Effect of Pressure on Pyrene Excimer Fluorescence in Toluene

Abstract

The pressure dependence of pyrene fluorescence in toluene has been measured to 10 kbar. The monomer and excimer fluorescence decay kinetics are analyzed to give the rate parameters for excimer formation, dissociation, and unimolecular decay as a function of pressure at 296, 320, and 340°K. Activation parameters are evaluated both as a function of temperature and as a function of pressure. The pressure dependence of the association is in one-to-one correspondence with the solvent viscosity. The rate of dissociation is strongly inhibited by high pressures. The volume change on excimer formation is −11 cm3/mole at 296°K. The enthalpy and free energy of excimer formation are −9.7 and −4.2 kcal/mole at 1 atm, and −3.6 and −6.7 kcal/mole at 10 kbar, respectively.