Syntheses and Dynamics of Donor−Acceptor [2]Catenanes in Water

A subset of mechanically interlocked molecules, namely, donor−acceptor [2]catenanes, have been produced in aqueous solutions in good yields from readily available precursors. The catenations are templated by strong hydrophobic and [π···π] stacking interactions, which serve to assemble the corresponding supramolecular precursors, prior to postassembly covalent modification. Dynamic 1H NMR spectroscopic investigations performed on one of these [2]catenanes reveal that the pirouetting motion of the butadiyne-triethylene glycol chain occurs with a dramatically lower activation enthalpy, yet with a much higher negative activation entropy in water, compared to organic solvents. The preparations of mechanically interlocked molecules in water constitute the basis for the future development of complex functional molecular machinery in aqueous environments.

以易得前驱体为原料，在水溶液中以高产率制备得到一类机械互锁分子（mechanically interlocked molecules）子集，即给体-受体[2]索烃（donor−acceptor [2]catenanes）。此类索烃化反应以强疏水作用及π···π堆积相互作用作为模板，先组装得到对应超分子前驱体（supramolecular precursors），随后再进行组装后共价修饰。针对其中一种[2]索烃开展的动态1H核磁共振光谱研究（Dynamic 1H NMR spectroscopic investigations）结果表明，与有机溶剂体系相比，丁二炔-三乙二醇链（butadiyne-triethylene glycol chain）的旋转运动在水相中的活化焓（activation enthalpy）显著更低，但其活化熵（activation entropy）则呈现出更强的负值。在水相中制备机械互锁分子的方法，为未来在水相环境中开发复杂功能性分子机器（complex functional molecular machinery）奠定了基础。