Nickel(II) complexes with N,N,O-donor Schiff bases. Self-assembly to two-dimensional network via hydrogen bonding

The syntheses, characterization and crystal structures of two mononuclear nickel(II) complexes are described. Reactions of Ni(O2CCH3)(2)center dot 4H(2)O with the Schiff bases derived from 2-pyridinecarbaldehyde and ortho-aminophenol (Hpaap) and 2-pyridinecarbaldehyde and ortho-aminobenzoic acid (Hpaab) in methanolic media afford the complexes in good yields. The elemental analysis, magnetic moments, and spectral features of the complexes are consistent with the formulae [Ni(paap)(2)]center dot CH3COOH center dot H2O and [Ni(paab)(2)]center dot 2H(2)O. Crystal data for [Ni(paap)(2)]center dot CH3COOH center dot H2O: monoclinic, P2(1)/c, a = 9.675(2) angstrom, b = 17.109(5) angstrom, c = 14.403(4) angstrom, beta = 92.903(11)degrees, V = 2381.1(11) angstrom(3), and Z = 4 and for [Ni(paab)(2)]center dot 2H(2)O: triclinic, P (1) over bar, a = 9.834(3) angstrom, b = 11.319(3) angstrom, c = 13.130(4) angstrom, alpha = 84.68(3), beta = 67.54(3), gamma = 85.49(2)degrees, V = 1343.4(6) angstrom(3), and Z = 2. In each complex, two tridentate monoanionic meridionally spanning ligands form a distorted octahedral N4O2 coordination sphere around the metal ion. In [Ni(paap)(2)]center dot CH3COOH center dot H2O, two metal coordinated phenolate-O atoms are hydrogen bonded to CH3COOH and H2O, respectively. Intramolecular C-H center dot center dot center dot O interactions involving the water molecule and the C-H from azomethine and aromatic fragments lead to a two-dimensional network of [Ni(paap)(2)]center dot CH3COOH center dot H2O in the crystal lattice. An uncoordinated carboxylate O-atom in [Ni(paab)(2)]center dot 2H(2)O is hydrogen bonded to both water molecules. One of the water molecules is again hydrogen bonded to the corresponding symmetry related water molecule forming a dimer. The azomethine groups and the metal coordinated carboxylate-O atoms in [Ni(paab)(2)] are involved in intermolecular C-H center dot center dot center dot O interactions forming a chain-like arrangement of the molecules. The water dimers act as bridges between these chains and a two-dimensional network of [Ni(paab)(2)]center dot 2H(2)O is formed.