INORGANIC CHEMISTRY | RESEARCH ARTICLE Nickel(II)-oxaloyldihydrazone complexes: Characterization, indirect band gap energy and antimicrobial evaluation

1 Abstract: A series of oxaloyldihydrazone ligands was prepared essentially by the usual condensation reaction between oxaloyldihydrazide and different aldehydes e.g. salicylaldehyde, 2-hydroxy-1-naphthaldehyde, 2-hydroxyacetophenone and 2-methoxy-benzaldehyde in 1:2 M ratio. The formed compounds were purified to give bis(salicylaldehyde)oxaloyldihydrazone (L 1 ), bis(2-hydroxy-1-naphthaldehyde) oxaloyldihydrazone (L 2 ), bis(2-hydroxyacetophenone)oxaloyldihydrazone(L 3 ) and bis(2-methoxy-benzaldehyde)oxaloyldihydrazone (L 4 ). All the oxaloyldihydrazones (L 1 -L 4 ) and their relevant solid nickel(II) complexes have been prepared and struc- turally characterized on the basis of the elemental analyses, spectral (UV-vis, IR, mass and 1 H NMR), magnetism and thermal (TG) measurements. The dihydrazones coordinate to the metal center forming mononuclear complexes with L 1 , L 3 and L 4 in addition to binuclear complex with L 2 . The metal center prefers tetrahedral stereo- chemistry upon chelation. The optical indirect band gap energy for all compounds underlies the range of semiconductor materials. The prepared ligands and their metal complexes have been assayed for their antimicrobial activity against fungi as well as Gram-positive and Gram-negative bacteria. The resulting data indicate the ability of the investigated compounds to inhibit the growth of some micro-or- ganisms, where L 2 showed the highest activity among all the compounds. Minimum inhibitory concentration (MIC) of L 2 against the growth of five micro-organisms was