Crystal structure, magnetic properties and molecular orbital calculations of a binuclear copper(II) complex bridged by an alkoxo-oxygen atom and an acetate ion

Abstract

[Cu 2(L)(O 2CMe)]·(C 3H 7NO) (L=1,3-bis(2,hydroxy-3-meythoxybenzlidene)propan-2-ol) was synthesized and its crystal structure determined. (C 21H 22N 2O 7Cu 2)·(C 3H 7NO) monoclinic, space group P2 1/ c, a=9.7670(10), b=21.059(2), c=12.5750(10) Å, β=92.308(8)°, V=2584.4(4) Å 3, Z=4. The Cu(II) ions are linked by the alkoxide oxygen of the Schiff base ligand on the oxygen atoms of the acetate ion. The Cu⋯Cu distance and Cu–O–Cu angle are 3.154(2) Å and 107.0(2)°, respectively. Temperature-dependent magnetic susceptibility measurements of the complex show an intramolecular antiferromagnetic coupling in the dimeric Cu(II) core. The super-exchange coupling constant (−2 J) is 185.4 cm −1. Ab initio restricted Hartree–Fock (RHF) and semi-empirical extended Hückel molecular orbital calculations were performed for the explanation of the significant differences in antiferromagnetic interactions between homologous μ-alkoxo and acetate bridged dicopper(II) complexes. Ab initio restricted RHF calculations have shown that the acetate bridge and alkoxide bridge contribute to the magnetic interaction countercomplementary to reduce antiferromagnetic interaction.