Oxovanadium(IV) and amino acids—VI. The systems glycylglycine and glycylglycylglycine + VO2+; a potentiometric and spectroscopic study

The equilibria in the systems glycylglycine and glycylglycylglycine + VO2- in aqueous solution have been studied in the pH range 1.5-4.5 by a combination of pH potentiometry and spectroscopy (EPR and visible absorption). The results of the various methods are made self-consistent. then rationalized assuming an equilibrium model including species MLH, ML2H-2, MLH-1, and several hydrolysis products (where HL denotes glycylglycine or glycylglycylglycine); individual formation constants and absorption spectra are given. Plausible isomeric structures for each stoichiometry are discussed.