INTRAMOLECULAR CHARGE-TRANSFER AND SOLVENT-POLARITY DEPENDENCE OF RADIATIVE DECAY-RATE IN PHOTOEXCITED DINAPHTHYLAMINES

It is shown that the radiative decay rate of the fluorescent state of 1,1'-dinaphthylamine decreases, while that of 2,2'-dinaphthylamine rem ains unchanged, as the polarity of the solvent is increased. These res ults, which are in accord with the predictions of INDO 1/S-CIS calcula tions, provide strong support to the conclusion that the lowest excite d singlet state of the dinaphthylamines is an intramolecular charge-tr ansfer state in solvents of high dielectric constants. The INDO 1/S me thod appears to be a reliable tool for investigating intramolecular ch arge transfer in these and related diaryl compounds.