Anion and symmetry effects on the electron spin resonance spectra of copper complexes. Part III

ESR spectra of calcium copper acetate hexahydrate and tetra-(6-aminohexanoic acid) copper(II) diperchlorate have been recorded for solutions in methanol, ethanol, dimethylformamide and pyridine at 295 and 77 K. The coordination around the Cu(II) ion in both there complexes is of dodecahedral symmetry, comprising both an elongated and a compressed tetrahedron of oxygen atoms. The spin-Hamiltonian parameters of the complexes in ethanol, methanol and dimethylformamide, obtained after fitting the spectra to an axially-symmetric spin-Hamiltonian, indicate an effectively flattened tetrahedron alone. In contrast, the spectra recorded for solutions in pyridine indicate octahedral coordination caused by substitution of the oxygen atoms by pyridine.