Intramolecular charge transfer near a hydrophobic surface. 2,6-p-Toluidinonaphthalene sulfonate in a reverse micelle

Abstract

Intramolecular charge transfer (ICT) processes of 2,6-p-toluidinonaphthalene sulfonate (TNS) in the water pool of sodium dioctyl sulfosuccinate (AOT) reverse micelle in heptane, is studied using picosecond emission spectroscopy. It is observed that while in aqueous solutions the lifetime (τ_f) of TNS is 80 ps, τ_f increases to 4 ns in the microemulsion with water to AOT ratio, w₀=4. With increase in w₀ as the water pool swells in size, the lifetime and quantum yield of emission decrease and the rate of the ICT process increases. However, the magnitude of the change (at most ≈70 times at w₀=4) in the rate of the ICT process of TNS compared to ordinary water is smaller than the several thousand fold retardation in the solvation dynamics of water in such a water pool relative to bulk water. This is attributed to the fact that while the solvation dynamics in the water pool is governed by the dielectric relaxation, dynamics of the ICT process is controlled by the static polarity of the medium.