Nicotinamide adenine dinucleotide hydride (NAD(P)H), a critical reductant in photosynthesis, acts as a hydride donor by transferring two electrons and one proton simultaneously to the oxidant, avoiding unfavorable radical intermediates in reduction processes. Recently, several NAD(P)H analogs have been designed to be regenerable reducing agents. The structural tunability to affect reducing power and regenerability make its analogues promising candidates for reducing CO2 into useful fuels. For example, 1,2-dihydropyridine is predicted to reduce CO2 into methanol and to be regenerable electrochemically. This talk will report our study of a broad range of dihydropyridine analogs as hydride donors for various reduction processes, including the reduction of CO2, carbonyls and imines. The set of dihydropyridine analogs covers a range of species including dihydropyridines, dihydroquinolines, dihydroisoquinoines, dihydrophenanthridines and dihydroacridines that are formed at various electrochemical potentials and which possess a range of hydride transfer abilities; we determine the latter as thermodynamic hydricities and kinetic hydride transfer barriers to various oxidants. The effects of increased aromatic rings and various functional groups with different electronegativity are accounted for the design of dihydropyridine analogs. Our results indicate that the hydride transfer reactions of the dihydropyridine analogs to CO2 and other unsaturated functional groups adhere to the Evans-Polanyi principle, which in addition to our computational prototyping approach, facilitates the rational design of thermodynamically and kinetically competent regenerable reducing agents.

Theoretical investigation of thermodynamic and kinetic properties of dihydropyridines in the catalytic reduction of CO2 and various unsaturated functional groups

249th National Meeting (2015)

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