Spectroscopic and potentiometric study of protonation and copper(II) complex formation of 3-amino-L-tyrosine

A pH-metric and spectroscopic (u.v.–visible and e.s.r.) study has been made of the proton and copper(II) complexes of 3-amino-L-tyrosine at 25 °C and I= 0.2 mol dm–3(KCl). The acid–base chemistry of the ligand has been characterised at both macroscopic and molecular levels by determining the microscopic constants of the overlapping protonation processes. It has been established that the ligand displays a marked ambidentate character in the copper(II) complexes. Accordingly, various monomeric complexes involving aminocarboxylate- and aminophenolate-type co-ordination, and dimeric complexes involving simultaneous metal-ion co-ordination at both binding sites, are formed.