Non-diffusion-controlled excimer formation with indane and acenaphthene. Kinetics and thermodynamics from picosecond-time-resolved fluorescence

Excimer formation with acenaphthene (AN) and indane (IN) in THF was studied using steady-state and picosecond-time-resolved fluorescence data as a function of temperature (173-298 K). Several methods of decay analysis (single decay deconvolution, global analysis and excimer deconvolution with monomer) were employed to extract all kinetic and thermodynamic parameters. In both cases, the transition temperature between the high and low temperature limits is low (182±5 K) due to efficient excimer dissociation. Excimer formation with these compounds is non-diffusion-controlled (the rate constants of excimer formation are eight- (AN) or nine- (IN) fold lower than the diffusional limit. This conclusion is opposite to the generally accepted concept that excimer formation is diffusion-controlled.