Two different mechanisms for the occurrence of S₂ fluorescence observed for 1,3,5-heptatrienylbenzene

Abstract

Fluorescence, fluorescence excitation and absorption spectra of 1,3,5-heptatrienylbenzene (MPP3) have been measured in the static vapour phase and in solution. It is shown that the MPP3 vapour exhibits prompt S₂ and S₁ fluorescence. The presence of two different mechanisms for the occurrence of the S₂ fluorescence is demonstrated for MPP3. That is, the S₂ fluorescence in the vapour phase is prompt fluorescence, the rate of which is fast enough to compete with internal conversion from S₂ to S₁, while in solution the S₂ fluorescence occurs as the result of the thermal activation of the S₁ state. The relaxation processes were discussed and the fluorescence property was compared with that of diphenylhexatriene.

Keywords:

• heptatrienylbenzene
• S₂ fluorescence
• excited states
• vapour
• relaxation processes

Disclosure statement

No potential conflict of interest was reported by the author.