Environment Perturbations of Proton Transfer Spectra of 2-（2’-Hydroxyphenyl） Benzoxazole

In this paper,the environment perturbations of the excited state intramolecular proton transfer （ESIPT） and its spectra of 2-（2’-Hydroxyphenyl） benzoxazole （HBO） in the polar solvent doped impurities,such as acid, base and water,have been studied systematically. The spectral characteristics of protonated HBO⁺,deprotonated HBO^- and some HBO-solvated in the solution systems perturbed are revealed and related to the properties of P-π conjugation of the hydroxyl O in HBO. ESIPT of HBO in the system perturbed is restricted to a considerable degree. In the system doped water with C_H2O＞1M,a new absorption band at 364nm and a new emission band at 432nm are found and ascribed to a stable HBO-monohydrate and an unstable HBO^-* anion formed in the excited state, respectively. In protonic solution of HBO, a similar absorption at 375nm and emission at 432nm are thought to result from the H-bonding HBO-monosolvate and its HBO^-* anion respectively,not from the rotamer Ⅲ of HBO.