Zhao Guang-Jiu, Han Ke-Li
State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, Liaoning, China.
J Phys Chem A. 2007 Sep 27;111(38):9218-23. doi: 10.1021/jp0719659. Epub 2007 Jul 4.
The time-dependent density functional theory (TDDFT) method was performed to investigate the excited-state hydrogen-bonding dynamics of fluorenone (FN) in hydrogen donating methanol (MeOH) solvent. The infrared spectra of the hydrogen-bonded FN-MeOH complex in both the ground state and the electronically excited states are calculated using the TDDFT method, since the ultrafast hydrogen-bonding dynamics can be investigated by monitoring the vibrational absorption spectra of some hydrogen-bonded groups in different electronic states. We demonstrated that the intermolecular hydrogen bond C=O...H-O between fluorenone and methanol molecules is significantly strengthened in the electronically excited-state upon photoexcitation of the hydrogen-bonded FM-MeOH complex. The hydrogen bond strengthening in electronically excited states can be used to explain well all the spectral features of fluorenone chromophore in alcoholic solvents. Furthermore, the radiationless deactivation via internal conversion (IC) can be facilitated by the hydrogen bond strengthening in the excited state. At the same time, quantum yields of the excited-state deactivation via fluorescence are correspondingly decreased. Therefore, the total fluorescence of fluorenone in polar protic solvents can be drastically quenched by hydrogen bonding.
采用含时密度泛函理论（TDDFT）方法研究了芴酮（FN）在供氢甲醇（MeOH）溶剂中的激发态氢键动力学。利用TDDFT方法计算了基态和电子激发态下氢键化的FN-MeOH复合物的红外光谱，因为通过监测不同电子态下一些氢键基团的振动吸收光谱可以研究超快氢键动力学。我们证明，在氢键化的FM-MeOH复合物光激发后，芴酮与甲醇分子之间的分子间氢键C=O...H-O在电子激发态下显著增强。激发态下氢键的增强可以很好地解释芴酮发色团在醇类溶剂中的所有光谱特征。此外，激发态下氢键的增强可以促进通过内转换（IC）的无辐射失活。同时，通过荧光进行的激发态失活的量子产率相应降低。因此，极性质子溶剂中芴酮的总荧光可被氢键大幅猝灭。
