Syntheses, crystal structures and antibacterial activities of six cobalt(II) pyrazole carboxylate complexes with helical character

Six new cobalt(II) complexes, [Co-1.5(HL)(3)(H2O)(3)]center dot H2O (1), [Co(HL)(2)(2,2'-bipy)] (2), [Co(HL)(2)(phen)] (3), [Co(HL)(2)(H2O)(2)]center dot(4,4'-bipy) (4), [Co(L)(4,4'-bipy)(H2O)]center dot H2O (5) and [Co(L)(4,4'-bipy)(0.5)(H2O)]center dot 1.5 H2O (6), (H2L = 5-chloro-1-phenyl-1H-pyrazole-3,4-dicarboxylic acid; 2,2'-bipy = 2,2'-bipyridine; phen = 1,10-phenanthroline; 4,4'-bipy = 4,4'-bipyridine) have been synthesized and characterized. Complexes 1-4 exhibit monomeric structures, but with the help of hydrogen bonding interactions all extend into 3D supramolecular networks with double-, single-, single- and quadruple-stranded helical chains, respectively. Complex 5 displays a layer structure comprising two kinds of single-stranded helical chains, and complex 6 also exhibits a layer structure, however, this consists of double-stranded and mesa-helical chains; the 2D structures of complexes 5 and 6 are further assembled into 3D and 2-fold interpenetrating 2D supramolecular networks through hydrogen bond interactions, respectively. The thermal stabilities of the title complexes have been discussed. Furthermore, the antibacterial activities of the title complexes against tested bacteria were studied and compared to the activities of free ligands. (c) 2012 Elsevier Ltd. All rights reserved.