Experimental study of the interaction of some coumarin derivatives with aniline in Triton-X-100 micelles

The interaction of some 3-carboxy-coumarin derivatives with Triton-X-100 micelles and subsequently with aniline was studied by means of steady-state and time-resolved (TR) fluorescence spectroscopy. The fluorescence of all coumarin derivatives was quenched in the presence of aniline. The quenching process was characterized by Stern-Volmer plots that display an upward curvature, analyzed in terms of the sphere of action model. In order to avoid the static quenching contribution and hence to have a better estimation of the dynamic Stern-Volmer constant, TR fluorescence measurements were carried out. The experimental TR data were rationalized in terms of the Marcus theory on the photoinduced electron transfer reactions. The plot of the dynamic quenching constant values in the Triton-X-100 micellar solution vs. the free energy change (Delta G degrees) for electron transfer reaction shows an inversion region as predicted by the Marcus theory. (C) 2011 Elsevier B.V. All rights reserved.