Three one-dimensional coordination polymers based on 1,1'-bis(pyridin-4-ylmethyl)-2,2'-bi-1H-benzimidazole and HgX2 (X = Cl, Br and I).

A new 2,2'-bi-1H-benzimidazole bridging organic ligand, namely 1,1'-bis(pyridin-4-ylmethyl)-2,2'-bi-1H-benzimidazole, C26H20N6, L or (I), has been synthesized and used to create three new one-dimensional coordination polymers, viz. catena-poly[[dichloridomercury(II)]-μ-1,1'-bis(pyridin-4-ylmethyl)-2,2'-bi-1H-benzimidazole], [HgCl2(C26H20N6)]n, (II), and the bromido, [HgBr2(C26H20N6)]n, (III), and iodido, [HgI2(C26H20N6)]n, (IV), analogues. Free ligand L crystallizes with two symmetry-independent half-molecules in the asymmetric unit and each L molecule resides on a crytallographic inversion centre. In structures (II)-(IV), the L ligand is also positioned on a crystallographic inversion centre, whereas the Hg centre resides on a crystallographic twofold axis. Compound (I) adopts an anti conformation in the solid state and forms a two-dimensional network in the crystallographic bc plane via π-π and C-H...π interactions. The three Hg(II) coordination complexes, (II)-(IV), have one-dimensional zigzag chains composed of L and HgX2 (X = Cl, Br and I), and the Hg(II) centres are in a distorted tetrahedral [HgX2N2] coordination geometry. Complexes (III) and (IV) are isomorphous, whereas complex (II) displays an interesting conformational difference from the others, i.e. a twist in the flexible bridging ligand.