Spectroscopic and Redox Properties of Pseudotetrahedral Copper(II) Complexes. Their Relationship to Copper Proteins

Abstract

Visible absorption and ESR spectra and redox potentials have been examined for a series of pyrrole-2-carboxaldehyde Schiff base copper(II) complexes, whose coordination stereochemistry is distorted to varying extents from square-planar to pseudotetrahedral geometry. There are smooth correlations among d–d band energies, A║, g║, A0, and g0 values. As the dihedral angle between chelate rings increases from 0 through 90°, g║ increases, |A║| decreases in an antiparallel fashion, and redox potentials shift systematically to more positive values. These observations are consistent with tetrahedral distortion at the metal binding sites of blue copper proteins. © 1977, American Chemical Society. All rights reserved.