Building Electron Transfer Cascades into Amphiphlic Donor-Acceptor Assemblies

在这个由化学系大分子、超分子和纳米化学项目资助的项目中，加州大学洛杉矶分校化学系的Sarah Tolbert、Benjamin Schwartz和Yves Rubin教授正在开发复杂的分子，这些分子将光转化为分离的电荷，可以驱动有用的化学反应。 在自然系统中，例如光合作用，光能的吸收可以有效地转化为分离的电荷。 然后，这些电荷可以用于进行一系列重要的化学反应，整个过程称为光化学。 利用现代合成化学，Tolbert，Schwartz和Rubin教授正在创造能够有效吸收光的分子，然后通过分子间的一系列级联来分离电荷。 然后，他们正在研究如何利用这些分离的电荷进行有用的化学反应。 在这个过程中，他们正在培养一批跨学科科学的研究生。这些学生正在进一步努力与大洛杉矶地区的广大中学生分享他们的光化学和光化学技术知识。教授托尔伯特，施瓦茨和鲁宾正在研究如何创建和利用人工电子转移级联使用强吸收π共轭聚合物和分子。产生人工电子转移级联的主要挑战首先是创建明确定义的供体/受体对，其次是将具有逐渐降低的LUMO的附加受体放置在精确位置处，使得它们的能量梯度导致最初创建的电荷对的空间分离。 级联正在构建开始与两亲性，水溶性π共轭聚合物组装成网络的电互连胶束。然后将共轭聚电解质与带电的C60衍生物或其他π共轭受体组装。 组装体的结构和聚合物供体和π-共轭电子受体的能量学正在调整。 电子转移级联的特点是使用超快瞬态吸收光谱，结构与所观察到的光化学性质。 优化的组件正在被调整为在还原反应中用作光敏剂。

In this project funded by the Macromolecular, Supramolecular and Nanochemistry Program in the Division of Chemistry, Professors Sarah Tolbert, Benjamin Schwartz, and Yves Rubin of the Department of Chemistry at the University of California, Los Angeles are developing complex molecules that will convert light into separated electrical charges that can drive useful chemical reactions. In natural systems, such as photosynthesis, the absorption of light energy can be translated efficiently into separated electrical charges. These charges can then be used to conduct a range of important chemical reactions, and the overall process is called photochemistry. Using modern synthetic chemistry, Professors Tolbert, Schwartz and Rubin are creating molecules that absorb light efficiently and then separate the electrical charges via a series of cascades across the molecules. Then, they are examining ways to use those separated charges to do useful chemistry. In the process, they are training a group of graduate students in interdisciplinary science. Those students are further working to share their knowledge of photochemistry and photochemical technologies with a broad range of middle and high school students in the greater Los Angeles area. Professors Tolbert, Schwartz and Rubin are studying ways to create and exploit artificial electron transfer cascades using strongly absorbing pi-conjugated polymers and molecules. The principal challenges in producing artificial electron transfer cascades are first to create well-defined donor/acceptor pairs and second to place additional acceptors with progressively lower LUMOs at precise positions so that their energy gradient leads to spatial separation of the initially created charge pair. The cascades are being constructed starting with amphiphilic, water-soluble pi-conjugated polymers that assemble into networks of electrically-interconnected micelles. The conjugated polyelectrolytes are then assembled with charged C60 derivatives or other pi-conjugated acceptors. The structure of the assembly and the energetics of both the polymer donor and the pi-conjugated electron acceptor are being tuned. The electron transfer cascades are being characterized using ultrafast transient absorption spectroscopy, and the structures are being correlated with the observed photochemical properties. Optimized assemblies are being adapted for use as photosensitizers in reduction reactions.