Date of Award

Spring 6-8-2019

Document Type

Thesis

Degree Name

Master of Science (MS)

First Advisor

Charles B. Musgrave

Second Advisor

Jennifer N. Cha

Third Advisor

Aaron M. Holder

Abstract

Rising atmospheric CO2 concentration and rapid depletion of fossil fuels necessitates the search for competent methods for CO2 conversion to fuels. Various studies demonstrate the ability of pyridinic derivatives to photoelectrochemically reduce CO2 to methanol. Here the thermodynamic and kinetic aspects of pyridines as hydride-donating catalytic reagents that transfer hydrides via their dihydropyridinic form are analyzed. We investigate the effects of functionalizing pyridinic derivatives with electron-donating and electron-withdrawing groups on hydride transfer catalyst strength – assessed via their hydricity and nucleophilicity – and the catalyst recyclability – assessed via reduction potential. We find that pyridines with electron-donating groups have stronger hydride-donating ability, but are less efficiently recycled (having more negative reduction potentials). In contrast, pyridines substituted with electron-withdrawing groups are more efficiently recycled but are weaker hydride donors. Functional group modification favorably tunes hydride strength or efficiency, but not both. This problematic coupling between the strength and recyclability of pyridinic hydrides is attributed to their aromatic nature. Several avenues are suggested for overcoming this difficulty.

Available for download on Sunday, October 10, 2021

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