POLAROGRAPHIC-REDUCTION OF PYRYLIUM-SALTS

The polarographic reduction of several pyrylium perchlorates in buffered and unbuffered solution was investigated at DME. In 0.1M LiCl-DMF, two waves are observed. The first wave is reversible and diffusion controlled representing the uptake of one electron, whereas the second wave is a catalytic reduction of the perchlorate ion. In buffered solutions (pH less-than-or-equal-to 5), only one wave is obtained and its i(l) decreases with pH due to the partial conversion of the pyrylium salt into a pseudo-base. The rate of conversion, electron affinities, ionization potentials and the energy levels of HOMO and LUMO of these compounds have been computed and a linear correlation shown to exist between the spectroscopic data and the redox potentials.