Analytical Sciences

Intramolecular Charge Transfer near a HydrophobicSurface.2,6-p-Toluidinonaphthalene Sulfonate in a Reverse Micelle

Debabrata MANDAL, Samir KumarPAL, Anindya DATTA and Kankan BHATTACHARYYA *

Department of PhysicalChemistry, Indian Association for the Cultivation of Science, Jadavpur, Calcutta 700 032, India

Intramolecular charge transfer (ICT) processes of2,6-p-toluidinonaphthalene sulfonate (TNS) in the water pool ofsodiumdioctyl sulfosuccinate (AOT) reverse micelle in heptane, is studied using picosecond emission spectroscopy. It isobserved that while in aqueous solutions the lifetime (tf) of TNS is 80 ps, tfincreases to 4 ns in the microemulsion withwater to AOT ratio, w0=4.With increase in w0 as thewater pool swells in size, the lifetime and quantum yield of emissiondecrease and the rate of the ICT process increases. However, the magnitudeof the change (at most ª70 times at w0=4) inthe rate of the ICT process of TNS compared to ordinary water is smallerthan the several thousand fold retardation in thesolvation dynamics of water in such a water pool relative to bulk water.This is attributed to the fact that while thesolvation dynamics in the water pool is governed by the dielectricrelaxation, dynamics of the ICT process is controlledby the static polarity of the medium. (Keywords: Reverse micelle, ultrafast charge transfer)

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