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Updated: Mar 1, 2026

Isotopic Effect in Double Proton Transfer Process of Porphycene Investigated by Enhanced QM/MM Method
Published on: July 19, 2019
Dynamics of excited-state intramolecular proton-transfer in 2-amino-3-(2'-benzazolyl)quinoline cations
Mikhail N Khimich1, Vladimir L Ivanov1, Mikhail Ya Melnikov1
1Chemistry Department Lomonosov Moscow State University, 119991 Moscow, Russia. mikhail.nick.kh@gmail.com.
Abstract:
It was found that cations formed by the protonation of 2-amino-3-(2'-benzoxazolyl)-quinoline (ABO) and 2-amino-3-(2'-benzothiazolyl)-quinoline (ABT) at the nitrogen atom of the quinoline ring exhibit excited-state intramolecular proton transfer (ESIPT). The two-band fluorescence of these cations is due to the emission from two species: the initial tautomer (short-wavelength band) and the ESIPT product (long-wavelength band). The relative intensity of the long-wavelength band depends on the basicity of the proton-accepting moiety and temperature. Quantum-chemical calculations demonstrated that ESIPT in cations involves overcoming a significant potential barrier, which increases with the decreasing basicity of the proton-accepting benzazole moiety. Using femtosecond absorption spectroscopy and nanosecond fluorescence spectroscopy, the effective ESIPT time in the studied cations was determined, which increased with decreasing temperature.
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