Cadmium(II) complexes with 3,5-di(1H-imidazol-1-yl)benzoate: topological and structural diversity tuned by counteranions

Four new coordination polymers [Cd(L)(OAc)]center dot H2O (1), [Cd(L)(mu(2)-OH)]center dot H2O (2), [Cd-2(L)(2)(mu(3)-SO4)(H2O)(2)]center dot 5H(2)O (3) and [Cd(L)(2)]center dot H2O (4) with different structures and topologies were obtained by solvo/hydrothermal reactions of varied Cd(II) salts with 3,5-di(1H-imidazol-1-yl) benzoic acid (HL) and 1,3-bis(4-pyridyl)propane (bpp). The structures of 1-4 were characterized by single-crystal X-ray diffraction analysis and the results showed that no bpp ligands were incorporated in the resulting complexes, and more interestingly, complexes 1-3 were obtained by reactions of metal to ligand ratio of 1 : 1, however, when the reactions were carried out with a metal to ligand ratio of 1 : 2, the resulting complexes had the same structure, namely [Cd(L)(2)]center dot H2O (4). In contrast to the 2D network with 6(3)-hcb topology of complex 1 with acetate as terminal ligand, complex 2 is a 3D(4,6)-connected net with mu(2)-hydroxyl bridging group. Complex 3 is an unprecedented 3D self-penetrating (3,4,5)-connected net with each sulfate as a mu(3)-bridge to link three Cd(II) atoms, and complex 4 is a 3D self-penetrating (3,5)-connected net formed by two alternate chiral helical chains linking 2-fold interpenetrating 2D (4,8(2)) nets. The results showed that the L- ligand has varied coordination modes and the counteranions have a great impact on the structure of the complexes.