Dynamics and Mechanisms of Electron Delocalization over Supramolecular Mixed Valence Systems

在这个由化学学部化学结构、动力学和机理B项目支持的项目中，加州大学圣地亚哥分校（UCSD）化学系的Clifford Kubiak教授正在开发用于下一代计算机的新型无机材料。这项研究的目标是开发和研究新的配合物，这些配合物可以经历皮秒（万亿分之一秒）电子转移或发生在电子基态的结构重排。这种超快分子变化可用于制造新型分子器件，包括用于信息存储的器件。该项目有可能影响涉及电子设备技术的更广泛的科学和工程界，其中一个关键目标是通过当前的互补金属氧化物半导体（CMOS）平台扩展信息处理。库比亚克集团在为学生提供高技术水平的教育和培训方面处于有利地位。涉及K-12学生的外展活动，特别是来自加州大学圣地亚哥分校普鲁斯学校和托里派恩高中的学生。该项目的重点是研究混合价系中的超快（皮秒）电子转移。混合价配合物通常由由桥分隔的两个相同的氧化还原活性中心组成。在混合价状态下，氧化还原中心仅在氧化态上有所不同，并且相对于电子自交换的歧化是稳定的。该小组表明，当桥接相互作用由氢键组成时，混合价态的电子转移（ET）相对于中性、等价、氢键二聚体每摩尔稳定约5千卡的氢键相互作用。该项目的一个核心问题是氢键是先于、跟随还是与ET同时发生。具体目标是：对ET如何在氢键间发生进行完整的物理描述；继续合成新的配合物，以更好地了解电子离域与氢键之间的相互作用；并研究超分子结构的自组装开关，这种超分子结构在还原时可以形成更强的氢键。与二维红外光谱实验室（2D IR）的合作为ET的动力学和机制以及发生在超快基态分子中的分子重排提供了新的光谱见解。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。

In this project, supported by the Chemical Structure, Dynamics & Mechanism B Program of the Chemistry Division, Professor Clifford Kubiak of the Department of Chemistry at the University of California, San Diego (UCSD) is developing new classes of inorganic materials for use in next generation computers. The goal of this research is to develop and study new complexes that undergo picosecond (a trillionth of a second) electron transfer or structural rearrangements that occur in electronic grounds states. Such ultrafast molecular changes may be used to make novel molecular devices including those for information storage. This project has the potential to impact the broader scientific and engineering communities involved in electronic device technologies where a critical goal is to extend information processing by the current Complementary Metal-Oxide-Semiconductor (CMOS) platforms. The Kubiak group is well-positioned to provide a highly technical level of education and training for students. Outreach activities involving K-12 students, especially those from the Preuss School at UCSD and Torrey Pines High School. The focus of the project is the investigation of ultrafast (picosecond) electron transfer in mixed valence systems. Mixed-valent complexes typically consist of two identical redox active centers that are separated by a bridge. In their mixed-valent state, the redox centers differ only in their oxidation states and are stabilized relative to disproportionation by electron self-exchange. The group has showed that when the bridging interaction is composed of a hydrogen bond, electron transfer (ET) in the mixed-valent state stabilizes hydrogen-bonding interactions by about 5 kcal per mole relative to the neutral, isovalent, hydrogen-bonded dimers. A core question of this project is whether the hydrogen bond precedes, follows, or occurs in concert with ET. The specific goals are: to develop a complete physical description of how ET occurs across hydrogen bonds; to continue the synthesis of new complexes to better understand the interplay between electron delocalization and hydrogen bonding; and to investigate the switched-on self-assembly of supramolecular structures that can form stronger hydrogen bonds when reduced. A collaboration with a 2-dimensional infrared spectroscopy lab (2D IR) provides new spectroscopic insights into the dynamics and mechanisms of ET and molecular rearrangements that occur in ultrafast ground state molecules.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.