Balancing ring and stopper group size to control the stability of doubly threaded [3]rotaxanes
Balancing ring and stopper group size to control the stability of doubly threaded [3]rotaxanes
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DOI：
10.1039/d3ob01123b
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发表时间：
2023-08-15
影响因子：
3.2
通讯作者：
Rowan，Stuart J.
中科院分区：
文献类型：
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作者：
Hertzog，Jerald E.;Liu，Guancen;Rowan，Stuart J.
合成双螺纹[3]轮烷需要使用比传统单螺纹[2]轮烷更大的环。获得稳定的双螺纹[3]轮烷与大环的关键挑战是找到环与塞子尺寸的正确组合。在这项研究中，一系列的双线程[3]轮烷衍生自五个不同大小的大环的大小范围内的40-48个原子和两个不同的终止基团，其中包含1或2个三（对叔丁基联苯）甲基部分，并检查其动力学稳定性。这些互锁化合物是使用金属模板的方法合成的，并充分利用质谱，NMR光谱和尺寸排阻色谱技术的组合进行表征。环尺寸对双螺纹[3]轮烷稳定性的影响通过使用1H-NMR光谱监测的动力学稳定性测试进行了研究。通过从48至40个原子每2个原子系统地收紧大环，可以获得宽范围的双螺纹互锁分子，其中可以调节大环从哑铃形物的室温滑移速率。使用具有48个原子的环的较大的终止基团导致没有可观察到的轮烷，46-44个原子的大环导致亚稳态轮烷物质，其滑移半衰期分别为0.55周和0.99周，而42个原子或更小的大环产生稳定的轮烷。较小尺寸的塞子不能完全稳定任何[3]轮烷结构，但使用42或40个原子的大环分别获得滑移半衰期为25 ± 2小时和13 ± 1天的亚稳态[3]轮烷。这些结果突出了相对较小的环尺寸变化对双螺纹[3]轮烷结构的显著影响，并为一系列高阶双螺纹互锁结构奠定了合成基础。
Synthesizing doubly threaded [3]rotaxanes requires the use of larger rings than more traditional singly threaded [2]rotaxanes. A key challenge in accessing stable doubly threaded [3]rotaxanes with large rings is finding the right combination of ring to stopper size. In this study, a series of doubly threaded [3]rotaxanes derived from five different sized macrocycles in the size range of 40–48 atoms and two different stopper groups, which contain 1 or 2 tris(p-t-butylbiphenyl)methyl moieties, were prepared and their kinetic stability examined. These interlocked compounds were synthesized using a metal-templated approach and fully characterized utilizing a combination of mass spectrometry, NMR spectroscopy, and size-exclusion chromatography techniques. The effect of ring size on the stability of the doubly threaded [3]rotaxane was investigated via kinetic stability tests monitored using 1H-NMR spectroscopy. By tightening the macrocycle systematically every 2 atoms from 48 to 40 atoms, a wide range of doubly threaded interlocked molecules could be accessed in which the rate of room temperature slippage of the macrocycle from the dumbbells could be tuned. Using the larger stopper group with a 48-atom ring results in no observable rotaxane, 46–44 atom macrocycles result in metastable rotaxane species with a slippage half-life of ∼5 weeks and ∼9 weeks, respectively, while macrocycles of 42 atoms or smaller yield a stable rotaxane. The smaller sized stopper is not able to fully stabilize any of the [3]rotaxane structures but metastable [3]rotaxanes are obtained with slippage half-lives of 25 ± 2 hours and 13 ± 1 days using macrocycles with 42 or 40 atoms, respectively. These results highlight the dramatic effect that relatively small ring size changes can have on the structure of doubly threaded [3]rotaxanes and lay the synthetic groundwork for a range of higher order doubly threaded interlocked architectures.