Chiral recognition of ferrocytochrome c(II) in electron-transfer reactions with cobalt(III) complexes

Abstract

Stereoselective electron-transfer reactions were carried out between ferrocytochrome c, cyt c(II) and the cobalt(III) complexes tris(2,2′-bipyridine)cobalt(III), [Co(bipy)₃]³⁺ and tris(pentane-2,4-dionato)cobalt(III), [Co(pd)₃]. The reduction of [Co(bipy)₃]³⁺ proceeds much more rapidly than that of [Co(pd)₃]. At the same time, the stereoselectivity for the former is much greater than for the latter. These results are interpreted in terms of incorporation of bipy into a hydrophobic crevice of cyt c(II). The stereoselectivity exhibits interesting dependences on the reaction conditions such as the ethanol content in the solvent, pH and temperature. These dependences are discussed in terms of the closeness of approach of the cobalt(III) complexes to the chiral groups of cyt c(II).