A bioinspired cobalt catalyst based on a tripodal imidazole/pyridine platform capable of water reduction and oxidation.

The prototypical drug carrier [Co(L)Cl]PF (1), where L is a tripodal amine bound to pyridine and methyl-imidazoles, had its electrocatalytic water splitting activity studied under different pH conditions. This species contains a high-spin 3d Co metal center, and is capable of generating both H from water reduction and O from water oxidation Turnover numbers reach 390 after 3 h for water reduction. Initial water oxidation activity is molecular, with TONs of 71 at pH 7 and 103 at pH 11.5. The results reveal that species 1 can undergo several redox transformations, including reduction to the 3d Co species that precedes a 3d hydride for water reduction, as well as nominal CoO and Co-OOH species required for water oxidation. Post-catalytic analyses confirm the molecular nature of reduction and support initial molecular activity for oxidation.