Synthesis and characterization of some potential antitumor palladium(II) complexes of 2-aminomethylbenzimidazole and amino acids

The stoichiometry and stability constants of complexes formed between [Pd(AMBI)(H2O)2]2+ (AMBI = 2-(aminomethyl)-benzimidazole) with some selected bio-relevant ligands containing different functional groups were investigated at 25°C and 0.1 mol L−1 ionic strength. The ligands used are imidazole, cysteine, glutathione (GSH), threonine, aspartic acid, 1,1-cyclobutane dicarboxylic acid (CBDCA) and lysine. The stoichiometry and stability constants of the formed complexes were reported and the concentration distribution of the various complex species was evaluated as a function of pH. The results show ring opening of CBDCA and monodentate complexation of the DNA constituent with the formation of [Pd(AMBI)(CBDCA–O)DNA], where (CBDCA–O) represents cyclobutane dicarboxylate coordinated by one carboxylate oxygen. The equilibrium constant of the displacement reaction of coordinated inosine, as a typical DNA constituent, by glutathione, as a typical thiol ligand, was investigated. The effect of dioxane on the formation constant of CBDCA with Pd(AMBI)2+ is reported. Five new palladium(II) complexes of the formula [Pd(AMBI)(AA)] n + (where AMBI = 2-aminomethyl benzimidazole, AA is an anion of glycine, alanine, cysteine, methionine, and serine) have been synthesized. These palladium(II) complexes have been ascertained by elemental, molar conductance, infrared and 1H-NMR spectroscopy. The isolated Pd(II) complexes were screened for their antibacterial and cytotoxic activities and the results are discussed.