Abstract
Cu(I) quantum yields were measured at 313 nm for copper(II)-amino acid complexes with eight amino acids in aqueous solutions. Photochemical formation of copper(I) has been systematically studied for copper(II) complexes in different conditions (changing pH and ligand concentration). Bathocuproine method was used to determine copper(I) concentration. For the 1:1 Cu(II) complexes (CuL), the Cu(I) quantum yields at 313 nm (ΦCu(I),CuL) are in the sequence (25 0C, ionic strength = 0.10 M): 2-AIBA > β-ala > ala, 2-ABA, nor > val > 4-ABA > gly, ranging from 0.279 to 0.06 (mol einstein-1). Experimental data show that the photoreactivity of Cu(II)/amino-acid complexes can be predicted by Cu(II) speciation in a wide range of the solution conditions, varying in pH and the total concentration of ligand. The stability of the carbon-center radical plays an important role on the Cu(I) quantum yield. The six-membered chelate ring of Cu(II)/amino-acid complexes has larger Cu(I) quantum yields than five-membered chelate ring, probably owing to the increasing of the intra-molecular electron-transfer rate.