Ligational behavior of N-substituted acid hydrazides towards transition metals and potentiation of their microbiocidal activity

Abstract

New complexes of Cu(II), Ni(II), and Co(II) with 3-benzoyl-1-[2-N-(substituted-2′-thienyl methylmethylene/methylene)] prop-2-ene-1-oic acid hydrazides have been synthesized and characterized by elemental analysis, molecular weight determination, molar conductance, and magnetic moment and spectroscopic techniques. Conductance measurements indicate the nonionic nature of the complexes. From the spectroscopic studies, it has been concluded that the N-substituted acid hydrazides act as tridentate ligands forming an ONS conjugate system and coordinating with metal ions through oxygen of carbonyl group, nitrogen of azomethine, and sulphur of thiophene moiety. Octahedral geometry has been proposed for all the complexes. The ligands and their complexes were tested for in vitro growth inhibitory activity against phytopathogenic fungi viz. Alternaria alternata, Colletotrichum capsicum, Fusarium oxysporum, and Rhizoctonia solani at 28°C; and bacteria viz. gram positive Bacillus subtilis and gram negative Escherichia coli at 37°C by a two-fold serial dilution technique. In some cases an increase in the biocidal activity of the ligands as a consequence of coordination with metal ions was observed in terms of minimum inhibitory concentration (MIC) values. The trend of growth inhibition in the complexes was found to be in the order: Cu > Ni > Co.