Spectroscopic properties of 2-hydroxypyridine and excited state anion formation

Abstract

<span style="font-size:11.0pt;font-family:" times="" new="" roman","serif";="" mso-fareast-font-family:calibri;mso-fareast-theme-font:minor-latin;color:#313131;="" mso-ansi-language:en-in;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">The <span style="font-size:11.0pt;font-family:" times="" new="" roman","serif";="" mso-fareast-font-family:calibri;mso-fareast-theme-font:minor-latin;color:#454545;="" mso-ansi-language:en-in;mso-fareast-language:en-us;mso-bidi-language:ar-sa"="">spec<span style="font-size:11.0pt;font-family:" times="" new="" roman","serif";mso-fareast-font-family:="" calibri;mso-fareast-theme-font:minor-latin;mso-ansi-language:en-in;mso-fareast-language:="" en-us;mso-bidi-language:ar-sa"="">tral properties of 2-hydroxypyridine (2HP) have been studied by absorption, emission, infrared and NMR spectroscopic techniques. Anion formation has been detected in pure water, and in presence of NaOH in ethanol in the excited state. It is established that an equilibrium state of hydrogen bonding interaction is reached during the lifetime of the excited state. The interaction equilibrium constants are estimated from the fluorescence intensity 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 the presence of free and dimer of 2HP in the ground state. Intramolecular and intermolecular proton transfer in 2HP arc discussed in the context of solvent effect. From nanosecond measurements and quantum yield of fluorescence, we have determined proton transfer rates.</span></span></span>