Synthesis, characterization, X-ray crystal structures and antibacterial activities of Schiff base ligands derived from allylamine and their vanadium(IV), cobalt(III), nickel(II), copper(II), zinc(II) and palladium(II) complexes

A new Schiff base ligand, HL2, and four new Schiff base complexes, NiL21, PdL21, NiL22 and ZnL22, have been prepared and characterized by elemental analysis (CHN), FT-IR and UV-Vis spectroscopy. H-1 and C-13 NMR techniques were employed for characterization of the ligand (HL2) and the diamagnetic complexes (PdL21 and ZnL22). The molecular structures of PdL21, NiL22 and ZnL22 complexes were determined by the single crystal X-ray diffraction technique. The crystallographic data reveal that in these complexes the metal centers are four-coordinated by two phenolate oxygen and two imine nitrogen atoms of two Schiff base ligands. The geometry around the metal center in the PdL21 and NiL22 complexes is square planar and for ZnL22 it is a distorted tetrahedral. In the end, five new (HL2, NiL21, PdL21, NiL22 and ZnL22) and six reported (HL1, VOL21, CoL31, CuL21, ZnL21 and Zn2L41) Schiff base compounds were tested for their in vitro antimicrobial activity against Staphylococcus aureus and Escherichia coli as examples of Gram-positive and Gram-negative bacterial strains, respectively, by disc diffusion method. (C) 2016 Elsevier B.V. All rights reserved.