Cage escape yields and direct observation of intermediates in photoinduced electron-transfer reactions of cis- and trans-stilbene

The cation radicals of cis- and trans-stilbene have been generated in solution under conditions where they do not interconvert by means of pulsed-laser-induced electron transfer from biphenyl to singlet 9,10-dicyanoanthracene followed by secondary electron transfer from the stilbenes to the biphenyl cation radical. The cis-stilbene cation radical is found to be configurationally stable on the microsecond time scale. Cage escape quantum yields have been measured for the photogenerated ion pairs of 9,10-dicyanoanthracene with cis-stilbene (0.134) and trans-stilbene (0.254), and these values have been used to analyze the quantum yields for electron-transfer-induced isomerization and oxygenation of the stilbenes.