Design, Synthesis and Supramolecular Assembly of Furan-Based Macrocycles: Understanding Intra- and Intermolecular Conjugation

在美国国家科学基金会化学部大分子、超分子和纳米化学项目的支持下，卡内基梅隆大学的Kevin Noonan和Tomasz Kowalewski的目标是开发和探索一类新的环状（或环状）有机分子，这些分子由较小的环（“环的环”）组成。一般来说，制造环状分子的途径包括弯曲线性分子以将其两端连接在一起。随着环的尺寸增加，很难达到“收支平衡”，从而导致所需结构的产量降低。Noonan和Kowalewski最近发现，小呋喃环的短线性链可以被修改成这样一种方式，它们可以自发地弯曲成大环状的形状。他们将探索将这种方法扩展到小环的不同变体，以调整不同潜在应用的特性。在这些循环结构中，一部分电子驻留在所谓的pi键中，在某些条件下使它们能够自由流动，从而使材料表现得像金属或半导体而不是绝缘体。因此，它们属于“绿色”有机电子材料家族，可以从生物质中提取，具有很高的可持续能源应用前景，如太阳能电池，显示器和燃料和化学品生成催化剂。这项工作的跨学科特征将导致培养具有独特技能的化学家，包括化学合成，新方法和先进的计算工具，以促进精确，高效和环保的化学合成。pi还将利用社交媒体和播客来提高公众对能源、可持续性和健康等重要社会科学概念的认识。Noonan和Kowalewski以及他们的研究团队将使用合成、计算和表征相结合的方法来建立呋喃大环库，并绘制其结构和性质之间的相互作用图。关键的合成策略将包括使用结构导向的酯侧基来促进有效的环化并扩展它以实现对这些分子的超分子组装的精确控制。计算将在自组装研究中发挥特别重要的作用，允许探索广泛的候选结构和场景。这将有助于确定所得到的纳米结构的分子内和分子间组织的性质。绘制这些材料的分子和超分子性质将与研究它们在氧化还原、电荷传输和离子结合过程中的行为并行和相关。此外，共轭大环的工作将通过解决分子结构和共轭对芳香稳定能的影响的关键问题，促进对芳香性的基本理解。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。

With the support of the Macromolecular, Supramolecular and Nanochemistry Program in the NSF Division of Chemistry, Drs. Kevin Noonan and Tomasz Kowalewski of Carnegie Mellon University aim to develop and explore a new class of cyclic (or ring-like) organic molecules comprised of smaller rings (“rings of rings”). Generally, the path to making cyclic molecules involves bending linear molecules to join the ends together. As the size of the ring increases, it can be difficult to make the “ends meet” resulting in lower yield of the desired structure. Noonan and Kowalewski recently discovered that short linear chains of small furan rings can be modified in such a way that they spontaneously bend into macrocyclic ring-like shapes. They will be exploring the extension of this method to different variants of small rings to tune the properties for different potential applications. In these cyclic structures, a portion of the electrons reside in so-called pi-bonds, which under certain conditions enables them to flow freely such that the material behaves as a metal or semiconductor rather than an insulator. As such, they belong to the family of “green” organic electronic materials that can be derived from biomass, with high promise for sustainable energy applications such as solar cells, displays, and catalysts for generation of fuels and chemicals. The interdisciplinary character of this work will lead to training of chemists with a unique skill set encompassing chemical synthesis, novel methods, and advanced computational tools facilitating precise, efficient, and environmentally friendly chemical synthesis. The PIs will also use social media and podcasts to raise public awareness on key scientific concepts of essential societal importance such as energy, sustainability, and health.Drs. Noonan and Kowalewski and their research teams will use a combination of synthesis, computation, and characterization to build a library of furan macrocycles and map the interplay between their structure and properties. The key synthetic strategy will involve using structure-directing ester side groups to promote efficient cyclization and extend it to achieve precise control of supramolecular assembly of these molecules. Computation will play a particularly important role in the studies of self-assembly by allowing exploration of a wide range of candidate structures and scenarios. It will help in determining the nature of intra- and intermolecular organization of the resulting nanostructures. Mapping the molecular and supramolecular properties of these materials will be paralleled, and correlated, with the investigation of their behavior in redox, charge transport and ion-binding processes. In addition, work on conjugated macrocycles will advance fundamental understanding of aromaticity by addressing key questions about the impact of molecular structure and conjugation on aromatic stabilization energy.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.