EXCITED-STATE ACIDITY OF BIFUNCTIONAL MOLECULES .2. PICOSECOND EMISSION OF 5-(2-HYDROXYPHENYL)-3-PHENYL-1,2,4-OXADIAZOLE

5-(2-Hydroxyphenyl)-3-phenyl-1,2,4-oxadiazole has been synthesized in high yields and the kinetics of its intramolecular proton-transfer process has been investigated by using steady-state and time-dependent picosecond laser spectroscopy. On the basis of these experimental determinations and the results of quantum-mechanical calculations, the structures of the two fluorescing species observed have been assigned to two different conformations of the same molecular structure, both being present in the ground state. Rapid proton transfer in the excited state is suggested as the predominant quenching process of one of these conformations.