UV-visible spectroscopy in the interpretation of the tautomeric equilibrium of N,N'(bis-3,5-di-bromo-salicyliden)-1,2-diaminobenzene and the redox activity of its Co(II) complex. A quantum chemical approach.

By means of quantum chemical calculations, the origin of the redox capability of N,N'(bis-3,5-di-bromo-salicyliden)-1,2-diaminobenzene Co (II) complexes, of major interest in the catalytic reduction of naphtas, is analyzed. The geometry, electronic structure and UV-vis spectra of both the complex and the ligand are studied. AM1 and INDO/1 hamiltonians are used for the conformational analysis, whereas the UV-visible spectra are accurately reproduced by means of WDO/S-CI calculations, justifying the color of the ligand and offering an explanation to the catalytic redox activity of the Co(II) complex, based on the electronic transitions associated to the spectroscopic features and the electronic characteristics of the redox states.