Activation Enthalpy and Entropy for the Formation of 9-Cyanophenanthrene Exciplexes

Exciplexes of 9-cyanophenanthrene with a series of weak electron donors with the Gibbs energy of electron transfer G_et* varying in the range –(0.02–0.09) eV were studied. The exciplexes exhibited fairly intense emission both in nonpolar and aprotic polar solvents. The kinetics of the exciplex formation was found to be controlled mainly by diffusion and reactant orientation. This is clearly manifested in the low-temperature region in which the activation enthalpy of exciplex formation is very close to the activation enthalpy of diffusion, and the activation entropy of exciplex formation does not exceed 18 J mol^–1 K^–1 in absolute value.