Synthesis, characterization and ESR studies of new copper(II) complexes of vicinal oxime ligands

Abstract

Ethoxylacetyl oxime ligands [HL, (1) and H2L1, (3)] react with copper(II) acetate monohydrate yield octahedral and square planar complexes, respectively. The complexes have been postulated due to elemental analyses, IR, UVVis. spectra, magnetic susceptibility, conductivity and ESR spectra. Molar conductance of the complexes in DMF indicates a non-ionic character. The ESR spectra of [(L)2Cu(H2O)2], (2) complex at room temperature and 77K are characteristic of an axial symmetry (dx2-y2) with covalent bond character and have a large line width typical of dipolar interactions. However, [(L1)Cu], (4) complex in the solid state showed spectra of marked broadening and loss of hyperfine splitting confirming spinexchange 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 (dx2-y2) with covalent bond character and an essentially square-planar arrangement around the copper(II) ion. The spectrum of [(L1)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 Å.