Two consecutive one-electron transfer processes of the reduction of hypericin were studied at a bare and an alkanethiol-modified polycrystalline gold electrode in acetonitrile by means of cyclic voltammetry and electroreflectance (ER) spectroscopy. The voltammetric response of hypericin at a bare gold electrode was found to be quasi-reversible at low sweep rates, and the participation of adsorbed hypericin in the voltammetric response was not detected. The redox reaction of hypericin was not inhibited but rather enhanced by the presence of an octadecanethiol film on the electrode surface, into which hypericin was presumably partitioned. In situ electroreflectance spectra displayed a feature of absorption spectral difference between hypericin and its reduction product at the electrode interface. The ER data were used to discuss the absorption spectra of one- and two-electron reduced forms of hypericin in the visible wavelength region. The use of hypericin as a photo-excitation center was examined in a photo-induced electron transfer system prepared by co-modification of a gold electrode with alkanethiol and N-butyl-N′-(4-mercaptobutyl)-4,4′-bipyridinium dihexafluorophosphate. The photo-induced electron transfer from photo-excited hypericin to the gold electrode with the help of mediation by a viologen moiety was observed.
All Science Journal Classification (ASJC) codes
- Analytical Chemistry
- Chemical Engineering(all)