Radical Cage Effects in Organometallic Chemistry

这一无机化学、生物无机化学和金属有机化学项目的奖项支持俄勒冈大学的David Tyler教授研究自由基反应化学中笼子效应的基本原理。基于溶剂的“微粘度”的新模型将探索溶剂仍然令人困惑的作用。研究的另一部分将集中在光产生的自由基笼对中，光的波长对笼效应有什么影响。初步结果显示出与理论预测相反的趋势。其他实验将探索自旋对两个金属自由基复合的影响，这一问题到目前为止还没有得到系统的解决。另一组实验将考察径向质量、大小和形状对笼子效应的影响。特别地，提出了笼子逃逸速率常数与笼子复合速率常数之比与质量的平方根除以自由基表面积成正比。这一假设将用不同质量和大小的自由基进行检验。如果这种关系是普遍的，它将为研究人员预测笼子重组效率提供一个强大的工具。飞秒激光泵浦-探测实验将被用来直接观察短寿命的自由基笼对。在这些实验中，将研究两个随机碰撞自由基的笼效应，以及由键均解形成的自由基笼对的笼效应。由于前者在笼子中相遇时最初具有随机取向，而后者最初是排列的，因此这种差异可能表现为笼子效应和笼子对的反应性的不同。研究生将参加成功的实习项目，通过将博士生安置在地区性公司或大学进行为期一年的实习，为他们在行业或教学领域的成功职业生涯做好准备。这里描述的研究还以合作研究项目的形式与区域公司和大学建立了更紧密的联系。这导致地区性学院的教授在泰勒教授的实验室休假，以及俄勒冈大学化学系此类学院和公司的学生使用这种仪器。

This award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports Professor David Tyler at the University of Oregon to investigate the fundamental, underlying principles of the cage effect in radical reaction chemistry. The still-confusing role of the solvent will be explored using a new model based on the "microviscosity" of the solvent. Another part of the research will focus on what effect the wavelength of light has on the cage effect in photogenerated radical cage pairs. Preliminary results show a trend opposite to that predicted by theory. Other experiments will probe spin effects on the recombination of two metal radicals, which has not been systematically addressed until now. Another set of experiments will examine the effects of radical mass, size, and shape on the cage effect. In particular, it is proposed that the ratio of the rate constants for cage escape to cage recombination is proportional to the square root of the mass divided by the surface area of the radical. This hypothesis will be tested with radicals of various masses and sizes. If this relationship is general, it will give researchers a powerful tool for predicting cage recombination efficiencies. Femtosecond timescale laser pump-probe experiments will be used to directly observe the shortlived radical cage pair. In these experiments, the cage effect for two randomly colliding radicals will be studied relative to the cage effect for a radical cage pair formed by bond homolysis. As former radicals initially have a random orientation when they meet in a cage, whereas the latter radicals are initially aligned, this difference may show up as a difference in the cage effect and in the reactivity of the cage pair. Graduate students will participate in successful internship programs, which prepare Ph.D. students for successful careers in industry or teaching by placing them in regional companies or in colleges for a one-term internship experience. The research described herein has also fostered closer ties to regional companies and colleges in the form of collaborative research projects. This has led to professors at regional colleges taking sabbatical leaves in the Professor Tyler's laboratory and to students at such colleges and companies using the instrumentation in the University of Oregon Department of Chemistry.