Catechol oxidase activity of comparable dimanganese and dicopper complexesElectronic supplementary information (ESI) available. CCDC 1476678, 1822646-1822648. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c8dt01378k

Synthetic Cu II 2 complexes have been widely investigated as model systems for catechol oxidase enzymes. The catechol oxidase reactivity of Mn II 2 complexes has been less explored, and the effect of metal substitution in catecholase mimics has not been explored. A series of Mn II 2 and Cu II 2 complexes supported by the same poly-benzimidazole ligand framework have been synthesised and investigated in catecholase activity in acetonitrile medium using 3,5-di- tert -butylcatechol (3,5-DTBC) as a substrate. The Cu II 2 complexes proved to be good catechol oxidase mimics with moderate k cat values (∼45 h −1 ). The kinetic parameters for Mn II 2 complexes exhibited lower k cat values (∼8-40 h −1 ) when compared to the Cu II 2 complexes. Our findings demonstrate that later transition metals supported by relatively electron rich ligands yield the highest k cat values for catechol oxidation. Dicopper complexes proved to be more reactive catechol oxidase mimics when compared to dimanganese complexes supported by identical ligand frameworks.