Dynamics and prototropic reactivity of electronically excited states in simple surfactant aggregates

Excitation of a molecule from the ground state to an electronically excited state can cause changes in its geometry, dipole moment, acidity or basicity, redox potentials and solvation. Bimolecular quenching of the excited state of the probe by other molecules present in the medium can be used to determine the mobilities of molecules and estimate microviscosities and encounter probabilities in the medium. Differences in excited state acidity or basicity relative to the ground state can be employed to investigate the dynamics of ultrafast proton transfer reactions. Three areas of current interest where fluorescent probes have served to elucidate important dynamic processes of molecules in simple self-aggregating surfactant systems such as aqueous micelles and reverse micelles are considered: (a) bimolecular quenching of excited states; (b) the dynamics of solvation of excited states and (c) ultrafast intermolecular excited state proton transfer (ESPT) reactions.