch copper titration with H 3 L3 in <1% water/DMF ....................................... 137 Figure A3.23 Batch uranyl titration with H 3 L3 in <1% water/DMF ....................................... 137 Figure A3.24 Batch cobalt titration with H 3 L3 in <1% water/DMF ........................................ 137 Figure A3.25 Batch uranyl titration with H 3 L3 in 10% water/DMF ........................................ 138 Figure A3.26 Batch cobalt titration with H 3 L3 in 10% water/DMF ........................................ 139 Figure A3.27 Batch copper titration with H 3 L3 in 20% water/DMF ....................................... 139 Figure A3.28 Batch cobalt titration with H 3 L3 in 20% water/DMF ........................................ 140 Figure A3.29 Batch copper titration with H 3 L3 in 30% water/DMF ....................................... 140 Figure A3.30 Batch cobalt titration with H 3 L3 in 30% water/DMF ........................................ 141 Figure A3.31 Batch copper titration with H 3 L3 in 40% water/DMF ....................................... 141 Figure A3.32 Batch uranyl titration with H 3 L3 in 40% water/DMF ........................................ 142 Figure A3.33 Batch cobalt titration with H 3 L3 in 40% water/DMF ........................................ 142 Figure A3.34 Batch cerium titration with H 3 L3 in 40% water/DMF ....................................... 143 Figure A3.35 Batch nickel titration with H 3 L3 in 40% water/DMF ........................................ 143 Figure A3.36 Batch gadolinium titration with H 3 L3 in 40% water/DMF ................................ 144 Figure A3.37 Batch copper titration with H 2 L1 in 20% water/DMF HEPES .......................... 144 Figure A3.38 Batch uranyl titration with H 2 L1 in 20% water/DMF HEPES ........................... 145 xiv Figure A3.39 Batch cobalt titration with H 2 L1 in 20% water/DMF HEPES ........................... 145 Figure A3.40 Batch copper titration fluorescence spectrum H 2 L1 20% water/DMF ............. 146 Figure A3.41 Batch uranyl titration fluorescence spectrum H 2 L1 20% water/DMF ............... 146 Figure A3.42 Batch copper titration fluorescence spectrum H 3 L3 40% water/DMF ............. 147 Figure A3.43 Batch uranyl titration fluorescence spectrum H 3 L3 40% water/ DMF ............. 147 Figure A4.1 Calculated 4-aminosalicylaldehyde, copper, and uranyl complex DMF ............. 148 Figure A4.2 Calculated 4-aminosalicylaldehyde, copper, and uranyl complex acetone .......... 149 Figure A4.3 Calculated 5-aminosalicylaldehyde, copper, and uranyl complex DMF ............. 149 Figure A4.4 Calculated 5-aminosalicylaldehyde, copper, and uranyl complex acetone .......... 150 Figure A4.5 Calculated 3-ethoxysalicylaldehyde, copper, and uranyl complex DMF ............ 150 Figure A4.6 Calculated 3-ethoxysalicylaldehyde, copper, and uranyl complex acetone ......... 151 Figure A4.7 Calculated 3-hydroxysalicylaldehyde, copper, and uranyl complex DMF .......... 151 Figure A4.8 Calculated 3-hydroxysalicylaldehyde, copper, and uranyl complex acetone ...... 152 Figure A4.9 Calculated 4-hydroxysalicylaldehyde, copper, and uranyl complex DMF .......... 152 Figure A4.10 Calculated 4-hydroxysalicylaldehyde, copper, and uranyl complex acetone .... 153 Figure A4.11 Calculated 4-chlorosalicylaldehyde, copper, and uranyl complex DMF ........... 153 Figure A4.12 Calculated 4-methoxysalicylaldehyde, copper, and uranyl complex DMF ....... 154 Figure A4.13 Calculated 4-methoxysalicylaldehyde, copper, and uranyl complex acetone .... 154 Figure A4.14 Calculated 5-hydroxysalicylaldehyde, copper, and uranyl complex DMF ........ 155 Figure A4.15 Calculated 5-hydroxysalicylaldehyde, copper, and uranyl complex acetone .... 155 Figure A4.16 Calculated 5-t-butylsalicylaldehyde, copper, and uranyl complex DMF ........... 156 Figure A4.17 Calculated 5-methylsalicylaldehyde, copper, and uranyl complex DMF .......... 156 Figure A4.18 Calculated 5-methylsalicylaldehyde, copper, and uranyl complex acetone ....... 157 xv Figure A4.19 Calculated 2,4,6-trihydroxysalicylaldehyde, copper, and uranyl complex DMF ............................................................................................................................. 157 Figure A4.20 Calculated 2,4,6-trihydroxysalicylaldehyde, copper, and uranyl complex acetone .......................................................................................................................... 158 Figure A4.21 Calculated 3,5-dichlorosalicylaldehyde, copper, and uranyl complex DMF ..... 158 Figure A4.22 Calculated triazine, copper, and uranyl complex DMF ..................................... 159 Figure A4.23 Calculated triazine, copper, and uranyl complex acetone .................................. 159 Figure A4.24 Calculated triazine, copper, and uranyl complex acetic acid ............................. 160 Figure A4.25 Calculated triazine, copper, and uranyl complex acetonitrile ............................ 160 Figure A4.26 Calculated 4,5-dimethyl triazine, copper, and uranyl complex DMF ................ 161 Figure A4.27 Calculated 4,5-di-t-butyl triazine, copper, and uranyl complex DMF ............... 161 Figure A4.28 Calculated 4,5-di-i-butyl triazine, copper, and uranyl complex DMF ............... 162 Figure A4.29 Calculated 4,5-dihexyl triazine, copper, and uranyl complex DMF .................. 163 Figure A4.30 Calculated 4,5-cylcohexane triazine, copper, and uranyl complex DMF .......... 163 Figure A4.31 Calculated 4,5-cyclohexane triazine, copper, and uranyl complex acetone ....... 164 Figure A4.32 Calculated 4,5-diphenyl triazine, copper, and uranyl complex DMF ................ 164 Figure A4.33 Calculated 2-thiolbenzaldehyde, copper, and uranyl complex DMF ................. 165 Figure A4.34 Calculated bi-pyridine, salicylaldehyde, copper, and uranyl complex DMF ..... 165 Figure A4.35 Calculated di-bipyridine, copper, and uranyl complex DMF ............................ 166 Figure A4.36 Calculated pyrrole, copper, and uranyl complex DMF ...................................... 166 Figure A4.37 Calculated pyrrole, copper, and uranyl complex acetone .................................. 167 Figure A4.38 Calculated pyridine, copper, and uranyl complex DMF .................................... 167 xvi Figure A4.39 Calculated pyridine, copper, and uranyl complex acetone ................................. 168 Figure A4.40 Calculated di-substituted pyridine amide on quinoxaline, copper, and uranyl complex DMF ............................................................................................................... 168 Figure A4.41 Calculated disubstituted pyridine amid on pyridine, copper, and uranyl complex DMF ............................................................................................................... 169 xvii List of Schemes Scheme 2.1 Synthesis of Ligands SH 2 L1 and SH 2 L2 ................................................................ 29 Scheme 3.1 Synthesis of quinoxalinol backbone ....................................................................... 44 Scheme 3.2 Synthesis of di-substituted ligand ........................................................................... 44 Scheme 3.3 Synthesis of mono-substituted ligand ..................................................................... 45 Scheme 4.1 Synthesis of triazine from quinoxalinol .................................................................. 87 xvii List of Abbreviations 6-31g(d) basis set AAS Atomic absorption spectrometry AES Atomic emision spectrometry B3LYP hybrid functional BTBP 6,6?-bis(5,6- dialkyl[1,2,4]triazine-3-yl)[2,2?]bipyridines BTP bis-1,2,4-triazin-3-yloligopyridines CHON Carbone, Hydrogen, Oxygen, Nitrogen principle CMPO (N,N?-diisobutylcarbamoylmethyl)-octylphenylphosphine oxide Cyanex 272 bis-(2,4,4-trimethylpentyl)phosphinic acid CyMe 4 -BTP 2,6- bis(5,5,8,8,-tetramethyl-5,6,7,8,- tetrahydrobenzo[1,2,4]triazine-3-yl)pyridine D2HEPA di-(2-ethylhexyl)-phosphoric acid DCM methylene chloride D Eu distribution of europium DFT density functional theory DIAMEX Diamide Extraction DIPEA di-isopropylethylamine DMDBTDMA N,N?-dimethyl-N,N?-dibutyltetradecylmalonamide DMDOHEMA N,N?-dimethyl-N,N?-dioctylhexylethoxymalonamide xix DMF N,N?-dimethylformamide DMSO dimethylsulfoxide DTPA diethylenetriamine-N,N,N?,N??,N??-pentacetic acid D U Distribution of uranium EtOH ethanol FBR fast breeder reactors FES flame emision spectrometry FP fision products GANEX Group Actinide Extraction HDEHP di(2-ethylhexyl)phosphoric acid HEPES (2-4[-(2-hydroxyethyl)piperazine-1-yl]ethanesulfonic acid) HOMO Highest occupied molecular orbital HSAB Hard-soft-acid base theory ICP Inductively couple plasma ICP-AES inductively couple plasma-atomic emision spectrometry ICP-MS inductively couple plasma-mas spectrometer ICP-OES Inductively Couple Plasma-Optical Emision Spectrometer K b binding constant LUMO lowest unoccupied molecular orbital m/z mas over charge MeOH Methanol MOX mixed oxide reactors NTO natural transition orbitals P&T Partitioning and transmutation xx PC88A 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester ppb parts per bilion ppm parts per milion PUREX Plutonium Uranium Recovery by Extraction Salqu di-substituted ligand SANEX Selective actinide extraction SERS surface enhanced raman spectroscopy SF Separation Factor SF separation factor defined as D U / D Eu SNF spent nuclear fuel SNF Spent Nuclear Fuel TALSPEAK Trivalent actinide-lanthanide separation by phosphorous reagent Extraction from Aqueous Komplexes TBP tri-n-butyl phosphate TDDFT time-dependent density functional theory TFA trifluoroacetic acid THF tetrahydrofuran TRUEX Transuranium Extraction UV-Vis Ultra-violet visible v/v volume/volume XAS X-ray absorption spectroscopy XRF X-ray fluorescence ? Extinction coeficient (M -1 ? cm -1 ) ! 1! Chapter 1 Introduction About 13-14% of the world?s electricity is produced from nuclear sources, and nuclear power is the dominant source of electrical power for most of Europe. Nuclear power should become a dominant source of electricity in the world because of the dependence on oil in manufacturing and petroleum products are highly sought after as chemical fedstocks. 1 Experts are predicting that the maximum alowable oil production using current methods wil occur in the next 5-25 years, and the needs of nuclear power and other alternative fuel sources is growing. 2 A shift away from oil as an energy source is critical for ensuring that energy remains available and reasonably priced. 2-4 As of the end of 2010, only 8.4% of the electrical supply of the United States civilian energy production was from nuclear power, 8% was from renewable sources such as wind and solar, with the remaining 83% from fossil fuels. 1 Along with wind and solar, nuclear energy is an atractive source because it can generate a significant amount of energy with minimal atmospheric emisions; 5 however, the use of actinides in both military and nuclear fuel applications has resulted in a plethora of waste and contamination isues. 6-9 Critical isues currently being addresed include stockpile ! 2! stewardship, long- term nuclear waste storage, recycling of spent fuel, and remediation and detection of actinides in the environment. 1,4,10 New technologies wil be required to support the next generation of nuclear power production; 2,3,8,9 however, reprocesing of nuclear fuel wastes is made much more dificult because of the gaps remaining in our fundamental understanding of f- element chemistry. A resurgence of interest in the chemistry of the actinides (in particular uranium, neptunium, and plutonium) has been inspired by the needs to addres these environmental concerns, to develop new separation technologies, and to continue to develop our fundamental understanding of the chemical behavior of actinides. 11-28 Some fundamental misunderstandings involve coordination of f- elements, radionuclide movement through the environment, and separation of nuclear waste streams for reprocesing. 1.1 Coordination Chemistry of the Actinides and Lanthanides Of the utmost concern in research for characterizing the 5f elements is the potential for radiological hazards and increasing expenses of working with and obtaining materials and equipment that must be dedicated for use with those materials. 11 Other metal ions have been used as les hazardous analogs for characterization such at Th(IV) and U(VI) complexes as models for the more highly active Pu(IV,VI), increasing the analytical tools available. 11 Because of their similar ionic radii, and, for the later actinides, similar oxidation states, lanthanide metals are ! 3! seen as potential coordination models for the actinide metals. Both 4f and 5f elements prefer large coordination numbers (8 or 9), posses flexible ligand coordination geometries, and can act as Lewis Acids in solution. 7 It is incorrect to asume that since lanthanides and actinides are similar in a number of ways, that their chemistry would be similar. While the lanthanides can be useful models, the actinides with their larger 5f orbitals, have a more covalent interaction with ligands, particularly soft donors, and therefore can form more stable complexes. 3,7,29 Covalent interaction in bonding of actinides is defined as mixing betwen two orbitals, in acordance with recently published studies. 30,31 There is an inherent flaw in relying on modeling of lanthanides to determine the smal diference betwen 4f and 5f elements that could be exploited for actinide selective extractions and sensing. 11 Although the models can be great tools, many systems make critical but erroneous asumptions in the characterization of the f-elements; therefore a crucial need of modern techniques for characterizing the chemistry of the actinides and their complexes stil exists. 11 1.2 5f Coordination Compounds For complete understanding of separation proceses or the usefulnes of ligands in the detection of actinides, it is best to establish bonding parameters across the 5f series. 32-34 Generaly, a multidentate ligand that contains soft donors such as nitrogen and sulfur would be used for liquid-liquid separations of trivalent lanthanides and actinides of diferent oxidation states due to the greater binding afinity betwen actinides and soft base ligands. Because the behavior of the 5f ! 4! orbitals have been much les studied, it is dificult to determine ligand selectivity and optimum eficiency for separations or sensing, or optimal coordination environment for these 5f metal ions in the solid state. 34 1.3 Sensing of Actinides in the Environment Prior to the Manhatan Project, the only radioactive actinide elements believed to be on the planet were those that were naturaly occurring ( 235,238 U, 232 Th), and the manmade isotopes that had been created in scientific research. 35 The Manhatan Project and eventual Cold War of the 1940s-1970s introduced considerable amounts of new radioisotopes, including most significantly, thousands of kilogram quantities of transuranium elements into the environment. 35 After the ban on atmospheric testing of nuclear weapons, the major significant injections of radioactivity into the environment have occurred due to the atomic testing program, and the disasters at Chernobyl in 1986, and Fukushima in 2011. 36 These disasters are not the only fears people have of nuclear materials. Due to the current threat of a dirty bomb atack and the possibility of a nuclear waste spil during transport prove that there is a clear need for a water-borne counter-terrorist technology, one capable of providing a stand-alone alarm sensing solution around a priority aset such as a water treatment plant or government instalation. 11 ! 5! 1.4 Methods for Detecting Actinides 1.41 Alpha Spectrometry Alpha spectrometry alows the analyst to identify and quantify individual ?- emiting radionuclide (isotopes) based on the detection of emited ?-particles and determination of ?-particle energies specific to the radionuclide of interest. 37 Among the methods suitable for isotopic determination of ?-nuclides (mas spectrum, neutron activation, ?-spectroscopy) ?-spectroscopy has an advantage of being low- cost and robust, and used in natural and technical samples. Although the range of ?- particles through mater is short (they can be stopped with a sheet of paper), analysis based on their detection posses advantages compared to the detection of ?-particle and ?-rays due to the extremely low backgrounds achievable. 37 Prior to alpha- radiometric analysis, pre-concentration and separation of the radionuclide from the matrix was required because of the relatively low radionuclide concentration in the samples. In addition, interference of inactive substances with the emited ?-particles will lead to a lower spectral resolution and higher detection limits. 38 The pre- concentration and separation procedures involve co-precipitation, extraction, and/or ion-exchange. 38 There are a number of spectral interference peaks from americium, plutonium, and neptunium when trying to detect thorium, uranium, neptunium, and plutonium isotopes. ! 6! Photon Electron Rejecting Liquid Alpha Spectroscopy (PERALS?) is a relatively new method that combines chemical separation by liquid-liquid extraction and the measurement of alpha activity by a water-imiscible scintilator. 39,40 This technique lowers the limit of detection by a factor of 10 in comparison with clasical alpha spectroscopy by rejecting up to 99.9% of ?-? background radiation; 39 however the alpha energy resolution of the PERALS spectrometer is rather poor in comparison to that of ? spectrometry. This analysis of ? nuclides therefore combines chemical separation by liquid-liquid extraction with measurement of ? activity by liquid scintilation in the same procedure. 41 Dacheux et. al developed a procedure to separate uranium, thorium, plutonium, americium, and curium nuclides from each other before ? liquid scintilation counting to improve the results. 41 1.42 Gamma Spectrometry Gama Spectrometry alows an analyst to identify and quantify individual actinide nuclides based on the detection of emited ?-rays possesing energies that are specific to the nuclear transition in the actinide of interest. 37 Unlike ?-particles, ?-rays are highly penetrating and the measurement of individual actinide ions is relatively straightforward because the peaks can be resolved individualy by high-resolution detectors. 37 This technique requires litle sample preparation, is non-destructive, and multiple radionuclides can be detected simultaneously. 37 Daughter products can also be detected and are sometimes the only route for determining 238 U and 232 Th, this requires an asumption of radioactive equilibrium. 37 The sensitivity is dependent on ! 7! the half-life of the radionuclide and the percent ?-ray intensity. 37 Of the transuranic actinides, 237 Np, 239 Pu, 240 Pu, and 241 Am can be detected. The plutonium isotopes have intensity yields < 1 x 10 -3 , making their direct determination in environmental samples impossible. 37 Broader applications of gama spectroscopy to most naturaly occurring actinides and the environmentaly important transuranic actinides are limited by typical long half-lives and/or low intensities for emited ?-rays. 37 1.43 Atomic Absorption Techniques Atomic Absorption techniques are used for quantitative determination of chemical elements based on the absorption and emision of electromagnetic radiation from the atoms and ions. This technique requires a standard, but it works by exciting electrons into higher orbitals by absorbing energy. Each energy is related to a specific electron transition on each individual element. 42 The actinides are able to be measured and determined by atomic absorption spectrometry (AS), atomic emision spectrometry (AES), flame emision spectrometry (FES), and inductively couple plasma atomic emision spectrometry (ICP-AES). 42 1.44 Inductively Coupled Plasma The Inductively Coupled Plasma (ICP) source is an efective and eficient atomization and ionization source that works best with aqueous samples, usualy in nitric acid. The high temperature of the ICP source is sufficient enough to ionize the ! 8! actinide elements for concentration determination. Progres in mas spectrometry has led to lowering the detection limits, while being fast and requiring les pre-analysis determination of the actinides from each other. 39 It is stil necesary to separate the actinides from the matrix, which contains elements that cause isobaric and polyatomic interferences. 39,43 Interferences such as 238 U, contributes to m/z during 237 Np determinations. 37 Isobaric interferences complicate total Pu isotopic analysis: 238 U interferes with 238 Pu, and 241 Am interferes with 241 Pu. These interferences can be minimized by utilizing chemical separation procedures such as coprecipitation, liquid-liquid extraction, ion exchange, extraction chromatography, or speciation separations. 37 1.45 Laser Induced Kinetic Phosphorimetry Phosphorimetry is a sensitive and selective analytical technique, with low detection limits and a large linear dynamic range for many phosphors. 44 Under excitation by ultraviolet and visible radiation, many uranyl compounds phosphoresce with the emision of a characteristic green light, while uranium in the +3, +4, and +5 oxidation states is non-luminescent due to the absence of ?yl oxygens. 44 In solution, uranyl wil quench, and therefore it must be protected by complexing it with phosphoric acid to increase the lifetime to a few hundred microseconds. 42 ! 9! 1.46 Ultra-Violet Visible Spectroscopy UV-Vis spectroscopy for use in trace metal analysis has been around for a long time. The important characteristics are wide applicability, high sensitivity, moderate to high selectivity, good acuracy, and most importantly for real-time field analysis, ease, and convenience. 45 Chemosensors are non-living molecules that bind selectively and often reversibly with an analyte which causes a change in one or more properties of the system such as color, fluorescence, or redox potential. 46 Recognition and signaling of ionic and neutral species of individual elements is one of the most extensively studied areas of supramolecular chemistry. 46 Among diferent types of chemosensors, colorimetric sensors are especialy atractive, since complexation can trigger a color change that can be sen without any equipment. This type of chemosensor can find direct applications in the development of optodes and disposable dip-stick arrays based on the absorption changes. 46 In these colorimetric chemosensors, a bathochromic or hypsochromic shift of absorption spectra, or visual color change, is caused by the respective increase or decrease in electron densities on the ligand and complex, which is more efectively carried by the asociation of a charged analyte such as a cation or anion, than a neutral molecule; 46 therefore, most chromogenic sensors are only useful for charged guests. 46 Expanded porphyrins have been recognized as ligands able to form complexes with cations that are too large to form stable 1:1 complexes with porphyrins. 47 These ! 10! systems have been exploited as colorimetric sensors in the detection of high-valent actinides (U VI, Np V , and Pu V ). 47 In 2004, Sesler and co-workers reported isoamethyrin, which undergoes a color change from yelow to pink on the exposure of the ions mentioned earlier. 48 In MeOH, color changes with Np and Pu were instantaneous, while the response to U was only fully achieved after 24 hours. 47 Isoamethyrin in MeOH-CH 2 Cl 2 95:5 (v/v), the ligand displayed a detection limit for the uranyl cation of ~6 ppm as determined by naked-eye analysis, and 30 ppb as recorded using a standard UV-Vis spectrometer. 47 The kinetics of uranyl complexation (>1 day) make the system impractical as a viable method for the determination of uranyl cation concentration, 49 and copper contamination can deactivate the sensor. ? Figure 1.1: Isoamethyrin In 2008, Melfi, Sesler and co-workers modified isoamethyrin and atached it to a plastic fiber optic for use in the detection of U VI cation in aqueous solution. 50 N H NNH HN 2 Cl ! 11! Several experiments were used to characterize the structure of the silica-water interface, which demonstrated that cation concentrations may be enhanced at the interface owing to the presence of the native negative charge deriving from the pH dependence of the SiOH groups on the surface. 50 Several chemophotonic molecules were developed as optical sensors for uranyl species; however, like most sensors, they are subject to competitive binding of other metal cations, (such as copper or iron), and therefore false-positive results. 51,52 The ligands in the extraction proceses described next are good starting points for sensors and vice-versa because they are often already selective for uranyl or actinides over other metal ions. 1.5 Background for Nuclear Fuel Recycling The operational life span of a fuel rod in a typical light water reactor is only about 3 years, with only 5% of the energy content contained in the fuel rod being used. 3,8 During the past 60 years, more than 1800 metric tons of plutonium, and substantial quantities of the ?minor? actinides, such as neptunium, americium, and curium have been generated in nuclear reactors. 53 There are two strategies concerning the disposition of these heavy elements in nuclear reactors: (1) to ?burn? or transmute the actinides using fast breeder reactors or acelerators; 54 and (2) to ?sequester? the actinides in chemicaly durable, radiation resistant materials that are suitable for geological disposal. 55 Reprocesing, while not being performed in the United States currently, is not new, as fuel rods were first procesed at the Savannah River Site, with commercial nuclear fuel being reprocesed at the West Valey Reprocesing ! 12! plant in New York. 56 Because current reprocesing strategies generate and isolate "weapons-grade" plutonium ( 239 Pu), President Carter suspended reprocesing of spent nuclear fuel (SNF) citing concerns for the potential for proliferation. 56 This has not stopped other nations such as France, the United Kingdom, Russia, Japan, and India from using nuclear power technology and reprocesing their spent fuel. 3 President Reagan lifted the reprocesing ban in 1981, but there was not a substantial enough subsidy to proced on a private basis, rendering reprocesing commercialy impractical. 56 Two reasons cited for considering reprocesing are 1) to increase the available energy from fisile and fertile atoms and (2) to reduce hazards and costs for handling the high-level wastes from the resultant fision products (FPs). 57 Figure 1.2: Fuel cycle decay to get to Pu-239 There is one additional problem with the reprocesing of spent nuclear fuel and that is the separation of the trivalent actinides from the trivalent lanthanides produced as FPs. This separation is dificult due to the similar oxidation states, chemical properties, and ionic radii. This separation is needed in order to reuse the actinides in either mixed-oxide (MOX) reactors (for uranium and plutonium) or fast- breeder reactors (FBR) (for neptunium, americium, and curium) as part of the partitioning and transmutation (P&T) strategy that is being explored in France and ! 13! Japan. 42 The lanthanides posses a large-cross section for neutron capture, thus as lanthanides build up from fision products, the nuclear chain reaction slows down. 58 1.6 Extraction Proceses 1.61 PUREX The Plutonium Uranium Recovery by Extraction (PUREX) proces is the most widely used recycling proces for commercial uranium fuel rods. 59,60 The extractant is tri-n-butyl phosphate (TBP) (30%) in either dodecane or kerosene as the solvent. 55,61 TBP has good radiolytic and chemical stability, low aqueous solubility, and its chelating properties made it possible to eficiently eliminate the undesired fision products and minor actinide by-products, while cleanly separating uranium and plutonium. 62 Like the first extraction proceses in the 1940s, extraction is repeated several times throughout the cycle even though the first few steps remove over 99% of U(VI) and Pu(IV), 90% of Np(V), and leaving al but 0.1% of the fision products and minor actinides in the aqueous rafinate. 61 After that, Pu and U are separated by reducing Pu(IV) to Pu(III) by a reducing agent such as hydroxylamine or N,N-diethyl-hydroxylamine causing it to precipitate out of solution. 61 The final cycle consists of stripping the uranium using dilute acid, then pasing through another cycle of extraction and precipitation for additional decontamination from plutonium and fision products. 62 Currently studied extraction proceses, such as the ones below, ! 14! hope to improve upon, use in conjunction with, or completely replace the PUREX proces. Figure 1.3: tri-n-butlyphosphate (TBP) 1.62 DIAMEX The Diamide Extraction (DIAMEX) proces was developed in France in the late 1980s as a follow-up proces to PUREX. The goal of this system was to separate the trivalent actinides from the lanthanides directly from the high activity PUREX rafinate. 63 As the name implies, this proces uses a diamide, N,N?-dimethyl-N,N?- dibutyltetradecylmalonamide (DMDBTDMA), a combustible solvating extractant in an aliphatic diluent as the solvent. 64 A new diamide, N,N?-dimethyl- N,N?dioctylhexylethoxymalonamide (DMDOHEMA) has been synthesized. It limits third phase formation due to increased molecular weight. It also enhances the afinity for minor actinides over lanthanide complexation and thereby increasing extraction eficiency. 64 While DMDOHEMA is robust against hydrolysis and radiolysis, there is a narrow range of nitric acid concentrations that alow for good recovery of the O P ! 15! trivalent actinides. 61 The other drawback is increased complexity as compared to TBP. 61 Figure 1.4: DMDBTDMA and DMDOHEMA 1.63 TRUEX TRUEX stands for Transuranium Extraction, in other words, extraction for the actinides beyond uranium. 65 This proces uses (N,N?-diisobutylcarbamoylmethyl)- octylphenylphosphine oxide (CMPO) wherein both the C=O and P=O groups act as bonding donors for extractions. 66 For each metal ion, there are three CMPO molecules. 66 Although the extractions for actinides were very good, the CMPO ligand could not diferentiate betwen the 4f and 5f elements needed for the transuranium extractions by themselves. 66 The first modification of this extraction proces was to combine it with the established PUREX proces to create an ?al-purpose? actinide extractant from nitric acid waste solutions. 61 While improvements were made imediately, such as the enhanced distribution ratios for Am III , further investigation had problems with stripping and recovery of the metal. 67 There was also the problem N O N C 4 H 91429 C 4 H 9 N O N C 8 H 1724 C 8 H 17 O 613 ! 16! of the lanthanides stil being extracted by the CMPO, further complicating reprocesing. 68 Figure 1.5: CMPO Much of the focus of research into improving the TRUEX proces since 1999 has been to atach CMPO to a fixed structures such as triphenoxy methane 68 , or the calixarenes, both the wide and narrow rim. 66,69 The goal was to take advantage of the 3 to 1 binding of the CMPO by preorganizing the supramolecular structure and creating a chelate efect to increase the selectivity for extractions in comparison to mono-CMPO extractants. 68 For the triphenoxy methane platform, it was observed that the ligand would selectively bind thorium over lanthanides, but would have problems binding any higher actinides. 68 The wide and narrow rim calix[4]arenes with CMPO both bound thorium over lanthanides, with the narrow-rim calixarene a considerably beter extractant for thorium and maintained the ability to extract it in > 2 M HNO 3 . 66 Higher actinide selectivity was unpredictable with some lanthanides having selectivity equal to the actinides. 68 Ph P O C 8 H 17 N iBu i ! 17! 1.64 Cyanex Cyanex 301 is the dithio analogue of the carboxylic acid Cyanex 272, which was originaly developed for selective extraction of zinc from calcium containing efluent streams. 70 Increasing the sulfur substitution increases the acidity of the extractants making them beter suited to extract the softer Lewis acids of the actinides versus the lanthanides. 71-73 While Cyanex 301 can only diferentiate betwen Am III and lanthanides in solutions at a pH lower than 3, the ligand wil decompose in these acidic solutions. 74-77 Further studies have been undertaken to investigate diferent dithiophosphinic acids for minor actinide extractions. 76,77 A modification involving an aromatic dithiophosphinic acid was syntheticaly chalenging but offered a more hydrolyticaly, radiolyticaly, and acidicaly stable system while exhibiting a separation factor (SF) of ~100000 at low pH. 75 This goes against the carbon, hydrogen, oxygen, and nitrogen (CHON) principle. In this principle, it is considered highly desirable to only contain the elements carbon, hydrogen, oxygen or nitrogen (C-H-O-N) because, if the ligand were to be incinerated, it would be a direct cause of acid rain, and thus has been minimaly investigated further. Figure 1.6: Cyanex 301 P S SH ! 18! 1.65 TALSPEAK Trivalent Actinide-Lanthanide Separation by Phosphorous reagent Extraction from Aqueous Komplexes (TALSPEAK) and reverse TALSPEAK are both, in principle, based on the extraction of lanthanides instead of actinides using di(2- ethylhexyl)phosphoric acid (HDEHP) or a similar cation exchanger, from an aqueous phase that uses polyaminopolyacetic acid complexants to retain the actinides. 78 Reverse TALSPEAK selectively strips the actinides from a loaded organic phase, a proces that could be used to recover actinides after reprocesing. 78 HDEHP is a cation exchanger and a chelating agent that in the organic phase, wil form a tris complex with lanthanides; distribution ratios were for both the actinides and lanthanides were found to be nearly 10 5 . 78 Using diethylenetriamine-N,N,N?,N?,N?- pentacetic acid (DTPA), a complete group separation was achieved using due to the three amine nitrogen atoms in a specific coordination geometry. 78 Recently, the Nash group discovered that a considerable potential for improvement of TALSPEAK-type separations would be achievable by matching the extractant and holdback reagent while reducing the acidity of the extractant. 58 The greater extraction strength of HDEHP may actualy be detrimental to the potential of TALSPEAK separations. 58 ! 19! Figure 1.7: HDEHP and DTPA 1.66 SANEX Another recently developed and promising extraction proces is the Selective Actinide Extraction proces (SANEX). 79 The first ligand studied was the bis- 1,2,4,triazin-3-yloligopyridine (BTP) which was identified as metal extractants specificaly with the ability to separate actinides(III) from lanthanides(III) in nitric acid media. 80-82 These early ligands were not able to withstand radiolytic degradation with atacks on the ?-benzylic hydrogen atoms by nitrogen oxoacids. 79,83 Figure 1.8: BTP P O OH C 8 H 17 817 N N N OHO OH O OH HOO OH O N RR ! 20! To prevent degradation, the ?-benzylic hydrogen atoms were replaced by alkyl groups, and eventualy, a cyclohexane ring with four methyl groups to form the 2,6-bis(5,5,8,8,-tetramethyl-5,6,7,8,-tetrahydrobenzo[1,2,4]triazine-3-yl)pyridine (CyMe 4 -BTP). 79,83 While this ligand was kineticaly slower for extractions, the distribution ratio of americium was higher, and the SF betwen Am III and Eu III was an order of magnitude higher. 79 This was the reference molecule until the 6,6?-bis(5,6- dialkyl[1,2,4]triazine-3-yl)[2,2?]bipyridines were developed. 83,84 Much like the BTPs, initialy alkyl groups were atached to the annulated rings but the eficiency was lower than that for the BTPs. Putting the same aliphatic ring system from the CyMe 4 - BTP on the BTBPs, the ligand exhibited afinity toward trivalent actinides and high SFs over the lanthanides while maintaining the stability in nitric acid and radiolytic degradation, alowing recycling of the organic phase in a continuous proces. 85,86 This ligand has since become the standard for the SANEX proces. 87 More ligands based on the triainzes are currently being developed include the bis-triazines atached to phenanthrolines. 88 This wil make the ligand more rigid, which should make complex formation more rapid and thermodynamicaly favored compared to the bipyridine analogues. 88 The extraction kinetics were much improved as compared to BTBP, and further applications in coordination chemistry are being investigated. 87 Combinations of various proceses are being studied to be used as a group actinide extraction proces (GANEX), with a combination of PUREX and SANEX leading the way. 89 The other combination is of TALSPEAK and the DIAMEX/SANEX proces. 89 ! 21! 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Chapter 2: Bis-dithiophosphonate ligands for metal extraction Portions are previously published in DeVore II, M.A., Gorden, A.E.V.; Polyhedron 2012, 42, 271-275 2.1 Introduction Organophosphorous extractants have played a major role in actinide extractions. 1 Many of these extractants are commercialy available, generaly inexpensive and stable, and have been widely studied in the last few decades, in particular with respect to transition metal separation from weakly acidic media. 2 Early work by Ritcey, Flett, and co-workers used di-(2-ethylhexyl)-phosphoric acid (D2EHPA) (figure 1), an alkylphosphoric acid. 2 The development of phosphonic and phosphinic acid extractants, such as 2-ethylhexylphosphonic acid mono-2 ethylhexyl ester (PC88A) and bis-(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272), have led to further improved separations following the order: phosphoric < phosphonic < phosphinic acid. 2-4 In more recent years, Cyanex 301 and 302 (figure 2.1) have received considerable atention for their ability to diferentiate betwen the trivalent lanthanides and actinides, 5,6 as wel as their ability to extract soft transition metals. 2 ! 27! What makes Cyanex 301 a good potential extraction agent is that it can clearly diferentiate betwen actinides and lanthanides in solutions of a pH lower than 3. 7 Whereas several methods of spent nuclear fuel (SNF) separations have focused on extraction agents containing a single dithiophosphinic acid group like Cyanex 301, we report the preparation and simple extractions with bis-dithiophosphinites. 8,9 The purpose of design herein is to incorporate two dithiophosphinic acid groups connected by a linker to take advantage of the chelate efect to increase selectivity for actinides. Figure 2.1: Organophosphorous reagents. P S SH R P S OH R R = P O OH P O Cyanex 301 Cyanex 302 TBP D2EHPA ! 28! 2.2 Experimental Laweson?s reagent, uranyl nitrate, cuprous chloride, gadolinium chloride, 1,3-propanediol, and 1,5-pentanediol, were purchased from Acros and used without any further purification. The pH was recorded on a Fischer Scientific AR15 pH meter. UV-Vis data was collected on a Cary 50 UV-Vis spectrophotometer with a xenon lamp in the range of 200-1100 nm. The 1 H, 13 C, and 31 P NMR data were recorded on a Bruker AV 250 spectrophotometer with CD 3 OD, CDCl 3 or d 6 -DMSO as the solvent using tetramethylsilane as the reference. 100 ppm standards were purchased and diluted to ~2 ppm and used for calibration of the inductively couple plasma-optical emision spectrometer (ICP-OES). Distribution is defined as [Metal] org / [Metal] aq . separation factor (SF) is defined as D Cu / D Uranyl . 2.3 Synthesis of the ligands Ligands were prepared acording to literature procedures. 8,9 To a solution of diol (10 mol) in toluene (30 mL), 4.0 g (10 mol) of Laweson?s Reagent was added. The mixture was stirred at 70?C until al the solids had disolved and left to stir overnight. The solvent was removed on a roto-vap until the remaining volume was ~10 mL. Hexane (30 mL) was added to precipitate the product as a green oil ! 29! confirmed by 1 H NMR (Scheme 2.1). The product could then be precipitated as a salt by bubbling NH 3 into the solution. Scheme 2.1: Synthesis of the ligands PMeO S - O(CH 2 ) n O P - OMe NH 4 + 4 + n = 3 SH 2 L1 5 L2 PMeO S OMe HO(CH 2 ) n OH Toluene PMeO S SH O(CH 2 ) n O P HS OMe NH 3 ! 30! 2.4 Extraction and Hydrolysis Studies Two-phase extraction studies in methylene chloride/water (DCM/H 2 O) were performed to determine the extraction capability for the removal of Cu 2+ ions from aqueous solution. The ligands SH 2 L1 and SH 2 L2, which are quantitatively soluble in DCM, were used for extraction studies. Fresh solutions of CuCl 2 ?2H 2 O, UO 2 (NO 3 ) 2 ?6H 2 O, or GdCl 3 were prepared in DI water, and the pH was adjusted with HNO 3 and KOH (?0.05). Simple extractions were tested at pH 4 with a ratio of 1:1 metal to ligand for compounds SH 2 L1 and SH 2 L2. The phases were agitated by stirring for the time periods indicated, then given 24 hours to equilibrate. After the equilibrium was complete, the organic layer drawn off into a separate vial. 2.5 Results and Discusion The ligands SH 2 L1 and SH 2 L2 each posses four potential donor atoms to complex with metal atoms and are designed to take advantage of the chelate efect to enhance the eficiency of extractions. Although there are only a few examples of metal complexes of similar ligands, mas spectrometry has shown that the complexes can be either mononuclear or dinuclear. 9 Dithiophosphinate ligands without the ! 31! carbon bridge, such as Cyanex 301, can form many crystalographic species. Verani and co-workers reported crystal structure with Pt 2+ , Pd 2+ , and Ni 2+ , were shown to have 1:2 metal to ligand complexes 10,11 , whereas Karakus and co-workers have described a 2:4 metal to ligand crystal structure with cadmium in which two ligands have both donors coordinating to a single cadmium ion, while the other two ligands bridge the two metal centers. 12 Crystals suitable for X-ray difraction were not able to be grown from SH 2 L1 and SH 2 L2. Stock solutions of SH 2 L1 and SH 2 L2 were prepared by disolving the respective ligand in DCM while an equivalent volume of an aqueous solution at pH 1- 14 (? 0.05, adjusted with HNO 3 and KOH) was added to separate vials each containing SH 2 L1 or SH 2 L2 in DCM and shaken for 60 seconds. The solutions were left undisturbed over night, the organic layer isolated and the UV-Vis spectra taken. The extent of the hydrolysis was interpreted relative to the spectra for the ligand at neutral pH. The two-phase hydrolysis study of SH 2 L1 indicated the ligand hydrolyzes in the extreme pH conditions of 1-2 and 12-14 whereas SH 2 L2 is hydrolyzed at pH 1-2 and 11-14. The UV-Vis spectra can be sen in Figures 2.2 and 2.3. ! 32! Figure 2.2: UV-Vis of the hydrolysis of SH 2 L1. X indicates neutral pH 0" 50" 100" 150" 200" 250" 300" 215" 235" 255" 275" 295" 315" 335" 355" 375" ? *1 0 3 &M (1& cm (1& Wavelength&(nm)& SH 2 L1& 0" 2" 4" 6" 8" 10" 12" 290" 340" ? *1 0 3 &M (1& cm (1& Wavelength&(nm)& pH 1! pH 2-10! pH 11-14! 0" 5" 10" 15" 20" 25" 30" 35" 40" 45" 215" 225" 235" 245" 255" 265" 275" 285" 295" ? " *1 0 3 "M (1 cm (1" Wavelength"(nm)" SH 2 L2" pH 1-2! pH 3-10! pH 11-14! ! 33! Figure 2.3: UV-Vis of the hydrolysis of SH 2 L2. X indicates neutral pH. The two phase extraction studies described herein were performed at pH 4.0 since the ligands only hydrolyze in extreme acidic conditions, typical of current extraction proceses. The ligands were disolved in DCM while the metal salts were disolved in the aqueous phase, both at a concentration of 10 ?M. The two phases were mixed by constant stirring on a magnetic stir plate for the indicated time. If the concentrations of the ligands went above 10 ?M, a third layer could clearly be visible, therefore using UV-Vis spectroscopy to track extractions based on the uranyl peak was undesirable. SH 2 L1 was able to extract about 48% (? 0.5) of the copper ions after 8 hours and 57% (? 0.5) after 12 hours; however, after 24 hours, the metal ion concentration in the aqueous phase increased to about 50% (? 0.3) of the original solution, indicative of a third phase formation (Figure 2.5). The extraction of uranyl was a modest 41% (? 0.7) after 8 and 12 hours, and just as with copper, there was a increase in the uranyl concentration in the aqueous phase. As would be predicted by hard-soft acid base theory (HSAB), the soft base sulfur donors have a poor afinity for the hard acid gadolinium and only 17% (? 1) was extracted was after 8 hours. ! 34! Figure 2.4: Percent extraction of copper ( ?), gadolinium (- - ), and uranyl (-) by SH 2 L1 at 8,12, and 24 hours. The distribution ratio of copper with SH 2 L1 was found to be ~1 but is much les for the other metal ions, meaning that approximately half the copper ions were extracted while les than half of other metal ions were extracted into the organic phase. However, the separation factor of uranyl over gadolinium is betwen 3-5, which indicates there is a extraction preference of uranyl over gadolinium for possible separation of trivalent actinides from lanthanides, with suitable modifications to the ligand. -5! 5! 15! 25! 35! 45! 55! 65! 0! 8 Hour! 12 Hour! 24 Hour! % Extr ac ti on ! Time! SH 2 L1 % Extraction! ! 35! Table 2.1: Distribution of metal ions after extraction by SH 2 L1 at 8,12, and 24 hours. SH 2 L2 has a five carbon linker chain and a bigger binding pocket for a metal ion complexation. After 8 hours, 80% (? 1) of the copper and after 24 hours, 95% (? 1) of the copper had been extracted into the organic phase. This proved interesting, so a shorter time scale was used to determine how quickly the copper could be extracted. After only 5 minutes of stirring, 87% (? 2) of the copper ions had been extracted from the aqueous phase. The extraction stays consistent at ~87% until about 8 hours before it drops to 80% (? 0.2) and increases again at 12 and 24 hours. Metal 8'Hour12'Hour24'Hour Copper 0.91 1.28 0.98 Gadolinium0.21 0.13 0.18 Uranyl 0.72 0.70 0.47 ! 36! Figure 2.5: Percent extraction of copper ( ?), gadolinium (- - ), and uranyl (-) by SH 2 L2 at 8,12, and 24 hours. 0! 10! 20! 30! 40! 50! 60! 70! 80! 90! 100! 0! 8 Hour! 12 Hour! 24 Hour! % Extr ac ti on ! Time! SH 2 L2 % Extraction! ! 37! Figure 2.6: Copper % extraction at shorter time lengths for SH 2 L2. The bigger pocket of SH 2 L2 does help the extraction of uranyl, gadolinium is also beter extracted as it increases from ~20% with SH 2 L1 to 50% SH 2 L2. SH 2 L2 also had isues of a third layer formation at higher concentrations, although not as severe as SH 2 L1. The third phase caused many problems, most notably not being able to track extraction by UV-Vis. Distribution of the copper ion increases after 8 hours to max of 20 after 24 hours, whereas gadolinium peaks at 12 hours and fals at 24 hours. The distribution of uranyl decreases betwen 8 and 12 hours, but then increases at 24 hours. The 0! 10! 20! 30! 40! 50! 60! 70! 80! 90! 100! 0 ! 5 M i nut e s ! 10 M i nut e s ! 20 M i nut e s ! 25 M i nut e s ! 35 M i nut e s ! 40 M i nut e s ! 45 M i nut e s ! 50 M i nut e s ! 55 M i nut e s ! 60 M i nut e s ! 120 M i nut e s ! 180 M i nut e s ! 240 M i nut e s ! 300 M i nut e s ! 360 M i nut e s ! 420 M i nut e s ! % Extr ac ti on ! Time! Copper % Extraction! ! 38! separation factor for SH 2 L2 for copper over uranyl increases with time. Although, it would be beter to have uranyl bind over copper, this is stil confirmation of a problem of uranyl and copper coordinating in the same binding pocket of a ligand. 13 Table 2.2: Distribution of metal ions after extraction by SH 2 L2 at 8, 12, and 24 hours. Table 2.3: Separation factor of copper over uranyl for SH 2 L2 2.6 Conclusions Extractions were performed using three metals (Cu 2+ , Gd 3+ , and UO 2 2+ ) with two bisdithiophosphinate ligands SH 2 L1 and SH 2 L2. These ligands undergo Metal 8'Hour 12'Hour 24'Hour Copper 4.17 11.69 20.68 Gadolinium 0.85 1.30 0.76 Uranyl 1.00 0.81 0.95 Separation*Factors 8*Hours 12*Hours 24*Hours D Cu /D U 4.18 14.52 21.85 ! 39! hydrolysis under very acidic conditions, unlike Cyanex 301, and therefore extractions were performed at pH 4. As expected, SH 2 L1 was not good at extractions of gadolinium as anticipated from the Pearson theory of Hard and Soft Acids and Bases. 14 It did have moderate extraction of both copper and uranyl at 50 and 40% respectively. SH 2 L2 with the two extra carbons for the linking chain, which increases the binding pocket, was a much beter ligand for the extraction of al three metals. Copper had the highest extraction with nearly 100% extraction. More improvements to the ligands need to be made so that they are soluble in more common organic solvents such as kerosene, to deter the formation of a third phase that would hinder extractions. ! 40! 2.7 References ! (1)! Musikas,!C.!Inorg.'Chim.'Acta!1987,!140,!197.! ! (2)! Sole,!K.!C.;!Hiskey,!J.!B.!Hydrometalurgy!1992,!30,!345.! ! (3)! Komasawa,!I.;!Otake,!T.!J.'Chem.'Eng.'Jpn.!1984,!17,!417.! ! (4)! Preston,!J.!S.!Hydrometalurgy!1982,!9,!115.! ! (5)! Hill,!C.;!Madic,!C.;!Baron,!P.;!Ozawa,!M.;!Tanaka,!Y.!J.'Aloys'Compd.! 1998,!271,!159.! ! (6)! Bhatacharya,!A.;!Mohapatra,!P.!K.;!Manchanda,!V.!K.!Sep.'Purif.' Technol.!2006,!50,!278.! ! (7)! Matloka,!K.!e.!a.!C.R.'Chimie!2007,!10.! ! (8)! Gataulina,!A.!R.;!Safin,!D.!A.;!Gimadiev,!T.!R.;!Pinus,!M.!V.!Transition' Met.'Chem.!2008,!33,!921.! ! (9)! Karakus,!M.;!Yilmaz,!H.;!Bulak,!E.!Rusian'Journal'of'Cordination' Chemistry!2005,!31,!316.! ! (10)! Aragoni,!M.!C.;!Arca,!M.;!Demartin,!F.;!Devilanova,!F.!A.;!Graif,!C.;! Isaia,!F.;!Lipolis,!V.;!Tiripichio,!A.;!Verani,!G.!Journal'of'the'Chemical'SocietyH Dalton'Transactions!2001,!2671.! ! (11)! Aragoni,!M.!C.;!Arca,!M.;!Demartin,!F.;!Devilanova,!F.!A.;!Graif,!C.;! Isaia,!F.;!Lipolis,!V.;!Tiripichio,!A.;!Verani,!A.!Eur.'J.'Inorg.'Chem.!2000,!2239.! ! (12)! Karakus,!M.;!Yilmaz,!H.;!Ozcan,!Y.;!Ide,!S.!Apl.'Organomet.'Chem.! 2004,!18,!141.! ! (13)! Sessler,!J.!L.;!Melfi,!P.!J.;!Pantos,!G.!D.!Cord.'Chem.'Rev.!2006,!250,! 816.! ! (14)! Pearson,!R.!G.!J.'Am.'Chem.'Soc.!1963,!85,!3533.! ! 41! Chapter 3: Quinoxolinol salen ligands for colorimetric sensors 3.1 Introduction Uranium is a naturaly occurring element found at trace levels in the environment, 1,2 and it is a significant soil and water contaminant at sites asociated with uranium mining, nuclear fuel production, and disposal. 3 Because uranyl is stable, water soluble, and mobile, it is readily transported through most soil matrices. The rate of uranyl migration depends on several parameters, including soil porosity and composition, water content, and temperature. 2-4 Methods that have been used for the detection of uranium include thin layer chromatography, 1,5 phosphorimetry, 6 fluorescence, 7,8 x-ray fluorescence, 9 inductively coupled mas spectrometry (ICP- MS), 10,11 surface enhanced Raman scatering (SERS), 12 and colorimetry. 13 Fluorimetry is a sensitive technique that is applicable even to low levels of uranium, 4,14 but the environment around a sensor or the presence of other naturaly occurring metals could quench the fluorescence, and designing a selective turn-on sensor is dificult. 6,15-17 X- ray fluorescence, a wavelength dispersive method, is not sensitive enough for estimation at low levels. Phosphorimetry, SERS, and ICP are not readily mobile, are expensive, and often require a labor-intensive sequence of sampling, chemical treatment, preparation, measurement, and data treatment, 12,18-20 making on-site, real- time sensing dificult. 2 ! 42! Colorimetric sensors have the potential advantage of on-site, real-time sampling and determination without complicated separations or costly instruments. Spectrophotometry has been increasingly employed in proces control since it is simple and adaptable technique. 4 UV-Vis units can be smal and portable, and thus, only require the ligand to bind to the metal. Only a few sensors for uranium have been reported, 2,13 and these probes are not selective for uranyl over copper or other metal ions. 4,21-25 Here, we report the application of a previously synthesized ligand in the molecular recognition of uranyl. 3.2 Experimental 3.21 General Procedure Dimethylformamide (DMF) was purchased and used without further purification. Uranyl(VI) acetate, copper(II) acetate, gadolinium(III) chloride, cobalt(II) nitrate, nickel(II) nitrate, and cerium(III) acetate were used without further purification. UV-Vis spectroscopy was performed on a Cary 50 UV-Vis spectrometer with a Xenon lamp with absorbance spectra from 200-1100 nm with a 1.0 cm width quartz cuvete. Fluorescence spectroscopy was performed on a Shimadzu RF-5301 PC fluorospectrophotometer with a 1.0 cm width quartz cuvete with an excitation wavelength of 350 nm and an emision spectrum of 375-900 nm. ! 43! 3.22 Synthesis of Ligands 26 The "salqu" ligand was synthesized as previously described by our group and disolved in DMF. 26 2,4-Difluoro-3,5-dinitro benzene was disolved in THF and d- leucine methyl ester and 2.2 equiv. of DIPEA were mixed together. Amonium hydroxide in water (3 equiv.), was employed in the substitution of the second fluorine. After reduction using wet Pd/C, the target intermediate was recrystalized from 95% ethanol (Scheme 1). For H 2 L1 and H 2 L2, 3,5-di-tert-butyl salicylaldehyde was disolved in EtOH with the intermediate and 5 mol% trifluroacetic acid (TFA) at 80 o C overnight to form the di-substituted ligand (Scheme 2). For H 3 L3, 3,5-di-tert- butyl salicylaldehyde was disolved in EtOH with the intermediate at 80 o C for 24 hours to form the mono-substituted salqu ligand (Scheme 3). 3.23 Metal Titration and K b Studies The ligands, H 2 L1 and H 3 L2, were disolved in DMF for metal titration and K b studies. Fresh solutions of Cu(OAc) 2 ?2H 2 O, UO 2 (OAc) 2 , Co(NO 3 ) 2 ?4H 2 O, Gd(OAc) 3 , Ce(OAc) 3 , and Ni(NO 3 ) 2 were disolved in deionized water and diluted to the appropriate concentrations with deionized water. Batch titrations were performed with constant ligand concentration and water content. Serial titrations were performed with no regard for dilution and final ligand concentration. K b studies were undertaken using non-linear regresion with a minimum sum of the least squares, by varying the ! 44! ligand concentration and keeping the metal concentration controlled. Al individual metal UV-Vis spectra for the descibed experiments are located in Appendix 1. Scheme 3.1: Synthesis of quinoxolinol backbone Scheme 3.2: Synthesis of di-substituted ligand FF O 2 NNO 2 F O 2 N H N NO 2 R 1 OMe H 2 O 2 N H N NO 2 R 1 Me N R 1 OH H 2 N 2 TH, Amino Acid 1 equiv. DIPE NH 4 OH THF Pd/C, NH 4 CO EtOH OH O N R 1 OH H 2 NNH 2 N R 1 OH N OHHO 2 mol % TFA EtOH, 1 our reflux R 1 = 2 L1 H 2 L2 ! 45! Scheme 3.3: Synthesis of mono-substituted ligand 3.3 Results The advantage to using the quinoxolinol salen (Salqu) ligands is that the conjugated pi-system results in more intense UV-Vis spectra, thereby, alowing lower concentrations to be used in sensing experiments. Batch titrations were performed to determine the selectivity and photo-physical responses of the ligands for various metals, with special atention paid to distinguishing the diferences betwen copper and uranyl, and uranyl and the ligand. Although the ligands themselves are not water- soluble, it was best to do as litle pre-treatment to the metal solutions as possible. The OH O N OH H 2 NNH 2 N OH NNH 2 OH EtOH, 24 our reflux H 3 L3 ! 46! ligands were tested for solubility in water, acetonitrile, dimethylsulfoxide (DMSO), N,N?-dimethylformamide (DMF), pyridine, methylene chloride (DCM), methanol, hexane, toluene, tetrahydrofuran (THF) and octanol. THF had the highest solubility of the ligands and was chosen as the starting solvent. There were only slight changes in the UV-Vis spectra of the metal complexes, and there was also the problem of the solvent evaporating. This evaporation creates potential problems if this ligand is used as pre-made solutions that need to be stored for a long time. The next logical step was to characterize the ligands in a higher boiling point solvent, such as DMF, that is still miscible with water. Batch and serial titrations were performed to determine any changes of the UV-Vis spectrum of the ligand as the metal concentrations increased. A batch titration was set up as ten vials al with the same ligand concentration and final water volume. Then, diferent concentrations of metal ranging from 20 ?M metal (1:1 metal to ligand) to 200 ?M (10:1 metal to ligand) were added to the vials labeled 1-10 respectively for the metal concentration they contained. The solutions were then stirred for 2 hours. During this time, the colors of the solutions changed, indicative of metal ion complexation. The procedure for the batch titration applied is detailed in Chart 3.1. ! 47! Chart 3.1: Batch titration set up for 20% water/DMF solution and 40 ?M ligand stock and 1 mM metal stock solution for final concentrations of 20 ?M ligand and the desired final concentration of metal. Total volume for each solution is 10 mL. Figure 3.1: Example of batch titration with uranyl and H 2 L1. The uranyl concentration was increased from a 1:1 metal to ligand ratio to a 10:1 metal to ligand ratio. Metal to Ligand RatioLigand in DMF(mL)Metal in water (mL)Water (mL)DMF (mL)Final Metal Concentration 1 : 1 5 0.21.83 20 uM 2 : 1 5 0.41.63 40 uM 3 : 1 5 0.61.43 60 uM 4 : 1 5 0.81.23 80 uM 5 : 1 5 1 1 3 100 uM 6 : 1 5 1.20.83 120 uM 7 : 1 5 1.40.63 140 uM 8 : 1 5 1.60.43 160 uM 9 : 1 5 1.80.23 180 uM 10 : 1 5 2 0 3 200 uM 0! 5! 10! 15! 20! 25! 30! 35! 40! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 20% Water/DMF Uranyl" Ligand! 1 to 1! 2 to 1! 3 to 1! 4 to 1! 5 to 1! 6 to 1! 7 to 1! 8 to 1! 9 to 1! 10 to 1! ! 48! To determine additional real-time data, serial titrations were performed. A typical procedure would start with a solution of ligand, to which an aliquot of aqueous metal solution would be added (0.1:1 metal to ligand for each aliquot). The resulting solution would be stirred for 5 minutes, measured, and then, the next aliquot added. This however, gives no regard as to the concentration of the water, and thus it had to be performed at low final water percentage to prevent the ligand from precipitating. Figure 3.2: Example of serial titration with uranyl and H 2 L1. Uranyl concentration was increased from a 0.1:1 metal to ligand to 100:1 metal to ligand ratio The first method tested was to perform the UV-Vis characterization with solute and chromophore disolved in DMF. This, of course, would require first concentrating whatever water sample was obtained, and then adding DMF to it and 0! 5! 10! 15! 20! 25! 30! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" Uranyl Serial H 2 L1 10uL base" Ligand! 1 tenth! 2 tenth! 3 tenth! 4 tenth! 5 tenth! 1 to 1! 2 to 1! 3 to 1! 4 to 1! 5 to 1! 6 to 1! 7 to 1! 8 to 1! 9 to 1! 10 to 1! 100 to 1! ! 49! asuming al trace metal disolves. While the full approach was not taken, the metals were disolved in a smal amount of water, and then diluted to the appropriate concentrations with DMF a few times to have les than 1% water in the total system with no precipitate observed. The graph for H 2 L1, with copper, and with uranyl can be sen in Figure 3.3. The ligand had a maximum absorbance at 387 nm with an extinction coeficient of 2.6 x 10 4 M -1 ? cm -1 . There is a substantial increase in absorption upon reaction with copper(II) acetate at 450 nm and 328 nm, with molar extinction coeficients of 3.9 x 10 4 M -1 ? cm -1 and 2.9 x 10 3 M -1 ? cm -1 , respectively. Concomitant with these increases, the band atributed to the free ligand decreases in intensity. Uranyl had a maximum absorbance peak at 376 nm, with an extinction coeficient of 2.8 x 10 4 M -1 ? cm -1 , a shift of 11 nm from the ligand peak. This separation betwen the ligand and uranyl, and betwen uranyl and copper, could be used to diferentiate the metals and distinguish actinides in the environment from other metals. ! 50! Figure 3.3: Combined UV-Vis spectra of H 2 L1 (20 ?M) with copper (20 ?M) and uranyl (200 ?M) in DMF after 2 hour stir. The water concentration was slowly increased by 5% until 25%, at which point, the ligand precipitated from solution. At 5% water/DMF, the ligand maximum absorbance is at 386 nm, a diference of 1 nm from <1% water. The uranyl peak has a maximum at 369 nm, a shift of 17 nm from the ligand, while the copper and cobalt peaks are at 448 nm and 430 nm respectively. 0! 5! 10! 15! 20! 25! 30! 35! 40! 45! 50! 275! 325! 375! 425! 475! 525! 575! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 DMF" Ligand! Copper! Uranyl! ! 51! Figure 3.4: Combined batch metal titration for copper (40 ?M), uranyl (120 ?M), and cobalt (40 ?M) with H 2 L1 (20 ?M) in 5% Water/DMF (v/v) At 10% water/DMF, the ligand has a maximum absorbance at 385 nm, a shift of 2 nm from the previous 5% water/DMF. Copper had a maximum absorbance at 450 nm, with a 3.2x10 4 M -1 ? cm -1 extinction coeficient. Cobalt had an absorbance maximum of 429 nm, with an extinction coeficient of 2.5 x10 4 M -1 ? cm -1 , while uranyl had an absorbance maximum peak of 367 nm, with a 2.5 x10 4 M -1 ? cm -1 extinction coeficient. 0! 5! 10! 15! 20! 25! 30! 35! 40! 45! 50! 250! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 5% Water/DMF " Ligand! Copper! Cobalt! Uranyl! ! 52! Figure 3.5: Combined batch metal titration for copper (40 ?M), uranyl (200 ?M), and cobalt (100 ?M) with H 2 L1 (20 ?M) in 10% Water/DMF (v/v) For 15% water/DMF the ligand maximum absorbance peak was at 389 nm, with an extinction coeficient of 2.5 x10 4 M -1 ? cm -1 . The copper absorbance maximum increased to 452 nm, with a fairly consistent 3.2 x10 4 M -1 ? cm -1 extinction coeficient. The cobalt complex had a higher energy increase in absorbance maximum to 417 nm, and an extinction coeficient of 2.3 x10 4 M -1 ? cm -1 . Uranyl had a maximum absorbance at 369 nm, and an extinction coeficient close to that of the ligand of 2.6 x10 4 M -1 ? cm -1 . 0! 5! 10! 15! 20! 25! 30! 35! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 10% Water/DMF" Ligand! Copper! Uranyl! Cobalt! ! 53! Figure 3.6: Combined batch metal titration for copper (40 ?M), uranyl (100 ?M), and cobalt (60 ?M) with H 2 L1 (20 ?M) in 15% Water/DMF (v/v) H 2 L1 in 20% water/DMF (v/v) had a maximum extinction coeficient for uranyl of 2.6 x10 4 M -1 ? cm -1 , at 367 nm. The cobalt complex has a peak at 436 nm, with an extinction coeficient of 2.1 x10 4 M -1 ? cm -1 . The copper complex has an extinction coeficient of 2.4 x10 4 M -1 ? cm -1 , at 450 nm. The other metals in figure 3.7 have litle to no shift from the ligand peak, at 390 nm, in the spectrum. 0! 5! 10! 15! 20! 25! 30! 35! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 15% Water/DMF" Ligand! Copper! Cobalt! Uranyl! ! 54! Figure 3.7: H 2 L1 with various metals in 20% water/DMF (v/v). 20 ?M ligand concentrations, 80 ?M metal concentration Table 3.2: Maximum absorbance and extinction coeficient for H 2 L1, copper and uranyl summary based on % water/DMF. H 2 L1 was also tested in acetone to determine if a diferent solvent could improve the kinetics of binding and/or alter the UV-Vis absorption. The ligand in acetone was not shown to improve, with either an increase in signal selectivity nor separation of the peaks, on any of the previous work performed in DMF, and was 0! 5! 10! 15! 20! 25! 30! 35! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 20% Water/DMF" Ligand! Cobalt! Uranyl! Copper! Nickel! Cerium! Gadolinium! % waterH2L1?*10 4 M -1 cm -1 Copper?*10 4 M -1 cm -1 Uranyl?*10 4 M -1 cm -1 Cobalt?*10 4 M -1 cm -1 < 1%3872.64503.93762.8- - 5%3862.44483.03692.54302.2 10%3852.44503.23672.54292.5 15%3892.54523.23692.64172.3 20%3902.74502.43672.64362.1 ! 55! actualy worse for kinetics. The first complexation of the metals by a color change took place after constantly stirring for 24 hours, indicating that the kinetics of the binding was greatly slowed, or possibly affected by the decrease in pH betwen DMF and acetone. Secondly, because the kinetics had slowed, the UV-Vis spectra did not show as significant of a change from the ligand maximum absorbance. After 5 hours, the copper peak at ~450 nm stil appears, but uranyl and cobalt give rise to spectra that are similar to that of the free ligand. Acetone also evaporates quickly at ambient conditions, and it is dificult to maintain the specific concentrations of stock solutions over long periods of time. Figure 3.8: H 2 L1 with various metals in 20% water/Acetone (v/v). 20 ?M ligand concentrations, 80 ?M metal concentration after a 5 hour stir 0! 5! 10! 15! 20! 25! 30! 320! 370! 420! 470! 520! 570! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 20% Water/Acetone" Ligand! Cobalt! Copper! Uranyl! ! 56! The di-substituted ligand with phenyl alanine (H 2 L2) was also tested at 20% water/DMF (v/v). The hypothesis was that the extra phenyl ring on the backbone could increase the sensitivity of the ligand and lower the detection limit of the metals It was observed that the shoulder in the spectra for H 2 L1 became a distinct peak at 450 nm for H 2 L2, conversely the peak for H 2 L1 at 367 nm is a shoulder for H 2 L2. The cobalt complex?s maximum absorbance shifted from 430 nm in H 2 L1 to 466 nm for H 2 L2, and the copper complex shifted only 6 nm from H 2 L1 to 456 nm for H 2 L2. Figure 3.9: H 2 L2 with various metals in 20% water/DMF (v/v). 20 ?M ligand concentrations, 80 ?M metal concentration The mono-substituted ligand (H 3 L3) was also investigated. This ligand was able to withstand up to 40% water without precipitating; however, the batch titration with uranyl at >1% water provided no evidence of uranyl binding due to no color 0! 5! 10! 15! 20! 25! 30! 250! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L2 20% Water/DMF" Ligand! Copper! Cobalt! Uranyl! ! 57! change or a shift in the absorbance maximum. The lack of a distinct peak could be a solvent interaction, or a dimerization preventing the change in absorbance, or it could be that the three donor atoms are not sufficient to bind the metal strongly. The least likely explanation is that the uranyl ion is too big to fit in the three donor binding pocket efectively. Copper did bind, but at a higher concentration as compared to the di-substituted ligand, H 2 L1. Copper had a maximum absorbance at 406 nm, a shift of 30 nm to lower energy from the ligand peak. Figure 3.10: H 3 L3 with various metals in DMF. 20 ?M ligand concentrations, 80 ?M metal concentration The water content was increased to 10% for the mono-substituted ligand, because it should at least be able to match the di-substituted ligand before precipitation. At 10% water/DMF (v/v), uranyl did not have any signs of binding, as 0! 5! 10! 15! 20! 25! 30! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 3 L3 DMF" Ligand! Copper! Uranyl! ! 58! there was no change in the UV-Vis absorbance. The main ligand peak at 406 nm was stil present for the copper complex, but there were broad peaks for equivalents 1-4 that turned into two shoulders as the concentration of the copper increased above 80 uM (Figure A3.24). The broad peaks are at 518 nm, whereas the shoulders are around 530 nm and 450 nm. Cobalt exhibited only a smal shift in the absorbance maximum at 412 nm, a shift of about 6 nm. Figure 3.11: H 3 L3 with various metals in 10% water/DMF (v/v). 20 ?M ligand concentrations, 200 ?M metal concentration After it became apparent that uranyl was not going to cause changes to the UV-Vis spectra with H 3 L3, further titrations were investigated with just copper and cobalt. The idea was that a two-ligand system could be used in a sample. H 3 L3 would be used first to bind to metals such as copper or cobalt, and then extracted. While it is 0! 5! 10! 15! 20! 25! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 3 L3 10% Water/DMF" Ligand! Copper! Uranyl! Cobalt! ! 59! preferred to avoid pre-purification, a similar ligand with good extraction kinetics that could be used on-site could be useful. Then, the analysis on the water sample for actinides could be preformed with H 2 L1. This leads to a pre-treatment of the sample of sorts, but it is a simple pre-treatment as compared to ion exchange resins or other techniques that may be used. For the 20% water/DMF (v/v) with H 3 L3, the copper spectrum was in general, much the same as it was for the 10% water/DMF. There are broad peaks al the way up to 7 equivalents, more equivalents than for 10% water/DMF. For 8, 9, and 10 equivalents, there is a shoulder at lower, and a peak at higher in energy than the broad peaks. The broad peaks have a maximum absorbance at ~508 nm. The shoulder is at ~520 nm while the peaks are at 463 nm. The cobalt complex spectrum is nothing like the 10% water/DMF spectra, the only major peak is obscured the by the main ligand peak. There is an increase in absorbance betwen 450 and 600 nm, indicating a charge-transfer band, but there is not a distinct absorbance peak like before. ! 60! Figure 3.12: H 3 L3 with various metals in 20% water/DMF (v/v). 20 ?M ligand concentrations, 200 ?M metal concentration The copper complex with H 3 L3 in 30% water/DMF (v/v), had broad peaks up to 4 equivalents with shoulders and a higher energy peak for al the other equivalents up to 10 equivalents. The broad peaks have a maximum absorbance of ~496 nm, whereas the shoulders are at about ~520 nm, and the higher energy peaks have a maximum absorbance ~463 nm. For the cobalt complex, the UV-Vis spectrum follows the same structure as was sen for the 20% water/DMF. The charge-transfer band, and a color change indicate the ligand did bind to copper. The cobalt complex has a smal shift off the ligand peak, with a shoulder around 500 and 550 nm. 0! 5! 10! 15! 20! 25! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 3 L3 20% Water/DMF" Ligand! Copper! Cobalt! ! 61! Figure 3.13: H 3 L3 with various metals in 30% water/DMF (v/v). 20 ?M ligand concentration, 200 ?M metal concentration The highest percentage of water that could be tolerated without ligand precipitation was 40%. Al the metals tested with H 2 L1 in 20% water/DMF were also tested with H 3 L3 in 40% water/DMF (v/v). Uranyl with the H 3 L3 ligand shows no change in the UV-Vis spectra, indicative of uranyl not bonding to the ligand, or not bonding strongly. Even the addition of up to 50 ?L (~18 equiv.) of triethylamine does not elicit a UV-Vis response from the uranyl complex. Gadolinium, cerium, and nickel, likewise, do not appear to bind H 3 L3 either, as evidenced by the lack of change in the UV-Vis spectrum with up to 10 equivalents of metal. One reason this could be the case is that Ni 2+ prefers to be in a square planar geometry and the ligand may not be able to accommodate that, whereas Cu 2+ can bind in square planar or in a 0! 5! 10! 15! 20! 25! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 3 L3 30% Water/DMF" Ligand! Copper! Cobalt! ! 62! tetrahedral. The maximum absorbance peak for the copper complex is 459 nm, a shift of 50 nm from the ligand. Cobalt has a shoulder located at ~ 480 nm. Figure 3.14: H 3 L3 with various metals in 40% water/DMF (v/v). 20 ?M ligand concentration, 200 ?M metal concentration Table 3.3: Maximum absorbance and extinction coeficient for H 2 L1 and metals summary based on % water/DMF. 0! 5! 10! 15! 20! 25! 275! 375! 475! 575! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 3 L3 40% Water/DMF" Ligand! Nickel! Copper! Uranyl! Gadolinium! Cerium! Cobalt! % waterH3L3?*10 4 M -1 cm -1 Copper?*10 4 M -1 cm -1 Uranyl?*10 4 M -1 cm -1 Cobalt?*10 4 M -1 cm -1 < 1%4052.84052.14052.8- - 10%4062.44131.94062.23101.5 20%4072.1413, 470 1.6, 1.3- - 4101.5 30%4082.1416, 4641.5, 1.5- - 4081.5 40%4082.34571.7- - 3991.3 ! 63! One possibility is that aggregation of the ligands could hinder the kinetics. In an atempt to limit aggregation of the ligand and improve the complexation kinetics, the use of HEPES (2-4[-(2-hydroxyethyl)piperazine-1-yl]ethanesulfonic acid) buffer was employed. HEPES is an inexpensive phosphate containing buffer component that has an efective pH range betwen 6.8-8.2, more typical of what you might find in a natural water flow from a river. Metals are also unlikely to bind the HEPES anion even at a 50 ?M total concentration. It was added to the individual metal solution before addition of ligand and adjusted to pH 7. In acetone, the addition of HEPES buffer greatly improved the kinetics over no buffer. Copper complexation took place in about 6 hours; whereas the uranyl and cobalt complexation took about 12 hours. The buffer also made the copper complex peak at 450 nm more defined. The cobalt peak can be sen increasing absorbance, whereas the uranyl peak shows a slight shift to higher energy from the ligand peak. For the HEPES buffer metal solution with the H 2 L1 in DMF, complexation of uranyl occurred in 1 hour, as opposed to the 2 hours required without the buffer. The addition of copper and cobalt stil elicited the same color change imediately after addition, as before. The uranyl complex peak was further shifted to 349 nm, but this would be overlapped by the copper complex peak at 355 nm. The main copper peak from before at 450 nm, was also higher energy shifted to 446 nm. ! 64! Figure 3.15: H 2 L1 (20 ?M) with various metals (80 ?M) in 20% water/DMF (v/v) with 50 ?M HEPES buffer. 3.4 Fluorescence Fluorescence spectroscopy is a valuable technique used in the detection of trace metals due to its sensitivity. 7 H 2 L1 and H 3 L3 both fluoresce at 350 nm wavelength excitation to give peaks at ~565 nm and 525 nm respectively. Within 5 seconds, quenching of the fluorescence was sen upon the addition of copper in both H 2 L1 and H 3 L3 whereas only a decrease in the emision was sen upon the addition of uranyl within 5 seconds. It took one equivalent of copper to cause a complete quench of H 2 L1 and two equivalents to cause a complete quench of H 3 L3. The uranyl intensity does not change after 2 hours. Such a significant rapid quenching of the copper signal would be useful to use in the distinguishing betwen copper and uranyl 0! 5! 10! 15! 20! 25! 30! 35! 40! 45! 50! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 20% water" DMF 50 uM HEPES buffer" Ligand! Cobalt! Copper! Uranyl! ! 65! ions in the sample or in combination with UV-Vis to detect metal and fluorescence to confirm the contribution of uranyl. There could be a problem of a smal amount of copper could that cause incomplete quenching, and therefore mimic the uranyl signal. This should be investigated further. Figure 3.16: Fluorescence of H 2 L1 with uranyl complex and copper complex after 2 hour stirring in 20% water/DMF (v/v) at 350 nm excitation ! 66! Figure 3.17: Fluorescence of H 3 L3 with uranyl complex and copper complex after 2 hour stirring in 40% water/DMF (v/v) at 350 nm excitation 3.5 Calculations Calculations in Gaussian 09 27 were used to determine the interactions betwen the HOMO and LUMO at the excitations that are causing the shifts sen in the spectra. The calculations were optimized using B3LYP 28 at the 6-31g(d) basis set and solvated in DMF, followed by time-dependent DFT (TDFT) to determine the excitations and a predicted UV-Vis in Gaussview. Although the calculated UV-Vis does not exactly match up to the experimental spectra (figure 3.19), the overal shape of the spectra is very similar with respect to the shifts of the complexes to higher and lower energies. Natural Transition Orbitals (NTO) 29 were used to identify the contributing orbitals in the HOMO-LUMO interaction. 0! 20! 40! 60! 80! 100! 120! 140! 160! 180! 200! 350! 450! 550! 650! 750! I n te n s i ty ! Wavelength (nm)! H 3 L3 40% Water/DMF! 350 nm Excitation! Ligand! Copper! Uranyl! ! 67! Figure 3.18: Optimized structures for uranyl and copper complex with bond distances comparing the uranyl crystal structure. 30 U-N1 2.551(3) U-N2 2.577(3) U-O1 2.254(2) U-O2 2.255(2) U-O3 yl 1.774(2) U-O4 yl 1.779(2) U-N1 2.539 U-N2 2.550 U-O1 2.257 U-O2 2.255 U-O3 yl 1.794 U-O4 yl 1.790 Cu-N1 1.940 Cu-N2 1.941 Cu-O1 1.904 Cu-O2 1.906 ! ! 68! Figure 3.19: Combined experimental and calculated UV-Vis spectra for H 2 L1. Calculated has a 30 nm shift to beter match up with experimental spectrum. For the uranyl complex, the HOMO orbital?s major contribution was from the ligand with a single electron going into the LUMO f-orbital on the metal. This higher energy excitation caused the absorbance to blue shift from the ligand peak. For the copper complex, the HOMO orbital was the d-orbital on the metal going to the ligand LUMO orbital, causing the lower energy shift from the ligand. 0! 10! 20! 30! 40! 50! 60! 250! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" Experimental and Calculated H 2 L1" Ligand! Calc Ligand! Copper! Calc Copper! Uranyl! Calc Uranyl! ! 69! Figure 3.20: Hole (HOMO) and particle (LUMO) for NTO analysis of the uranyl complex. Figure 3.21: Hole (HOMO) and particle (LUMO) for NTO analysis of the copper complex ! 70! These diferent excitations are caused as the two metals interact with the ligand, and is a step to predicting the best ligand for selectivity and sensing. Other ligands detailed in Chapter 4 that were not selective, al had the same interaction with the metals whether it was metal to ligand, or ligand to metal in the HOMO to LUMO. 3.6 Binding Constants Table 3.4: Average of binding constants from two replications of data collection and extinction coeficients for H 2 L1 with uranyl copper and cobalt Table 3.5: Average of binding constants from two replications of data collection and extinction coeficients for H 3 L3 complexes with copper and cobalt. The binding constants and extinction coeficients were calculated using non- linear regresion with the sum of the least squares of the UV-Vis spectra, changing the ligand concentration with the metal concentration remaining constant. The Log K? Log K? Log K? Log K? Uranyl3.883.20E+043.576.50E+043.802.97E+043.523.38E+04 Copper 4.224.43E+044.164.16E+044.273.90E+044.282.99E+04 Cobalt 3.774.31E+043.835.89E+043.628.29E+043.795.52E+04 DMF5% Water 10% Water 20% Water H 2 L1 Log K? Log K? Copper 3.744.78E+043.042.13E+05 Cobalt 3.092.30E+053.442.93E+04 DMF 10% water ! 71! titrations were alowed to stir for 24 hours to ensure complete complexation. The solver program in Excel was used to determine the smalest number for the sum of the squares and have the model fit the experimental data as best as it could. The data gave a K and extinction coeficient in the answer. 3.7 Colorimetry Figure 3.22: H 3 L3 colorimetry 40% water/DMF Figure 3.23: H 2 L1 colorimetry 20% water/DMF The other advantage of the Quinoxolinol salen ligands is that upon metal complexation, the ligand changed from a light green-yelow to a yelow, orange, or red color depending on the ligand and metal coordinated. Ni has a smal shift in ! 72! maximum absorbance from the ligand and an increasing absorbance at ~450 nm that caused the color change. 3.8 Conclusion A series of batch and serial titrations were analyzed at varying metal concentrations with two ligands, H 2 L1 and H 3 L3. H 2 L1 was shown that it could be used as a UV-Vis sensor for uranyl due to the higher energy shift of the absorbance peak in the uranyl complex, compared to copper, which gave a lower energy shift in the spectrum relative to the ligand. The uranyl peak was also separated from the ligand by ~20 nm. The ligand could be used in up to 20% water before precipitation. Other metals such as gadolinium, nickel, and cerium gave litle to no shift from the ligand peak. H 3 L3, while able to withstand a higher water content (40%), was not a good sensor for uranyl. The spectrum did not change betwen the ligand and uranyl. The same metals tested by titration with H 2 L1 were also tested with H 3 L3 and only copper and cobalt gave any change in the UV-Vis spectrum. Calculations were performed to determine the viability of the current ligand system (H 2 L1), and to also determine what modifications to the quinoxolinol and binding pocket could be made to improve either, the selectivity or sensitivity of the ! 73! ligand, or both. NTO analysis on the current ligand system showed that the uranyl peak is caused by an excitation from the ligand HOMO to a LUMO f-orbital of uranyl, while the copper excitation was caused by a HOMO d-orbital on the metal being excited to the ligand LUMO. Further calculations for the modifications of the ligand are reported in Chapter 4. ! ! 74! 3.9 References ! (1)! Hodisan,!T.;!Curtui,!M.;!Haiduc,!I.!J.#Radioanal.#Nucl.#Chem.!1998,! 238,!129.! ! (2)! Lee,!J.!H.;!Wang,!Z.!D.;!Liu,!J.!W.;!Lu,!Y.!J.#Am.#Chem.#Soc.!2008,!130,! 14217.! ! (3)! Pestov,!D.;!Chen,!C.!C.;!Nelson,!J.!D.;!Anderson,!J.!E.;!Teper,!G.!Sens.# Actuators,#B!2009,!138,!134.! ! (4)! 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Chapter 4: Quinoxolinol based sensors for molecular recognition: A TDDFT computational study 4.1 Introduction Since the 1950s, nuclear weapons, power reactors, medical, and research activities have introduced many diferent radionuclides into the environment. 1 It is important to fundamentaly study the actinides because of their use in nuclear energy and nuclear materials, where such isues as long-term storage of nuclear waste, environmental cleanup, and actinide separations need to be addresed. 2 The development of sensors for the detection of metal ions is an ongoing chalenge that is atracting the atention of researchers across a range of disciplines. 3 In the case of chemical agents that trigger an easy-to-monitor response (e.g., optical, fluorescent, electrochemical), otherwise known as chemosensors (sensors for short), both sensitivity and selectivity are critical elements of a succesful design. 3 This is particularly true for sensors developed for f-elements, since specific action recognition is critical to identifying species that might be present in the environment as the result of a radioactive spil or a terrorist atack involving a dirty bomb. 3 ! Typical analytical methods used include inductively coupled plasma mas- spectrometry (ICP-MS), 4,5 capilary electrophoresis, fluorescence, 6 X-ray fluorescence ! 77! (XRF), 7 phosphorimetry, 8 and colorimetry. 9 These methods tend to be costly, involve multiple sample manipulations, and often have insufficient selectivity and/or sensitivity. 3,10-12 One of the methods proposed for nuclear waste treatment and actinide separation involves the coordination of actinide ions with polydentate ligands, exploiting this chelate efect. 2,13 Previous ligands proposed as chemosensors for actinides include expanded porphyrins 14,15 and related Schif-base macrocycles 16 , calixarenes 17 , crown-ethers 18-20 , aza-crowns 21 , and Arsenazo III. 3,22 With this study, we sought to use a two fused ring system (quinoxaline) to increase the binding and modify the coordination pocket to increase the selectivity for uranyl over copper. This backbone also fluoresces, providing an additional means of identifying a sensor, but those calculations are not performed or described here. 4.2 Methods Calculations in Gaussian 09 23 to determine the source of the shifts of H 2 L1 were performed using the hybrid DFT B3LYP 24 basis set and solvated using the SCRF keyword with N,N?-dimethylformamide. The Stuttgart efective core potential basis set was used for uranium, replacing 60 core electrons to acount for scalar- relativistic efects. 25,26 The 6-31g(d) 27,28 basis set was used for al carbon, nitrogen, oxygen, hydrogen and copper atoms. Al structures were converged with the default self-consistent-field (tight) convergence cutoffs. 29 The optimized structure of the uranyl complex was in close relation to the published uranyl crystal structure. After optimization, time-dependent DFT (TDFT) 30-37 was used to determine the excited ! 78! states and predicted UV-Vis spectra for the ligand and metal complex. The calculated UV-Vis did match the general spectrum shape but was shifted to higher energies. Natural transition orbitals (NTO) 38 were investigated to determine the HOMO to LUMO interaction causing the changes in the absorbance maximum and the diferences betwen the metal complexes. 4.3 Results This series of calculations was undertaken to try to characterize how the quinoxolinol ligand system UV-Vis spectra diferentiates betwen the copper and uranyl complexes and to predict the spectroscopic signal response generated. Further, it was investigated as to how this system might be modified to further improve the separation of the peaks and increase the extinction coeficient, thus improving the sensitivity. The current salqu system has a shift to higher energy excitations from the ligand peak for uranyl, whereas there is a shift to lower energy excitations for copper as sen below in Figure 4.1. The uranyl complex has a peak at 370 nm and a shoulder at 450 nm corresponding to extinction coeficients of 2.6 x10 4 M -1 ? cm-1 and 1.9 x10 4 M -1 ? cm -1 respectively for those peaks. Copper has peaks at 450 nm and 327 nm corresponding to a 2.5 x10 4 M -1 ? cm-1 extinction coeficient for both peaks. ! 79! Figure 4.1: Experimental salqu with copper and uranyl complex The calculated absorbance spectrum (figure 4.1), although shifted to slightly higher energies (~30 nm), matches the general shape of the spectrum found in the experimental. The uranyl extinction coefficient is 4.8 x10 4 M -1 ? cm -1 at the peak and 3.7 x10 4 M -1 ? cm -1 at the shoulder. The most influential excitation for the peak at 343 nm is an excitation at 308 nm. The copper extinction coeficient is 4.7 x10 4 M -1 ? cm -1 at 343 nm and 3.9 x10 4 M -1 ? cm -1 at 421 nm. For copper, the most influential excitation is at 421 nm. To begin to understand the excitations causing the shift in the spectra, natural transition orbitals were applied to the excitation states. These would provide information as to what singlet excitation was causing the shifts, whether it was simply a pi to pi*, metal to ligand, or ligand to metal transitions. Acording to the NTO calculations, the carbon atoms on carbons on the lower quinoxolinol ring and on the 0! 10! 20! 30! 40! 50! 60! 250! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" Experimental and Calculated H 2 L1" Ligand! Calc Ligand! Copper! Calc Copper! Uranyl! Calc Uranyl! ! 80! phenyl rings occupy the majority of the hole and the uranium f-orbital atom occupies over 70% of the particle orbital. Looking at the next orbitals of the hole ? 1 and particle + 1 it is even more of a ligand to metal transition with uranium f-orbital occupying over 90% orbital particle + 1 orbital. The copper complex has the opposite singlet excitation. Copper occupies >70% of the d-orbital in the hole and the ligand occupies the majority of the particle orbital. Hole -1 and particle +1 also show a more defined metal to ligand transition. Three rules were developed to determine if the modified ligands were aceptable; (1) the copper complex peak must not overlap with the uranyl complex peak, (2) the uranyl complex peaks needs to be at least 10-15 nm from any other peak, (3) a higher extinction coeficient of the uranyl complex over any other peaks should be considered as this is a measure or sensitivity. The H 2 L1 ligand by itself has a pi to pi* transition as would be expected. For the uranyl complex with H 2 L1, there is a ligand to metal excitation into the f-orbital of the uranium. The copper(II) complex with H 2 L1 has a d-orbital metal to ligand excitation from the HOMO to the LUMO. 4.31 Salicylaldehydes The first series of calculations to modify the ligand was to incorporate diferent salicylaldehyde moieties and thereby determine if the diference was electronic in nature. The first test was for no substituents on the salicylaldehyde, and ! 81! then these results were used to determine what additional modifications to make. A range of commercialy available salicylaldehydes was with electron-donating and electron-withdrawing groups in the 3, 4, 5, and 6 positions, including some with substituents on multiple positions was characterized. These included 3-ethoxy, 3,5- dichloro, 4-amino, 4-chloro, 4-hydroxy, 4-methoxy, 4,6-hydroxy, 5-amino, 5- hydroxy, 5-methyl, and 5-t-butyl. Of these, none were more selective or sensitive than the experimental ligand, with the salicylaldehyde being the best of the computed ligands. The 4-chlorosalicylaldheyde is a possible improvement as it has a higher extinction coeficient at higher energy than the free ligand, which would need to be further probed experimentaly. Figure 4.2: Salicylaldehyde representation N N OH HO OH R 1 R 1 ! 82! Table 4.1: Salicylaldehyde derivatives with absorbance maximums. Green highlight is the best and yelow is a possibility. Figure 4.3: Calculated salicylaldehyde spectrum with copper and uranyl complex in DMF Ligand?*10 4 M -1 cm -1 Copper?*10 4 M -1 cm -1 Uranyl?*10 4 M -1 cm -1 H220, 257, 3534.0, 3.7, 4.1220, 336, 4044.9, 4.2, 4.1220, 3204.4, 4.1 3-ethoxy219, 3575.7, 4.9231, 3585.4, 5.5226, 3345.5, 4.7 3,5-dichloro223, 3676.2, 4.2236, 347, 4035.4, 4.6, 4.0231, 266, 3364.6, 3.6, 4.1 4-amino218, 3343.9, 5.6216, 3934.5, 6.8221, 3762.6, 5.9 4-chloro220, 260, 3624.1, 4.1, 4.5223, 3994.7, 5.3224, 276, 3684.0, 3.8, 4.8 4-hydroxy217, 264,3514.0, 3.4, 4.7221, 3884.3, 5.7224, 3653.4, 5.0 4-methoxy218, 271, 3533.9, 3.5, 5.1222, 3834.7, 6.3224, 3633.4, 5.6 4,6-hydroxy322, 3594.5, 4.5225, 3835.2, 6.6225, 275, 3553.0, 2.9, 5.3 5-amino235, 3626.0, 3.6242, 344, 5065.0, 4.9, 2.1217, 266, 3255.6, 3.9, 4.5 5-hydroxy219, 288, 3774.1, 3.2, 4.3227, 341, 4654.9, 4.7, 2.6222, 264, 3413.5, 3.7, 4.6 5-methyl217, 278, 3634.3, 2.9, 4.7225, 336, 4175.4, 4.3, 3.7222, 268,3444.0, 3.6, 4.5 5-t-butyl216, 277, 3614.7, 3.0, 4.0227, 340, 4115.6, 4.8, 3.5226, 268, 3433.9, 4.0, 4.7 R1 ?ax Abs (nm) 0" 10" 20" 30" 40" 50" 60" 200" 250" 300" 350" 400" 450" 500" 550" 600" ? *1 0 3 &M (1& cm (1& & Wavelength&(nm)& Salqu&DMF& Ligand" Copper" Uranyl" ! 83! 4.32 Schiff Bases Changing the substituents on the phenyl rings did not appear to improve upon the selectivity already established with the experimental ligand. One additional point of diversity to change is the binding pocket while keeping the imine to keep the synthesis simple. To make a comparable series, the components chosen for the binding pocket are al softer base-donating nitrogens, from pyrroles, pyridines, bipyridines, 2-amionobenzaldehyde. Softer donors were chosen as they have been recently shown by k-edge XAS to beter interact with the 5f-orbitals of the actinides, creating more covalent bonds. 39 Also, softer donors are being considered as both a replacement and a co-extractant in Europe for the PUREX proces. 40 The European system dubbed SANEX uses bis-triazines atached to a softer donor backbone, such as pyridines 41 , bi-pyridines 42 , and phenanthrolines. 43 Figure 4.4: Schif base changes to the ligand N N R 1 R 1 ! 84! Table 4.2: Schif base derivatives with their maximum absorption peaks. The 2-aminobenzaldehyde based salqu ligand (Figure 4.4) was the best of the Schif bases measured and it is the candidate to replace the 3,5-di-tert- butylsalicylaldehyde currently in use. While 2-aminobenzaldehyde is expensive, 2- nitrobenzaldehyde is not and can be easily reduced to the amine by catalytic hydrogenation by paladium on carbon, or ferrous sulfate and amonia before being distiled off as pure product. 44 As can been sen in the figure below, the copper, uranyl, and ligand peaks are separated at ~280 ? 380 nm. The copper complex has a higher energy peak that could be used to help diferentiate it from the uranyl complex at 530 nm. Ligand?*10 4 M -1 cm -1 Copper?*10 4 M -1 cm -1 Uranyl?*10 4 M -1 cm -1 pyrrole204, 262, 3462.8, 2.4, 5.8234, 3623.6, 5.33645.5 pyridine211, 287, 3583.2, 3.9, 3.3215, 245, 3883.0, 3.5, 5.7214, 270, 3872.7, 3.1, 5.4 bi249, 3597.0, 4.6246, 3835.3, 5.5239, 3955.5, 5.6 2-amino benzaldehyde222, 3744.3, 4.0226, 282, 5073.8, 5.3, 5.1225, 265, 331, 4644.8, 3.7, 5.3, 1.6 R1 ?max Abs (nm) ! 85! Figure 4.4: 2-aminobenzaldehyde with quinoxolinol backbone Figure 4.5: Calculated 2-aminobenzaldehyde Schif base spectrum with the copper and uranyl complex. N OH N NH 2 H 0" 10" 20" 30" 40" 50" 60" 180" 280" 380" 480" 580" 680" 780" 880" 980" ? *1 0 3 &M (1& cm (1& & Wavelength&(nm(& 2(aminobenzaldehyde&DMF& Ligand" Copper" Uranyl" N OH NH2H ! 86! 4.33 Triazine To continue the investigation with ligands based on those used in the SANEX proces, 2,3,6-triazine groups were incorporated with the quinoxolinol backbone for comparison. Syntheticaly, this adds four steps to the synthesis. The first step is a Sandmeyer reaction to replace the amines with nitriles. Hydrazine hydrate is then used to add two nitrogens, followed by an ?-diketone addition to complete the rings. Because of the pyridine rings, only one nitrogen on each triazine binds to the metal, but since pyridines are not incorporated into the quinoxolinol, the calculations were done with the 1,2 nitrogens of the triazine both binding the metals. The procedure for making this syntheticaly is very chalenging and has not been completed to date for the quinoxolinol backbone. The coordination shown in figure 4.6 is not currently in the literature. Any coordination to the 1,2,4-triazine is coordinated to the 2-N and a pyridine or some other coordinating molecule atached to the triazine by a linker is also bound to the metal. 45,46 Since there is not another group atached, for the purpose of these calculations, the 1,2-nitrogens to help fil the coordination sphere. Future experiments wil determine if this coordination is feasible and calculations can be modified to reflect the changes. ! 87! Scheme 4.1: Synthesis of triazine from quinoxaline N OH NH 2 H 2 N N OH N 2 + Cl -- Cl + 2 HCl CuCN NaNO 2 N OH CNNC N OH H 2 N + NH 2 N -- R 1 O 1 H 2 -N N OH NN R 1 1R1 1 ! 88! Figure 4.7: Showing the binding with two of the three triazine nitrogens for uranyl in the calculations. Copper is bound the same way for the calculations. Table 4.3: R 1 groups to complete the triazine, maximum absorbance and extinction coeficient. The best ?-diketone was diacetyl to complete the triazine ring. Copper and uranyl both give the same shift away from the ligand, but the diference is around 225 nm when uranyl has a higher energy peak as compared to the copper complex. At 450 Ligand?*10 4 M -1 cm -1 Copper?*10 4 M -1 cm -1 Uranyl?*10 4 M -1 cm -1 H240, 3041.0, 5.4314, 4863.8, 0.33095.6 t-butyl201, 2774.0, 6.8225, 303, 5213.3, 5.4, 0.3239, 3082.8, 6.2 i-but257, 3266.7, 3.5260, 4909.9, 0.6265, 5729.4, 0.7 methyl2756.8242, 302, 5002.3, 6.7, 0.1222, 303, 4422.8, 6.8, 0.2 phenyl222, 2984.3, 7.63427.63368.4 hexyl2756.9231, 301, 4992.7, 5.2, 0.5229, 3032.8, 6.9 1,2-cylcohexane2746.8234, 299, 5092.7, 5.6, 0.4242, 3022.3, 6.7 R1 ?ax Abs (nm) ! 89! nm, both complexes have a shoulder but the uranyl has a higher extinction coeficient, so that could possibly be another way to diferentiate the two metals. The diketone consisting of iso-butyl groups and a di-aldehyde would be worth pursuing for synthesis and further characterization by experiment. Figure 4.8: Calculated di-acetyl spectrum for triazine quinoxolinol with copper and uranyl complex. 4.34 Pyridine Amides Macrocycles such as crown ethers, aza-crowns, and expanded porphyrins have long been proposed for selective coordination to actinide metal ions. 2,3 In keeping with the commonly held premise that the softer donors are more selective for actinides, a 2,6-pyridine-dicarboxylic acid or the di-acid chloride could be used to N OH ! 90! potentialy create a 6-N macrocycle, with the size big enough to fit the actinides, but would force a twist in the ligand to bind to transition metals. Although the goal is the macrocycle, three other ligands could be made as wel; a mono-substituted with one pyridine and one quinoxolinol, a di-substituted around the quinoxolinol and a di- substituted around the pyridine (Figure 4.). These macrocycles are also known for being anion receptors for ions such as chlorine, fluorine, and nitrate. 47 Figure 4.9: Pyridine-amide ligand designes After optimization of the coordinated geometry of the complexes, actinides fit into the macrocycle much beter than the transition metals. The transition metals only NNH O N HN O NHOOH 2 H 2 N NNH O N HO O N O OH OH ! 91! bind to one side of the macrocycle and to fil a 4 th coordination site if needed, the ligand twists under itself. This may not happen experimentaly because of the strain (not calculated here) on the molecule, thus the last coordination site would likely be filed with a solvent molecule. The actinides fit with only a slight twist of the macrocycle to acommodate the later actinides such as plutonium and americium Figure 4.10: Optimized geometry of uranyl complex of pyridine amide macrocycle ! 92! Figure 4.11: Optimized geometry of copper complex of pyridine amide macrocycle Figure 4.12: Calculated spectrum of amide pyridine macrocycle with copper and uranyl complex While the uranyl and copper complex peaks overlap, the uranyl has a higher extinction coeficient which could be one way to distinguish betwen the two metals. 0! 20! 40! 60! 80! 100! 120! 180! 230! 280! 330! 380! 430! 480! 530! 580! ? *10 3 M -1 cm -1 " Wavelength (nm)" Amide Pyrdine Macrocycle" Ligand! Copper! Uranyl! ! 93! There is a smal diference betwen the peaks at 379 for copper and 387 for uranyl. The di-substituted ligand on the pyridine has the potential to be a good ligand depending on experimental outcomes. In this case, the uranyl peak also has a higher extinction coeficient than the copper complex, and there is an absorbance maximum unique to the copper complex. The di-substituted on the quinoxolinol is a diferent story. The uranyl complex has les extinction coeficient and the peaks overlap with the copper complex. Future work wil continue with the mono-substituted ligand. 4.35 Isopththaldehyde A second macrocycle was proposed using isophthaldehyde. The geometry of the complexes was questionable for actinides, with the metal being either above or below the macrocycle. The transition metals fit in the middle of the macrocycle perfectly. There is not bending other than the backbone when the transition metal is bound. Figure 4.13: Optimized geometry of isophthaldehyde macrocycle with uranyl. ! 94! 4.4 Conclusions After preliminary examination of H 2 L1 to se if the calculations would be satisfactory, a number of ligands were investigated for their use as potential UV-Vis sensors for uranyl and compared to a known interference metal, copper for comparison. The first calculations were to modify the existing salicylaldehyde, with diferent substituents and se if the electronics could enhance selectivity or sensitivity. These calculations did not improve upon either the selectivity or sensitivity as compared to the calculated spectra for H 2 L1. Next diferent salicylaldehydes with softer N-donors were tested with the quinoxolinol backbone. These were chosen to enhance the ligand to metal excitation and would hopefully give beter selectivity, with sensitivity remaining about the same as compared to H 2 L1. The calculations predict that 2-aminobenzaldehyde with the quinoxolinol backbone would give the best separation of absorbance peaks betwen the uranyl complex, copper complex, and the ligand. Finaly, following the SANEX proces for nuclear fuel separations in Europe, triazines was investigated with diferent substituents in the 4,5 positions. The best was methyl groups at the 4,5-position to improve selectivity, sensitivity appeared to decrease. Other ligands that would be of interest would include the pyridine amide macrocycle (Figure 4.14) the pyridine amide disubstituted on the pyridine (Figure 4.15), and the diacetyl triazine (Figure 4.6). The diacetyl triazine provides a greater extinction coeficient at lower energies, but the limits of detection would not be lower to do the lower overal extinction coeficient. The diacetyl also has a uranyl complex peak at very high energy that ! 95! could diferentiate it from the ligand or copper complex. Whereas a normal salicylaldehyde would be comparable to the experimental 3,5-di-tert-butyl salicylaldehyde, it does not appear to be beter than the ones currently being experimentaly used. Further experimental work should focus on softer donor ligands such as the triazine and the 2-aminobenzaldehyde. ! 96! 4.5 References ! (1)! 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Chapter 5: Uranyl vs. Europium extractions from nitric acid 5.1 Introduction Nuclear fuel reprocesing is going to play an important part in the future, as more and more reactors are built to provide the necesary electricity demanded by society, and renewable energy stil as yet cannot keep up with the demand for energy. At present, over half of the world?s spent nuclear fuel is produced in a ?once-through cycle.? 1,2 There are two approaches considered when managing the radioactive byproducts of nuclear fision: the open fuel cycle in which spent fuel elements are managed as waste, and the closed-loop fuel cycle in which spent fuel undergoes separation to recover byproducts for reuse and recycle (leaving the les useful materials for disposal as waste). 3 In the open loop (once-through) fuel cycle, the fuel elements remain intact and are the waste form, stored in concrete and stel casks til geological disposal. 3 Currently practiced in France, the closed loop fuel cycle recycles U and Pu isotopes only using tri-n-butyl phosphate, while al other materials are converted to glas for disposal. 3 The current problem with this recycling is the separation and isolation of weapons grade plutonium ( 239 Pu) in any separations proces, leading to proliferation and security isues, 4 as wel as the minor actinides left in the procesed waste. 5 ! 100! The procesed nuclear fuel could be stored in a deep geological depository but the fuel wil remain radioactive for milions of years, and storage is not favored by the public. 6 There is an alternative method to the leftover spent fuel after the recycling proces that could render the fuel safer and more suitable for geological storage. Of the transuranium elements, the minor actinides americium and curium have especialy high radiotoxicities, making them desirable to remove them from spent nuclear fuel and deal with them separately. 7,8 The removal of U and Pu reduced the radiotoxicity significantly as is, but the additional removal of the minor actinides would reduce the storage time to 300 years, from 9000 years. 6 It is stil important to separate Am and Cm from the lanthanides because of the neutron capture ability of the lanthanides is 40 times greater than the actinides. 6 One possible future scenario is the conversion or transmutation of these long-lived minor actinides, into short-lived isotopes by irradiation with neutrons in a fast reactor. 9,10 Many extraction proceses have been studied as indicated in chapter 1, such as PUREX, 11 DIAMEX, 12 TRUEX, 13 TALSPEAK, 3 and SANEX 14 but there remains room for improvement, and it is the hope that the ligands used in sensing could have a dual use in extractions. The research below was to test the sensing ligand ?Salqu? as an extractant for uranyl versus europium, as a model for actinides versus lanthanides. ! 101! 5.2 Experimental The Salqu (H 2 L1) ligand was synthesized as previously described and disolved in 1-octanol to the desired concentration (Se figure 5.1.) The extractions were performed by shaking equal volumes of aqueous (0.1 ? 1.0 x10 -5 M HNO 3 ) and organic phase for 1 minute and alowing the phases 2 hours to setle. The aqueous phase was removed and taken to ICP-OES to determine the metal concentration. The ligand was also compared to a normal Salen ligand, and the quinoxalinol backbone disolved in 1-octanol at the same molar concentrations. Distribution and separation factors were calculated to determine the extraction ability and selectivity of the ligands for the two metals. Distribution (D) is defined as the concentration of the organic phase divided by the concentration in the aqueous phase. Separation factor (SF) is defined as D U / D Eu . ! 102! H 2 L1 Salen 2-quinoxalinol backbone Figure 5.1: Ligands used in extractions N OH N OHHO OH N HO N OH HNNH 2 ! 103! 5.3 Results With the selectivity for uranyl over lanthanides acording to the UV-Vis spectra, this H 2 L1 ligand should be a good step towards ideas of future ligands for the reprocesing of nuclear fuel. The first test was to determine if the ligand would not decompose in 3 M nitric acid, the concentration of the aqueous phase at which current separations of nuclear fuel take place. There was an imediate color change of the ligand in octanol from yelow to red as the two phases were shaken and mixed. This would typicaly indicate the double bond of the Schif base breaking down to a single bond and would hinder binding. Thus, the ligand was decomposing and would not be useable under extreme acidic conditions. The highest concentration of nitric acid able to be used was 0.1 M HNO 3 and extractions were tested al the way to 1 x 10 -5 M HNO 3 , typical of a mixed N-, O-donor extractant. 6 At a 1 to 1 molar ratio of metal to ligand, al three ligands are increase the extraction of both metals as the nitric acid concentration decreases with the highest increases betwen 0.01 and 0.0001 M HNO 3 . Unexpectedly, the softer donors of the amines on the quinoxalinol increased the europium extraction as well, as nitrogens do not typicaly form strong bonds with lanthanides. The separation factors were within the same range betwen 5 and 7 and the majority is below 10, which is a general threshold for good selectivity. The only one above 10 is the quinoxalinol at a very low nitric acid concentration, which is not suitable for nuclear fuel waste extractions. To increase the extraction eficiency and amount of uranyl extracted, higher ! 104! concentrations of ligands were used: 0.5 mM, 0.75 mM, and 1.0 mM. This should increase the distribution of uranyl with the same distribution for europium, thereby increasing the separation factor. Figure 5.2 a: H 2 L1 distribution of uranyl and europium at 1 to 1 molar concentrations 0! 0.5! 1! 1.5! 2! 2.5! 3! 3.5! 4! 4.5! 0.00001!0.0001!0.001!0.01!0.1!1! D i s tr i b u ti on ! [HNO 3 ]! H 2 L1! Uranyl! Europium! ! 105! Figure 5.2 b: Salen distribution of uranyl and europium at 1 to 1 molar concentrations Figure 5.2 c: Quinoxalinol distribution of uranyl and europium at 1 to 1 molar concentrations 0! 0.5! 1! 1.5! 2! 2.5! 3! 3.5! 0.00001!0.0001!0.001!0.01!0.1!1! D i s tr i b u ti on ! [HNO 3 ]! Salen! Uranyl! Europium! 0! 0.5! 1! 1.5! 2! 2.5! 3! 3.5! 0.00001!0.0001!0.001!0.01!0.1!1! D i s tr i b u ti on ! [HNO 3 ]! Quinoxolinol! Uranyl! Europium! ! 106! Figure 5.3: Separation factor for the three ligands at 1 to 1 molar ratio 5.31 0.5 mM ligand concentration Much like what was sen with a 1 to 1 molar ratio of ligand to metal, the eficiency of the extraction increases for H 2 L1 as the concentration of nitric acid decreases. The europium extraction greatly increases at 1.0 x 10 -4 M HNO 3 , even being extracted more than uranyl. The uranyl extraction was les with more ligand than compared to the 1 to 1 extractions, especialy at lower concentrations of nitric acid. Salen had the opposite efect of what has been sen previously. The uranyl extraction becomes les whereas the europium extraction stays the same or slightly increases. The uranyl decreasing in distribution ratio wil cause the separation factor to decrease as wel making the selectivity poor. Why is it that europium was extracted more for H 2 L1 than salen at the same nitric acid concentration. Could the backbone 1! 3! 5! 7! 9! 11! 0.00001!0.0001!0.001!0.01!0.1!1! D U /D Eu ! [HNO 3 ]! Selectivity! H2L1! Salen! Quinoxolinol! ! 107! play a role in binding? One would not expect that the quinoxalinol alone would be very good for extraction in general, but it should stil extract more uranyl than europium, because the amines would act more favorably as donors to uranyl than europium. By looking at 0.75 mM of quinoxalinol, the same increase in europium extraction occurred so maybe the quinoxalinol realy did do the extractions that wel at that concentration of nitric acid. Perhaps, at the lower concentrations of nitric acid, the metal salt is being stripped of the nitrates and able to bind more tightly to the ligands. Figure 5.4 a: H 2 L1 (0.5 mM) distribution ratio for uranyl and europium 0! 0.5! 1! 1.5! 2! 2.5! 3! 3.5! 4! 4.5! 0.00001!0.0001!0.001!0.01!0.1!1! D i s tr i b u ti on ! [HNO 3 ]! H 2 L1! Uranyl! Europium! ! 108! Figure 5.4 b: Salen (0.5 mM) distribution ratio for uranyl and europium Figure 5.4 c: Quinoxalinol backbone (0.5 mM) distribution ratio for uranyl and europium. 0! 0.2! 0.4! 0.6! 0.8! 1! 1.2! 1.4! 1.6! 1.8! 0.00001!0.0001!0.001!0.01!0.1!1! D i s tr i b u ti on ! [HNO 3 ]! Salen! Uranyl! Europium! 0! 0.5! 1! 1.5! 2! 2.5! 3! 3.5! 4! 4.5! 0.00001!0.0001!0.001!0.01!0.1!1! D i s tr i b u ti on ! [HNO 3 ]! Quinoxolinol! Uranyl! Europium! ! 109! As would be expected with the increasing extraction of europium by al the ligands as the nitric acid concentration became les, but was stil in the range for higher nitric acid concentrations as with the 1:1 metal to ligand ratio. No ligand had les selectivity than H 2 L1 as it greatly increased the extraction of europium at lower nitric acid concentrations. As of this point, increasing the ligand concentration does not increase the extraction of uranyl, nor does it increase the selectivity. Figure 5.5: Separation factors for the three ligands at 0.5 mM concentration 5.32 0.75 mM ligand concentration Increasing the H 2 L1 ligand concentration to 0.75 mM also did not improve the extraction of uranyl, but greatly increased the extraction of europium at lower concentrations of nitric acid, to a point that the selectivity of uranyl is les than for 0! 1! 2! 3! 4! 5! 6! 7! 8! 0.00001!0.0001!0.001!0.01!0.1!1! D U /D Eu ! [HNO 3 ]! Selectivity! H2L1! Salen! Quinoxolinol! ! 110! europium (Figure 5.6a). Unlike the other extractions sen so far, but what sems typical for salen, is that the extraction ability stayed relatively the same at about a distribution of 3. The europium was extracted more at lower nitric acid concentrations to around 0.6. The higher nitric acid concentrations only had a distribution of 0.5 (Figure 5.6b). The quinoxalinol follows the same trend as at 0.5 mM concentration but there is more europium than uranyl extracted at 1x10 -4 but decreases at 1x10 -5 M HNO 3 (Figure 5.6c). The uranyl was extracted more as wel as can be sen at the higher distribution at those concentrations, but quinoxalinol is not a good ligand for separating the groups at these nitric acid concentrations. It is stil odd that the uranyl does not have a higher distribution ratio than europium due to the hard soft acid base theory. Figure 5.6 a: H 2 L1 (0.75 mM) distribution ratio for uranyl and europium 0! 0.5! 1! 1.5! 2! 2.5! 3! 3.5! 4! 0.00001!0.0001!0.001!0.01!0.1!1! D i s tr i b u ti on ! [HNO 3 ]! H 2 L1! Uranyl! Europium! ! 111! Figure 5.6 b: Salen (0.75 mM) distribution for uranyl and europium Figure 5.6 c: Quinoxalinol backbone (0.75 mM) distribution of uranyl and europium. 0! 0.2! 0.4! 0.6! 0.8! 1! 1.2! 1.4! 1.6! 1.8! 2! 0.00001!0.0001!0.001!0.01!0.1!1! D i s tr i b u ti on ! [HNO 3 ]! Salen! Uranyl! Europium! 0! 0.5! 1! 1.5! 2! 2.5! 3! 3.5! 0.00001!0.0001!0.001!0.01!0.1!1! D i s tr i b u ti on ! [HNO 3 ]! Quinoxolionl! Uranyl! Europium! ! 112! As the graph below suggests (Figure 5.7), there is a downward trend in selectivity, as the concentration of nitric acid decreases. This is because more europium is being extracted at those concentrations limiting the selectivity. The quinoxalinol had the worst at the 1x10 -5 M HNO 3 while the separation is similar for 0.1 to 1x10 -3 M HNO 3 . Figure 5.7: Separation factors for the three ligands at 0.75 mM concentration 5.33 1.0 mM ligand concentration Following the current trends with an exces of ligand, the H 2 L1 ligand is increasing extraction of europium at lower concentrations of nitric acid, with a general increase in the extraction of uranyl (Figure 5.8a). It was expected that at such a high concentration of ligand compared to the metal, that the uranyl would be greatly 1! 2! 3! 4! 5! 6! 7! 8! 0.00001!0.0001!0.001!0.01!0.1!1! D U /D Eu ! [HNO 3 ]! Selectivity! H2L1! Salen! Quinoxolinol! ! 113! more extracted but this is shown to not be the case. Salen extraction of uranyl remained roughly the same as the nitric acid concentration changed (Figure 5.8b). The europium extraction was also very close to being the same except at 0.0001 M HNO 3 . For the first time with quinoxaline, the europium extraction does not have a distribution ratio greater than 1 (Figure 5.8c). The uranyl extraction is relatively steady til 0.00001 M HNO 3 concentration where it increases up to around 3.5, much higher than the ~1.5 from higher nitric acid concentrations. Figure 5.8 a: H 2 L1 (1.0 mM) distribution of uranyl and europium 0! 0.5! 1! 1.5! 2! 2.5! 3! 0.00001!0.0001!0.001!0.01!0.1!1! D i s tr i b u ti on ! [HNO 3 ]! H 2 L1! Uranyl! Europium! ! 114! Figure 5.8 b: Salen (1.0 mM) distribution ratio for uranyl and europium Figure 5.8 c: Quinoxalinol (1.0 mM) distribution for uranyl and europium 0! 0.2! 0.4! 0.6! 0.8! 1! 1.2! 1.4! 1.6! 1.8! 2! 0.00001!0.0001!0.001!0.01!0.1!1! D i s tr i b u ti on ! [HNO 3 ]! Salen! Uranyl! Europium! 0! 0.5! 1! 1.5! 2! 2.5! 3! 3.5! 4! 0.00001!0.0001!0.001!0.01!0.1!1! D i s tr i b u ti on ! [HNO 3 ]! Quinoxolinol! Uranyl! Europium! ! 115! The H 2 L1 ligand has a sharp decrease in selectivity as more europium was extracted at lower concentrations of nitric acid (Figure 5.9). The Salen ligand remained relatively unchanged except for at 0.0001 M HNO 3 due to the increase in europium extraction and unchanged uranyl extraction at that concentration. The quinoxalinol ligand was unchanged until the lowest nitric acid concentration when it reaches above 10 for the separation factor. This is due to the greater extraction of uranyl with a low extraction of europium. Further study into improved systems and new ligands with the calculations wil be discussed in the next chapter. Figure 5.9: Separation factors for H 2 L1, Salen, and Quinoxalinol at concentration of 1.0 mM Extractions with this mixed N- and O- donor ligands are typical of other N- and O- donor ligands where the extraction increases as the nitric acid concentration 1! 3! 5! 7! 9! 11! 0.00001!0.0001!0.001!0.01!0.1!1! D U /D Eu ! [HNO 3 ]! Selectivity! H2L1! Salen! Quinoxolinol! ! 116! decreases. The increasing europium extraction was something unexpected that happened with al the ligands. These ligands are not suitable for nuclear fuel extractions. 5.4 Conclusions The ability of H 2 L1 and salen to extract more uranyl at lower concentrations of nitric acid is consistent with other mixed N, O ? donor ligands from previous extractants. This hinders these ligands as nuclear fuel waste extractants because they cannot be used at 3M nitric acid concentrations. Across the board the extractions were similar for every experiment with the uranyl distribution above 1 and the europium distribution below 1. The only exceptions was for europium having a distribution greater than 1 was for increased concentrations of H 2 L1, and lower nitric acid concentrations for the quinoxalinol backbone. The separation factors, although above 1, were not above 10, which is considered the threshold of good selectivity for separations. The next step if so desired, would be to use H 2 L1 as a stripping agent from a loaded organic phase. Much work stil needs to be done to increase the selectivity of these ligands for use as nuclear fuel extractants. ! 117! 5.5 References ! (1)! Mathur,!J.!N.;!Murali,!M.!S.;!Nash,!K.!L.!Solvent(Extr.(Ion(Exch.!2001,! 19,!357.! ! (2)! Schaffer,!M.!B.!Energy(Policy!2011,!39,!1382.! ! (3)! Nilsson,!M.;!Nash,!K.!L.!Solvent(Extr.(Ion(Exch.!2007,!25,!665.! ! (4)! Ewing,!R.!C.!Comptes(Rendus(Geoscience!2011,!343,!219.! ! (5)! Lewis,!F.!W.;!Harwood,!L.!M.;!Hudson,!M.!J.;!Drew,!M.!G.!B.;!Wilden,! A.;!Sypula,!M.;!Modolo,!G.;!Vu,!T.UH.;!Simonin,!J.UP.;!Vidick,!G.;!Bouslimani,!N.;! Desreux,!J.!F.!Procedia(Chemistry!2012,!7,!231.! ! (6)! Hudson,!M.!J.;!Harwood,!L.!M.;!Laventine,!D.!M.;!Lewis,!F.!W.!Inorg.( Chem.!2013,!52,!3414.! ! (7)! Choppin,!G.!R.;!Liljenzin,!J.UO.;!Rydberg,!J.!Radiochemistry(and( Nuclear(Chemistry;!3rd!ed.;!ButerworthUHeineman:!Woburn,!Masachusets,! 2002.! ! (8)! Birkett,!J.!E.;!Carrott,!M.!J.;!Fox,!O.!D.;!Jones,!C.!J.;!Maher,!C.!J.;!Roube,! C.!V.;!Taylor,!R.!J.;!Wodhead,!D.!A.!Chimia!2005,!59,!898.! ! (9)! Boubals,!N.;!Drew,!M.!G.!B.;!Hill,!C.;!Hudson,!M.!J.;!Iveson,!P.!B.;! Madic,!C.;!Rusel,!M.!L.;!Youngs,!T.!G.!A.!J.(Chem.(Soc.,(Dalton(Trans.!2002,!55.! ! (10)! Sakamoto,!Y.;!Garnier,!J.UC.;!Rouault,!J.;!Grandy,!C.;!Faning,!T.;!Hill,! R.;!Chikazawa,!Y.;!Kotake,!S.!Nucl.(Eng.(Des.!2013,!254,!194.! ! (11)! Mckibben,!J.!M.!Radiochimica(Acta!1984,!36,!3.! ! (12)! SerranoUPurroy,!D.;!Baron,!P.;!Christiansen,!B.;!Malmbeck,!R.;!Sorel,! C.;!Glatz,!J.!P.!Radiochimica(Acta!2005,!93,!351.! ! (13)! Mincher,!B.!J.;!Schmit,!N.!C.;!Case,!M.!E.!Solvent(Extr.(Ion(Exch.! 2011,!29,!247.! ! (14)! Whittaker,!D.!M.;!Grifiths,!T.!L.;!Helliwell,!M.;!Swinburne,!A.!N.;! Natrajan,!L.!S.;!Lewis,!F.!W.;!Harwod,!L.!M.;!Pary,!S.!A.;!Sharad,!C.!A.!Inorg.( Chem.!2013,!52,!3429.! ! 118! Chapter 6 Conclusions and Future Work Much research has focused on creating sensors for the selective recognition of actinide metals that is inherently dificult due to the strong coordination of transition metal ions to the same sorts of binding pockets. Perhaps, it is beter investigate ligands that would provide a unique signal for the actinides as they would for other metals, a green light for actinides, and a red light for transition metals, and yelow light for lanthanides. The other way to diferentiate them is through UV-Vis spectroscopy, where the ligand when bound to the metal, would give a maximum absorbance that is diferent from the ligand and any competing metals. It would be fine if al the actinide absorbencies overlapped so long as they were diferent than the ligand and competing metals. This investigation began with the ligand H 2 L1, a quinoxolinol salen ligand. With many pi-bonds, this ligand should create a high signal to noise ratio to help with sensitivity. H 2 L1 proved to be a good sensor for uranyl over copper and other metals that were tested. This ligand disolved in dimethylformamide (DMF), had a maximum absorbance of ~389 nm depending on the concentration of water in the sample with an extinction coeficient of 2.6x10 4 M -1 ? cm -1 at a ligand concentration of 20 ?M. Maximum water concentration could only be 20% before precipitation. Upon the addition of 1 equivalent of copper acetate solution, the ligand color would ! 119! change from a fluorescent yelow to a orange-yelow and the UV-Vis spectrum would indicate a maximum absorbance at 450 nm with an extinction coeficient of ~3.2 x10 4 M -1 ? cm -1 across al concentrations of water. The detection limit for copper with this ligand was ~1 ppm. With the addition of 4 equivalents of uranyl, after two hours of constant stirring, the ligand would change in color from a fluorescent yelow to a more dull yelow. Equivalents 1-3 show no color change to the naked eye but the UV- Vis spectrum would show an increasing shoulder at 450 nm and a smal higher energy shift from the ligand. The higher energy shift reached a maximum at 4 equivalents of uranyl, with a maximum absorbance of ~368 nm and an extinction coeficient of 2.6x10 4 M -1 ? cm -1 , giving a detection limit of ~20 ppm. The addition of 1 equivalent of cobalt solution causes a change in the ligand solution color to an orange with a maximum absorbance at ~433 nm and an extinction coeficient of 2.1x10 4 M -1 ? cm -1 , with a detection limit equal to copper, of ~1 ppm. Other metals such as nickel, cerium and gadolinium, have < 3 nm or no shift from the ligand and only nickel has a color change due to an increasing absorbance ~450 nm. The mono-substituted ligand H 3 L3 was also investigated in DMF with varying metals and percentage of water. This ligand could withstand up to 40% water in solution. The ligand, however, was not a good sensor for uranyl. This could be due to binding not being strong enough, or it doesn?t bind at al. Copper and cobalt were stil investigated for increasing concentrations of water, and al metals that were tested for H 2 L1 were tested at 40% water/DMF for H 3 L3. Copper and cobalt had color changes and changes in the UV-Vis spectrum. Uranyl did not exhibit a color change and there ! 120! was not a change in the UV-Vis spectrum after 24 hours of stirring. Future mono- substituted ligands, should be investigated as potential sensors, but this ligand is not one of them. A mono-substituted bi-pyridine would fil the coordination sphere of uranyl beter than a salicylaldehyde can, and thus should be investigated. H 2 L1 became the starting point to design new ligand to test as sensors for actinides. In order to understand H 2 L1 and facilitate any new ligand designs, computational chemistry of the ligands was explored and in particular time-dependent density functional theory (TD-DFT) was used to predict the UV-Vis spectrum of the free ligand, with uranyl, and with copper. While the calculations do not agree with the experiment 100%, they have proven to be fairly useful tool in this research. The calculations can be performed generaly in les than a wek using the supercomputer and are a quick way to determine if a particular ligand could be useful for detection of actinides versus other metals in the UV-Vis. The calculations have drawbacks such as the use of a mixed solvent system. A true mixed solvent system explicitly adds to the cost of the calculation, greatly decreasing eficiency. Even the interaction of just three solvent molecules increases the computational complexity and cost significantly. From the calculations, it was determined that the ligand by itself was a pi to pi* interaction as would be expected of the system. The uranyl complex absorbance peak at 369 nm was the cause of a ligand to metal f-orbital singlet excitation from the HOMO to the LUMO. The copper complex absorbance at 450 nm was the cause of a metal d-orbital to the ligand excitation from the HOMO to the LUMO. The first ! 121! atempts to try to increase this shift were purely electric in changing the substituents around the salicylaldehyde from t-butyl groups to other electron donating and withdrawing groups, with a normal salicylaldehyde having no other substituents being the best, but not beter than the original ligand. Next, using ligands known for their ligand to metal excitations such as bi-pyridine and other soft nitrogen containing donors were tested. The best of this group was the 2-aminobenzaldehyde providing the best separation of absorbance peaks. The final test was to try to mimic the SANEX extraction proces by using 2,3,6-triazines. The best was the 4,5-dimethyl- 2,3,6-triazine but the ligand synthesis has been complicated and thus has not been prepared. Studies are currently underway to atach the 2-aminobenzaldehyde to the 2- quinoxolinol backbone after synthesizing the 2-aminobenzaldehyde from 2- nitrobenzaldehyde using ferrous sulfate and amonia. ! 122! bis-4,5-dimethyl-2,3,6-triazine 2-aminobenzaldehyde with quinoxolinol backbone Figure 6.1: Best ligands acording to the calculations. While H 2 L1 did not improve upon current extraction strategies, the mixed N,O-donor ligand was typical of other ligands of the same type in that their best N OH NN N OH N NH 2 H ! 123! extraction was at lower nitric acid concentrations (< 0.1 M). The ligand did extract more uranyl than europium that is needed of an extractant for nuclear fuel waste, but the selectivity determined by the separation factor was below 10, considered the threshold for a good extractant. Exces ligand caused problems at the lowest nitric acid concentration (1x10 -5 M) tested, when as much europium was extracted as uranyl, causing the separation factor to decrease to 1. This does not support a case for extractants being good sensors and vice versa, nor do it dispel it, having a dual sensor/extractant does not work with this ligand. 6.1 Future Work The sensors and computational component of them have the best potential for the future. Sensors for actinides are being studied much les than for extractants of nuclear fuel waste. Any new ligands synthesized should be tested for both molecular recognition and extractions, even if the ligand decomposes in stronger nitric acid (> 1 M). The next group should be have the utmost concern with decreasing the detection limit from ~25 ppm to ~20 ppb. This can be achieved by increasing the number of conjugated pi-bonds in the ligand system, which wil increase the signal to noise ratio, increasing the selectivity. A good starting point would be to use 2,3- diaminosphenazine or 2,3-diaminoanthracene with 3,5-di-t-butylsalicylaldehyde or 2- aminobenzaldehyde. Calculations on these ligands should only take a couple of extra ! 124! days due to the larger system. The synthesis would be similar to H 2 L1 by adding 3,5- di-t-butylsalicylaldehyde to the diamino in ethanol and heating to reflux. Figure 6.2: Salazine with 3,5-di-t-butylsalicylaldehyde If that does not reduce the detection limit enough, macrocycles would be the best way to go before the ligand precipitates, and doesn?t disolve in any solvent. The macrocycles need to be big enough to acommodate the actinides which should make any competing transition metals only bind to one side of the macrocycle if at al. Early atempts to make the free macrocycle have failed. A chlorine anion was determined to be bound in the pyridine amide macrocycle (Figure 6.2). Atempts to template around uranyl to form the macrocycle have also been unsuccesful. Calculations show that this could be a promising ligand. Pyridine dicarboxylic acid should form an amide with the amines for the backbones, but the conversion of the carboxylic acids to acid chlorides is a beter starting to point to achieve the desired N N HOOH ! 125! amides. An increase in sensitivity for the macrocycles could be to use phenazine as backbone (Figure6.3). Figure 6.3: Phenazine with pyridine amides to form a 6N-donor macrocycle. N O HNNH O N N OO N ! 126! Apendix 1 for Chapter 3 Figure A3.1: Batch copper titration for H 2 L1 (20 ?M) in 5% water/DMF (v/v). Concentrations shown are final concentrations of metal. 0! 5! 10! 15! 20! 25! 30! 35! 250! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 5% Water/DMF Copper" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! ! 127! Figure A3.2: Batch uranyl titration for H 2 L1 (20 ?M) in 5% water/DMF (v/v). Concentrations shown are final concentrations of metal. Figure A3.3: Batch cobalt titration for H 2 L1 (20 ?M) in 5% water/DMF (v/v). Concentrations shown are final concentrations of metal. 0! 5! 10! 15! 20! 25! 30! 35! 40! 275! 325! 375! 425! 475! 525! 575! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 5% Water/DMF Uranyl " Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! 0! 5! 10! 15! 20! 25! 30! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 5%Water/DMF Cobalt" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! ! 128! Figure A3.4: Batch copper titration for H 2 L1 (20 ?M) in 10% water/DMF (v/v). Concentrations shown are final concentrations of metal. Figure A3.5: Batch uranyl titration for H 2 L1 (20 ?M) in 10% water/DMF (v/v). Concentrations shown are final concentrations of metal. 0! 5! 10! 15! 20! 25! 30! 35! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelegnth (nm)" H 2 L1 10% Water/DMF Copper" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! 0! 5! 10! 15! 20! 25! 30! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 10% Water/DMF Uranyl" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! ! 129! Figure A3.6: Batch cobalt titration for H 2 L1 (20 ?M) in 10% water/DMF (v/v). Concentrations shown are final concentrations of metal. Figure A3.7: Batch copper titration for H 2 L1 (20 ?M) in 15% water/DMF (v/v). Concentrations shown are final concentrations of metal. 0! 5! 10! 15! 20! 25! 30! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 10% Water/DMF Cobalt" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! 0! 0.1! 0.2! 0.3! 0.4! 0.5! 0.6! 0.7! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 15% Water/DMF Copper" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! ! 130! Figure A3.8: Batch uranyl titration for H 2 L1 (20 ?M) in 15% water/DMF (v/v). Concentrations shown are final concentrations of metal. Figure A3.9: Batch cobalt titration for H 2 L1 (20 ?M) in 15% water/DMF (v/v). Concentrations shown are final concentrations of metal. 0! 5! 10! 15! 20! 25! 30! 300! 350! 400! 450! 500! 550! 600! ? * 10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 15% Water/DMF Uranyl" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! 0! 5! 10! 15! 20! 25! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 15% Water/DMF Cobalt" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! ! 131! Figure A3.10: Batch copper titration for H 2 L1 (20 ?M) in 20% water/DMF (v/v). Concentrations shown are final concentrations of metal. Figure A3.11: Batch uranyl titration for H 2 L1 (20 ?M) in 20% water/DMF (v/v). Concentrations shown are final concentrations of metal. 0! 0.1! 0.2! 0.3! 0.4! 0.5! 0.6! 0.7! 0.8! 250! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 20% Water/DMF Copper" Ligand! 10 uM! 20 uM! 0! 5! 10! 15! 20! 25! 30! 35! 40! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 20% Water/DMF Uranyl" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! ! 132! Figure A3.12: Batch cobalt titration for H 2 L1 (20 ?M) in 20% water/DMF (v/v). Concentrations shown are final concentrations of metal. Figure A3.13: Batch cerium titration for H 2 L1 (20 ?M) in 20% water/DMF (v/v). Concentrations shown are final concentrations of metal. 0! 5! 10! 15! 20! 25! 30! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 20% Water/DMF Cobalt" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! 0! 5! 10! 15! 20! 25! 30! 35! 250! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 20% Water/DMF Cerium" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! ! 133! Figure A3.14: Batch nickel titration for H 2 L1 (20 ?M) in 20% water/DMF (v/v). Concentrations shown are final concentrations of metal. Figure A3.15: Batch gadolinium titration for H 2 L1 (20 ?M) in 20% water/DMF (v/v). Concentrations shown are final concentrations of metal. 0! 5! 10! 15! 20! 25! 30! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 20% Water/DMF Nickel" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! 0! 5! 10! 15! 20! 25! 30! 35! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 20% Water/DMF Gadolinium" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! ! 134! Figure A3.16: Batch copper titration for H 2 L1 (20 ?M) in 20% water/acetone (v/v). Concentrations shown are final concentrations of metal. Figure A3.17: Batch uranyl titration for H 2 L1 (20 ?M) in 20% water/acetone (v/v). Concentrations shown are final concentrations of metal. 0! 5! 10! 15! 20! 25! 30! 325! 375! 425! 475! 525! 575! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 20% Water/Acetone Copper" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 0! 5! 10! 15! 20! 25! 30! 325! 375! 425! 475! 525! 575! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 20% Water/Acetone Uranyl" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! ! 135! Figure A3.18: Batch cobalt titration for H 2 L1 (20 ?M) in 20% water/acetone (v/v). Concentrations shown are final concentrations of metal. Figure A3.19: Batch copper titration for H 2 L2 (20 ?M) in 20% water/DMF (v/v). Concentrations shown are final concentrations of metal. 0! 5! 10! 15! 20! 25! 30! 325! 375! 425! 475! 525! 575! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 20% Water/Acetone Cobalt" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 0! 5! 10! 15! 20! 25! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L2 20% Water/DMF Copper" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! ! 136! Figure A3.20: Batch uranyl titration for H 2 L2 (20 ?M) in 20% water/DMF (v/v). Concentrations shown are final concentrations of metal. Figure A3.21: Batch cobalt titration for H 2 L2 (20 ?M) in 20% water/DMF (v/v). Concentrations shown are final concentrations of metal. 0! 5! 10! 15! 20! 25! 30! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L2 20% Water/DMF Uranyl" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 0! 5! 10! 15! 20! 25! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelngth (nm)" H 2 L2 20% Water/DMF Cobalt" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! ! 137! Figure A3.22: Batch copper titration for H 3 L3 (20 ?M) in < 1% DMF (v/v). Concentrations shown are final concentrations of metal. Figure A3.23: Batch uranyl titration for H 3 L3 (20 ?M) in < 1% DMF (v/v). Concentrations shown are final concentrations of metal. 0! 5! 10! 15! 20! 25! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 3 L3 DMF Copper" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! 0! 5! 10! 15! 20! 25! 30! 35! 40! 250! 300! 350! 400! 450! 500! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 3 L3 DMF Uranyl" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! ! 138! Figure A3.24: Batch copper titration for H 3 L3 (20 ?M) in 10% water/DMF (v/v). Concentrations shown are final concentrations of metal. Figure A3.25: Batch uranyl titration for H 3 L3 (20 ?M) in 10% water/DMF (v/v). Concentrations shown are final concentrations of metal. 0! 5! 10! 15! 20! 25! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavlength (nm)" H 3 L3 10% Water/DMF Copper" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! 0! 5! 10! 15! 20! 25! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 3 L3 10% Water/DMF Uranyl" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! ! 139! Figure A3.26: Batch cobalt titration for H 3 L3 (20 ?M) in 10% water/DMF (v/v). Concentrations shown are final concentrations of metal. Figure A3.27: Batch copper titration for H 3 L3 (20 ?M) in 20% water/DMF (v/v). Concentrations shown are final concentrations of metal. 0! 5! 10! 15! 20! 25! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 3 L3 10% Water/DMF Cobalt" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! 0! 5! 10! 15! 20! 25! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 3 L3 20% Water/DMF Copper" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! ! 140! Figure A3.28: Batch cobalt titration for H 3 L3 (20 ?M) in 20% water/DMF (v/v). Concentrations shown are final concentrations of metal. Figure A3.29: Batch copper titration for H 3 L3 (20 ?M) in 30% water/DMF (v/v). Concentrations shown are final concentrations of metal. 0! 5! 10! 15! 20! 25! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 3 L3 20%Water/DMF Cobalt" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! 0! 5! 10! 15! 20! 25! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 3 L3 30% Water/DMF Copper" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! ! 141! Figure A3.30: Batch cobalt titration for H 3 L3 (20 ?M) in 30% water/DMF (v/v). Concentrations shown are final concentrations of metal. Figure A3.31: Batch copper titration for H 3 L3 (20 ?M) in 40% water/DMF (v/v). Concentrations shown are final concentrations of metal. 0! 5! 10! 15! 20! 25! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 3 L3 30% Water/DMF Cobalt" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! 0! 2! 4! 6! 8! 10! 12! 14! 16! 18! 20! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 3 L3 40% Water/DMF Copper" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! ! 142! Figure A3.32: Batch uranyl titration for H 3 L3 (20 ?M) in 40% water/DMF (v/v). Concentrations shown are final concentrations of metal. Figure A3.33: Batch cobalt titration for H 3 L3 (20 ?M) in 40% water/DMF (v/v). Concentrations shown are final concentrations of metal. 0! 5! 10! 15! 20! 25! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 3 L3 40% Water/DMF Uranyl" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! 0! 5! 10! 15! 20! 25! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 3 L3 40% Water/DMF Cobalt" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! ! 143! ? Figure A3.34: Batch cerium titration for H 3 L3 (20 ?M) in 40% water/DMF (v/v). Concentrations shown are final concentrations of metal. Figure A3.35: Batch nickel titration for H 3 L3 (20 ?M) in 40% water/DMF (v/v). Concentrations shown are final concentrations of metal. 0! 5! 10! 15! 20! 25! 30! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 3 L3 40% Water/DMF Cerium" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! 0! 5! 10! 15! 20! 25! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 3 L3 40% Water/DMF Nickel" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! ! 144! Figure A3.36: Batch gadolinium titration for H 3 L3 (20 ?M) in 40% water/DMF (v/v). Concentrations shown are final concentrations of metal. Figure A3.37: Batch copper titration for H 2 L1 (20 ?M) in 20% water/DMF (v/v) with 50 ?M HEPES buffer. Concentrations shown are final concentrations of metal. 0! 5! 10! 15! 20! 25! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 3 L3 40% Water/DMF Gadolinium" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! 0! 5! 10! 15! 20! 25! 30! 35! 40! 45! 50! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 20% Water/DMF" 50 uM HEPES buffer Copper" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! ! 145! Figure A3.38: Batch uranyl titration for H 2 L1 (20 ?M) in 20% water/DMF (v/v) with 50 ?M HEPES buffer. Concentrations shown are final concentrations of metal. Figure A3.39: Batch cobalt titration for H 2 L1 (20 ?M) in 20% water/DMF (v/v) with 50 ?M HEPES buffer. Concentrations shown are final concentrations of metal. 0! 5! 10! 15! 20! 25! 30! 35! 40! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 20% Water/DMF" 50 uM HEPES buffer Uranyl" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 0! 5! 10! 15! 20! 25! 30! 35! 40! 45! 50! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" H 2 L1 20% Water/DMF" 50 uM HEPES buffer Cobalt" Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! ! 146! Figure A3.40: Fluorescence batch titration of H 2 L1 with copper in 20% water/DMF (v/v) at 350 nm excitation. Concentrations are final metal concentrations Figure A3.41: Fluorescence batch titration of H 2 L1 with uranyl in 20% water/DMF (v/v) at 350 nm excitation. Concentrations are final metal concentrations 0! 2! 4! 6! 8! 10! 12! 14! 16! 18! 20! 400! 450! 500! 550! 600! 650! I n te n s i ty ! Wavelength (nm)! H 2 L1 20% Water/DMF ! Copper 350 nm Excitation! Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! 0! 2! 4! 6! 8! 10! 12! 14! 16! 18! 20! 400! 450! 500! 550! 600! 650! I n te n s i ty ! Wavelength (nm)! H 2 L1 20% Water/DMF ! Uranyl 350 nm Excitation! Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! ! 147! Figure A3.42: Fluorescence batch titration of H 3 L3 with copper in 40% water/DMF (v/v) at 350 nm excitation. Concentrations are final metal concentrations Figure A3.43: Fluorescence batch titration of H 3 L3 with copper in 40% water/DMF (v/v) at 350 nm excitation. Concentrations are final metal concentrations. 0! 20! 40! 60! 80! 100! 120! 140! 160! 180! 200! 350! 450! 550! 650! I n te n s i ty ! Wavelength (nm)! H 3 L3 40% Water/DMF! Copper 350 nm Excitation! Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! 0! 20! 40! 60! 80! 100! 120! 140! 160! 180! 200! 350! 450! 550! 650! I n te n s i ty ! Wavelength (nm)! H 3 L3 40% Water/DMF! Uranyl 350 nm Excitation! Ligand! 20 uM! 40 uM! 60 uM! 80 uM! 100 uM! 120 uM! 140 uM! 160 uM! 180 uM! 200 uM! ! 148! Appendix 2 for Chapter 4 Figure A4.1: Calculated 4-aminosalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in DMF 0! 10! 20! 30! 40! 50! 60! 70! 80! 200! 250! 300! 350! 400! 450! 500! 550! 600! 650! 700! ? *10 3 M -1 cm -1 " Wavelength (nm)" 4-aminosalicylaldehyde DMF" Ligand! Copper! Uranyl! ! 149! Figure A4.2: Calculated 4-aminosalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in acetone Figure A4.3: Calculated 5-aminosalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in DMF 0! 10! 20! 30! 40! 50! 60! 70! 200! 250! 300! 350! 400! 450! 500! 550! 600! 650! 700! ? *10 3 M -1 cm -1 " Wavelength (nm)" 4-aminosalicylaldehyde Acetone" Ligand! Copper! Uranyl! 0! 10! 20! 30! 40! 50! 60! 70! 200! 300! 400! 500! 600! 700! 800! ? *10 3 M -1 cm -1 " Wavelength (nm)" 5-aminosalicylaldehyde DMF" Ligand! Copper! Uranyl! ! 150! Figure A4.4: Calculated 5-aminosalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in acetone Figure A4.5: Calculated 3-ethoxysalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in DMF 0! 10! 20! 30! 40! 50! 60! 70! 200! 300! 400! 500! 600! 700! 800! ? *10 3 M -1 cm -1 " Wavelength (nm)" 5-aminosalicylaldehyde Acetone" Ligand! Copper! Uranyl! 0! 10! 20! 30! 40! 50! 60! 200! 250! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" 3-ethoxysalicylaldehyde DMF" Ligand! Copper! Uranyl! ! 151! Figure A4.6: Calculated 3-ethoxysalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in acetone Figure A4.7: Calculated 3-hydroxysalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in DMF 0! 10! 20! 30! 40! 50! 60! 200! 250! 300! 350! 400! 450! 500! 550! 600! 650! 700! ? *10 3 M -1 cm -1 " Wavelength (nm)" 3-ethoxysalicylaldhehyde Acetone" Ligand! Copper! Uranyl! 0! 10! 20! 30! 40! 50! 60! 200! 250! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" 3-hydroxysalicylaldhehyde DMF" Ligand! Copper! Uranyl! ! 152! Figure A4.8: Calculated 3-hydroxysalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in acetone Figure A4.9: Calculated 4-hydroxysalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in DMF 0! 10! 20! 30! 40! 50! 60! 200! 300! 400! 500! 600! 700! 800! 900! 1000! ? *10 3 M -1 cm -1 " Wavelength (nm)" 3-hydroxysalicylaldehyde Acetone" Ligand! Copper! Uranyl! 0! 10! 20! 30! 40! 50! 60! 200! 250! 300! 350! 400! 450! 500! 550! 600! 650! 700! ? *10 3 M -1 cm -1 " Wavelength (nm)" 4-hydroxysalicylaldehyde DMF" Ligand! Copper! Uranyl! ! 153! Figure A4.10: Calculated 4-hydroxysalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in acetone Figure A4.11: Calculated 4-chlorosalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in DMF 0! 10! 20! 30! 40! 50! 60! 200! 250! 300! 350! 400! 450! 500! 550! 600! 650! 700! ? *10 3 M -1 cm -1 " Wavelength (nm)" 4-hydroxysalicylaldehyde Acetone" Ligand! Copper! Uranyl! 0! 10! 20! 30! 40! 50! 60! 200! 250! 300! 350! 400! 450! 500! 550! 600! 650! 700! ? *10 3 M -1 cm -1 " Wavelength (nm)" 4-chlorosalicylaldehyde DMF" Ligand! Copper! Uranyl! ! 154! Figure A4.12: Calculated 4-methoxysalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in DMF Figure A4.13: Calculated 4-methoxysalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in acetone 0! 10! 20! 30! 40! 50! 60! 70! 200! 250! 300! 350! 400! 450! 500! 550! 600! 650! 700! ? *10 3 M -1 cm -1 " Wavelength (nm)" 4-methoxysalicylaldehyde DMF" Ligand! Copper! Uranyl! 0! 10! 20! 30! 40! 50! 60! 70! 200! 250! 300! 350! 400! 450! 500! 550! 600! 650! 700! ? *10 3 M -1 cm -1 " Wavelength (nm)" 4-methoxysalicylaldehyde Acetone" Ligand! Copper! Uranyl! ! 155! Figure A4.14: Calculated 5-hydroxysalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in DMF Figure A4.15: Calculated 5-hydroxysalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in acetone 0! 10! 20! 30! 40! 50! 60! 200! 300! 400! 500! 600! 700! 800! ? *10 3 M -1 cm -1 " Wavelength (nm)" 5-hydroxysalicylaldehye DMF" Ligand! Copper! Uranyl! 0! 10! 20! 30! 40! 50! 60! 200! 300! 400! 500! 600! 700! 800! ? *10 3 M -1 cm -1 " Wavelength (nm)" 5-hydroxysalicylaldehyde Acetone" Ligand! Copper! Uranyl! ! 156! Figure A4.16: Calculated 5-t-butylsalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in DMF Figure A4.17: Calculated 5-methylsalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in DMF 0! 10! 20! 30! 40! 50! 60! 200! 250! 300! 350! 400! 450! 500! 550! 600! 650! 700! ? *10 3 M -1 cm -1 " Wavelength (nm)" 5-t-butylsalicylaldehyde DMF" Ligand! Copper! Uranyl! 0! 10! 20! 30! 40! 50! 60! 200! 250! 300! 350! 400! 450! 500! 550! 600! 650! 700! ? *10 3 M -1 cm -1 " Wavelength (nm)" 5-methylsalicylaldehyde DMF" Ligand! Copper! Uranyl! ! 157! Figure A4.18: Calculated 5-methylsalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in acetone Figure A4.19: Calculated 2,4,6-trihydroxysalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in DMF 0! 10! 20! 30! 40! 50! 60! 200! 250! 300! 350! 400! 450! 500! 550! 600! 650! 700! ? *10 3 M -1 cm -1 " Wavelength (nm)" 5-methylsalicylaldehyde Acetone" Ligand! Copper! Uranyl! 0! 10! 20! 30! 40! 50! 60! 70! 200! 250! 300! 350! 400! 450! 500! 550! 600! 650! 700! ? *10 3 M -1 cm -1 " Wavelength (nm)" 2,4,6-trihydroxybenzaldehyde DMF" Ligand! Copper! Uranyl! ! 158! Figure A4.20: Calculated 2,4,6-trihydroxysalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in acetone Figure A4.21: Calculated 3,5-dichlorosalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in DMF 0! 10! 20! 30! 40! 50! 60! 70! 200! 250! 300! 350! 400! 450! 500! 550! 600! 650! 700! ? *10 3 M -1 cm -1 " Wavelength (nm)" 2,4,6-trihydroxybenzaldehyde Acetone" Ligand! Copper! Uranyl! 0! 10! 20! 30! 40! 50! 60! 70! 200! 250! 300! 350! 400! 450! 500! 550! 600! 650! 700! ? *10 3 M -1 cm -1 " Wavelength (nm)" 3,5-dichlorosalicylaldehyde DMF" Ligand! Copper! Uranyl! ! 159! Figure A4.22: Calculated triazine, copper complex, and uranyl complex UV-Vis spectrum in DMF Figure A4.23: Calculated triazine, copper complex, and uranyl complex UV-Vis spectrum in acetone 0! 10! 20! 30! 40! 50! 60! 200! 250! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 c m -1 " Wavelength (nm)" Triazine DMF" Ligand! Copper! Uranyl! 0! 1! 2! 3! 4! 5! 450! 500! 550! 600! Wavelength (nm)" 0! 10! 20! 30! 40! 50! 60! 200! 250! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" Triazine Acetone" Ligand! Copper! Uranyl! ! 160! Figure A4.24: Calculated triazine, copper complex, and uranyl complex UV-Vis spectrum in acetic acid Figure A4.25: Calculated triazine, copper complex, and uranyl complex UV-Vis spectrum in acetonitrile 0! 10! 20! 30! 40! 50! 60! 70! 200! 250! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" Triazine Acetic Acid" Ligand! Copper! Uranyl! 0! 10! 20! 30! 40! 50! 60! 70! 200! 250! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" Traizine Acetonitrile" Ligand! Copper! Uranyl! ! 161! Figure A4.26: Calculated 4,5-dimethyl triazine, copper complex, and uranyl complex UV-Vis spectrum in DMF Figure A4.27: Calculated 4,5-di-t-butyltriazine, copper complex, and uranyl complex UV-Vis spectrum in DMF 0! 10! 20! 30! 40! 50! 60! 70! 80! 200! 250! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" 4,5-dimethyl (diacetyl) triazine DMF" Ligand! Copper! Uranyl! 0! 0.5! 1! 1.5! 2! 2.5! 3! 400! 500! 600! Wavelength (nm)" 0! 10! 20! 30! 40! 50! 60! 70! 80! 180! 230! 280! 330! 380! 430! 480! 530! 580! ? *10 3 M -1 cm -1 " Wavelength (nm)" 4,5-di-tert-butyl Traizine DMF" Ligand! Copper! Uranyl! ! 162! Figure A4.28: Calculated 4,5-di-i-butyltriazine, copper complex, and uranyl complex UV-Vis spectrum in DMF 0! 20! 40! 60! 80! 100! 120! 200! 300! 400! 500! 600! 700! 800! 900! 1000! 1100! ? *10 3 M -1 cm -1 " Wavelength (nm)" 4,5-di-iso-butyl Triazine DMF" Ligand! Copper! Uranyl! 0! 2! 4! 6! 8! 10! 400! 600! 800! Wavelength (nm)" ! 163! Figure A4.29: Calculated 3-ethoxysalicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in DMF Figure A4.30: Calculated 4,5-cylcohexane, copper complex, and uranyl complex UV-Vis spectrum in DMF 0! 10! 20! 30! 40! 50! 60! 70! 80! 200! 300! 400! 500! 600! 700! 800! ? *10 3 M -1 cm -1 " Wavelength (nm)" 4,5-dihexyl Triazine DMF" Ligand! Copper! Uranyl! 0! 10! 20! 30! 40! 50! 60! 70! 80! 200! 300! 400! 500! 600! 700! 800! 900! 1000! ? *10 3 M -1 cm -1 " Wavelength (nm)" 4,5-cylcohexane Triazine DMF" Ligand! Copper! Uranyl! ! 164! Figure A4.31: Calculated 4,5-cyclohexane, copper complex, and uranyl complex UV-Vis spectrum in acetone Figure A4.32: Calculated 4,5-diphenyltriazine, copper complex, and uranyl complex UV-Vis spectrum in DMF 0! 10! 20! 30! 40! 50! 60! 70! 80! 200! 300! 400! 500! 600! 700! 800! 900! 1000! ? *10 3 M -1 cm -1 " Wavelength (nm)" 4,5-cylcohexane Triazine Acetone" Ligand! Copper! Uranyl! 0! 10! 20! 30! 40! 50! 60! 70! 80! 90! 200! 300! 400! 500! 600! 700! 800! 900! 1000! 1100! ? *10 3 M -1 cm -1 " Wavelength (nm)" 4,5-diphenyl Triazine DMF" Ligand! Copper! Uranyl! ! 165! Figure A4.33: Calculated 2-thiobenzaldehyde, copper complex, and uranyl complex UV-Vis spectrum in DMF Figure A4.34: Calculated bipyridine salicylaldehyde, copper complex, and uranyl complex UV-Vis spectrum in DMF 0! 10! 20! 30! 40! 50! 60! 70! 80! 90! 200! 300! 400! 500! 600! 700! 800! ? *10 3 M -1 cm -1 " Wavelength (nm)" 2-thiolbenzaldehyde DMF" 2 Thiol! Copper! Uranyl! 0! 10! 20! 30! 40! 50! 60! 200! 300! 400! 500! 600! 700! 800! ? *10 3 M -1 cm -1 " Wavelength (nm)" Bipyridine, salicylaldehyde DMF" Ligand! Copper! Uranyl! ! 166! Figure A4.35: Calculated bis-bipyridine, copper complex, and uranyl complex UV- Vis spectrum in DMF Figure A4.36: Calculated pyrrole, copper complex, and uranyl complex UV-Vis spectrum in DMF 0! 10! 20! 30! 40! 50! 60! 70! 80! 200! 250! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" Dibypyridine DMF" Ligand! Copper! Uranyl! 0! 10! 20! 30! 40! 50! 60! 70! 200! 250! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" Pyrrole DMF" Ligand! Copper! Uranyl! ! 167! Figure A4.37: Calculated pyrrole, copper complex, and uranyl complex UV-Vis spectrum in acetone Figure A4.38: Calculated pyridine, copper complex, and uranyl complex UV-Vis spectrum in DMF 0! 10! 20! 30! 40! 50! 60! 200! 250! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 c m -1 " Wavelength (nm)" Pyrrole Acetone" Ligand! Copper! Uranyl! 0! 10! 20! 30! 40! 50! 60! 200! 250! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" Pyridine DMF" Ligand! Copper! Uranyl! ! 168! Figure A3.39: Calculated pyridine, copper complex, and uranyl complex UV-Vis spectrum in acetone Figure A3.40: Calculated di-substituted pyridine amide on quinoxaline, copper complex, and uranyl complex UV-Vis spectrum in DMF 0! 10! 20! 30! 40! 50! 60! 200! 250! 300! 350! 400! 450! 500! 550! 600! ? *10 3 M -1 cm -1 " Wavelength (nm)" Pyridine Acetone" Ligand! Copper! Uranyl! 0! 10! 20! 30! 40! 50! 60! 70! 200! 300! 400! 500! 600! 700! 800! ? *10 3 M -1 cm -1 " Wavelength (nm)" Di-substituted Pyridine Amide on the Quinoxaline" Ligand! Copper! Uranyl! ! 169! Figure A4.41: Calculated disubstituted pyridine amide on pyridine, copper complex, and uranyl complex UV-Vis spectrum in DMF 0! 10! 20! 30! 40! 50! 60! 70! 80! 90! 100! 180! 380! 580! 780! 980! ? *10 3 M -1 cm -1 " Wavelength (nm)" Di-substitued on Pyridine Amide Quinoxaline" Ligand! Copper! Uranyl!