Novel Complexes for the Electrochemical and Photochemical Reduction of CO2

The increase in the concentration of CO2 a greenhouse gas is causing significant environmental harm and this has necessitated the catalytic conversion of CO2 via molecular catalysts as a viable pathway for reducing the global footprint of CO2. On this perspective, this thesis explores the assembly of molecular compounds with novel architectures and the assessment of how the ensuing structural and electronic novelty influences the catalytic ability and mechanistic pathway of the CO2 reduction reaction. A particular emphasis will be placed on the evaluation of catalytic activity and features prompting selectivity for CO2 reduction to specified products. In Chapter 3 we report the electrocatalytic reduction of CO2 by three rhenium tricarbonyl complexes containing asymmetric diimine ligands with a pyridine moiety bound to an oxazoline and probe the influence of enhanced nucleophilicity on the catalytic activity. Taking inspiration from our observations in Chapter 3, we investigate in Chapter 4 the effect of conjugation in the ligand backbone through fusing of aromatic rings to extend the π system and shift the reduction potential to less negative values. In Chapter 5, motivated by the excellent catalytic properties of the re-based complexes, we replace the expensive and precious rhenium metal by the economically viable and earth abundant nickel metal and thereafter appraise the catalytic activities of the resulting nickel complexes. In chapter 6 we evaluate CO2 photocatalysis of the compounds presented in chapters 3 and 4. In chapter 7 we evaluate the CO2 photocatalytic ability of a supramolecular construct where a metalloporphyrin is the visible-light absorber