Rational Design of Supramolecular Assemblies via Incommensurate Geometries and Coordination Number

这个无机、生物无机和有机金属化学项目的奖项支持加州大学伯克利分校的Kenneth N Raymond博士设计、合成和评估高对称性、纳米级分子团簇的研究。这些集群被设计成由许多小而简单、相同的亚单元自组装而成。建模研究将集中于制造空腔比立方纳米大得多的簇。这项工作将解决由于集群的疏水性空腔而导致的主/客形成稳定性丧失与扩大进入内部的便利性以允许更快速的客人交换之间的权衡。新的设计将包括二十面体和带正电荷和负电荷的簇（改变主人/客人的偏好特征）。研究超分子性质的广泛领域包括热力学量的量热定量、自组装的动力学研究、超分子手性、主客体相互作用以及电子和分子输运。需要解决的问题之一是，客体分子是否通过由配体解离形成空腔而形成的开口进入超分子空腔，或者客体分子是否通过宿主结构中的缝挤入。模型研究表明，客人的退出可能是通过集群的合作扭曲而不是部分分离发生的。由于金属顶点的三角螺旋桨手性和金属顶点之间的机械连接，即使更换了簇的组件，簇也是同手性的、可分解的和保持其手性的。集群将准备与客人内部更对映体选择性。其他目标是将团簇附着在固体载体上，并制备可切换的团簇，其主客体性质可以通过电化学或光化学方式改变。具有不同氧化态金属离子顶点的簇可以作为多达九种不同氧化还原态的电子载体。不稳定的高氧化态团簇将由更不稳定的低氧化态络合物通过氧化到不稳定的状态来制备。在设计的、手性的、纳米尺寸的烧瓶内进行化学反应的能力打开了有前途的应用，可能会改善化学分离和选择性化学反应性。学生将学习超分子设计、合成、表征和超分子反应机制。

This award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports research by Dr. Kenneth N Raymond of the University of California at Berkeley to design, synthesize and evaluate high-symmetry, nanometer scale molecular clusters. The clusters are designed to be self-assembled from a number of small and simple, identical subunits. Modeling studies will focus on making clusters with cavities much larger than a cubic nanometer. The work will address the trade-off between loss of stability in host/guest formation due to the hydrophobic cavity of the cluster as compared to expanding the ease of access to the interior to allow more rapid guest exchange. New designs will include icosahedra and clusters with positive as well as negative charges (changing the host/guest preference characteristics). The broad areas of supramolecular properties under investigation include calorimetric quantification of thermodynamic quantities, kinetic studies of self-assembly, supramolecular chirality, guest-host interactions and electron and molecular transport. Among questions to be addressed is whether guest molecules enter the supramolecular cavity through an opening made by a the dissociation of a ligand forming the cavity or whether the guest molecule squeezes in through a seam in the host structure. Modeling studies suggest that exit of the guest probably occurs through a cooperative distortion, rather than partial dissociation, of the cluster. Because of trigonal propeller chirality at the metal vertices and mechanical linkage between the metal vertices, the clusters are homochiral, resolvable and retain their chirality even when components of the cluster are replaced. Clusters will be prepared with guest interiors that are much more enantiomerically selective. Other goals are the attachment of clusters to solid supports and the preparation of switchable clusters whose host/guest properties can be altered either electrochemically or photochemically. Clusters with varying oxidation state metal ion vertices can act as electron carriers through as many as nine different redox states. Non-labile higher oxidation state clusters will be prepared from the more labile lower oxidation state complexes by oxidation to a less labile state.The ability to do chemistry inside designed, chiral, nanometer sized flasks opens promising applications that may improve chemical separations and selective chemical reactivity. Students will be trained in supramolecular design, synthesis, characterization, and supramolecular reaction mechanisms.