Journal of the American Chemical Society vol:113 issue:18 pages:6849-6857
The efficiency with which the intramolecular exciplex between pyrene and indole or between pyrene and a tertiary amine decays to the locally excited triplet state of pyrene is determined using laser-induced optoacoustic spectroscopy. Upon increasing the solvent polarity, the relative efficiency of this intersystem crossing process decreases compared to the efficiency of the internal conversion process to the singlet ground state. These results can be rationalized in the framework of the Marcus theory. The results obtained by laser-induced optoacoustic spectroscopy are confirmed by transient absorption spectroscopy of the pyrene triplet in the case of the intramolecular exciplex of 1-(1-pyrenyl)3-N,N-dimethylaminopropane.