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首页> 外文期刊>Chemistry: A European journal >Introducing negative charges into bis-p-phenylene crown ethers: A study of bipyridinium-based [2]pseudorotaxanes and [2]rotaxanes
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Introducing negative charges into bis-p-phenylene crown ethers: A study of bipyridinium-based [2]pseudorotaxanes and [2]rotaxanes

机译：在双对亚苯基冠醚中引入负电荷：基于联吡啶的[2]假轮烷和[2]轮烷的研究

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This paper describes novel host-guest systems comprising viologen cations (guests) and the derivatives of bis-para-phenylene-34-crown-10 (hosts) with anionic groups COO- or SO3-. The structure of the resulting charge-compensated host-guest complexes, their association constants and their electrochemical behaviour have been studied. In the solid state, the viologen cations thread the negatively charged crown ethers forming electroneutral zwitterion-like [2]pseudorotaxane salts; in solution this threaded geometry is preserved. The association constants of [2]pseudorotaxane salts incorporating the 1,1'-diethylviologen moiety in solution are significantly higher than those of previously reported analogues. The extrapolated association free energies in non-aqueous media exceed -40 kJ center dot mol(-1) at 25 degrees C. This significant increase of the interaction free energy makes these compounds stable even in aqueous solutions. The association constants of [2]pseudorotaxane salts incorporating sterically more hindered 1,1'diethyl-3,3'-dimethylviologen moieties are significantly lower. Structurally related [2]rotaxane salts, in which the oppositely charged ionic components are mechanically interlocked, have been prepared in good yields. It has been shown that [2]rotaxane salts incorporating anti-isomers of bisfunctionalised crown ethers are cycloenantiomeric. In both [2]pseudorotaxane and [2]rotaxane salts, the electrostatic interactions between the viologen moieties and the negatively charged crown ethers lead to very significant negative shifts of viologen reduction potentials up to 450 mV. The findings of the present study are valuable for the design of nanoscale molecular electronic devices.
机译：本文介绍了一种新型的主客体系统，该系统包含紫罗兰色阳离子（客体）和带有阴离子基团COO-或SO3-的双-对亚苯基-34-crown-10（主体）的衍生物。研究了所得电荷补偿的主客体复合物的结构，缔合常数及其电化学行为。在固态下，紫精阳离子穿入带负电的冠醚，形成电子中性的两性离子状[2]假轮烷盐;在解决方案中，将保留此螺纹几何形状。溶液中结合有1,1'-二乙基紫罗兰部分的[2]假轮烷盐的缔合常数明显高于先前报道的类似物。非水介质中的外推缔合自由能在25摄氏度时超过-40 kJ中心点mol（-1）。相互作用自由能的这种显着增加使得这些化合物即使在水溶液中也稳定。掺入在空间上更受阻的1，1′-二乙基-3，3′-二甲基紫罗兰部分的[2]伪轮烷盐的缔合常数明显更低。已经以良好的产率制备了结构相关的[2]轮烷盐，其中带相反电荷的离子成分机械互锁。已经显示掺入双官能化冠醚的反异构体的[2]轮烷盐是环对映异构体。在[2]假轮烷和[2]轮烷盐中，紫精部分与带负电的冠醚之间的静电相互作用导致紫精还原电位的最大负迁移达到450 mV。本研究的发现对于纳米分子电子器件的设计是有价值的。

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