Hydrogen-Bonded One-Dimensional Zigzag Pairs and Helical Dimers in an Enolic 4-Terpyridone Based Nickel(II) Dicyanamide Supramolecule

Abstract

The synthesis, characterization, and crystal engineering of an enolic 4-terpyridone (L1) based three-dimensional supramolecule, [NiII(L1)2](dicyanamide)2·2H2O, have been described. One aim of this study has been to demonstrate that the H−O−pyridine−M−pyridine−O−H moiety in [M(L1)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 P1̄ with the following unit cell parameters: a = 8.7482(9) Å, b = 9.0810(7) Å, c = 20.5411(18) Å, α = 92.143(7)°, β = 93.011(8)°, γ = 94.315(7)°, 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.