Palladium(II) complex taken as a model of an antitumour agent: Synthesis and equilibrium investigation involving biologically relevant ligands

Pd(DHP)Cl₂ and Pd(DHP)(CBDCA) complexes (DHP = 1,3-diamino-2-hydroxopropane and CBDCA = 1,1-cyclobutanedicarboxylate), were synthesized and characterized by elemental analysis, IR and NMR spectral measurements. The coordination of Pd(DHP)(H₂O)₂]²⁺ with some selected bio-relevant ligands, containing different functional groups was investigated. The ligands used are amino acids, peptides, DNA constituents and dicarboxylic acids. Stoichiometry and stability constants of the complexes formed are reported at 25 °C and 0.1 M ionic strength. The results show the formation of 1:1 complexes with amino acids and dicarboxylic acids. DNA constituents form 1:1 and 1:2 complexes. Peptides form both 1:1 complexes and the corresponding deprotonated amide species. The effect of chloride ion concentration and dioxane on the acid dissociation constants of 1,1-cyclobutane dicarboxylic acid (CBDCAH₂) and the formation constant of its complex with Pd(DHP)²⁺ was reported. The equilibrium constants for the displacement of coordinated ligands as uracil, glycine or methionine by cysteine are calculated. The results are expected to contribute to the chemistry of antitumour agents.