A PEGylated Tin Porphyrin Complex for Electrocatalytic Proton Reduction: Mechanistic Insights into Main-Group-Element Catalysis

Electrocatalytic proton reduction to form dihydrogen (H-2) is an effective way to store energy in the form of chemical bonds. In this study, we validate the applicability of a main-group-element-based tin porphyrin complex as an effective molecular electrocatalyst for proton reduction. A PEGylated Sn porphyrin complex (SnPEGP) displayed high activity (-4.6 mA cm(-2) at -1.7 V vs. Fc/Fc(+)) and high selectivity (H-2 Faradaic efficiency of 94 % at -1.7 V vs. Fc/Fc(+)) in acetonitrile (MeCN) with trifluoroacetic acid (TFA) as the proton source. The maximum turnover frequency (TOFmax) for H-2 production was obtained as 1099 s(-1). Spectroelectrochemical analysis, in conjunction with quantum chemical calculations, suggest that proton reduction occurs via an electron-chemical-electron-chemical (ECEC) pathway. This study reveals that the tin porphyrin catalyst serves as a novel platform for investigating molecular electrocatalytic reactions and provides new mechanistic insights into proton reduction.

Automated summary

The study validates the effectiveness of a main-group-element-based tin porphyrin complex as a molecular electrocatalyst for proton reduction. The PEGylated Sn porphyrin complex exhibited high activity and high selectivity in acetonitrile. Spectroelectrochemical analysis and quantum chemical calculations provided insights into the mechanism of proton reduction.