Effect of metal ion substitution on the catalytic activity of a pentanuclear metal complex.

A pentanuclear cobalt complex that consists of five cobalt ions and six bpp- ligands (Co5, Hbpp = 3,5-bis(2-pyridyl)pyrazole) was synthesized and crystallographically characterized. Electrochemical measurements indicate that Co5 has multielectron transfer ability. We also found that Co5 reduces CO2 to CO under photoirradiation in the presence of a photosensitizer.