Voltammetric behavior of 1,2-dihydroxyanthraquinones attached to glassy carbon electrodes and their surface complexation with copper

The adsorption behavior of 1,2-dihydroxyanthraquinones on electrochemically treated GC electrodes has been analyzed on the basis of the Frumkin adsorp tion isotherm allowing for long-range interactions between adsorbed species . Their slow-scan voltammetric response corresponded with a voltammetric th eory for reversible surface reactions accompanied by intermolecular interac tions. The negative interaction parameter obtained indicated a repulsive in teraction between the surface-confined species, which bound Cu2+ firmly at weakly acidic pHs. Although 1,2-dihydroxyanthraquinones behave normally as a bidentate ligand, the surface-immobilized species formed only a 1:1 compl ex with Cu(II), probably because of motional restraints imposed on them. Th e 1,2-dihydroxy groups of the ligand chelated a partially hydrolyzed copper (II) species, their oxidation thus being depressed. Surface-bound copper un derwent a two-electron redox reaction repetitively without being released f rom the surface. (C) 2000 Elsevier Science S.A. All rights reserved.