Thermally assisted and heavy-atom assisted intersystem crossing in meso-substituted anthracenes

Abstract A single linear correlation between the activation energy of S 1 —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 S 1 depend in the same way on the change of S 1 energy by substitution or solvent relative to the energy of the accepting triplet T n . The anomalous increase of fluorescence of Br-substituted anthracenes in heavy-atom containing solvents is consistent with a widening of the S 1 —T n energy gap due to the changing solvent.