Electrode Potentials of Nickel((III,II)-Peptide Complexes

Abstract

Standard electrode potentials from 0.96 to 0.79 V are determined for a series of 30 NiIII,II-peptide couples in aqueous solution. The values of E° decrease with the number of deprotonated peptide groups and can increase with bulky C substituents depending upon their position in the amino acid residues. Histidine-containing peptide complexes have relatively high electrode potentials. Ligand effects on the values of E° are much smaller for the nickel peptides than for the corresponding copper peptides, which is indicative of the relative advantages in ligand field stabilization of d8 vs. d9 and d7 electronic configurations in the square-planar and tetragonal environments of the peptide complexes. © 1977, American Chemical Society. All rights reserved.