Richter Addo, GeorgeSwann, Matthew2020-08-262020-08-262020-12https://hdl.handle.net/11244/325415Divestment from fossil fuels is necessary in order to lessen the impacts of climate change across the planet. One alternative to fossil fuels is hydrogen gas, which is utilized in syn gas and hydrogen fuel cells. However, the production of hydrogen gas is often extremely costly. One of the primary ways by which hydrogen gas is produced is by water splitting/water oxidation catalysts. Recent work on water oxidation catalysts have demonstrated Ru(V) oxo complexes to be high performance, eclipsing the activity of natural water oxidation systems, such as the oxygen-evolving complex that splits water in photosynthesis. Water oxidation occurs in two distinct steps, the hydrogen reduction reaction and the oxygen evolution reaction (OER). The OER is usually the rate limiting portion of the reaction for WOCs. One of the mechanisms by which the OER occurs, is the intermolecular bimolecular (I2M) mechanism. The I2M mechanism does not require water to evolve oxygen, unlike other WOCs. Thus, the I2M mechanism can be applied to a wider array of catalytic reactions, such as oxygen-atom transfer reactions (OAT) and small molecule splitting (CO2 splitting, N2O splitting). Optimizing catalysts for the I2M mechanism then provides a general method for increasing catalytic efficiency. To this end, we have selected a series of ruthenium (V) oxo coordination compounds to evaluate their ability to undergo the OER by a slightly modified I2M mechanism. The coordination compounds selected contain the ligands: nitrilotriacetate (NTA), bipyridine dicarboxylate, porphyrin, dimethyl glyoxime, and α-hydroxyacid (AHA). The aim of this work is to computationally determine the gas phase ground-state thermodynamics and transition states involved in this reaction and to determine the effect charge, coordination number, and solvation have on reactivity. We have also sought to synthesize a few of these oxo-ruthenium complexes in order to experimentally evaluate their OER reactivity. Computational analysis of the complexes showed exceedingly large free energies of O-O radical coupling for anionic complexes, suggesting that anionic complexes would not be OER catalysts. Comparing the activation barriers for radical coupling of our neutral complexes with those found in the literature suggests that neutral complexes may experience the lowest barrier, and thus make faster OER catalysts. Examining the coordination number of the ruthenium atoms in these complexes suggests that sterically crowded complexes feature extremely downhill total free energies, providing a large driving force so that the reaction proceeds in the forward direction. Complexes that yield low coordinate numbers upon O2 evolution on the other hand feature large uphill total free energies. For favorable OER thermodynamics oxo complexes should have a coordination number of 6 or 7, otherwise large thermodynamic barriers may prohibit reactivity. Solvation of the NTA complexes by water showed that high polarity solvents may inhibit the O-O coupling step, but overall drive more favorable overall OER thermodynamics. Experimentally, we synthesized the (C3H7)4N[(AHA)2RuVO] complex to satisfactory purity. The AHA complex was then utilized in photolysis and thermolysis experiments, to determine the stability and reactivity of the species. These experiments seemed to indicate to that the complex undergoes decomposition under both conditions, indicating that this complex may not be able to catalyze the OER reaction under anything other than milquetoast conditions, if at all. A number of synthetic methods were employed to synthesize an NTARuO(L) complex, with varying results. While none of the methods produced an easily characterizable and isolable complex, they did highlight the need for acidic and oxidizing conditions in order to bind NTA to Ru, lest it be out competed by softer bases such as pyridine. Understanding the ability of Ru(V) Oxo complexes to undergo the OER carries widespread implications on not just water splitting, but to a number of other chemical processes. The results herein lay out a number of important aspects that should be considered when designing OER catalysts.ComputationalChemistryOxygen Evolution