Stabilizing intramolecular cobalt–imidazole coordination with a remote methyl group in the backbone of a cofactor B₁₂–protein model

Abstract

This communication describes the stabilizing effect (ΔΔG° = -4 kJ mol) of a remote methyl group in the backbone of a cobalamin-enzyme mimic on intramolecular imidazole-cobalt coordination. For this purpose, two B derivatives with an appended imidazole base were synthesized and analysed with spectrophotometric pH titrations. Qualitative conformation analysis of the backbone structure suggests that a thermodynamically unfavoured gauche interaction in the base-off form of a model containing an (R)-configured CH group at position C176 of the linker between the corrin ring and the terminal imidazole ligand steers the base toward cobalt coordination.

Crystallographic and (spectro)electrochemical characterizations of cobalt(II) 10-phenyl-5,15-di-p-tolylporphyrin

“…Electrocatalytic four electrons reduction of O2 to H2O by cobalt porphyrins has been extensively studied so far not only because of its biological relevance, but also due to its technological significance such as in fuel cells [21,22]. Furthermore, the studies of cobalamin and its derivatives/analogues have significantly contributed to increase the popularity of Co(II) complexes [23][24][25][26]. It was also found that the reactivity of axial ligation of cobalt porphyrin play a pivotal role in a number of bio-and 'bio-inspired' catalytic transformations.…”