Synthesis, crystal structure, spectroscopic characterisation and magnetic properties of [Cu_2(BIBM)_2]·4H_2O (BIBM = bis(2-imidazolylbis(methoxycarbonyl)methylmethane)

摘要

The structure adn spectroscopic and magnetic properties of bis(#mu#-1, 2, 3-oxalato)bis[bis(2-imidazolyl)bis(methoxycarbonyl)·methylmethane]dicopper(II) tetrahydrate are described. The compound is built of centrosymmetric neutral dimeric [Cu_2(BIBM)_2(C_2O_4)_2] entities linked through hydrogen bonds involving water molecules and oxalate groups. In the dimeric unit the two centrosymmetrically related copper — which are involved in CuN_2O_2O'_2 chromophores lying in an elongated octahedral environment —are bridged through the oxalate group which acts in a bidentate-monodentate (#pu#-1, 2, 3) fashion. Both electronic and EPR spectr are indicative of an essentially d_x2-y2 ground state for the copper(II) ions. Magnetic susceptibility measurements in the range 1.8-200 K show very weak antiferromagnetic exchange between the dopper(II) ions (2J = -0.35 cm~-1). This feature is discussed on the basis of the relative orientation of the coordination polyhedron around the metal atom and the bridging network.