Excited-state intramolecular proton transfer in 2-(2′-tosylaminophenyl)benzimidazole
Excited-state intramolecular proton transfer in 2-(2′-tosylaminophenyl)benzimidazole
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DOI：
10.1021/jp0204915
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发表时间：
2002-08-29
影响因子：
2.9
通讯作者：
VanDerveer, DG
中科院分区：
文献类型：
--
作者：
Fahrni, CJ;Henary, MM;VanDerveer, DG
研究了2-（2 ′-对甲苯磺酰胺基苯基）苯并咪唑（TPBI）在一系列不同溶剂中的光谱性质。如通过吸光度、稳态和时间分辨发射光谱所揭示的，该分子经历快速激发态分子内质子转移（ESIPT）以产生具有大量子产率（0.5）的相应互变异构物种的发射。无论溶剂的性质如何，荧光发射都显示出单指数衰减动力学（τ = 4.5 ns）。基态平衡主要由一个单一的旋转异构体和少量的去质子化阴离子。TPBI的X-射线结构显示出沿芳基-苯并咪唑键轴沿着的大量面外扭曲，这可能是由于甲苯磺酰胺和苯并咪唑环之间的T-堆积相互作用。从头计算表明，在气相中没有不同的结构，π堆叠相互作用和大大减少的扭转角。在DFT计算的基础上，预测了顺式和反式旋转异构体在基态和激发态相互转化的大能垒，这与所有实验数据一致。TPBI的基态平衡和ESIPT过程基本上不受溶剂性质的影响，这对细胞生物学中的传感应用特别感兴趣。
The spectroscopic properties of 2-(2'-tosylaminophenyl)benzimidazole (TPBI) have been studied in a series of different solvents. As revealed by absorbance, steady-state, and time-resolved emission spectroscopy, the molecule undergoes fast excited-state intramolecular proton transfer (ESIPT) to yield emission of the corresponding tautomeric species with a large quantum yield (0.5). The fluorescence emission shows monoexponential decay kinetics (tau = 4.5 ns) regardless of the nature of the solvent. The ground-state equilibrium is dominated by a single rotamer and small amounts of the deprotonated anion. The X-ray structure of TPBI shows a substantial out-of-plane twist along the aryl-benzimidazole bond axis, which is presumably due to T-stacking interactions between the tosylamide and benzimidazole rings. Ab initio calculations suggest a different structure in the gas phase without,pi-stacking interactions and a substantially reduced twist angle. A large energy barrier for interconversion of the cis- and trans-rotamers in the ground and excited state has been predicted on the basis of DFT calculations, which is in agreement with all experimental data. The ground-state equilibrium and ESIPT process of TPBI are essentially unaffected by the nature of the solvent, which is of particular interest to sensing applications in cell biology.