Department of Chemistry, Indian Institute of Technology Guwahati, Guwahati, 781039, India.
Photochem Photobiol Sci. 2020 Jun;19(6):844-853. doi: 10.1039/c9pp00490d. Epub 2020 Oct 27.
In aqueous solution, 2-(4-fluorophenylamino)-5-(2,4-dihydroxybenzeno)-1,3,4-thiadiazole (FABT) was found to emit dual emission and the longer wavelength emission was assigned to the combination of aggregation and conformational change. In a number of molecules that possess an intramolecular hydrogen bond between the proton donor and the acceptor, the longer wavelength emission is often observed due to the emission from the tautomer formed by excited state intramolecular proton transfer (ESIPT). Therefore, an analogue of FABT, 2-phenylamino-5-(2-hydroxybenzono)-1,3,4-thiadiazole (PHBT), was synthesized to determine the origin of the longer wavelength emission. The luminescence of PHBT and its methoxy derivatives was studied and compared with that of FABT. Theoretical calculations were also performed on both FABT and PHBT. Based on the experimental and theoretical investigations, the nonexistence of the keto tautomer in the ground state and the origin of the longer wavelength emission are divulged.
在水溶液中，2-(4-氟苯基氨基)-5-(2,4-二羟基苯并)-1,3,4-噻二唑（FABT）被发现具有双发射，较长波长的发射归因于聚集和构象变化的组合。在许多分子中，质子供体和受体之间存在分子内氢键，由于激发态分子内质子转移（ESIPT）形成的互变异构体的发射，通常观察到较长波长的发射。因此，合成了 FABT 的类似物 2-苯氨基-5-(2-羟基苯并)-1,3,4-噻二唑（PHBT），以确定较长波长发射的起源。研究了 PHBT 及其甲氧基衍生物的发光，并与 FABT 进行了比较。还对 FABT 和 PHBT 进行了理论计算。基于实验和理论研究，揭示了在基态中不存在酮式互变异构体和较长波长发射的起源。
