Author ORCID Identifier

https://orcid.org/0009-0009-3443-4548

Date Available

12-15-2025

Year of Publication

2025

Document Type

Master's Thesis

Degree Name

Master of Science (MS)

College

Arts and Sciences

Department/School/Program

Chemistry

Faculty

Aron Joel Huckaba

Faculty

Kenneth Graham

Abstract

Increasing anthropogenic emission of CO2 into the atmosphere is a global issue that shows no signs of deceleration due to the current trends in dependencies on fossil fuels for energy demand. Although deleterious in nature, this greenhouse gas can serve as a useful feed-stock for the production of small-carbon-chain commercial chemicals if the factors owing to its inertness can be overcome. Fortuitously, CO2’s chemically inert nature is already circumvented in nature through an elegant cascade of biochemical reactions known as photosynthesis, which nearly all plants and some families of bacteria exploit to produce simple sugars for metabolic utilization. Plants achieve this incredible feat using an enzyme dubbed RuBisCO to catalytically lower the activation energy of the system to fix ~3-10 CO2 molecules per second, which is rather slow and inefficient compared to other enzymes. Improving upon nature’s design, researchers have long sought to design and synthesize efficient catalysts (photo/electro) for the reduction of CO2. This thesis is focused on the synthesis and evaluation of novel pyridyl-azolo ligands that, when chelated to rhenium, can be utilized in the homogenous photocatalytic reduction of CO2 to produce valuable chemicals from the once inert gas. The first project focuses on our first attempt to synthesize D-π-A structural ligands using pyridyl-imidazoles to utilize the subsequent intraligand charge transfer for productive photocatalysis. While unsuccessful synthetically, a select few of the complexes we obtained set new benchmarks for formate production for Re(I) photocatalysts in the field. The next project focuses on the successful attempt to synthesize the full D-π-A structural ligands utilizing benzimidazoles in place of imidazoles for synthetically more accessible ancillary coupling partners. Due to the tautomerization inherent in these fused-ring systems, we were able to isolate two different charge-transfer isomers and study their effects on the complexes’ optical properties and photocatalytic efficiencies. These two projects aim to fundamentally study and improve Re(I) photocatalyst ligand design philosophy for more efficient and productive photocatalysts.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2025.579

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