Obtaining and Research of Palladium Complexes with 4-aminopiridine

Abstract

The obtaining and investigation of various complex compounds of the biologically active aromatic heterocyclic ligands with platinum and palladium are of interest due to their potential medical applications. To that end, 4-amino pyridine containing cyclic and exocyclic nitrogen atoms has been used. The main aim of this work is to clarify which nitrogen atom of the ligand composes stronger and more stable bond. For that purpose, the synthesis of palladium salts with ligand has been accomplished within a wide interval of pH (3-12) and temperature (50-800C). The cation-anion and neutral complex compounds have been obtained depending on stoichiometric ratio of the reacting components, temperature and pH and was further studied. As a result of IR-spectroscopic investigation of synthesized complexes, the acquired information demonstrated that the pyridine nitrogen atom of the ligand is protonated and composes outer sphere as monocharged cation. However, tetraacidoanion is formed in the inner sphere. In the alkaline medium the ligand is monodentately coordinated with palladium through nitrogen atom of pyridine. The exocyclic nitrogen atom of the ligand does not participate in the coordination regardless of pH of the medium and stoichiometric ratio of the taken compounds. As a result of investigation of the thermal stability of the complexes it was determined that the neutral complexes are decomposed without melting at higher temperature than cation-anion complexes. It has been found that one of the factors that affects thermal stability is the steric structure of the complexes. The initial biological probes were accomplished and the correlation between their biological activities, composition and structures of complexes were determined. Despite the fact of taking the same medium and ligand, the cation-anion complexes indicate completely different biological activities than neutral ones.