Co(iii) corroles with pendant amidophenol and amidopyridine as proton-relay arms to facilitate the electrocatalytic hydrogen evolution reaction†

It is known that the efficiency of the hydrogen evolution reaction (HER) can be promoted by the presence of proton relay groups neighboring a catalytic metal center. This work reports the synthesis of two new Co(iii) corroles (2 and 3) with hangman proton relay groups for the electrocatalytic HER. When using trifluoroacetic acid (TFA) as a proton source, complexes 2 and 3 exhibited turnover frequencies (TOFs) of 219.36 s⁻¹ and 199.57 s⁻¹, respectively. The catalytic HER undergoes via the EECEC or EECC pathway (E: electron transfer; C: charge transfer) depending on the acidity and concentration of the proton source. Moreover, complex 2 and 3 also showed good HER activity in aqueous media with Faraday efficiencies (FEs) of 93.6% and 89.2% respectively.