QUENCHING OF SUBSTITUTED NAPHTHALENES FLUORESCENCE BY CHLOROMETHANES

The fluorescence quenching of some substituted naphthalenes by chlorom ethanes such as carbontetrachloride (CCl4), chloroform (CKCl3) and dic hloromethane (CH2Cl2) have been studied in a large number of solvents in room temperature. The quenching rate constants (k(q)) have been det ermined for all the fluorophores in all the solvents. For CCl4 quenchi ng the k(q) depends on solvent viscosity whereas for CHCl3 and CH2Cl2 it depends neither on solvent viscosity nor on solvent polarity. From the results the quenching mechanism is explained in terms of an encoun ter complex formation for CCl4 quenching and an intermediate donor-acc eptor complex formation for CHCl3 and CH2Cl2 quenching in the excited state.