Quenching of substituted naphthalenes fluorescence by chloromethanes

The fluorescence quenching of some substituted naphthalenes by chloromethanes such as carbontetrachloride (CCl4), chloroform (CHCl3) and dichloromethane (CH2Cl2) have been studied in a large number of solvents in room temper ature. The quenching rate constants (kq) have been determined for all the fluorophores in all the solvents. For CCl4 quenching the kq depends on solvent viscosity whereas for CHCl3 and CH2C12 it depends neither on solvent viscosity nor on solvent polarity. From the results the quenching mechanism is explained in terms of an encounter complex formation for CCl4 quenching and an intermediate donor-acceptor complex formation for CHCl3 and CH2Cl2 quenching in the excited state. © 1995.