Photophysics of tropolone

The excited state fluorescence lifetimes of isolated tropolone in a supersonic expansion have been measured as a function of vibrational energy in the Evib=0–293 cm−1 region. A fluorescence quantum yield of 0.06 is estimated for the zero-point level of S1; the lifetimes decrease rapidly with increasing vibrational energy. Semi-empirical calculations of the energies of nearby excited states suggest that intersystem crossing to T3 may dominate the non-radiative decay of vibrationless S1, whereas the decrease of lifetime with increasing Evib is due to an increasing rate of internal conversion via the `proximity effectʹ.