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

[Cu2(L)(O2CMe)]·(C3H7NO) (L ¼ 1,3-bis(2,hydroxy-3-meythoxybenzlidene)propan-2-ol) was synthesized and its crystal structure determined. (C21H22N2O7Cu2)·(C3H7NO) monoclinic, space group P21=c, a ¼ 9:7670ð10Þ; b ¼ 21:059ð2Þ; c ¼ 12:5750ð10Þ A ° , b ¼ 92:308ð8Þ8; V ¼ 2584:4ð4Þ A ° 3, Z ¼ 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) A ° and 107.0(2)8, respectively. Temperature-dependent magnetic susceptibility measurements of the complex show an intramolecular antiferromagnetic coupling in the dimeric Cu(II) core. The superexchange coupling constant ð22JÞ is 185.4 cm21. Ab initio restricted Hartree–Fock (RHF) and semi-empirical extended Hu¨ckel molecular orbital calculations were performed for the explanation of the significant differences in antiferromagnetic interactions between homologous m-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. q 2004 Elsevier B.V. All rights reserved