Ultrafast excited state intermolecular proton transfer dynamics of 2-(4′-Pyridyl)benzimidazole inside the nanocavity of reverse micelles

Abstract

Abstract The effect of AOT reverse micelle on the excited state prototropism of 2-(4′-pyridyl)benzimidazole (4PBI) have been explored by steady-state and time-resolved fluorescence spectroscopy. It has been observed that the effect AOT reverse micelle is remarkably different form the CTAB reverse micelle on the photophysics of 4PBI. The ESPT dynamics in AOT reverse micelle approaches to bulk water at higher water concentration whereas no ESPT is observed in CTAB reverse micelle even at high w0 value. In AOT reverse micelle, 4PBI can penetrate the interfacial wall and undergo ESPT processes. This process might be initiated by the electrostatic interaction between the negatively charged interface of AOT reverse micelle and positively charged monocation ca. tautomer, which is selectively stabilized. In addition, no such possibility is observed in CTAB reverse micelle. The ESPT dynamics of dye was found to be slowed down inside the AOT reverse micelle. The observed slow ESPT dynamics in reverse micelle compared to bulk water is mainly attributed to the slow hydrogen-bonded network dynamics of water molecules inside the nanopools of AOT reverse micelle.