K-XANES Investigations of Some Copper(II) Complexes

Abstract

X-ray absorption near edge structure (XANES) measurements on K edges of copper are employed to study the structure of four copper complexes viz., Cu(dmg)2 [bis-dimethylglyoximato copper(II)]; Cu(sal)2 [bis-salicylaldoximato copper(II)]; Cu(dmg)2Cl2 [chlorine adduct of Cu(dmg)2]; and Cu(sal)2Cl2 [chlorine adduct of Cu(sal)2]. The present XANES studies reveal that metal-ligand bond in Cu(dmg)2 is much more covalent than in Cu(sal)2. For both chlorine adducts, a linear polymeric structure, in which the planar Cu(dmg)2 or Cu(sal)2 units are joined by Cl-Cl molecule, is suggested. The higher values of the edge-shifts in the two chlorine adducts have been attributed to the six coordinate geometry in Cu(dmg)2Cl2 and Cu(sal)2Cl2. The small absorption maxima appearing on the low-energy sides of the main K edge and the principal absorption peak A have been assigned transitions 1s → 3d (empty or partially filled orbitals) and 1s → 4s* respectively.