X-Ray Absorption Near Edge Structure Study and DV-Xα Calculations on Some Square-planar Copper(II) Complexes with Macrocyclic Ligands

Abstract

Abstract The electronic states of copper(II) ions containing the square-planar tetraaza or diazadioxa macrocyclic copper(II) complexes abbreviated as Cu(N4-Paen), Cu(N4-[14]-ph-NO2>, Cu(N4-[14]-Me,-NO2), Cu(N4-[14]-Me), Cu(N2O2-ph), Cu(N2O2-ph-Me), Cu(N2O2-Me,-ph- NO2), Cu(N2O2-Me), where Pa, [14], ph, and Me represent pyrrolemethylamine, 14-membered macrocycle, phenyl, and methyl groups, respectively, were investigated in the solid state by means of X-ray absorption near edge structure (XANES). The peaks in the measured XANES spectra shifted to the lower energy side with increasing the electron density of a central copper(II) ion. The molecular orbital calculations for the tetraaza copper(II) complexes were carried out by the DV-Xα method, and their theoretical XANES spectra, atomic-charges, and bond-charges were estimated. The peaks of the measured XANES spectra could be assigned to the electron transition mainly from Culs orbital to Cu4p and/or Cu4s orbitals from comparison with the theoretical spectra. The values of the atomic-charge of the copper atoms and the bond-charge of the Cu-N bonds in the complexes are consistent with their peak positions in the measured XANES spectra.