A Time-Resolved EPR Study of a New Zwitterion Undergoing Photoinduced Intramolecular Electron Transfer

We report on an unusual intramolecular electron transfer following the photoexcitation of the ground, charge separated, state of the zwitterionic compound, tetraphenylhexaazaanthracene, which results in a neutral biradical product. The reaction, studied by time-resolved electron paramagnetic resonance (TREPR) spectroscopy, could be carried out only when liquid crystals were used as the orienting solvents. On the basis of the analysis of the magnetic, kinetic, and polarization parameters of the TREPR spectra, the radical pair genesis is attributed to an intramolecular electron transfer from the singlet excited state.