Singlet excited-state “energy hopping” in alkylbenzenes

The quenching of toluene fluorescence by cis-6-phenyl-2-hexene has been studied to determine the rate of singlet “energy hopping” in dilute solutions of alkylbenzenes. The singlet lifetime date have been analyzed by the Stern-Volmer method to give the quasi-isoenergetic rate, k_q, as 1.2 × 10¹⁰ M^?1?1. The result is consistent with an excimer formation dissociation mechanism for alkylaromatic singlet energy transfer in dilute solution.