Redox chemistry of 1,2-dihydroxynaphthalene, 1,2-naphthosemiquinone and 1,2-naphthoquinone and their complexes with manganese(II) and manganese(III)

• Published in: Transition metal chemistry (Weinheim) 1997-04, Vol.22 (2), p.150
• Main Authors: Bodini, Mario E, Arancibia, Veronica
• Format: Article
• Language: English
• Subjects: Chemistry
• ISSN: 0340-4285; 1572-901X
• DOI: 10.1023/A:1018467114048

Cyclic voltammetry and controlled-potential electrolyses were carried out on solutions of 1,2-naphthoquinone (1,2-NQ), 1,2-dihydroxynaphthalene [1,2-Di(OH)-Cat] and their reduction and oxidation products in dimethyl sulfoxide. A study of the interaction of these species with MnII and MnIII has been undertaken. The complexes MnIII(Cat2-)33-, MnII(Cat2-)22- and MnII-(Cat2-), where Cat2- represents the dianion of 1,2-dihydroxynaphthalene, were obtained in solution and the species MnIISQ has been detected only on the surface of the electrode. An attempt to obtain the latter complex quantitatively caused intramolecular charge-transfer yielding the more stable MnIII-catechol complex. The MnIII-semiquinone complex is unstable and the ligand is easily oxidized. The charge-transfer reaction between MnIII(Cat2-)33- and MnII(Cat2-)22- is observed at -0.54/-0.52 V versus s.c.e. whereas the MnII complexes are reduced beyond the electrochemical window (at a potential more negative than -2.00 V versus s.c.e). On the other hand, all these species are destroyed when the coordinated ligand is oxidized. U.v.-vis. spectroscopy and magnetic susceptibility measurements were performed on the compounds in solution in order to characterize and to confirm the oxidation states of the metal ion in the species.[PUBLICATION ABSTRACT]