Solvated electron precursors: a computational approach to the development of novel catalysts from gas-phase to condensed-phase

Abstract

The solvated electron precursor (SEP) is a complex consisting of a positively charged metal core, Mn+, surrounded by sufficient ligands, L, whose coordination leads to n number of valence electrons being displaced from the metal to periphery of the complex as Mn+Lx@ne–. These solvated electrons occupy hydrogenic type orbitals which surround the periphery of the SEP complex. Here, multi-reference wavefunction and density functional theory calculations are employed to demonstrate the systematic development of SEPs as novel catalytic material. The first detailed mechanistic study for the use of SEPs as a catalyst for CO2 functionalization is presented. The reaction pathways for conversion of CO2 to formic acid/methyldiol and to δ-lactone are studied computationally. The use of aliphatic chains and diamine chains is introduced as a means for bridging two SEPs together and are denoted as linked-SEPs. The isoelectronic systems of (NH3)3Be(CH2)nBe(NH3)3 and (NH3)3LiNH2(CH2)nH2NLi(NH3)3 are studied, with each SEP terminus bearing 1 diffuse electron in a s-type orbital. The coupling of these electrons is investigated as a function of chain length. The system of (NH3)3B(CH2)nB(NH3)3 is studied as well, with each SEP terminus bearing two diffuse electrons. Finally, observations from the Li-diamine linked-SEP system inspired the proposal of a novel material consisting of a grid of Li+ linked by diamine chains. The proposed material is diamond-like in structure, where carbon atoms have been replaced with Li+ and C−C bonds with diamines. Each lithium tetra-amine center is surrounded by a diffuse orbital occupied by one solvated electron. The electronic band structure and magnetic properties are investigated as a function of diamine chain length illustrating the ability to produce materials of metallic or semiconductor character by tuning the chain length. We propose the SEP materials as a highly tunable redox active catalyst where reactivity may be controlled by varying pore size and functionalization of carbon chains. Critically, presented gas-phase calculations accurately predict material behaviors, offering an avenue for further development of SEP materials and testing of their tunability. This work in total presents a systematic approach for the design of novel catalytic materials, beginning with high level gas-phase calculations which inform the development of the condensed phase.