Relation between magnetic, spectroscopic and structural properties of binuclear copper(II) complexes of pentadentate Schiff-base ligand, semi-empirical and ab-initio calculations

Abstract

The synthesis and characterization of [Cu-2(L-1)(3,5 prz)] (L-1=1,3-Bis(2-hydroxy-3,5-chlorosalicylideneamino)propan-2-ol) 1 and of [Cu-2(L-2)(3,5 prz)] (L-2=1 3-Bis(2-hydroxy-bromosalicylideneamino)propan-2-ol) 2 are reported. The compounds were studied by elemental analysis, infrared and electronic spectra. The structure of the Cu-2(L-1)(3,5 prz)] complex was determined by x-ray diffraction. The magnetochemical characteristics of these compounds were determined by temperature-dependent magnetic susceptibility measurements, revealing their antiferromagnetic coupling. The superexchange coupling constants are 210 cm(-1) for 1 and 440 cm(-1) for 2. The difference in the magnitude of the coupling constants was explained by the metal-ligand orbital overlaps and confirmed by ab-initio restricted Hartree-Fock (RHF) calculations. In order to determine the nature of the frontier orbitals, Extended Huckel Molecular Orbital (EHMO) calculations are also reported.