Photophysics and Photochemistry of Cyclic Enones

该奖项是在有机动力学项目中颁发的，以支持纽约大学的David Schuster博士对环不饱和酮的光化学和光物理的研究。利用纳秒闪光光解、光声量热法和时间分辨共振拉曼光谱研究了环烯酮在有烯烃和无烯烃情况下形成的三重态激发态和反应中间体的性质。目标是获得数据，这将允许规范分子结构和能量的单线态和三重态，环烯酮的应变反式异构体和三重态1,4-双基中间体。这些研究将确定环烯酮三联体中的能量弛豫如何受到环尺寸和取代的影响，以及分子结构如何影响从三联体激发态到基态的自旋反转速率，这在有机光化学中具有重要意义。对合成上重要的环烯酮与烯烃的光环加成进行机理研究。特别是，为了确定任何类型的烯-烯复合物是否在生成三联体1,4-双自由基的反应途径上，将测定烯-烯三联体被烯烃猝灭和环加合物形成时的二次氘同位素效应。

This award is made in the Organic Dynamics Program to support the research of Dr. David Schuster of New York University on the photochemistry and photophysics of cyclic unsaturated ketones. Properties of triplet excited states and reaction intermediates formed in the photoexcitation of cyclic enones in the presence and absence of alkenes will be studied by nanosecond flash photolysis, photoacoustic calorimetry and time-resolved resonance Raman spectroscopy. The goal is to obtain data which will allow specification of the molecular structures and energies of singlet and triplet states, strained trans isomers of cyclic enones and of triplet 1,4-biradical intermediates. These studies will establish how energetic relaxation in cyclic enone triplets is affected by ring size and substitution and how molecular structure affects rates of spin inversions to ground states from triplet excited states, a matter of fundamental significance in organic photochemistry. Mechanistic studies of the synthetically important photocycloaddition of cyclic enones to olefins will be carried out. In particular, secondary deuterium isotope effects will be determined for quenching of enone triplets by alkenes and for formation of cycloadducts in order to determine if enone-alkene exciplexes of any kind are on the reaction pathway to triplet 1,4-biradicals.