Department of Chemistry, Northwestern University, 2145 Sheridan Road, Evanston, Illinois 60208, USA.
Org Biomol Chem. 2011 Oct 21;9(20):7126-33. doi: 10.1039/c1ob05913k. Epub 2011 Aug 30.
A limited range of redox-active, rotaxane-based, molecular switches exist, despite numerous potential applications for them as components of nanoscale devices. We have designed and synthesised a neutral, redox-active [2]rotaxane, which incorporates an electron-deficient pyromellitic diimide (PmI)-containing ring encircling two electron-rich recognition sites in the form of dioxynaphthalene (DNP) and tetrathiafulvalene (TTF) units positioned along the rod section of its dumbbell component. Molecular modeling using MacroModel guided the design of the mechanically interlocked molecular switch. The binding affinities in CH(2)Cl(2) at 298 K between the free ring and two electron-rich guests--one (K(a) = 5.8 × 10(2) M(-1)) containing a DNP unit and the other (K(a) = 6.3 × 10(3) M(-1)) containing a TTF unit--are strong: the one order of magnitude difference in their affinities favouring the TTF unit suggested to us the feasibility of integrating these three building blocks into a bistable [2]rotaxane switch. The [2]rotaxane was obtained in 34% yield by relying on neutral donor-acceptor templation and a double copper-catalysed azide-alkyne cycloaddition (CuAAC). Cyclic voltammetry (CV) and spectroelectrochemistry (SEC) were employed to stimulate and observe switching by this neutral bistable rotaxane in solution at 298 K, while (1)H NMR spectroscopy was enlisted to investigate switching upon chemical oxidation. The neutral [2]rotaxane is a chemically robust and functional switch with potential for applications in device settings.
尽管作为纳米器件组件，它们在许多潜在应用中具有吸引力，但目前存在的氧化还原活性轮烷型分子开关的种类有限。我们设计并合成了一种中性氧化还原活性[2]轮烷，其中包含一个缺电子的均苯四甲酰亚胺（PmI）环，该环围绕两个富电子识别位点，这些识别位点以二氧杂萘（DNP）和四硫富瓦烯（TTF）单元的形式存在，位于其哑铃型分子组件的棒状部分。使用 MacroModel 进行分子模拟指导了机械互锁分子开关的设计。在 298 K 时，自由环与两个富电子客体之间在 CH(2)Cl(2)中的结合亲和力很强——一个客体（K(a) = 5.8 × 10(2) M(-1)）含有 DNP 单元，另一个客体（K(a) = 6.3 × 10(3) M(-1)）含有 TTF 单元——相差一个数量级的亲和力有利于 TTF 单元，这使我们想到将这三个构建块集成到双稳态[2]轮烷开关中的可行性。[2]轮烷是通过依赖中性供体-受体模板和双铜催化的叠氮-炔环加成（CuAAC）以 34%的产率获得的。循环伏安法（CV）和光谱电化学（SEC）用于在 298 K 下刺激和观察中性双稳态轮烷在溶液中的开关，同时（1）H NMR 光谱用于研究化学氧化时的开关。中性[2]轮烷是一种化学稳定且具有功能的开关，具有在器件环境中应用的潜力。
