Long-Lived Fluxional Barbaralyl Cations

总的来说，将原子结合在一起制造分子的共价键是易于拉伸和弯曲的柔性键。这种灵活性赋予了分子的三维形状一定程度的响应性，这是决定分子物理性质和调节分子与其他分子相互作用的关键。例如，药物在蛋白质结合部位的分子识别可以在一个或两个结合伙伴中诱导组织。相互有利的空间排列(构象)是稳定的。在某些情况下，分子的结构动力学可以扩展到其构象的变化之外，包括其组成的变化(即，其原子骨架的变化)。被称为“动态共价”反应的过程依赖于性质上可逆的化学转化，允许特定的共价键在相同的条件下自由断裂和形成。通过这种方式，分子碎片聚集在一起，反复破裂，可逆地形成不同形状和大小的不同化合物。这项研究项目旨在探索一类相当独特的化合物的构成动力学。将要开发的“Barbaralyl阳离子”是以笼状排列的九个碳原子为核心构建的。每个碳原子都与两到三个类似的原子相连。由于这种特殊的组成和组成核心的共价键的类型，碳原子能够相互可逆地交换键，与它们的邻居交换位置。当一个键断裂时，会产生另一个键，结果是重阳离子核是“流动的”。当不同的基团被添加到这个流动的核心上时，分子作为一个整体发展出能够戏剧性地改变其形状的性质，不仅在其构象方面，而且在其组成方面。它会变成一种“变形分子”。与绝大多数动态共价过程不同，这种重排完全在单个分子内进行，这意味着它的发生速度不依赖于其他反应物的存在及其浓度。分子中心的键发生交换，导致外部官能团的位置和方向发生变化，从而产生数百个(甚至数千个！)重要的是，在这项研究中开发的变形分子不需要繁重的准备，而是将使用相对简单的方法来制备，克服了与过去研究的少数相关变形分子相关的主要障碍之一。最终，这种发生在单个分子内的构成动力学将提供一种新的手段，通过它来寻找与任何感兴趣的目标具有相互稳定的结合相互作用的结构。因此，应用可能在于改进分子成分的设计，以检测医学上相关的物种。

The covalent bonds that hold atoms together to make molecules are, by and large, flexible linkages that are prone to stretching and bending. This flexibility imparts a degree of responsiveness to molecules' three-dimensional shape that is key in determining their physical properties and mediating their interactions with other molecules. For example, the molecular recognition of a pharmaceutical within the binding site of a protein can induce organisation in one, or even both, of the binding partners. A mutually favourable spatial arrangement (conformation) is stabilised.In certain cases, the structural dynamics of molecules can be extended beyond changes in their conformation to include changes in their constitution (i.e., changes in their atomic skeleton). Processes termed 'dynamic covalent' reactions rely upon chemical transformations that are reversible in nature, allowing specific covalent bonds to be broken and formed freely under the same set of conditions. In this way, molecular fragments come together and break apart over and over again, reversibly forming different compounds of varying shapes and sizes. This research project seeks to explore constitutional dynamics in a rather unique class of compounds. The 'barbaralyl cations' that will be developed are built around a core of nine carbon atoms in a cage-like arrangement. Each carbon atom is connected to two or three similar neighbours. As a result of this particular composition and the type of covalent bonds that make up the core, the carbon atoms are able to reversibly trade bonds with one another, switching positions with their neighbours. As one bond breaks, another is made and the outcome is that the barbaralyl cation core is 'fluxional'. When different groups are appended to this fluxional core, the molecule as a whole develops the property of being able to change its shape dramatically, not just in terms of its conformation, but also in terms of its constitution. It becomes a 'shapeshifting molecule'. Unlike the vast majority of dynamic covalent processes, this rearrangement occurs entirely within single molecules, meaning that the rate at which it occurs is not dependent on the presence of other reactants and their concentration. The linkages at the centre of the molecule interchange, causing the positions and orientations of the functional groups around the exterior to be switched and giving rise to hundreds (or even thousands!) of different structural permutations.Importantly, the shapeshifting molecules developed during this research will not require onerous preparation, but rather they will be made using relatively straightforward methods, overcoming one of the major impediments associated with the handful of related shapeshifting molecules that have been studied in the past. Ultimately, constitutional dynamics of this kind, occurring within a single molecule, will offer a new means through which to search for structures with mutually stabilising binding interactions with conceivably any target of interest. Applications, therefore, may lie in the improved design of molecular components for sensing medicinally relevant species.