A One-dimensional Cobalt Coordination Polymer Based on Biphenyl-2,3,3?,5?-tetracarboxylic Acid and N-donor Ancillary Ligands: Crystal Structure and Magnetic Property

Hydrothermal reactions of biphenyl-2,3,3?,5?-tetracarboxylic acid(H4bptc) with cobalt salt in the presence of 1,4-bis(2-pyridylmethyl)piperazin(bpmp) afforded one novel coordination polymer, namely, [Co(H2bptc)(bpmp)0.5(H2O)]n(1). Its structure was established by single-crystal X-ray diffraction analysis and further characterized by elemental analysis, IR spectra and TG analysis. Complex 1 crystallizes in monoclinic, space group P21/c with a = 11.4839(11), b = 16.6690(16), c = 11.5559(11) ?, V = 2201.8(4) ?3, Mr = 539.35, Dc = 1.627 g/cm3, μ(MoK α) = 0.841 mm-1, F(000) = 1108, Z = 4, the final R = 0.0309 and w R = 0.0705 for 4090 observed reflections(I > 2σ(I)). Complex 1 displays a one-dimensional(1D) chain bridged by bpmp. Two carboxylic groups of H4 bptc ligand adopt μ01-η1:η1 and μ1-η1:η coordination modes to bridge adjacent Co(Ⅱ) ions together with bpmp ligand to give alternately arranged left- and right-handed helical chains. In addition, variable-temperature magnetic susceptibility measurements indicate that complex 1 shows weak antiferromagnetic interactions between the adjacent Co(Ⅱ) ions.