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首页> 外文期刊>Advanced Functional Materials >Using Molecular Force to Overcome Steric Barriers in a Springlike Molecular Ouroboros
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Using Molecular Force to Overcome Steric Barriers in a Springlike Molecular Ouroboros

机译：利用分子力克服类似弹簧的分子衔尾叶中的立体障碍

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A mechanically interlocked and self-complexing molecular ouroboros that incorporates the π-electron-rich monopyrrolotetrathiafulvalene (MPTTF) unit and the π-electron-poor tetracationic macrocycle cyclobis(paraquat-p-phenylene) (CBPQT~(4+)) has been synthesized and characterized. The molecular ouroboros constitutes an interesting class of redox-active interlocked molecules that is structurally similar to the image of the Serpent biting its own tail, whereas, and towards advanced functionality, its mode of action resembles a wound spring. Electrochemical methods and short timescale UV-vis-NIR (NIR: near IR) chemical switching experiments verified the reversible oxidation and reduction of the molecular ouroboros akin to the build-up and release of tension in a spring. Building out from this concept, it was determined by the time evolution of the ~1H NMR and UV-vis-NIR spectra, however, that the initially interlocked molecular ouroboros is converted into a linear non-interlocked state by the employment of an appropriate oxidation-reduction cycle. The oxidation-induced dethreading process occurs when the dicationic MPTTF~(2+) unit is kept within close proximity to the CBPQT~(4+) ring by the circular interlocked structure in order to maintain the electrostatic repulsive force between the MPTTF~(2+) unit and the CBPQT~(4+) ring for longer periods of time. The resulting high-energy, and now tightly wound, interlocked conformation overcomes a steric barrier in many minutes, relaxing thermodynamically to form the lowest-energy linear state in an irreversible process that would otherwise be kinetically improbable without the oxidation.
机译：结合了富含π电子的单吡咯并四硫富瓦烯（MPTTF）单元和贫π电子的四阳离子大环环双（百草枯-对亚苯基）（CBPQT〜（4+））的机械互锁和自络分子和特点。分子肌纤维构成一类有趣的氧化还原活性互锁分子，其结构类似于蛇咬自己尾巴的图像，而就高级功能而言，其作用方式类似于缠绕弹簧。电化学方法和短时程紫外可见近红外（NIR：近红外）化学转换实验证实了可逆的氧化和还原的分子肌腱在弹簧中的形成和释放。从这个概念出发，它是由〜1H NMR和UV-vis-NIR光谱的时间演变确定的，但是，通过适当的氧化作用，最初互锁的分子肌硼蛋白被转化为线性非互锁状态-减少周期。当专用的MPTTF〜（2+）单元通过圆形互锁结构保持在靠近CBPQT〜（4+）环以保持MPTTF〜（2）之间的静电排斥力时，就会发生氧化诱导的脱螺纹过程。 +）单元和CBPQT〜（4+）响起更长的时间。所产生的高能，现在紧密缠绕的互锁构象在许多分钟内克服了空间障碍，在不可逆过程中热力学松弛以形成最低能线性状态，否则该过程在动力学上就不可能被氧化。

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