Tyrosinate and lysinate as bridging residues in copper(II) dipeptide complexes

A pH-metric study, together with some supporting spectroscopy (u.v.–visible, c.d., and e.s.r.), was made on copper(II) complexes of L-phenylalanyl-L-tyrosine, L-tyrosyl-L-phenylalanine, L-lysyl-L-tyrosine, and L-tyrosyl-L-lysine at 25 °C and l= 0.2 mol dm–3(KCl). It was established that in dilute aqueous solutions, besides metal–ligand co-ordination characteristic of simple dipeptides, there are interactions between copper(II) and the side-chain phenolate group of the tyrosine residue and/or the Iµ-amino group of the lysine residue. In these dimeric species, both the lysine and the tyrosine moieties can behave as bridges between monomeric complexes.