The influence of perchlorates on the fluorescence quenching of 9,10-dichloroanthracene by bromide salts in acetone

Fluorescence quenching of 9,10-dichloroanthracene by lithium bromide and te tra-n-butylammonium bromide in acetone has been investigated in the presenc e of perchlorate salts. In the presence of LiBr, the Stern-Volmer (S-V) plo ts exhibit downward curvatures indicating that two species are responsible for the quenching process, namely free bromide anions and lithium bromide i on pairs. The addition of a perchlorate salt modifies the S-V dependencies due to the influence of perchlorates on the degree of lithium bromide disso ciation. The association constant of lithium bromide has been determined by conductivity measurements and it agrees well with the estimates made from the fluorescence quenching measurements. The mechanism of fluorescence quen ching by lithium bromide is discussed on the basis of electron transfer and the heavy-atom effect. (C) 1999 Elsevier Science B.V. All rights reserved.