ESR-SPECTRA OF CU(II) COMPLEXES WITH BIOLOGICALLY IMPORTANT LIGANDS AT 77-K

Low-temperature powder ESR studies of Cu(sal)2·4H2O, Cu(sal)2(2-pycar)2 and Cu(sal)2(3-pycar)2 (sal = salicylate ion, pycar = pyridylcarbinol) are reported. Spin-Hamiltonian parameters (obtained from experimental spectra, by the nonlinear optimization method) indicate, that the unpaired electron is in the antibonding ψb molecular orbital in all complexes, which clearly demonstrates an elongated tetragonal bipyramidal coordination around Cu(II). Spin-Hamiltonian parameters are used to estimate the molecular orbital coefficients for the Cu(sal)2(2-pycar)2 and Cu(sal)2(3-pycar)2. © 1990.