Understanding Energy and Electron Transfer in Multi-Metal Coordination Compounds

化学部的化学结构动力学和机制（CSDM-A）项目支持佛罗里达大学瓦莱里娅·克莱曼教授的工作，研究一类有机金属分子的性质，这些分子有望成为太阳能收集器或电子运动的管道（分子线）。有机金属分子由有机成分（主要是碳和氢原子）和金属原子组成，金属原子在分子与光的相互作用中起着关键作用。该项目的主要重点是了解吸收光后的第一步，能量如何通过不同的分子结构传输，以及分子结构如何帮助增强和控制能量传输过程。这个项目包括通过改变所使用的金属原子的种类或金属原子附着的附近有机结构（称为“配体”）来调整分子的电子特性。通过观察暴露在光线下的能量和电子如何在分子中移动，克莱曼研究小组可以提供开发基于有机金属分子的高效太阳能捕获和传输系统所需的基本信息。值得注意的是，有机金属系统中的能量和电子转移过程发生在非常快的时间尺度（百万分之一秒的百万分之一）。因此，这些研究利用超快激光光谱工具，包括使用克莱曼实验室开发的多维光谱。该项目旨在基本理解激发态动力学参数导致光诱导能量转移，光诱导多电子氧化还原反应，以及它们的竞争，因为它们是由金属中心和有机配体的性质调制的。要回答的一个主要问题是矢量能量传递与激发态的潜在离域的作用。在此背景下，该项目为探索氰基桥接金属二聚体、低聚物和纳米颗粒的激发态动力学和耦合开辟了一个新的场所，使用超快宽带瞬态吸收光谱结合二维电子光谱来探索多金属结构中光激发后的初始步骤，有机配体允许调节其HOMO-LUMO间隙和状态耦合。研究将包括增加复杂性的组装，其中光物理可以通过不同有机配体的取向进行调制，并且金属中心通过NC桥共价结合，其自身的轨道不能捕获激发，但可以打开不同中心之间的耦合通道。这个项目更广泛的影响包括通过与布宜诺斯艾利斯大学（阿根廷）的一个实验室合作实现研究生教育的国际化。此外，本科生、研究生和博士后学生将学习使用最先进的工具，并精通最新的光谱技术进步，为他们在工业和/或学术界的职业生涯做好准备。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 Chemical Structure Dynamics and Mechanism (CSDM-A) program of the Chemistry Division supports the work of Professor Valeria Kleiman at the University of Florida to investigate the properties of a class of organometallic molecules that show promise as solar-energy harvesters or conduits for electron motion (molecular wires). Organometallic molecules consist of an organic component (mostly carbon and hydrogen atoms) and metal atoms which play a key role in how the molecules interact with light. The main focus of this project is to understand the first steps following absorption of light, how the energy is transported through the different molecular architectures and how the structure of the molecules can help enhance and control the energy transport process. This project involves tuning the electronic properties of the molecules by varying the kinds of metal atoms used or the nearby organic structures (called "ligands") to which the metal atoms are attached. By observing how energy and electrons move through molecules after they are exposed to light, the Kleiman research team can provide the fundamental information that will be needed to develop efficient solar energy capture and transport systems based on organometallic molecules. It is noted that energy and electron transfer processes in organometallic ssytems occur in very fast time scales (a millionth of a millionth of a second). Thus, these studies utilize ultrafast laser spectroscopy tools, including the use of multidimensional spectroscopies developed in the Kleiman laboratory.The project aims at fundamental understanding of the excited state dynamical parameters leading to photoinduced energy transfer, photoinduced-multielectron-redox reactions, and their competition, as they are modulated by the nature of the metal center and the organic ligands. A major question to answer is the role of vectorial energy transfer vs potential delocalization of the excited states. Within this context the project opens a new venue for the exploration of excited state dynamics and couplings of cyano-bridged metallo-dimers, oligomers and nanoparticles using ultrafast broadband Transient Absorption Spectroscopy combined with 2-Dimensional Electronic Spectroscopy to explore the initial steps following photoexcitation in multi-metal architectures with organic ligands that allow the modulation of their HOMO-LUMO gaps and state couplings. The investigations will include assemblies of increased complexity where the photophysics can be modulated by the orientation of different organic ligands, and where metal centers are covalently bound through NC bridges whose own orbitals cannot trap the excitation but can open coupling-channels between different centers. The broader impact of this project includes the internationalization of graduate education through the collaboration with a laboratory in the University of Buenos Aires (Argentina). Additionally, undergraduate, graduate and postdoc students will learn to use state of the art tools and become proficient in recent spectroscopy technological advances preparing them for careers in industry and/or academia.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.