Robust heteromeric hydrogen-bonded self-assemblies based on [M(H2biim)2(H2O)n]2+ (M = Cd2+, Co2+Zn2+ n=1, 2) building blocks and carboxylates

Four new complexes [Zn(H(2)biim)(2)(H2O)(2)](Hbdc)(2). (H(2)biim)(.)2H(2)O (1), [Zn(H(2)biim)(2)(H2O)](bdc)(CH3OH)-C-. (2), [Co(H(2)biim)(2)(H2O)(2)](Hbtc)(.)4H(2)O (3) and [Cd(H(2)biim)(2) (H2O)(bdc)](H2O)-H-. (4) (where H(2)biim = 2,2'-biimidazole, bdc = 1,3-benzenedicarboxylate and btc = 1,3,5-benzenetricarboxylate) have been synthesized and characterized by single-crystal X-ray diffraction. The [M(H(2)biim)(2)(H2O)(n)](2+) building blocks are assembled with carboxylates via charge-assisted N-(HO)-O-... and O-(HN)-N-... hydrogen bonds ((NO)-O-... = 2.607 similar to 2.926 angstrom, angle N-H-O = 151 similar to 176 degrees) into 1-D ribbons (1-3) and 3-D network (4). The ribbons are further arranged into 3-D networks via hydrogen bonds between carboxylate and water molecules as well as the free H2biim molecule (1) or methanol molecule (2). In complex 2, the CH3OH molecules are clathrated in the cavities. The results show that three robust heteromeric hydrogen-bonded synthons, namely R-2(2)(9), R-2(2)(7) and C(4)[R-2(2)(9)], can be exploited to assemble the [M(H(2)biim)(2)(H2O)(n)](2+) (M = Cd, Co and Zn, n = 1, 2) building blocks with dicarboxylates and tricarboxylate into multi-dimensional networks.