Synthesis of cobalt A2B triaryl corroles bearing aldehyde and amide pyridyl groups and their performance in electrocatalytic hydrogen evolution

Abstract

Four A₂B type cobalt triaryl corrole complexes (1–4) bearing aldehyde and pyridyl substituents at the 10-meso-phenyl group with different spatial configurations have been synthesized and thoroughly characterized using high-resolution mass spectrometry, nuclear magnetic resonance spectroscopy (NMR), X-ray photoelectron spectroscopy, and single-crystal X-ray diffractometry. These complexes all exhibited good activity in the electrocatalytic hydrogen evolution reaction (HER) when acetic acid, trifluoroacetic acid (TFA) or p-toluenesulfonic acid (TsOH) was used as the proton source. The Tafel catalytic plot revealed the intrinsic characteristics of the catalytic activity. The HER followed the EECEC pathway when acetic acid was used as a proton source, while it proceeded through the EECC or EECEC pathway when using TFA or TsOH as the proton source, depending on the acid concentration. The presence of Co^III–H was detected by ¹H NMR, which provided evidence for the catalytic mechanism. The amide pyridyl may function as the proton relay group since the meta-substituted cobalt corroles 3 and 4 exhibited significantly higher turnover frequency (TOF)_max values than corroles 1 and 2 in an organic medium.