Synthesis, Characterization and ESR Studies of New Copper(II) Complexes of Vicinal Oxime Ligands

Ethoxylacetyl oxime ligands [HL, (1) and H2L 1, (3)] react with copper(II) acetate monohydrate yield octahedral and square planar complexes, respectively. The complexes have been postulated due to elemental analyses, IR, UV-Vis. spectra, magnetic susceptibility, conductivity and ESR spectra. Molar conductance of the complexes in DMF indicates a non-ionic character. The ESR spectra of [(L)(2)Cu(H2O)(2)], (2) complex at room temperature and 77K are characteristic of an axial symmetry (d(x2-y2))with covalent bond character and have a large line width typical of dipolar interactions. However, [(L-1)Cu], (4) complex in the solid state showed spectra of marked broadening and loss of hyperfine splitting confirming spin-exchange interactions between the copper(II) sites. The spectrum of the doped copper(II) complex at room temperature showed super-hyperfine splitting from coordinated nitrogen atoms and it has an axial type (d(x2-y2)) with covalent bond character and an essentially square-planar arrangement around the copper(II) ion. The spectrum of [(L-1) Cu], (4) in frozen methanol at 77K was characteristic of the triplet state of a dimer species and the distance found between the two copper(II) centers was calculated and is equal to 4.8 angstrom.