Rational Design of Supramolecular Assemblies via Incommensurate Geometries and Coordination Number

该无机、生物无机和有机金属化学项目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簇的研究。 这些簇被设计为由许多小而简单、相同的子单元自组装而成。 建模研究将集中于制造空腔远大于立方纳米的簇。 这项工作将解决由于簇的疏水腔而导致主体/客体形成稳定性损失与扩大进入内部的便利性以允许更快速的客体交换之间的权衡。 新设计将包括二十面体和带有正电荷和负电荷的簇（改变主人/客人的偏好特征）。 正在研究的超分子特性的广泛领域包括热力学量的量热定量、自组装动力学研究、超分子手性、客体相互作用以及电子和分子传输。 需要解决的问题是客体分子是否通过形成空腔的配体解离形成的开口进入超分子空腔，或者客体分子是否通过主体结构中的接缝挤入。 模型研究表明，客体的退出可能是通过集群的合作扭曲而不是部分解离而发生的。 由于金属顶点处的三角螺旋桨手性和金属顶点之间的机械连接，团簇是同手性的、可解析的，并且即使当团簇的组分被替换时也保留其手性。 集群将配备更具对映体选择性的客用内饰。其他目标是将簇附着到固体支持物上，以及制备可切换簇，其主体/客体特性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通过多达九种不同的氧化还原态充当电子载体。 不稳定的高氧化态簇将从更不稳定的低氧化态络合物通过氧化至不太不稳定的状态来制备。在设计的手性纳米尺寸烧瓶内进行化学反应的能力开启了有希望的应用，可以改善化学分离和选择性化学反应性。 学生将接受超分子设计、合成、表征和超分子反应机制的培训。

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.