Optical absorption and luminescence spectra of 2,5-di-(2-benzoxazolyl)phenol in the solid state

Abstract

Optical absorption and luminescence spectra of 2,5-di-(2-benzoxazolyl)phenol in its solid state are measured and analyzed. The photoluminescence spectrum of this material is found to exhibit both low-and high-frequency fluorescence bands in the solid state. The dual fluorescence observed is caused by close energies of enol and keto structures in the excited states. The changes found in the fluorescence spectrum are attributed to distortion of molecule in the excited state.

Vibronic structure of absorption spectrum of 2,5-di-(2-benzoxazolyl)phenol

“…1). Another structure II formed by the rotation of a non-hydrogen-bonded benzoxazole moiety is calculated to be less stable by about 0.01 eV [3].DBP demonstrates two bands in the fluorescence spectrum: the first with normal Stokes shift and the second with anomalously large Stokes shift. The fluorescence with the large Stokes shift is attributed to the transitions in the keto structure formed by ESIPT.…”

“…An organic compound 2,5-di-(2-benzoxazolyl)phenol(DBP) is an organic compound that undergoes excited-state intramolecular proton transfer (ESIPT) [1][2][3][4]. The most stable molecular structure in the ground state S0 is the enol form I with a hydrogen bond OH…N (Fig.…”

“…The fluorescence with the large Stokes shift is attributed to the transitions in the keto structure formed by ESIPT. At least a part of the fluorescence with the usual Stokes shift is attributed to the transitions in the structure due to difference in the fluorescence excitation spectra [1][2][3]. The absorption spectrum of DBP in solution (Fig.…”

“…2), as well as the spectrum of the related compound 2,5-bis(6-methyl-2benzoxazolyl)phenol [4,5], exhibit sharp vibronic bands at room temperature. The spectra of the transitions to the first S1 and second S2 excited states are overlapping [3,5]. In this work we perform theoretical modeling of the absorption of DBP in order to find out the molecular vibrations, which are manifested in the spectrum.…”