In situ electrochemical reduction of some naphthazarin derivatives. An electron spin resonance and INDO study

Abstract

Twelve naphthazarin derivatives were reduced electrochemically giving rise to the corresponding semiquinone anion radicals. Their e.s.r. spectra were recorded in situ and their hyperfine coupling constants and g factor were evaluated. For this purpose, SCF INDO MO calculations were performed in order to obtain an approximate value of the different coupling constants. The structure of these radicals was also deduced from these calculations, showing a strong linear O–H–O hydrogen bond, free rotation of the methyl group, and the absence of hyperfine interactions in the methoxy-group.