CHEMICAL RELEVANCE OF THE COPPER(II) L-CARNOSINE SYSTEM IN AQUEOUS-SOLUTION - A THERMODYNAMIC AND SPECTROPHOTOMETRIC STUDY

The copper(II)-L-carnosine (L-) system has been re-investigated in aqu eous solution, at I = 0.1 mol dm-3, different temperatures (5 less-tha n-or-equal-to t less-than-or-equal-to 45-degrees-C) and with metal to ligand ratios ranging from 3:1 to 1:3. Both potentiometry and visible spectrophotometry were employed. From an overall consideration of all experiments, CuLH!2+, CuL!+, CuLH-1!-degrees, Cu2L2H-2!-degrees an d Cu2LH-1!2+ were recognized as the species which provide the best in terpretation of experimental data. The complex formation constants, de termined at different temperatures, allowed us to obtain reliable valu es of DELTAH-degrees and good estimates of DELTAC(p)-degrees. From vis ible spectrophotometric measurements, carried out at different pH and metal to ligand ratios, it was possible to calculate the electronic sp ectrum of each complex formed in solution. A structure is also propose d for each species, on the basis of thermodynamic and spectral results .