SPECTROSCOPIC STUDY OF COMPLEX FORMATION OF COPPER(II) WITH (S)-?-[3-ISOBUTYL-4-(2-METALLYL)-5-THIOXO-1,2,4-TRIAZOL-1-YL]-?-ALANINE IN AQUEOUS SOLUTION

The complex formation of (S)-beta-[3-isobutyl-4-(2-methallyl)-5-thioxo-1,2,4-triazol-1-yl]-alpha- alanine amino acid with copper(II) chloride in aqueous solution has been investigated by means of UV-Vis and IR spectroscopy at 25 degrees C. The molar ratio method was used to determine the composi-tion of that complex. It has been established that a complex compound of the ML2 type is formed in aqueous solution. Based on the data of UV-Vis spectra, the stability constant of this complex was calculated. The stability constant of the ML2 type complex is equal to (4.23 +/- 0.27)center dot 106 L2 center dot mol-2. In addition, on the basis of IR spectroscopy data the formation of the complex was confirmed, and the centers of the ligand involved in the complex formation were identified. In the IR spectrum of the complex isolated from the solution and dried in air, a new weak absorption band appears, which is characteristic of the coordination of the copper(II) ion with the carboxylate ion. In addition, there is a shift of the stretching vibration band of the N-H amino group to the region of large values, which indicates the participation of the lone electron pair of the nitrogen of the amino group in the formation of coordination with the copper(II) ion. Moreover, an absorption band of coordination water in the structure of the complex is also observed. Based on the data obtained, the structure of the chelate complex has been proposed, in which the copper(II) cation is bound to the oxygen atom of the carboxylate anion by electrostatic interaction, and to the nitrogen atom of the amino group by a covalent bond by the donor-acceptor mechanism. And the octahedral coordination sphere of the copper(II) ion is complemented by two water molecules.