THERMALLY ASSISTED AND HEAVY-ATOM ASSISTED INTERSYSTEM CROSSING IN MESO-SUBSTITUTED ANTHRACENES

A single linear correlation between the activation energy of S1-T intersystem crossing and the logarithm of the bimolecular fluorescence quenching rate constant by haloalkanes for meso-substituted anthracenes in fluid solutions is established. It is concluded that both the monomolecular and the heavy-atom-assisted deactivation of S1 depend in the same way on the change of S1 energy by substitution or solvent relative to the energy of the accepting triplet Tn. The anomalous increase of fluorescence of Br-substituted anthracenes in heavy-atom containing solvents is consistent with a widening of the S1-Tn energy gap due to the changing solvent. © 1979.