Photoreactivity of a push-pull merocyanine in static electric fields: a three-state model of isomerization reactions involving conical intersections.
Photoreactivity of a push-pull merocyanine in static electric fields: a three-state model of isomerization reactions involving conical intersections.
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静电场中推拉部花青的光反应性：涉及圆锥形交叉的异构化反应的三态模型。
DOI：
10.1021/jp904097k
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
Y. Haas
中科院分区：
文献类型：
--
作者：
X. Xu;A. Kahan;S. Zilberg;Y. Haas
使用简单的三态模型讨论原型推拉部花青的光化学。作为丁二烯的衍生物，该模型重点关注丁二烯主链两个双键周围的两个异构化反应。作为在两端被电子供体和电子受体取代的分子，其结构及其光化学预计会受到环境的强烈影响。在极性溶剂中，各异构化反应的两性离子过渡态是稳定的，其能量与双自由基处于同一数量级；这导致了允许交叉的对称性（S(0)/S(1) 圆锥形交叉）。结果表明，施加外部电场或改变溶剂极性会改变不同过渡态以及圆锥交叉点的相对能量，从而获得不同的光化学产物。特别是，发现圆锥形交叉点的存在取决于这些外部参数。这项工作为 Squillacote 等人表达的想法提供了理论基础。 (J. Am. Chem. Soc. 2004, 126, 1940) 关于光化学反应的静电控制。
The photochemistry of a prototype push-pull merocyanine is discussed using a simple three-state model. As a derivative of butadiene, the model focuses on two isomerization reactions around the two double bonds of the butadiene backbone. As a molecule substituted by an electron donor and electron acceptor at opposite ends, its structure as well as its photochemistry are expected to be strongly affected by the environment. In polar solvents, a zwitterion transition state for each of the isomerization reactions is stabilized, and its energy is on the same order as that of the biradical one; this leads to the symmetry allowed crossing (S(0)/S(1) conical intersection). It is shown that applying an external electric field or varying the solvent polarity changes the relative energies of the different transition states as well as that of the conical intersection, and thus different photochemical products can be obtained. In particular, the very existence of conical intersections is found to depend on these external parameters. This work provides a theoretical foundation for ideas expressed by Squillacote et al. (J. Am. Chem. Soc. 2004, 126, 1940) concerning the electrostatic control of photochemical reactions.