Khimich Mikhail N, Ivanov Vladimir L, Melnikov Mikhail Ya, Shelaev Ivan V, Gostev Fedor E, Nadtochenko Victor A, Uzhinov Boris M
Chemistry Department Lomonosov Moscow State University, 119991 Moscow, Russia.
N.N. Semenov Institute of Chemical Physics, Russian Academy of Sciences, Moscow, Russia.
Photochem Photobiol Sci. 2017 Jul 1;16(7):1139-1145. doi: 10.1039/c7pp00104e. Epub 2017 Jun 5.
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.
研究发现，2-氨基-3-(2'-苯并恶唑基)-喹啉（ABO）和2-氨基-3-(2'-苯并噻唑基)-喹啉（ABT）在喹啉环氮原子上质子化形成的阳离子表现出激发态分子内质子转移（ESIPT）。这些阳离子的双波段荧光源于两种物质的发射：初始互变异构体（短波长波段）和ESIPT产物（长波长波段）。长波长波段的相对强度取决于质子接受部分的碱性和温度。量子化学计算表明，阳离子中的ESIPT涉及克服一个显著的势垒，该势垒随着质子接受苯并唑部分碱性的降低而增加。利用飞秒吸收光谱和纳秒荧光光谱，测定了所研究阳离子中的有效ESIPT时间，该时间随温度降低而增加。
