This work deals with the use of 2-cyano-2-arylpropanoic acids as chemical fuels for an acid–base operated molecular switch that consists of a Sauvage-type catenand composed of two identical macrocycles incorporating a phenanthroline unit. When used as a base promoter of the decarboxylation of propanoic acid derivatives, the switch undergoes large amplitude motion from the neutral catenand to a protonated catenate and back again to the neutral state. The rate of back proton transfer, which determines the rate of the overall process, was markedly affected by para-substituents in the order Cl > H > CH₃ > OCH₃ (ρ = +5.2). Thus, the time required to complete a full cycle was almost two days for the OCH₃ derivative and dropped to a few minutes for the Cl derivative. These results show for the first time that the rate of operation of a molecular switch can be regulated by variations in the fuel structure.

中文翻译：

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燃料结构的变化控制着化学燃料分子开关的来回运动速率

这项工作涉及使用2-氰基-2-芳基丙酸作为酸碱型分子开关的化学燃料，该分子开关由Sauvage型链环组成，由两个相同的大环并结合有菲咯啉单元组成。当用作丙酸衍生物的脱羧反应的基础促进剂时，该开关经历从中性链链到质子化的链状酸盐并再次回到中性状态的大幅度运动。反质子转移的速率决定了整个过程的速率，其显着受对位取代基的影响，顺序为Cl> H> CH ₃ > OCH ₃（ρ = +5.2）。因此，对于OCH _3而言，完成一个完整周期所需的时间几乎是两天衍生物，并下降至Cl衍生物的几分钟。这些结果首次表明，可以通过燃料结构的变化来调节分子开关的工作速率。