Control of redox potential by deprotonation of coordinated 1H-imidazole in complexes of 2-(1H-imidazol-2-yl)pyridine

Complexes [ML3](2+) of the bidentate ligand 2-(1H-imidazol-2-yl)pyridine were prepared with iron(II), cobalt(II), and ruthenium(II). ne electronic spectra suggest the ligand to be a weaker sigma-donor and pi-acceptor than the closely related 2,2 '-bipyridine. The complexes are readily deprotonated by addition of base, and the effect of the deprotonation is to lower the M-III/M-II redox potential by roughly 900 mV. This is roughly 75% of the drop observed for related complexes of 2,6-di-1H-imidazol-2-ylpyridine, and suggests the effect to be largely coulombic in origin.