EQUILIBRIUM STUDIES OF DIBUTYLTIN(IV) COMPLEXES WITH AMINO-ACIDS AND PEPTIDES

Complex formation equilibria of dibutyltin(IV) with amino acids and pe ptides have been investigated. Stoichiometry and stability constants f or the complexes formed were determined at 25 degrees C and ionic stre ngth 0.1 M NaNO3. The results showed the formation of 1:1 and 1:2 (org anotin : ligand) complexes with amino acids. The effect of the pK(a) v alue of the amino acid on the stability,constant of its complex specie s was elucidated. Peptides form both 1:1 complexes and the correspondi ng deprotonated amide species. In the latter species the binding with dibutyltin(IV) :occurs through the terminal amino group, carboxylate o xygen and the amide nitrogen atoms. The concentration distribution of the complexes in solution was evaluated.