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1. The effect of thread-like monomer structure on the synthesis of poly[ n ]catenanes from metallosupramolecular polymers

   https://doi.org/10.1039/d2sc05542b  

   Tranquilli, Marissa M.; Rawe, Benjamin W.; Liu, Guancen; Rowan, Stuart J. (March 2023, Chemical Science)

   The main-chain poly[ n ]catenane consists of a series of interlocked rings that resemble a macroscopic chain-link structure. Recently, the synthesis of such intriguing polymers was reported via a metallosupramolecular polymer (MSP) template that consists of alternating units of macrocyclic and linear thread-like monomers. Ring closure of the thread components has been shown to yield a mixture of cyclic, linear, and branched poly[ n ]catenanes. Reported herein are studies aimed at accessing new poly[ n ]catenanes via this approach and exploring the effect the thread-like monomer structure has on the poly[ n ]catenane synthesis. Specifically, the effect of the size of the aromatic linker and alkenyl chains of the thread-like monomer is investigated. Three new poly[ n ]catenanes (with different ring sizes) were prepared using the MSP approach and the results show that tailoring the structure of the thread-like monomer can allow the selective synthesis of branched poly[ n ]catenanes. 

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2. Synthesis of linear [7]- and [8]catenanes

   https://doi.org/10.1016/j.xcrp.2023.101767  

   Harlan, Gray H; Tran, Sheila L; Colley, Nathan D; Nosiglia, Mark A; Zhang, Yipei; Barnes, Jonathan C (January 2024, Cell Reports Physical Science)

   Catenanes are a family of mechanically interlocked molecules that consist of molecular rings that can be interlocked to give linear, radial, or cyclic structures. Although chemists have pursued extended linear poly[n]catenane architectures for many decades, there still exists a fundamental gap between the synthesis of well-defined, linear oligomers and that of disperse polymers that are often produced as a mixture of architectures. Here, we report two convergent one-pot syntheses that “zip-tie” together two pre-made [3]catenanes by first using orthogonal metal templation with phenanthroline (Cu(I)) and terpyridine (Fe(II)) ligands. These pre-catenate complexes were subjected to a ring-closing metathesis step to afford discrete, linear [7]- and [8]catenanes. The successful synthesis and isolation of the discrete [7]- and [8]catenanes were confirmed using multiple methods of characterization. Because these record-setting linear [n]catenanes possess open phenanthroline metal-binding sites at each end, further expansion to all-interlocked linear poly[n]catenanes is a realistic proposition. 

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3. Template‐Directed Synthesis and Isolation of Unimolecular Oligo[ n ]catenanes Using a One‐Pot CuAAC “Click” Reaction Approach

   https://doi.org/10.1002/chem.202501344  

   Tran, Sheila_L; Harlan, Gray_H; Puckowitz, David_E; Wohlstadter, Nathan_E; Zhang, Yipei; Colley, Nathan_D; Barnes, Jonathan_C (May 2025, Chemistry – A European Journal)

   Abstract Within the field of mechanically interlocked molecules, catenanes have garnered much interest in the past few decades due to their chain‐like architecture of interlocked molecular rings. This interest stems from their unique properties and degrees of freedom that are distinct in comparison to traditional molecular architectures, a fact that makes catenanes potentially attractive building blocks in the construction of next‐generation polymeric materials. Most approaches to make unimolecular [n]catenanes are either low yielding or are laborious, often relying on multistep pathways for preparation and purification. Therefore, developing efficient syntheses for [n]catenanes remains an important challenge for chemists. Here, we describe a template‐directed one‐pot approach that overcomes the limitations of multistep syntheses by using simple, symmetrical phenanthroline‐based building blocks and CuAAC “click” chemistry to yield a series of unimolecular [n]catenanes. This methodology relies on simultaneous copper(I)‐based templation and click chemistry, ultimately resulting in a one‐pot synthetic strategy to make either a [2]catenane in high yield (82%) or a batch of well‐defined linear [2]–[5]catenanes (and trace amounts of a [6]catenane) in an 18% overall yield, depending on the rate of addition of the alkyne‐ and azide‐functionalized precursors (i.e., slowly or all at once). Such kinetic control represents a potential pathway toward the preparation of higher‐order [n]catenanes capable of further chain extension using very simple precursors. 

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4. Syntheses of three-dimensional catenanes under kinetic control

   https://doi.org/10.1073/pnas.2118573119  

   Wu, Yong; Guo, Qing-Hui; Qiu, Yunyan; Weber, Jacob A.; Young, Ryan M.; Bancroft, Laura; Jiao, Yang; Chen, Hongliang; Song, Bo; Liu, Wenqi; et al (March 2022, Proceedings of the National Academy of Sciences)

   Although catenanes comprising two ring-shaped components can be made in large quantities by templation, the preparation of three-dimensional (3D) catenanes with cage-shaped components is still in its infancy. Here, we report the design and syntheses of two 3D catenanes by a sequence of S N 2 reactions in one pot. The resulting triply mechanically interlocked molecules were fully characterized in both the solution and solid states. Mechanistic studies have revealed that a suit[3]ane, which contains a threefold symmetric cage component as the suit and a tribromide component as the body, is formed at elevated temperatures. This suit[3]ane was identified as the key reactive intermediate for the selective formation of the two 3D catenanes which do not represent thermodynamic minima. We foresee a future in which this particular synthetic strategy guides the rational design and production of mechanically interlocked molecules under kinetic control. 

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5. Exploring the Impact of Ring Mobility on the Macroscopic Properties of Doubly Threaded Slide‐Ring Gel Networks

   https://doi.org/10.1002/anie.202411172  

   Oh, Jongwon; Liu, Guancen; Kim, Hojin; Hertzog, Jerald E; Nitta, Natsumi; Rowan, Stuart J (September 2024, Angewandte Chemie International Edition)

   Abstract The integration of mechanically interlocked molecules (MIMs) into polymeric materials has led to the development of mechanically interlocked polymers (MIPs). One class of MIPs that have gained attention in recent years are slide‐ring gels (SRGs), which are generally accessed by crosslinking rings on a main‐chain polyrotaxane. The mobility of the interlocked crosslinking moieties along the polymer backbone imparts enhanced properties onto these networks. An alternative synthetic approach to SRGs is to use a doubly threaded ring as the crosslinking moiety, yielding doubly threaded slide‐ring gel networks (dt‐SRGs). In this study, a photo‐curable ligand‐containing thread was used to assemble a series of metal‐templated pseudo[3]rotaxane crosslinkers that allow access to polymer networks that contain doubly threaded interlocked rings. The physicochemical and mechanical properties of these dt‐SRGs with varying size of the ring crosslinking moieties were investigated and compared to an entangled gel (EG) prepared by polymerizing the metal complex of the photo‐curable ligand‐containing thread, and a corresponding covalent gel (CG). Relative to the EG and CG, the dt‐SRGs exhibit enhanced swelling behavior, viscoelastic properties, and stress relaxation characteristics. In addition, the macroscopic properties of dt‐SRGs could be altered by “locking” ring mobility in the structure through remetalation, highlighting the impact of the mobility of the crosslinks. 

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