Medium Matters: Merging Photochemistry with Supramolecular-, Nano-, and Green Chemistries

生物系统中化学过程的效率和选择性往往源于高度受限和有组织的环境中反应物的局部化。其中一些过程（如光合作用）利用光作为驱动反应的能量来源。迈阿密大学Vaidhyanathan Ramamurthy教授的研究项目侧重于对密闭空间中分子特性的基本理解，并探索利用光在水中引发反应。长期目标是通过开发有效的方法，通过水的转化（避免与使用有机溶剂有关的环境问题），捕捉太阳光（一种可持续的能源）并将其转化为化学能，从而满足国家在可持续性方面的需要。该跨学科项目涉及国内和国际合作，为研究生和博士后研究人员提供研究培训。此外，Ramamurthy教授还接触了美国国内外大学的本科生和研究生，并通过他的一般讲座来激励年轻的研究人员成为成功的科学家，这些讲座强调了基础科学在日常应用中的重要性。为了了解分子在密闭环境中的行为，提高水中反应的选择性和效率，Ramamurthy教授的团队合成了水溶性空腔体，这些空腔体可以封装有机分子，并作为尺寸为几埃的反应容器。研究小组研究了通过光诱导电子转移，从被封装的供体穿过囊壁到外部的受体（例如，水溶性敏化剂或TiO2），利用太阳能在水中进行化学转化，在胶囊中产生活性有机自由基离子。所研究的光化学反应包括烯烃和环丙烷的几何异构化反应、生成富能量环丁烷的环加成反应、生成高应变分子的价异构化反应和环还原反应。光谱研究，包括超快（ns-fs）实验，用于测量电子转移速率，识别自由基中间体，确定中间体的反应性，并阐明产物结构。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The efficiency and selectivity of chemical processes in biological systems often stem from the localization of reactants in highly restricted and organized environments. Some of these processes (e.g., photosynthesis) harness light as the source of energy for driving the reactions. The research program of Prof. Vaidhyanathan Ramamurthy at University of Miami focuses on fundamental understanding of the properties of molecules in confined space and exploring the use of light to initiate reactions in water. The long-term goal is to address the national needs in sustainability by developing efficient methods for capturing and converting sunlight (a sustainable source of energy) into chemical energy through transformations in water (that avoids environmental issues associated with the use of organic solvents). This interdisciplinary project involving domestic and international collaborations provides research training to graduate students and postdoctoral researchers. Additionally, Prof. Ramamurthy reaches out to undergraduate and graduate students at universities within and outside USA and motivates young researchers toward becoming successful scientists through his general lectures that highlight the importance of basic science in the context of everyday applications. With the goal of understanding the behavior of molecules in confined environments and enhancing the selectivity and efficacy of reactions in water, Prof. Ramamurthy's group synthesizes water-soluble cavitands that encapsulate organic molecules and serve as reaction vessels with dimensions of a few angstroms. The research team investigates the generation of reactive organic radical ions in the capsule by photoinduced electron transfer from encapsulated donors across the capsular wall to acceptors (e.g., a water-soluble sensitizer or TiO2) present outside, harnessing solar energy for chemical transformations in water. The photochemical reactions being studied include the geometric isomerization of olefins and cyclopropanes, cycloaddition reactions to produce energy rich cyclobutanes, valence isomerization to generate highly strained molecules and cycloreversion reactions. Spectroscopic studies, including ultrafast (ns-fs) experiments, are performed to measure the rates of electron transfer, identify the radical ion intermediates, determine the reactivity of the intermediates, and elucidate the product structures.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.