A new copper(II) coordination polymer containing chains of interconnected paddle-wheel antiferromagnetic clusters

The construction of supra­molecular architectures based on inorganic–organic coordination frameworks with weak noncovalent inter­actions has implications for the rational design of functional materials. A new crystalline binuclear copper(II) one-dimensional polymeric chain, namely catena-poly[[[tetra­kis­(μ-4-aza­niumyl­butano­ato-κ2O:O′)dicopper(II)(Cu—Cu)]-μ-chlorido-[di­aqua­dichlo­rido­copper(II)]-μ-chlorido] bis­(perchlorate)], {[Cu3Cl4(C4H9NO2)4(H2O)2](ClO4)2}n, was obtained by the reaction of 4-amino­butyric acid (GABA) with CuCl2·2H2O in aqueous solution. The structure was established by single-crystal X-ray diffraction and was also characterized by IR spectroscopy and magnetic measurements. The crystal structure consists of [{Cu2(GABA)4}{CuCl4(H2O)2}]+ cations and isolated perchlorate anions. Two symmetry-related CuII centres are bridged via carboxyl­ate O atoms into a classical paddle-wheel configuration, with a Cu...Cu distance of 2.643 (1) Å, while bridging Cl atoms complete the square-pyramidal geometry of the metal atoms. The Cl atoms connect the paddlewheel moieties to a second CuII atom lying on an octa­hedral site, resulting in infinite helical chains along the c axis. The packing motif exhibits channels containing free perchlorate anions. The crystal structure is stabilized by hydrogen bonds between the perchlorate anions, the coordinated water mol­ecules and the ammonium groups of the polymeric chains. The magnetic analysis of the title compound indicates a nontrivial anti­ferromagnetic behaviour arising from alternating weak–strong anti­ferromagnetic coupling between neighbouring CuII centres