795241-80-4Relevant articles and documents
Electron-transfer reactions of copper(I) and copper(III) complexes
Lappin, A. Graham,Youngblood, Michael P.,Margerum, Dale W.
, p. 407 - 413 (2008/10/08)
The reactions of bis(2,9-dimethyl-1,10-phenanthroline)copper(I), Cu1(dmp)2+, and of bis(2,9-dimethyl-4,7-diphenyl-1,10-phenanthrolinedisulfonate)cuprate(I), CuI(dpmp)23-, with copper(III)-oligopeptide complexes are quite rapid with rate constants varying from 2 × 104 M-1 s-1 to 2.5 × 108 M-1 s-1, indicating that outer-sphere electron transfer occurs. The cross exchange rate constants, k12, for the reactions CuIII(peptide) + CuIL2→k12 CuII(peptide) + CuIIL2, where L is dmp or dpmp2-, are determined for a series of copper(III) peptides, where the E°12 values vary from -0.11 to +0.32 V. The values of k12 for the reduction of copper(III) by CuI(dmp)2+ exhibit a correlation with E°12 consistent with the Marcus theory. This is not the case for the reductions with CuI(dpmp)23-, which have unusual behavior in two regards. First, the observed first-order rate constants reach limiting values as the concentration of excess reductant increases, but limiting values are not observed if Cu(III) is used in excess. Second, the k12 rate constants (obtained under conditions where the rate depends on both the Cu(III) and the Cu(I) concentrations) approach a limiting value of 106 M-1 s-1 and are independent of E°12. Neither anomalous behavior is observed for the CuI(dmp)2+ reactions with Cu(III) complexes.
