Copper(II)-methylmalonate complexes with unidentate N-donor ligands: Syntheses, structural characterization and magnetic properties

Two new methylmalonate-bridged copper(II) complexes with the formulas [Cu(3-Ipy)(Memal)(H2O)] (1) and [Cu(2,4'-bpy)(Memal)(H2O)] center dot 3H(2)O (2) [Memal = methylmalonate dianion, 3-Ipy = 3-iodopyridine, 2,4'-bpy = 2,4'-bipyridine] have been synthesized and characterized by X-ray diffraction. Both compounds crystallize in the monoclinic space group P2(1)/n and Z = 4, with unit cell parameters a = 8.5874(13)angstrom, b = 7.1738(14)angstrom, c = 19.093(5)angstrom, beta = 99,509(15)degrees in 1 and a = 17.375(4)angstrom, b = 7.3305(14)angstrom, c = 14.247(3)angstrom, beta = 111.409(15)degrees in 2. The structures of 1 and 2 consist of zigzag chains of anti-syn carboxylate-bridged copper(II) ions running along the b direction. The pyridine-like ligands occupy one equatorial position of the copper environment avoiding the formation of the sheet-like arrangement observed in previously reported Memal complexes. The chains are grouped together in hydrophilic layers through hydrogen bonds and the layers are pillared through the 3-Ipy (1) and 2,4'-bpy (2) ligands which are stacked through pi-pi interactions involving alternatively aromatic ligands from two adjacent chains. Magnetic susceptibility measurements of both compounds in the temperature range 2-290 K show the occurrence of intrachain ferromagnetic interactions between the copper(II) ions [J = +2.66(2) cm(-1) (1) and J = +2.62(2)cm(-1) (2)]. (C) 2009 Elsevier Ltd. All rights reserved.