Two new 8-hydroxy-5-quinolyl substituted dioxotetraamine macrocyclic ligands containing two independent chelating groups were prepared. As pH titration and UV absorption experiments indicated, in the copper(Ⅱ ) complex of molar ratio metal:ligand=1:1, 8-hydroxyquinolyl was 100% chelated to copper(Ⅱ) ion while dioxotetraamine was only partially so over pH 3～9. Studies on the acid-induced dissociations of such complex species MLH^-^1 AT at various temperatures and acid concentrations were conducted. Based on the experimental data an appropriate reaction mechanism was suggested. The results showed that the dissociation mechanism was different from the classical one, while the partly coordinated dioxotetraamine macrocycles in the copper complexes played important roles during the pre-equilibrium process.

Key words: HYDROXY QUINOLINES, DECOMPOSITION, REACTION KINETICS, REACTION MECHANISM, COPPER COMPLEX, POTENTIOMETRIC TITRATION, DIOXOTETRAAMINE, MACROCYCLIC COMPOUNDS