Polycarboxylate anions effect on the structures of a series of transition metal-based coordination polymers: Syntheses, crystal structures and bioactivities

Five novel transition metal (Zn, Cd, Mn and Co)-based coordination polymers 1-5 with a flexible rodlike N, N'-donor ligand (bbi = 1,1'-(1,4-butanediyl)bis(imidazole)) and four O-donor polycarboxylate anions (H(2)oxa = oxalic acid; H(2)fma = fumaric acid; H(2)bpdc = 2,2'-biphenyldicarboxylic acid; H(4)cit = citric acid) have been successfully synthesized and characterized by elemental analysis, IR spectra, and X-ray diffraction, namely {[Zn(bbi)(3)(NO3)]Br center dot 2H(2)O}(n) (1), [Zn(oxa)(bbi)](n) (2), [Mn(fma)(2)(bbi)(2)(H2O)(2)](n) (3), [Cd-2(bpdc)(2)(bbi)(2)](n) (4) and {[Co-8(cit)(4)(bbi)(6)(H2O)(10)]center dot 7H(2)O}(n) (5). Compounds 1-5 display various coordination motifs due to different conformations of the bbi ligand, at the same time, owing to diverse coordination modes of the polycarboxylate ligands. And the effect of the polycarboxylate ligands plays important roles in the construction of extended networks. Compounds 1, 2 and 5 all exhibit 2D layer structures, in which 1 displays a 3-fold interpenetration framework containing 2D networks with (6,3) topology and 2 is a 2D structure with (4,4) topology. Compound 5 contains a 2D 4(4) grid-like layer with (4(4).6(2)) topology composed of octanuclear cobalt clusters. Two high-dimensional compounds (3D) with a microporous network, containing 1D flower-like metal-organic motifs interlinked by bbi ligands for 4 and a 3-fold interpenetrating network with 6(6)-dia topology by considering the manganese ion as a four-connected node for 3, are observed. The biological activities of the title compounds have been studied. The results indicate that 1-5 exhibit certain selective antimicrobial activities against Escherichia coli, Staphylococcus aureus and Enterobacter aerogenes, besides, 5 exhibits more obvious radical-scavenging activities than that of bbi ligand. Furthermore, Solid-state properties of thermal stability and the photoluminescence properties at room temperature for these crystalline materials have also been investigated. (C) 2012 Elsevier B. V. All rights reserved.