ELECTRON-TRANSFER REACTIONS OF COPPER(III)-PEPTIDE COMPLEXES WITH "TRIS(1,10-PHENANTHROLINE)COBALT(II)

Tripeptide and tetrapeptide complexes of Cu(III) rapidly oxidize Co(phen)32+ showing that outer-sphere electron transfer occurs. The rates for reactions between Co(phen)32+ and ten different uncharged copper(III)-peptide complexes (with E° values for the cross exchange ranging from 0.23 to 0,56 V) exhibit a linear free energy dependence: log k12 = 0.25 (±0.02) log K12 + 4.4 (±0.2). The slope is much less than that predicted by the usual formulation of the Marcus theory. Nevertheless, electron transfer involving copper(III,II)-peptide complexes is shown to be a very facile process. © 1979, American Chemical Society. All rights reserved.