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Abstract:
The spectra of 2,5-bis(2-benzoxazolyl)hydroquinone (BBXHQ) in solid argon at 15 K reveals two species. The major species (96%) undergoes very efficient excited-state intramolecular proton transfer (ESIPT) after excitation to S1. It is assigned to the isolated BBXHQ molecule (solvated by argon atoms) in which ESIPT is not thermally activated. Either no energy barrier exists or it can be overcome by proton tunneling with a rate constant greater than 8 × 1010 s−1. The minor species produces only fluorescence with a normal Stokes shift, indicating the absence of ESIPT. It is tentatively assigned to a dimer of BBXHQ.
