Picosecond spectroscopy of intramolecular proton transfer in aromatic molecules

Picosecond spectroscopic techniques were used to study excited-state proton transfer in 2-(2'- hydroxyphenyl)-benzothiazole (HBT) molecules. The formation of a new tautomer and decay of the fluorescent state of HBT molecules dissolved in C₂Cl₄ and pyridine was studied. Proton transfer took place less than 5 ps after excitation and was observed by recording the stretching bands of C=O and NH groups formed by proton transfer. The excited-state lifetimes of the tautomer were 320 and 20 ps for HBT molecules in C₂Cl₄ and pyridine solutions, respectively.