Synthesis, spectral characterization, crystal structure and antibacterial studies of diorganotin(IV) complexes with isonicotinoyl hydrazone derivatives

Abstract

The new diorganotin(IV) complexes R2SnL (L=La: R=Me 1, Ph 2; L=Lb: R=Me 3, Ph 4, L=Lc: R=Me 5, Ph 6, Bu 7) have been synthesized by the reaction of the hydrazone ligands N′-(5-bromo-2-hydroxybenzylidene) isonicotinohydrazide (H2La), N′-((2-hydroxynaphthalen-1-yl)methylene) isonicotinohydrazide (H2Lb) and N′-(2,4-dihydroxybenzylidene) isonicotinohydrazide (H2Lc) with diorganotin(IV) dichloride. The synthesised compounds have been investigated by elemental analysis, together with IR, 1H and 119Sn NMR spectroscopy. The structures of H2La, H2Lb and 3 have also been confirmed by X-ray crystallography. On the basis of these data, H2La and H2Lb are present in the keto-amine tautomeric form and intermolecular N–H⋯N hydrogen bonds form 1D chain structures. The hydrazone ligands act as tridentate dibasic in the enol form and are coordinated via the imine nitrogen, phenolate and enolate oxygen atoms. The in vitro antibacterial activity of the ligands and their complexes has been evaluated against Gram-positive (Bacillus subtilis and Staphylococcus aureus) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria and compared with standard antibacterial drugs. The R2SnLc complexes exhibited greater activities than the other compounds.