Hexa- and polynuclear copper(II) coordination compounds based on the carbonato bridge: Synthesis, crystal structures and magnetic properties

The crystal structures of polynuclear copper(II) complexes containing the bidentate bpy ligand (bpy = 2,2'-bipyridine) with varied coordination modes of the carbonato bridging ligand, a hexanuclear compound [Cu-6(bpy)(10)(mu-OH)(2)(mu-CO3)(2)](CF4SO3)(6)(DMF)(2)(H2O)(4) (1) and a polymeric compound {[Cu-3(bpy)(3)(mu-OH)(2)(mu-CO3)(2)](H2O)(6.5)} (2) are described. Compound 1 consists of the di-mu-hydroxidobis(2,2'-bipyridine)copper(II) groups coordinated with trans-axially at each copper atom by [mu-carbonato-bis(bpy)copper(II)] moieties, forming a hexanuclear copper(II) compound. Each copper(II) ion has a distorted square-pyramidal environment in which three Cu(II) atoms are linked through oxygen atoms of the bridged ligand by the mu(3)-eta(2):eta(1)-CO3 coordinated mode. Compound 2 consists of two independent di-mu-hydroxido-bis(2,2'-bipyridine)copper(II) dinuclear units which are connected to the central moiety by two different coordination modes of the carbonate bridging ligands, mu-eta(1):eta(1) (anti-anti) and mu-eta(2):eta(1)-CO3 configurations. Each Cu(II) ion has a distorted square-pyramidal geometry. The repeating units give rise to a one-dimensional chain along b-axis. The lattice structures are stabilized by stacking interaction between pyridine groups of bpy chelated ligands of different units. The spectroscopic properties (IR, Reflectance and EPR spectra) and the magnetic susceptibility data of both compounds are investigated. (C) 2007 Elsevier B.V. All rights reserved.