| Autor: |
Fahrni, C. J., Henary, M. M., VanDerveer, D. G. |
| Zdroj: |
The Journal of Physical Chemistry - Part A; August 2002, Vol. 106 Issue: 34 p7655-7663, 9p |
| Abstrakt: |
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 (τ = 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 π-stacking interactions between the tosylamide and benzimidazole rings. Ab initio calculations suggest a different structure in the gas phase without π-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. |
| Databáze: |
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