Effect of reverse micelles on the intramolecular excited state proton transfer (ESPT) and dual luminescence behaviour of 3-hydroxyflavone

Abstract

The excited-state proton transfer and dual emission behaviour of 3-hydroxyflavone (3HF) have been investigated in reverse micelles of sodium bis(2-ethylhexyl) sulphosuccinate (AOT)/ n-heptane at different values of water to surfactant molar ratio ( W O ). The green tautomet emission (λ max ≈ 524 nm) and blue-violet normal emission (λ max ≈ 400 nm) originate from two different ground state populations of 3HF molecules, which are located respectively in the apolar phase and at the interphase of the reverse micelles, proximal to the AOT head groups. With increasing W 0 the relative yield of the green emission band is enhanced with a concomitant decrease in that of the blue-violet emission. This is interpreted in terms of the population of 3HF molecules which are initially located in the interfacial region proximal to the polar head groups being “pushed” out into the apolar phase, where external hydrogen bonding perturbations are minimized.