Hydrogen bond directed 1D to 3D structures of square-planar Ni(II) complexes and their antimicrobial studies

A series of new mononuclear nickel(II) complexes derived from dicyandiamide (dcda) and Ni(ClO4)(2)center dot 6H(2)O in various alcohol solutions was synthesized and characterized. Nucleophilic addition of the alcohol to the nitrile (-C equivalent to N) group of the dcda was observed in all complexes, yielding [Ni(L-Me)(2)](ClO4)(2) (1), [Ni(L-Et)(2)](ClO4)(2) (2), [Ni(L-Pr-n-)(2)](ClO4)(2) (3) and [Ni(L-Bu-n)(2)](ClO4)(2) (4) in methanol, ethanol, n-propanol and n-butanol, respectively. The complexes were characterized by microanalysis (CHN), IR and mass spectroscopies. Crystal structures of the complexes (2-4) were determined by single crystal X-ray diffraction studies. In the structures of the synthesized complexes, the Ni(II) ion is in a square planar arrangement being coordinated to four nitrogen atoms of two in situ formed ligands. Hydrogen bonding directed packing of the structures were analysed. The structurally characterized complexes were then screened for their antibacterial activity against three different bacterial strains (Lactococcus lactis, Streptococcus thermophilus and Escherichia coli) using disk diffusion and spectrophotometric methods. The nickel(II) complexes displayed higher activity than dicyandiamide against the same microorganisms under identical experimental conditions. (C) 2017 Elsevier B.V. All rights reserved.