Influence of ligand structure on the dimerization of copper(II) N-substituted hydroxamates according to EPR data

Abstract

Compounds CuL2, where L = R1N(O)–(O)CR2, R1 = C6H5, R2 = C6H5 (I); R1 = C6H5, R2 = CH3 (II); or R1 = 2,4,6-(CH3)3C6H2, R2 = CH3 (III) have been structurally studied by electron paramagnetic resonance (EPR) in methylene chloride. Spectra of two forms of the compounds, which according to the EPR data are mononuclear, are observed in all solutions at room temperature. In frozen solutions of complexes I and II, spectra of monomeric and dimeric forms of the complex are recorded; in a frozen solution of III, spectra of two monomeric forms of the complex. The absence of dimers in the frozen solution of III is explained by the presence of steric hindrances for the rapprochement of monomeric complexes. Relative concentrations of the forms and their magnetic resonance parameters have been determined using mathematical modeling of the shape of the EPR line.