Spectroscopic properties of 2-hydroxypyridine and excited state anion formation

The spectral properties of 2-hydroxypyridine (2HP) have been studied by abs orption, emission, infrared and NMR spectroscopic techniques. Anion formati on has been detected in pure water, and in presence of NaOH in ethanol in t he excited state. It is established that an equilibrium state of hydrogen b onding interaction is reached during the lifetime of the excited state. The interaction equilibrium constants are estimated from the fluorescence inte nsity measurements. It is proposed that the low energy emission spectra are due to excited state intramolecular proton transfer (ESIPT) and formation of 2-pyridone (2PD) tautomer of 2HP. Infrared and NMR spectra of 2HP show t he presence of free and dimer of 2HP in the ground state. Intramolecular an d intermolecular proton transfer in 2HP are discussed in the context of sol vent effect. From nanosecond measurements and quantum yield of fluorescence , we have determined proton transfer rates.