Complex formation reactions and equilibrium studies of mixed ligand complexes of diaqua (1-Phenyl piperazine)(Palladium)(II) with some biologically relevant ligands.

Abstract

With the perpose of the search of new antitumor metal complexes, the complex-formation reactions of [Pd(Phenpip)(H₂O)₂]²⁺ (Phenpip = 1-Phenylpiperazine) with some selected bio-relevant ligands, containing different functional groups (amino acids, peptides, DNA constituents and dicarboxylic acids) were investigated. Stoichiometry and stability constants for the complexes formed are reported. The results show the formation of 1 : 1 complexes with amino acids and dicarboxylic acids. The effect of chelate ring size of the dicarboxylic acid complexes on their stability constants was examined. Peptides form both 1 : 1 complexes and the corresponding deprotonated amide species. Structural effects of the peptide on the amide deprotonation were investigated. DNA pyrimidinic constituents, such as uracil, uridine, thymidine and thymine, form 1 : 1 and 1 : 2 complexes, whereas purinic constituents, such as inosine, inosine 5´-monophosphate (5-IMP) form only 1 : 1 complexes. The stability constant of the complexes formed in solution were determined and the binding centres of the ligands were assigned. The concentration distribution diagrams of the complexes were evaluated