Speciation of the mixed-ligand oxovanadium(IV) complexes with 2,2'-Bipyridine and 1,10'-Phenthroline and some bidentate amino acids by potentiometric tritrations

The speciation of the ternary VO2+- 1,10'-Phenanthroline (Phen, L) and VO2+- 2,2'-Bipyridine (Bipy, L) complexes with the amino acids: Glycine (Gly, HB), alpha-Alanine (alpha-Ala, HB), beta-Alanine (beta-Ala, HB), Serine (Ser, HB), Threonine (Thr, HB), Leucine (Leu, HB), Isoleucine (Ile, HB), Valine (Val, HB), Tryptophan (Thr, HB), Glutamine (Gln, HB), Methionine (Met, HB) and Phenylalanine (Phe, HB) were obtained via potentiometric titrations done at 25 degrees C using 1.0 mol.dm-3 NaCl as the ionic medium. The analysis of the experimental data were done with the program LETAGROP, and the HYSS program was used to obtain the distribution diagrams. Related stability parameters including Delta log10 K, log10 X and % R.S were determined only for the Bipy. In the case of the Phen these parameters could not be obtained because the complex [VO(L)(B)]+ was not detected with this ligand.