Spectroscopic studies of complexation of p-phenylenediamine with micelles and reverse micelles of Tweens

The electron donor–acceptor (EDA) interactions were studied using p-phenylenediamine as donor and polyoxyethylene–sorbitan–monolaurate (Tween 20), polyoxyethylene–sorbitan–monopalmitate (Tween 40), polyoxyethylene–sorbitan–monostearate (Tween 60) and polyoxyethylene–sorbitan–monooleate (Tween 80) as acceptor in micellar and reverse micellar environments. A charge transfer (CT) absorption band was observed and the experimental CT transition energies are well correlated (through Mulliken’s equation) with the vertical electron affinity of the acceptors. Oscillator strengths, transition dipole moments, resonance energies and formation constants of the EDA complexes have been estimated. The experimental results were explained using a theoretical model in favour of electric dipole–dipole interaction between the donor and acceptor.