摘要
A multicomponent [2]rotaxane designed to operate as a molecular shuttle driven by light energy has been constructed, and its properties have been investigated. The system is composed of (1) a light-fueled power station, capable of using the photon energy to create a charge-separated state, and (2) a mechanical switch, capable of utilizing such a photochemically generated driving force to bring about controllable molecular shuttling motions. The light-fueled power station is, in turn, a dyad comprising (i) a -electron-accepting fullerene (C60) component and (ii) a light-harvesting porphyrin (P) unit which acts as an electron donor in the excited state. The mechanical switch is a redox-active bistable [2]rotaxane moiety that consists of (i) a tetrathiafulvalene (TTF) unit as an efficient -electron-donor station, (ii) a dioxynaphthalene (DNP) unit as a second -electron-rich station, and (iii) a tetracationic cyclobis(paraquat-p-phenylene) (CBPQT4+) -electron-acceptor cyclophane, which encapsulates the better -electron-donating TTF station. Diethylene glycol spacers were conveniently introduced between the electroactive components in the dumbbell-shaped thread to facilitate the template-directed synthesis of the [2]rotaxane. A modular synthetic approach was undertaken for the overall synthesis of this multicomponent bistable [2]rotaxane, beginning with the syntheses of the PC60 dyad unit and the two-station TTFDNP-based [2]rotaxane separately, using conventional synthetic methodologies. These two components were finally stitched together by an esterification to afford the target rotaxane. Its structure was characterized by 1H NMR spectroscopy and mass spectrometry as well as by UVvisNIR absorption spectroscopy and voltammetry. The observations reflect remarkable electronic interactions between the various units, pointing to the existence of folded conformations in solution. The redox-driven shuttling process of the CBPQT4+ ring between the two competitive electron-rich recognition units, namely, TTF and DNP, was investigated by electrochemistry and spectroelectrochemistry as a means to verify its operational behavior prior to the photophysical studies related to light-driven operation. The oxidation process of the TTF unit is dramatically hampered in the rotaxane, thereby reducing the efficiency of the shuttling motion. These results confirm that, as the structural complexity increases, the overall function of the system no longer depends simply on its “primary” structure but also on higher-level effects which are reminiscent of the secondary and tertiary structures of biomolecules.
摘要译文
的多组分[2]轮烷设计成操作作为分子梭由光能驱动已建成的，其性能进行了研究。该系统是由（1）一个光为燃料的功率站，能够使用光子能量来创建一个电荷分离状态的，和（2）的机械开关，能够利用这样的光化学反应产生的驱动力带来可控的分子穿梭运动。光为燃料的电站，反过来，一对子包括（i）一个π电子接受性富勒烯（C 60）成分和（ii）一个捕光卟啉（P）的单元，其对作为激发态的电子供体。机械开关是氧化还原活性双稳态[2]轮烷的部分，它由（ⅰ）一种硫富瓦烯（TTF）单元作为有效的π电子施主站，（ii）一种dioxynaphthalene（DNP）单元作为第二π电子的富站，和（iii）一个tetracationic cyclobis（百草枯 - 对亚苯基）（CBPQT SUP 4 / SUP）π电子受体环芳，它封装好 - 电子给体TTF站。二乙二醇间隔物的哑铃形螺纹的电部件之间被便利地引入以促进模板指导合成的[2]轮烷的。模块化合成方法是进行这种多组分双稳[2]轮烷的整体合成，与PC 60对子单元的合成和双站TTFDNP基[2]轮烷分别开始，使用常规合成方法。这两个组件通过酯化得到目标轮烷终于缝合在一起。其结构特点是SUP 1 / SUP H-NMR光谱和质谱分析以及由UVvisNIR吸收光谱法和伏安。观察反映各单元之间显着的电子相互作用，指向在溶液折叠构象的存在。在CBPQT SUP 4 / SUP两个有竞争力的富电子识别单位之间的环，即TTF和DNP的氧化还原驱动穿梭的过程中，由电化学和光谱电化学研究，以验证其经营行为之前，相关的光驱动操作光物理研究的一种手段。在TTF单元的氧化过程显着地阻碍了在轮烷，从而减小往复运动的效率。这些结果证实，作为结构复杂性的增加，该系统的整体功能不再单纯依赖于它的“主”结构，而且在更高级别的效果这让人想起生物分子的二级和三级结构。
Sourav Saha; Amar H. Flood; J. Fraser Stoddart; Stefania Impellizzeri; Serena Silvi; Margherita Venturi;Alberto Credi;. A Redox-Driven Multicomponent Molecular Shuttle[J]. Journal of the American Chemical Society, 2007,129(40): 12159-12171