Mechanically interlocked molecules consisting of radially conjugated macrocycles

Mechanically interlocked molecules (MIMs) not only represent non-trivial synthetic challenges that require the state of the art in structural designs and precise preparations, but also play critical roles for artificial molecular machines and stimuli-responsive functional materials owing to their inherent dynamic characteristics. The precision synthesis of MIMs remains a central theme in supramolecular chemistry. Evolving from low-yield statistical threading approaches, template-directed strategies have become predominant methodologies for the construction of MIMs. Macrocyclic components, serving as fundamental building blocks in MIMs, play a pivotal role in both structural design and functional exploration. Radially conjugated macrocycles (RCMs) with rigid molecular frameworks exhibit unique optoelectronic and supramolecular properties. Consequently, MIMs constructed from RCMs not only enrich topological diversity and expand material boundaries of MIMs, but also provide advantageous platforms for investigating emerging functionalities, making them highly attractive synthetic targets. However, the precise synthesis of such interlocked architectures remains challenging due to the significant molecular strain in the conjugated skeletons. Recent advances in RCMs synthetic methodologies, when synergized with template-directed strategies, have initiated the convergence between RCMs and MIMs research domains. Since the inaugural synthesis of RCM-derived MIMs in 2018, this field has undergone transformative progress over the past decade.

The research group led by Huan Cong, a professor at the Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, has made significant contributions to this field. Their recent review systematically summarizes advances in MIMs derived from RCMs, emphasizing their innovative structural designs and synthetic methodologies. This comprehensive review has been published in Nano Research on June 24, 2025.

“In this review, we categorize these developments by molecular topologies, including catenanes, rotaxanes, and knots, providing a comprehensive overview of the state-of-the-art in this area. Early efforts focused on overcoming the synthetic challenges of highly strained interlocked architectures, while recent advances have established diverse synthetic strategies to enhance efficiency, enable site-specific functionalization, and achieve precise bond formation and cleavage. Current synthetic breakthroughs not only extend the applications of classical templates, but also innovatively introduce novel approaches to achieve construct unprecedented all-benzene interlocked architectures.” said Huan Cong, the corresponding author of the review paper.

   As a novel class of conjugated macrocycles, RCMs offer new perspectives for investigating the functional properties of MIMs. Past and current research in this field has primarily focused on synthetic methodologies and structural characterization. Building on the inherent properties of RCMs and the dynamic characters endowed by the MIMs, investigations on the functional properties thus far have emerged along two directions: molecular motion behaviors and photophysical features.

The research team outlines the properties of RCM-derived MIMs. “These research advances not only preliminarily reveal the intrinsic structure-property relationships of RCM-derived MIMs, but also lay a crucial foundation for their potential applications. Particularly, with the increasingly efficient methodologies for precise synthesis of RCM-derived MIMs, the research frontier in this field is expected to shift progressively from ‘how to construct novel architectures’ to ‘how to explore new functionalities’ We anticipate that the unique properties of these molecules will continue to be uncovered.”

This field is now rapidly advancing, with a promising future that will not only generate new synthetic methodologies, structural motifs, and functional discoveries, but also drive broader applications including but not limited to supramolecular chemistry, molecular topology, molecular machines, and smart optoelectronic materials.

About the Authors

For more information, please visit our research group’s homepage: https://www.x-mol.com/groups/huan_cong

About Nano Research

Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 7,000 articles. In 2024 InCites Journal Citation Reports, its 2024 IF is 9.0 (8.7, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.