Crystal structure and magnetic properties of the flexible self-assembled two-dimensional square network complex [Cu-2(mal)(2)(H2O)(2)(4,4 '-I-bpy)] (H(2)mal = malonic acid and 4,4 '-bpy=4,4 '-bipyridine)

The copper(II) complex [Cu-2(mal)(2)(H2O)(2)(4,4 ' -bpy)] (1) (H(2)mal = ma lonic acid and 4,4 ' -bpy = 4,4 ' -bipyridine) has been prepared and its st ructure determined by single crystal X-diffraction methods. Compound 1 has a two-dimensional square grid network structure. The square grids are stack ed parallel but in a staggered manner on each other along the c-axis, with an interlayer separation of 3.850(1) Angstrom. Each layer contains a large cavity of 15.784(1) x 15.784(1) Angstrom with each edge shared by one malon ate group and one 4,4 ' -bpy ligand and a small planar square of 4.644(1) x 4.644(1) A with Cu(II) ions and malonate groups at each corner and side, r espectively. Each copper atom is in a distorted square-pyramidal surroundin g with three carboxylate-oxygen atoms from two malonate groups and one nitr ogen atom from a 4,4 ' -bpy ligand building the equatorial plane and a wate r molecule in the axial position. Each 4,4 ' -bpy molecule exhibits the bis -monodentate bridging mode whereas the malonate simultaneously adopts the b identate (at one copper atom) and monodentate (at the adjacent copper atom) coordination modes. The bridging carboxylato exhibits the anti-syn coordin ation mode. The magnetic properties of 1 have been investigated in the temp erature range 1.9-300 K and they correspond to a dominant ferromagnetic cou pling through bridging malonato within the small square defined by four cop per(II) ions (J = + 12.4(1) cm(-1)) and much weaker intrasheet antiferromag netic coupling between copper(II) ions through bridging 4,4 ' -bpy (j(eff) = - 0.052(1) cm(-1)). (C) 2001 Elsevier Science B.V. All rights reserved.