ELECTROCHEMICAL AND SPECTROSCOPIC STUDIES OF 2,3-DIHYDROXYBENZOIC ACID, ITS OXIDATION-PRODUCTS AND THEIR INTERACTION WITH MANGANESE(II), INDIMETHYL-SULFOXIDE SOLUTIONS

The electrochemical and spectroscopic behaviour of 2,3-dihydroxybenzoi c acid (2,3-DHBA) and its oxidized forms have been studied in dimethyl sulfoxide solutions under aerobic and anaerobic conditions. The produ cts resulting from the reaction with manganese(II) (in dimethyl sulfox ide) are also studied by cyclic voltammetry, u.v-vis., n.m.r, and e.s. r. spectroscopies. Under anaerobic conditions the anions of the ligand form stable complexes with manganese(II) and (III) of MnL2 type, whil e in the presence of air the oxidized forms of the ligand react with m anganese(II) to give mixed-valence species. The chemical stability of the semiquinone and its manganese complexes in addition to its photose nsitivity is noteworthy. Calculations show that the electrogenerated m anganese(III)-(2,3-DHB-semiquinone) system is stable, but redox-active and can undergo a two-electron exchange (per monomer). The dimeric (o r oligomeric) species should be good candidates for water oxidation st udies.