Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States.
J Am Chem Soc. 2021 May 26;143(20):7740-7747. doi: 10.1021/jacs.1c01885. Epub 2021 May 17.
Molecular spur gear dynamics with high gearing fidelity can be achieved through a careful selection of constituent molecular components that favorably position and maintain the two gears in a meshed configuration. Here, we report the synthesis of a new macrocyclic molecular spur gear with a bibenzimidazole stator combined with a second naphthyl bis-gold-phosphine gold complex stator to place two 3-fold symmetric 9,10-diethynyl triptycene cogs at the optimal distance of 8.1 Å for gearing. Micro electron diffraction (μED) analysis confirmed the formation of the macrocyclic structure and the proper alignment of the triptycene cogs. Gearing dynamics in solution are predicted to be extremely fast and, in fact, were too fast to be observed with variable-temperature H NMR using CDCl as the solvent. A combination of molecular dynamics and metadynamics simulations predict that the barriers for gearing and slippage are ca. 4 kcal mol and ca. 9 kcal mol, respectively. This system is characterized by enhanced gearing fidelity compared to the acyclic analog. This is achieved by rigidification of the structure, locking the two triptycenes in the preferred gearing distance and orientation.
通过仔细选择合适的分子成分，可以实现具有高传动比保真度的分子齿轮传动。在此，我们报告了一种新的大环分子齿轮的合成，该分子齿轮由联苯并咪唑定子与第二个萘基双金-膦金配合物定子结合，将两个 3 重对称的 9,10-二乙炔基三芴基齿轮置于最佳的 8.1Å 传动比距离。微电子衍射（μED）分析证实了大环结构的形成和三芴基齿轮的正确排列。预测溶液中的齿轮动力学非常快，实际上，使用 CDCl 作为溶剂的变温 1H NMR 无法观察到。分子动力学和元动力学模拟的组合预测，齿轮传动和滑动的势垒分别约为 4 kcal mol 和约 9 kcal mol。与非循环类似物相比，该系统的齿轮传动保真度更高。这是通过结构的刚性化实现的，将两个三芴基锁定在优选的齿轮传动距离和方向。
