Spectrophotometric studies of copper (II) complexes of glycylglycine.

Spectrophotometric studies are presented of the glycylglytine-copper(I1) [GG-Cu(II)] system in aqueous solution under conditions in which the ligand is present in great excess (up to 1000: 1). In highly basic solution (pH 12 to 13) the spectral absorption maximum changes with increasing ligand concentration from 640 to 540 rnp. The spectral data are interpreted in terms of an equilibrium between two dominant species, and the species responsible for the 540 rnp peak is concluded to be the heretofore unobserved Cu(GG)*-*. Comparison studies under similar conditions for copper complexes of glycine, glycylglycylglycine, and glycylsarcosine are presented and discussed.