EXCIPLEX PHOTOPHYSICS .6. QUENCHING OF ALPHA-CYANONAPHTHALENE BY 1,2-DIMETHYLCYCLOPENTENE IN SLIGHTLY POLAR-SOLVENTS

The kinetic behavior of the exciplex formed between electronically excited α-cyanonaphthalene and ground-state 1, 2-dimethylcyclopentene in nonpolar and slightly polar solvents is reported. Analysis of two-component fluorescence decay curves indicates that in each solvent exciplex formation and decay in general follow the simple “excimer-type” mechanism. Rate constants associated with this type of mechanism were calculated. From their temperature dependence ΔH°, ΔS°, and ΔG° for the exciplex equilibrium reaction in three solvents were determined. As solvent polarity increased ΔS° was found to become less negative while the exciplex binding energy remained constant. Trends in the values of the rate constants and thermodynamic properties are compared with other published data. Solvent participation in exciplex formation is invoked in order to account for the observed changes in the thermodynamic properties. © 1979, American Chemical Society. All rights reserved.