Metallapolyynes: Archetypes for Understanding and Rationally Designing Conjugated Transition-Metal Compounds and Materials

Michael D. Hopkins博士，匹兹堡大学化学系，由化学系无机、生物无机和有机金属项目支持，研究共轭过渡金属化合物和材料。该项目旨在回答两个问题：(1)金属换碳如何影响π共轭有机化合物的电子结构？(2)这对提高这些材料的技术性能有什么意义？将制备一系列多炔，其中碳原子被金属中心系统地取代，并用电子和振动光谱、电化学和x射线晶体学来探测它们的键合。最初的研究将集中在简单的化合物上，以建立金属配体多键的基本结构和键性质。然后，将研究共轭pi系统中可能含有金属原子的越来越复杂的化合物，以评估金属原子参与离域键合网络的性质和程度。要研究的变量包括金属的性质，它的配体和氧化态，聚乙烯链的长度，以及pi网络中金属中心的数量和分布。这项工作在基础层面上是重要的，因为所提出的化合物代表了一个难得的机会来检查系统，可以使用通常用于有机和其他更适合无机系统的模型在理论上描述。结果将是连接考虑分子电子结构的两种方式的概念桥梁。从更实际的角度来看，这些结果将适用于光学和电子材料的设计。由于本研究中制备的金属聚ynes与目前在许多应用中使用的共轭有机材料之间存在密切的结构和电子关系，因此在本项目中建立的相关性将允许后者的技术上有价值的特性以合理的方式扩展到前者。有待开发的金属多炔的两个特性是分子内电子耦合和非线性光学响应。

Dr. Michael D. Hopkins, Department of Chemistry, University of Pittsburgh, is supported by the Inorganic, Bioinorganic, and Organometallic Program of the Chemistry Division for the study of conjugated transition metal compounds and materials. The project aims to answer two questions: (1) How does metal-for-carbon substitution affect the electronic structures of pi-conjugated organic compounds? and (2) What implications does this hold for improving the technological properties of these materials? A series of polyynes in which carbon atoms are systematically replaced by metal centers will be prepared and their bonding probed by electronic and vibrational spectroscopy, electrochemistry, and X-ray crystallography. Initially the study will concentrate on simple compounds in order to establish fundamental structural and bonding properties of metal-ligand multiple bonds. Then increasingly complex compounds, which potentially contain metal atoms within conjugated pi systems, will be studied in order to assess the nature and extent of a metal atom's participation in delocalized bonding networks. Variables to be investigated include the nature of the metal, its ligands and oxidation state, the length of the polyyne chain, and the number and distribution of metal centers within the pi network. This work is significant at a fundamental level because the proposed compounds represent a rare opportunity to examine systems that can be theoretically described both using models commonly employed for organic and others that are more appropriate for inorganic systems. The outcome will be conceptual bridges to link the two ways of considering the electronic structure of molecules. From a more practical viewpoint, the results will be applicable to the design of optical and electronic materials. Because of close structural and electronic relationship between the metallapolyynes prepared in this investigation and the conjugated organic materials currently used in a number of applications, the correlations established during this project will allow the technologically valuable properties of latter to be extended in a rational fashion to the former. Two specific properties of metallapolyynes that will be developed are intramolecular electronic coupling and nonlinear optical responses.