Syntheses and characterizations of square planar nickel(II) complexes with pendant ligands: Examples of bi-dentate bonding modes of potentially tri- and tetra-dentate Schiff bases

Four square planar nickel(II) complexes, [Ni(L-1)(2)] (1), [Ni(L-2)(2)] (2), [Ni(L-3)(NHEt2)] (3) and [Ni(han)(2)] (4), where HL1 = 1-(3-hydroxypropyliminomethyl)naphthalene-2-ol, HL2 = 1-(5-hydroxy-3-oxapentyliminomethyl)naphthalene-2-ol, H2L3 = 2-(2-hydroxy-3-methoxybenzylideneamino)phenol and Hhan = 1-hydroxy-2-acetonaphthone, have been prepared and characterized by elemental analyses. IR and UV-Vis spectroscopy and single crystal X-ray diffraction studies. The potential tridentate ONO-donor ligand HL1 and potential tetradentate ONOO-donor ligand HL2 coordinate the nickel(II) only through the amine N and phenolic O to form complexes 1 and 2 respectively, i.e. the ligands act as pendant ligands. On the other hand, the potential tetradentate ONOO-donor Schiff base H2L3 coordinates the nickel(II) only through the amine N atom and two phenolic O atoms to form complex 3, i.e. it also acts as pendant ligand. Complex 4 is formed by the reaction of nickel(11) with 1-hydroxy-2-acetonaphthone. H-bonding, C-H center dot center dot center dot pi and pi center dot center dot center dot pi interactions form supra-molecular assembly. (C) 2013 Elsevier Ltd. All rights reserved.