State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, P. R. China.
Phys Chem Chem Phys. 2011 Dec 14;13(46):20766-71. doi: 10.1039/c1cp21470e. Epub 2011 Oct 14.
The fluoride-sensing mechanism of the sensor 2-(2'-phenylurea-phenyl)benzoxazole (PUBO) has been investigated by means of the TD-DFT method. The present theoretical study indicates that there is an excited-state intramolecular proton transfer (ESIPT) process in the sensor PUBO. The added fluoride anion could capture the proton in the free N-H moiety instead of the hydrogen-bonding one. The experimental UV/Vis and fluorescence spectra (J. Org. Chem. 2007, 72, 62) are well reproduced by the calculated vertical excitation energies in the ground state and the first singlet excited state. For example, the calculated emission wavelength of PUBO at 534 nm is very close to the fluorescence band at 554 nm. Furthermore, we theoretically confirmed that the added fluoride anions could inhibit the ESIPT process in PUBO. But different from the classical ESIPT-inhibition mechanism, the ESIPT process in the sensor PUBO is inhibited by the high energy barrier of its deprotonated form rather than by the absence of the transferred proton.
通过 TD-DFT 方法研究了传感器 2-(2'-苯甲脒基-苯基)苯并恶唑（PUBO）的氟传感机制。本理论研究表明，传感器 PUBO 中存在激发态分子内质子转移（ESIPT）过程。外加的氟阴离子可以捕获游离 N-H 部分的质子，而不是氢键中的质子。实验上的 UV/Vis 和荧光光谱（J. Org. Chem. 2007, 72, 62）通过在基态和第一单重激发态中计算的垂直激发能很好地再现。例如，PUBO 的计算发射波长为 534nm，非常接近 554nm 的荧光带。此外，我们从理论上证实，外加的氟阴离子可以抑制 PUBO 中的 ESIPT 过程。但与经典的 ESIPT 抑制机制不同，传感器 PUBO 中的 ESIPT 过程是被其去质子化形式的高能量势垒而不是缺少转移质子所抑制。
