Halogen substituted A2B type Co(III)triarylcorroles: Synthesis, electronic structure and two step modulation of electrocatalyzed hydrogen evolution reactions

• Seven low symmetric A2B type Co(III)triarylcorroles have been reported.
• The electronic structure has been characterized by optical spectroscopy, electrochemistry, spectroelectrochemistry and TD-DFT calculations.
• These Co(III)corroles are highly effective catalysts for unusual two steps modulation of hydrogen evolution reactions (HERs).

Seven low symmetry A2B type Co(III)triarylcorroles with electron withdrawing meso-aryl substituents have been synthesized and characterized. A detailed analysis of the optical and redox properties has been carried out by comparing their optical spectroscopy, electrochemistry and spectroelectrochemistry to trends predicted in a series of DFT and TD-DFT calculations. The results demonstrate that Co(III)corroles are highly effective catalysts for hydrogen evolution reactions (HERs). Moreover, there is a marked enhancement in their homogenous catalytic ability when halogen atoms are introduced at the B position, which demonstrates that facile modifying the meso-aryl rings is a effective strategy for developing new HER catalysts. The electrochemical results demonstrate that an unusual two step modulation of HER reactions can be achieved by using singly and doubly electrochemical reduced cobalt triarylcorroles anions.