Direct observation and kinetic characterization of o-quinodimethane and its radical cation variant generated in a photoinduced electron-transfer reaction of 1,2-bis(α-styryl)benzene

Nanosecond time-resolved absorption spectroscopy on the laser flash photolysis of 1,2-bis(α-styryl)benzene (1) under N-methylquinolinium tetrafluoroborate–toluene-sensitized conditions in acetonitrile confirmed that an o-quinodimethane radical cation (2+, λmax = 569 nm) decayed and the corresponding neutral prototype (2, λmax = 444 nm) rose with rate constants of 5.6 and 5.9 × 105 s−1, respectively, showing the first agreement in kinetics between a reactive radical cation intermediate intervening in chemical reaction and the corresponding neutral species formed by back electron transfer.