Taking Supramolecular Assembly to the Next Level: Assembly of Flexible Molecules with Complex Internal Structure and Chemistry

芝加哥大学的卡尔·弗里德获得了化学部化学理论、模型和计算方法计划颁发的奖项，该奖项旨在研究分子在非共价键合有序超分子结构中的平衡自组装。这种现象普遍存在于化学、材料科学和生物学中，其控制在工业和医学中有许多应用。早期的研究阐明了这种自发的和可逆的组织的一般潜在原理，其基础是忽略了分子内部结构细节的模型。目前的工作正在扩展这些理论进步，以解释组装单元的化学结构、它们的几何形状以及它们的相互作用(通常是方向性的)的强烈而往往微妙的影响。早期发展的晶格团簇理论形式被推广到包括(I)强的和/或吸引的相互作用和(Ii)柔性/可变形的分子。目标是描述五种定性不同类型的结构化单元的自组装，包括组装成链和网络结构。分子内和分子间的结构和热力学贡献是非相加的，增加了计算挑战，但也与现实的化学结合有关。这类新的自组装理论使人们能够研究普遍存在的热熵补偿现象，在这种现象中，预计会导致(反应)热焓变化的东西对系统的修饰在很大程度上被相应的熵变化所补偿(反之亦然)。当溶液中的分子自发地聚集在一起并组织起来时，自下而上地制造用于工业和医学的材料成为可能。从Freed和他的团队的工作中，这种情况发生的环境变得更加清楚，他们正在开发描述这种平衡自组装过程中相邻分子的化学结合的计算工具。不同的结构可能会产生不同的结构，例如链和网络结构，结果可能会受到单个分子的形状和振动和旋转行为的影响。这项工作的目标是了解不同分子如何产生不同的结果，并利用这一知识来控制自组装，以便在自下而上的材料设计中充分利用它。

Karl Freed of the University of Chicago is supported by an award from the Chemical Theory, Models and Computational Methods program in the Chemistry Division to investigate equilibrium self-assembly of molecules into non-covalently bonded ordered supramolecular structures. This phenomenon is pervasive in chemistry, materials science, and biology, and its control has numerous applications in industry and medicine. Earlier studies elucidated general underlying principles of this spontaneous and reversible organization based on models that ignored details of the internal structure of the molecules. The current work is extending those theoretical advances to account for the strong and often subtle influence of the chemical structure of the assembling units, their geometrical shapes, and their mutual (often directional) interactions. The Lattice Cluster Theory formalism developed earlier is being generalized to include (i) strong and/or attractive interactions and (ii) flexible/deformable molecules. The goal is to describe five qualitatively different types of self-assembly of structured units, including assembly into chains and network structures. The intramolecular and intermolecular structure and thermodynamics contributions are nonadditive, adding computational challenge but also relevance to realistic chemical association. This new class of self-assembly theories enables examination of the ubiquitous enthalpy-entropy compensation phenomenon, where modification of a system by what is anticipated to produces large changes in the enthalpy (of a reaction) is largely compensated by a corresponding change in the entropy (and vice versa).The bottom-up manufacture of materials for applications in industry and medicine is made possible when molecules in solution come together and organize spontaneously. The circumstances under which this occurs have become clearer from the work of Freed and his group, who are developing computational tools describing the chemical association of neighboring molecules in this process of equilibrium self-assembly. Different structures may result, for example, chains and network structures, and the outcomes can be influenced by the shapes and vibrating and rotating behavior of the individual molecules. The goals of the work are to understand how different outcomes occur for different molecules and to use this knowledge to control self-assembly so that it can be fully exploited in bottom-up material design.