Synthesis and crystal structure of poly[(3-amino-1,2,4-triazole)(μ(3)-1H-benzimidazole-5,6-di-carboxyl-ato)cobalt(II)].

The asymmetric unit of the title coordination polymer, [Co(C(9)H(4)N(2)O(4))(C(2)H(4)N(4))] (n) or [Co(L (1))(L (2))] (n) , consists of one crystallographically independent Co(2+) centre, one L (1) (2-) ligand and one L (2) ligand (L (1) = 1H-benzimidazole-5,6-di-carb-oxy-lic acid, L (2) = 3-amino-1,2,4-triazole). The Co(2+) centre is coordinated by two carboxyl-ato-O atoms from two independent L (1) (2-) ligands and two nitro-gen atoms from L (2) and another L (1) ligand. Thus, the metal center adopts a four-coordinate mode, forming a tetra-hedral geometry. Inter-estingly, through the combination of two L (1) (2-), two L (2) ligands and two Co(2+) ions, a basic repeating unit is constructed, resulting in the formation of a one-dimensional straight chain structure. These chains are further expanded to the final three-dimensional framework via N-H⋯O hydrogen-bonding inter-actions.