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博士和Tomasz Koalewski博士致力于开发和探索一类由较小环(环的环)组成的新的环状(或环状)有机分子。通常，制造环状分子的途径包括弯曲线形分子以将末端连接在一起。随着环尺寸的增加，很难使“收支平衡”，从而导致所需结构的成品率较低。努南和科瓦列夫斯基最近发现，小呋喃环的短线性链可以被修饰，使它们自发弯曲成大环状环状。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，这使它们能够自由流动，从而使材料的行为像金属或半导体，而不是绝缘体。因此，它们属于可从生物质中提取的“绿色”有机电子材料家族，在太阳能电池、显示器以及用于产生燃料和化学品的催化剂等可持续能源应用方面前景看好。这项工作的跨学科性质将导致培养具有独特技能的化学家，包括化学合成、新颖的方法和促进精确、高效和环境友好的化学合成的先进计算工具。PI还将利用社交媒体和播客来提高公众对关键科学概念的认识，这些概念具有重要的社会意义，如能源、可持续发展和健康。努南和科瓦列夫斯基及其研究团队将结合合成、计算和表征来建立呋喃大环库，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高效的环化反应，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，因为它允许探索广泛的候选结构和场景。这将有助于确定所产生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属性将与对它们在氧化还原、电荷传输和离子结合过程中的行为的研究平行并相互关联。此外，关于共轭大环的工作将通过解决有关分子结构和共轭对芳香族稳定能量的影响的关键问题来促进对芳香性的基本理解。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.