Photophysics Laboratory, Department of Physics, DSB Campus, Kumaun Universit, Nainitial 263002, Uttarakhand, India.
J Phys Chem A. 2012 Jul 12;116(27):7272-8. doi: 10.1021/jp210516t. Epub 2012 Jun 28.
In the present work we report some hitherto unnoticed features in the steady state and time-resolved measurements of isoquinoline in water and trifluoroethanol (TFE). Absorption spectra reveal that in water, neutrals as well cationic species are present. Emission spectrum shows structured features at shorter wavelengths accompanied with a broad band around 375 nm, which correspond to neutrals and cations respectively. However, time-resolved data indicate that protonation does not take place in the excited state in water. On the contrary, in stronger hydrogen bonding solvent TFE, distribution of decay components is observed and at longer wavelengths a small rise time is present. This is ascribed to neutral and cation-like species present in the ground as well as in the excited state. The difference in the results is explained in terms of different excited state potential energy surfaces for water and TFE; particularly, the presence of a rather small barrier for protonation in case of TFE.
在本工作中，我们报道了异喹啉在水和三氟乙醇（TFE）中的稳态和时间分辨测量中一些迄今为止未被注意到的特征。吸收光谱表明，在水中存在中性体和阳离子体。发射光谱在较短波长处显示出结构化特征，伴随着一个约 375nm 的宽带，分别对应于中性体和阳离子体。然而，时间分辨数据表明，在水中质子化不会发生在激发态。相反，在氢键更强的溶剂 TFE 中，观察到衰减分量的分布，并且在较长波长处存在一个较小的上升时间。这归因于在基态和激发态中存在中性体和类阳离子体。结果的差异可以用水和 TFE 的不同激发态势能面来解释；特别是，在 TFE 的情况下，质子化的势垒相当小。
