Photoactivation of Distal Groups in Polyfunctional Molecules

有机化学和高分子化学项目的这项拨款支持光诱导化学反应机制的研究。莫里森博士在光化学反应中的重点是紧密但形式上非共轭的官能团之间的相互作用，这些官能团在光吸收产生的激发态中相互作用。这样的系统作为许多光诱导的生命过程化学序列的模型是很重要的。例如，在光合作用中，叶绿素中的一个“天线”基团获取光能，然后将其传递给附近的“受体”，以启动化学变化。双功能分子的光化学反应大致可细分为：(A)涉及两个官能团之间的键形成，和(B)主要只涉及两个基团中的一个的光化学反应，然后非反应部分充当获取光子的“天线”。在后一种情况下，现在认识到可以导致远端反应基团激活的各种机制。反应基团在紫外光谱中可以是相对透明的(例如氯、甲氧基和烯烃取代基)，或者本身能够被吸收(例如酮)，但仍然可能被ATENA选择性地激活。这项研究主要针对“B类”系统。寻找答案的基本问题包括：(1)激活远端官能团的各种机制有多普遍，有什么立体电子限制；(2)如何综合利用这些现象；以及(3)它们如何反映在复杂分子的光稳定性中？作为之前由基金会拨款CHE-8318825资助的研究的结果，莫里森博士还启动了涉及金属离子在光化学中的催化和在气相中的光化学的研究。这两个项目都发现了新的和耐人寻味的化学，其扩展包括在本计划中。

This grant in the Organic and Macromolecular Chemistry Program supports research on the mechanisms of light-induced chemical reactions. Dr. Morrison's focus in photochemical reactions is the interaction of close, but formally non-conjugated functional groups which interact in the excited states generated by light absorption. Such systems are important as models for many of the light-induced chemical sequences of life processes. In photosynthesis, for example, one "antenna" group in chlorophyll harvests light energy and then transfers it to a nearby "receptor" for initiating chemical changes. Photochemical reactions of bifunctional molecules can be broadly subclassified into those (a) involving bond formation between the two functionalities, and (b) those primarily involving only one of the two groups, the non-reacting moiety then serving as an "antenna" to harvest photons. In the latter case, a variety of mechanisms are now recognized which can lead to activation of the distal, reacting group. The reacting group may either be relatively transparent in the ultraviolet spectrum (examples are chlorine, carbethoxy, and alkene substituents), or be itself capable of asborption (a ketone, for example), but still potentially selectively activated by the atenna. This research is primarily addressed to "Class b" systems. The basic questions for which answers are sought include: (1) How general, and with what stereoelectronic limitations, are the various mechanisms for activiting distal functionalities; (2) How may these phenomena be utilized synthetically; and (3) How are they reflected in the photostability of complex molecules? As an out growth of research previously supported by Foundation Grant CHE-8318825, Dr. Morrison has also initiated studies involving metal ion catalysis in photochemistry and photochemistry in the gas phase. Both projects have uncovered new and intriguing chemistry, the extensions of which are included in the present program.