Otolski Christopher J, Mohan Raj A, Sharma Gaurav, Prabhakar Rajeev, Ramamurthy Vaidhyanathan, Elles Christopher G
Department of Chemistry , University of Kansas , Lawrence , Kansas 66045 , United States.
Department of Chemistry , University of Miami , Coral Gables , Florida 33146 , United States.
J Phys Chem A. 2019 Jun 20;123(24):5061-5071. doi: 10.1021/acs.jpca.9b03285. Epub 2019 Jun 11.
Ultrafast spectroscopy reveals the effects of confinement on the excited-state photoisomerization dynamics for a series of alkyl-substituted trans-stilbenes encapsulated in the hydrophobic cavity of an aqueous supramolecular organic host-guest complex. Compared with the solvated compounds, encapsulated trans-stilbenes have broader excited-state absorption spectra, excited-state lifetimes that are 3-4 times longer, and photoisomerization quantum yields that are 1.7-6.5 times lower in the restricted environment. The organic capsule disrupts the equilibrium structure and restricts torsional rotation around the central C═C double bond in the excited state, which is an important motion for the relaxation of trans-stilbene from S to S. The location and identity of alkyl substituents play a significant role in determining the excited-state dynamics and photoisomerization quantum yields by tuning the relative crowding inside the capsule. The results are discussed in terms of distortions of the ground- and excited-state potential energy surfaces, including the topology of the S-S conical intersection.
超快光谱揭示了一系列封装在水性超分子有机主客体复合物疏水腔内的烷基取代反式芪的受限环境对其激发态光异构化动力学的影响。与溶剂化化合物相比，封装的反式芪具有更宽的激发态吸收光谱、长3至4倍的激发态寿命以及在受限环境中低1.7至6.5倍的光异构化量子产率。有机胶囊破坏了平衡结构，并限制了激发态下围绕中心C═C双键的扭转旋转，这是反式芪从S态弛豫到S态的重要运动。烷基取代基的位置和特性通过调节胶囊内部的相对拥挤程度，在决定激发态动力学和光异构化量子产率方面起着重要作用。结果从基态和激发态势能面的畸变角度进行了讨论，包括S-S锥形交叉点的拓扑结构。
