POTENTIOMETRIC AND SPECTROSCOPIC STUDY OF TERNARY COMPLEXES OF COPPER(II), SUBSTITUTED 1,10-PHENANTHROLINES AND OXIDIZED GLUTATHIONE

A series of ternary systems consisting of copper(II), oxidised glutath ione (a S-S' bonded hexapeptide) and five differently substituted 1,10 -phenanthrolines has been studied in aqueous solvent in the range pH 3 -8. The stability constants of the complexes formed, together with the relevant distributions as a function of pH, have been evaluated by el aboration of data from acid-base potentiometric titrations. Electron p aramagnetic resonance and electronic spectroscopy have been used to id entify the chromophore in the 1 : 1 : 1 complexes, Le. the ternary spe cies are in all cases the predominant ones at pH close to the physiolo gical values. The data from the spectroscopic measurements, when consi dered together with the trend in stability constant values, allowed re asonable hypotheses about the effect of the substituents on the phenan throline ring on the stability and configuration of the complexes.