ESR and optical absorption studies on the copper (II) interaction with aromatic amino acids

Electron spin resonance and optical absorption studies have been done in order to investigate the interaction between Cu2+ and aromatic amino acids in aqueous solution at 77 K and at room temperature as well. Depending on the concentration each aromatic amino acid can form two different kinds of complexes with Cu2+ which can be characterized by its ESR pattern. Additional information was obtained from optical d-d and CT transitions.