A palladium(II) complex: Synthesis, structure, characterization, electrochemical behavior, thermal aspects, BVS calculation and antimicrobial activity

Abstract

The reaction of equimolar proportions of Na2[PdCl4] and 1-(4-methylimidazol-5-yl) phenylhydrazonopropane-2-one oxime (LH), a 1:1 Schiff-base condensate of 1-hydrazono-1-phenyl-propan-2-one oxime (1) and 4-methylimidazole-5-carboxaldehyde, in methanol gives rise to [Pd(L)(Cl)] (2) in a satisfactory yield. The title monomeric palladium(II) complex, 2, has been characterized by C, H and N microanalyses, 1H and 13C NMR, FAB-MS, FT-IR, UV–Vis spectra, molar electric conductivity measurements and room temperature magnetic susceptibility measurements. The X-ray crystal structures of 1 and 2 have been determined. The structure of 1, a precursor of the ligand (LH), shows that the methyl and phenyl groups are in an ‘anti’ disposition. Compound 1 crystallizes in the monoclinic space group P21 with a=6.9503(5), b=6.4535(3), c=10.1631(6)Å, V=455.04(5)Å3 and Z=2. The structure of 2 reveals that it is a distorted square-planar palladium(II) compound. The palladium center is in an ‘N3Cl’ coordination chromophore. Complex 2 crystallizes in the tetragonal space group I41/a with a=22.5744(3), b=22.5744(3), c=13.2967(2)Å, V=6776.05(16)Å3 and Z=16. The thermal and electrochemical aspects of 2 have been studied. Electrochemical studies in DMF show a Pd(II) to Pd(III) oxidation at 0.573V, along with a reduction of Pd(II) to Pd(I) at −0.757V versus Ag/AgCl. A Bond-Valence Sum (BVS) model calculation was performed to assign the oxidation state of the palladium center in 2. The in vitro antimicrobial activity of 2 was tested against both Gram positive and Gram negative bacteria. Complex 2 exhibits satisfactory bacteriostatic activity.