Ultrafast Spectroscopic Studies of Polyene Photochemistry

在化学学部物理化学专业的这个项目中，密歇根大学化学系的Roseanne J. Sension教授将研究小多烯分子凝聚相反应中能量的重新分配，以及溶剂参数对这种重新分配的影响。简单的二烯和三烯物种将作为复杂有机生物分子的原型进行研究。具体来说，飞秒吸收光谱将用于研究1,3,5-己三烯、2,4-己二烯、1,3-丁二烯的顺-反异构化反应和环己二烯的电开环反应。流体环境中化学转化的详细机制仍然是化学中最重要的未解决问题之一。虽然人们对低压气相系统中分离分子的化学反应动力学给予了很多关注，但从生物、环境或工程的角度来看，大多数有趣的反应都发生在流体凝聚相环境中。在这个项目中所做的研究将解决其中的一些问题，以达到两个目标。1)详细了解多烯的电子结构在其光化学中所起的作用；2)详细了解能量再分配在控制多烯反应中所起的作用，因为这是大多数（如果不是全部的话）化学反应的最终因素，无论是在凝聚相中还是在孤立分子中。从原型分子的研究中推导出的原理将适用于一般的凝聚相反应动力学。

In this project in the Physical Chemistry program of the Chemistry Division, Prof. Roseanne J. Sension of the Chemistry Department of the University of Michigan will investigate the redistribution of energy in condensed phase reactions of small polyene molecules, and the influence of solvent parameters on this redistribution. Simple diene and triene species which serve as prototypes of complex bioorganic molecules will be investigated . Specifically, femtosecond absorption spectroscopy will be used to investigate the cis-trans isomerization reactions of 1,3,5-hexatriene, 2,4-hexadiene, 1,3-butadiene, and the electrocyclic ring opening reaction of cyclohexadiene. The detailed mechanism of chemical transformation in fluid environments remains among the most important unresolved problems in chemistry. While much attention has been given to chemical reaction dynamics of isolated molecules in low pressure gas phase systems, the majority of interesting reactions from a biological, environmental,, or engineering perspective, occur in fluid condensed phase environments. The research done in this project will attack some of these problems in order to meet two goals. 1) To develop a detailed understanding of the role that the electronic structure of polyenes plays in their photochemistry, and 2) to develop a detailed understanding of the role that energy redistribution plays in controlling polyene reactions since this is the ultimate factor in most, if not all, chemical reactions, be they in condensed phases or in isolated molecules. The principles deduced from the studies carried out in this research on prototype molecules will have application to general condensed phase reaction dynamics.