During recent decades, the blossoming of the field of mechanically interlocked molecules (MIMs), i.e., molecules containing mechanical or topological bonds such as rotaxanes, catenanes, and knots, has been reported in the literature. Taking advantage of the rapid development of diverse synthetic strategies, the precise control of both the architectures and topologies of MIMs has become realizable, which thus enables the construction of MIMs with specially desired functions. By mimicking biomolecular machines, a variety of MIM-based artificial molecular machines such as molecular shuttles, molecular muscles, molecular motors, and molecular assemblers have been constructed and operated by relying on the unique interlocked structures and controllable intramolecular movements. Two pioneers in this field, J. Fraser Stoddart and Jean-Pierre Sauvage, were awarded the 2016 Nobel Prize in Chemistry, thereby marking a golden age of MIMs. Along with the burgeoning of MIMs, the engineering of mechanical bonds into macromolecular scaffolds such as polymers or dendrimers has become an attractive topic since the targeted novel mechanically bonded macromolecules would feature interesting processable and mechanical properties, making them excellent candidates for practical applications such as device fabrication or smart materials. In particular, rotaxane dendrimers, attributed to the combination of the advantageous features of both rotaxanes (controllable dynamic motions) and dendrimers (nanoscale highly branched architectures), have evolved as versatile platforms for extensive applications such as gene delivery, light harvesting, and molecular nanoreactors. However, compared with the widely investigated polyrotaxanes and polycatenanes, in-depth investigations on rotaxane dendrimers have rarely been explored mainly because of the synthetic challenge that makes the preparation of diverse rotaxane dendrimers, especially high-generation ones, extremely difficult. During recent years, through the rational design and synthesis of organometallic rotaxane units as key building blocks, the employment of a controllable divergent approach led to the successful synthesis of a variety of rotaxane dendrimers with precise arrangements of rotaxane units as well as stimuli-responsive sites and functional groups. More importantly, on the basis of the synthetic accessibility to diverse rotaxane dendrimers, rotaxane dendrimers have been proven to hold great promise for extensive applications in diverse fields such as light harvesting, photocatalysis, and soft actuators. In this Account, we summarize our expedition in rotaxane dendrimers, including addressing the synthetic challenges, investigating their stimuli-responsive properties, expanding their potential applications, and inventing higher-order daisy chain dendrimers. We believe that this Account will inspire scientists from various disciplines to explore these appealing and versatile higher-order mechanically bonded macromolecules.

中文翻译：

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轮烷树枝状聚合物：巨人之间的联盟

近几十年来，机械互锁分子 (MIM) 领域的蓬勃发展，即包含机械或拓扑键的分子，如轮烷、链烷和结，已在文献中报道。利用各种合成策略的快速发展，可以实现对 MIM 架构和拓扑结构的精确控制，从而可以构建具有特定功能的 MIM。通过模仿生物分子机器，依靠独特的互锁结构和可控的分子内运动，构建并运行了多种基于MIM的人工分子机器，如分子穿梭机、分子肌肉、分子马达、分子组装机等。该领域的两位先驱，J. Fraser Stoddart 和 Jean-Pierre Sauvage，获得了 2016 年诺贝尔化学奖，从而标志着 MIM 的黄金时代。随着 MIM 的蓬勃发展，将机械键工程化到大分子支架（如聚合物或树枝状聚合物）中已成为一个有吸引力的话题，因为有针对性的新型机械键合大分子将具有有趣的可加工性和机械性能，使其成为实际应用（如设备）的绝佳候选者制造或智能材料。特别是轮烷树枝状大分子，由于结合了轮烷（可控动态运动）和树枝状大分子（纳米级高度支化结构）的优势特征，已发展成为广泛应用的多功能平台，如基因传递、光收集和分子纳米反应器. 然而，与广泛研究的聚轮烷和聚环烷烃相比，对轮烷树枝状大分子的深入研究很少被探索，主要是因为合成挑战使得制备各种轮烷树枝状大分子，尤其是高代轮烷大分子极其困难。近年来，通过以有机金属轮烷单元为关键构建单元的合理设计和合成，采用可控发散的方法，成功合成了多种轮烷树枝状大分子，其具有精确的轮烷单元排列和刺激响应位点和官能团。更重要的是，基于对各种轮烷树枝状大分子的合成可及性，轮烷树枝状大分子已被证明在光收集、光催化和软致动器等不同领域的广泛应用中具有广阔的前景。在本报告中，我们总结了我们在轮烷树枝状大分子方面的探索，包括解决合成挑战、研究其刺激响应特性、扩展其潜在应用以及发明更高阶的菊花链树枝状大分子。我们相信，这篇报道将激励来自不同学科的科学家探索这些吸引人的、多功能的高阶机械键合大分子。并发明了高阶菊花链树枝状聚合物。我们相信，这篇报道将激励来自不同学科的科学家探索这些吸引人的、多功能的高阶机械键合大分子。并发明了高阶菊花链树枝状聚合物。我们相信，这篇报道将激励来自不同学科的科学家探索这些吸引人的、多功能的高阶机械键合大分子。