pH-metric, visible, UV and ESR spectral studies of the copper(II)-DL-3,4-dihydroxyphenylalanine (DL-DOPA) and the copper(II)-aminoacid-pyrocatechol systems were used to draw conclusions on the complexes formed in the copper(II)-DOPA system. The stability constants of these complexes were determined from the pH-metric data. It was found that at lower pH(<5) aminoacid type complexes of composition CuH2A and Cu(H2A)2 are formed, while at higher pH values (>9) the pyrocatechol type complex Cu(HA)2 and its deprotonated species are formed. In the intermediate pH range cyclic and open-chain dimeric species are produced, together with a complex containing both N,O and O,O bonds. The existence of this complex is also supported by the fact that formation of the mixed ligand complex is favoured in the copper(II)-pyrocatechol-alanine and copper(II)-pyrocatechol-phenylalanine systems.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry
- Materials Chemistry