Hydrogen-bonded one-dimensional zigzag pairs and helical dimers in an enolic 4-terpyridone based nickel(II) dicyanamide supramolecule

The synthesis, characterization, and crystal engineering of an enolic 4-terpyridone (L-1) based three-dimensional supramolecule, [Ni-II(L-1)(2)](dicyanamide)(2)(.)2H(2)O, have been described. One aim of this study has been to demonstrate that the H-O-pyridine-M-pyridine-O-H moiety in [M(L-1)(2)](n+) can participate in extended hydrogen-bonding interactions and, thus, can act as a building block to generate supramolecular frameworks. A second objective has been to stabilize a coordination compound containing dicyanamide in only noncoordinating form, which in turn would get involved in extended hydrogen bondings. The title compound crystallizes in the triclinic space group P (1) over bar with the following unit cell parameters: a = 8.7482(9) angstrom, b = 9.0810(7) angstrom, c = 20.5411(18) angstrom, alpha = 92.143(7)degrees, beta = 93.011(8)degrees, gamma = 94.315(7)degrees, and Z = 2. In this compound, the metal center is hexacoordinated by the three pyridine nitrogens of each of the two enolic 4-terpyridones. A number of hydrogen bonds, involving the H-O-pyridine-M-pyridine-O-H moiety and a few C-H hydrogens of the dication as well as the two noncoordinating dicyanamide anions and two waters of crystallization, results in the generation of three-dimensional assembly in this molecule. The fragment analyses reveal the existence of helical dimers and a pair of one-dimensional chains. The overall three-dimensional structure of the title compound can be considered as the stitching of the two-dimensional sheets, which consist of the interlinked pairs of one-dimensional chains, by the second type of one-dimensional chains created due to the attachment of the helical dimers, which in turn consist of the hydrogen-bonded monomers.