Toward the recognition of enolates/dicarboxylates:: Syntheses and X-ray crystal structures of supramolecular architectures of Zn(II)/Cd(II) using 2,2′-biimidazole

Six coordination complexes, {[M(H(2)biim)(2)(H2O)(2)]X-2+(2-)}-(nH(2)O) [(H(2)biim = biimidazole); {M = Zn (1), Cd (2); X = squarate; = 2}: {M = Zn (3), Cd (4); X = glutarate; n = 4}; {M = Zn (5), X = succinate; n = 4}; {M = Cd (6), X = succinate; n = 2}], have been synthesized and characterized by X-ray single-crystal structure determination. The crystal packing of all the complexes reveals that cationic [M(H(2)biim)(2)(H2O)(2)](2+) fragments are self-assembled by recognition of enolate/dicarboxylate anions by the uncoordinated N-H motif of H(2)biim resulting in one-dimensional supramolecular ribbons. The parallel ribbons are stitched across by water-mediated hydrogen bonding and pi-pi interactions leading to two types of topology: one is a two-dimensional brick wall (1, 2, 6), and the other is a three-dimensional architecture (3-5). In two structures (1, 2) interesting sandwiched pi-pi interactions were observed.