Molecular Borromean links based on metallocages

Molecular Borromean links based on metallocages | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Molecular Borromean links based on metallocages Guo-Xin Jin, Hai-Ning Zhang This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4824942/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 14 Jan, 2025 Read the published version in Nature Synthesis → Version 1 posted You are reading this latest preprint version Abstract The Borromean link, which is characterized by structural integrity and aesthetic beauty, represents one of the most intriguing entanglements. However, the vast majority of Borromean links consist of three identical macrocycles, and there are very few examples of links constructed from dimeric cages. Here, facilitated by multiple aromatic stacking interactions between components, we demonstrate that two molecular cage-based Borromean links containing more than 1100 nonhydrogen atoms, especially 24 rhodium(III)/iridium(III) and six sodium(I) ions, can be constructed in high yield through the strategic selection of a tetrapyridyl ligand based on dibenzo-18-crown-6 and two binuclear building units, as demonstrated by X-ray crystallographic analysis, detailed nuclear magnetic resonance (NMR), electrospray ionization-time-of-flight/mass spectrometry (ESI-TOF/MS), and elemental analysis. Physical sciences/Chemistry/Coordination chemistry/Organometallic chemistry/Ligands Physical sciences/Chemistry/Supramolecular chemistry/Self-assembly Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Introduction As the most familiar example of a Brunnian link, the Borromean link 1-4 is a prime link and generally refers to a topology consisting of three relatively independent but interlocked rings, with no interlocking between any two of them (Figure 1A). This structural feature means that disconnection of one of the rings results in complete separation of the remaining two rings 5 . The construction of topological structures with structural integrity and aesthetics at the molecular level has long been regarded as a challenge in synthetic chemistry 2 , and the pioneering work by Seeman’s group on the first-ever artificial construction of such topologies using specific interactions between different DNA fragments inspired chemists to think about how to rationally construct these structures by means of chemical synthesis 6 . Stoddart and coworkers ingeniously utilized the transition metal ion Zn II as a template for self-assembly of molecular Borromean link precursors induced by metal–ligand coordination bonds and achieved the first synthesis of a molecular Borromean link with organic skeletons in a wholly synthetic molecular form after covalent ring closure and removal of the templating agent 7 . Our group first obtained molecular Borromean links with metallo-backbones via the co-driven self-assembly of coordination and noncovalent interactions 8,9 and summarized the design strategy applicable to controlled construction of such molecular Borromean metalla-links 10,11 . Inspired by the above two synthetic strategies, researchers have realized a series of molecular Borromean links through rational design and efficient construction 11-13 . The first interlocked-cage structures reported by Fujita et al. subsequently inspired synthetic chemists to successfully construct cage-based interlocked structures featuring organo- or metallo-backbones 14 . However, among these reported structures, most of them involve dimeric catenation of cages 15-24 , while trimeric catenation structures are rare. Recently, Mastalerz and coworkers synthesized three interlocked, identical organic cages, but their topology was not a molecular Borromean link 25 . To date, molecular Borromean links are usually formed by three interlocked macrocycles and not by three interlocked cages (Figure 1B). Therefore, we aimed to develop a level-up strategy for constructing a new generation of cage-based molecular Borromean metalla-links. By following the strategy suitable for fabricating molecular Borromean metalla-links 10,11 , we first obtained the molecular Borromean link 4 consisting of six 2 ligands and six 3 binuclear building units (Figure 1C). Then, accounting for the characteristics of the target structure, the existing strategy for ring-based molecular Borromean links was extended to a suitable strategy for cage-based molecular Borromean links. In line with this upgraded strategy, we designed and synthesized tetrapyridyl ligand 6 and selected two binuclear units, 7 and 8 , to achieve the first synthesis of two cage-based molecular Borromean metalla-links (Figure 1C), as confirmed by X-ray crystallographic analysis, detailed nuclear magnetic resonance (NMR), electrospray ionization-time-of-flight/mass spectrometry (ESI-TOF/MS), and elemental analysis. Results and Discussion Synthesis and Characterization of Molecular Borromean Link 4 To construct a molecular Borromean link ( BL ) based on three metalla-rectangles, dipyridyl ligand 2 , which features a naphthyl plane, and binuclear building unit 3 were strategically selected, and the synthesis of 2 from 1 as well as its characterization can be found in the Supplementary Information (Scheme S1, Figures S1 –S4). As shown in Fig. 2 A, ligand 2 serves as the length side, building unit 3 serves as the width side, and the difference between the length and the width is approximately 7 Å, which meets the requirements of the construction strategy considering the bond length of Rh-N (ca. 2.1 Å). As shown in Fig. 2 B, a yellow solution of 4 can be obtained by reacting ligand 2 with building unit 3 in acetonitrile at a stoichiometric ratio of 1:1 for 24 h at room temperature, and then, an orange crystalline solid is obtained in 91% yield by removing the solvent under vacuum. With the slow diffusion of diisopropyl ether into an acetonitrile solution of 4 at 298 K over five days, yellow block crystals suitable for single-crystal X-ray diffraction (SCXRD) were obtained. According to X-ray crystallographic analysis, compound 4 crystallized in the triclinic space group P ī with one molecule in the unit cell, and its solid-state structure was determined to have a BL topology, in which three equivalent rings adopted a distorted rectangle-like conformation with average length and width (Rh···Rh separations) of 20.7817( 15 ) and 12.9129( 13 ) Å, respectively (Fig. 3 A– 3 D). To determine the reasons for the stabilization of this topological structure, independent gradient model (IGM) analysis based on the promolecular density 26–28 was conducted using the wavefunction software Multiwfn 3.8 26 . With the help of the Visual Molecular Dynamics (VMD) program 29 , the analysis revealed six large green isosurfaces between the naphthyl and phenazinyl planes and twelve small green isosurfaces between the hydrogen atoms of the naphthyl group and nearby pyridyl planes, which confirmed the occurrence of CH···π and π···π interactions in the stacking assembly (Figure S5). Coupled with the X-ray crystallographic analysis results (Fig. 3 E), the three chemically nonconnected, distorted rectangles were determined to be held together by the offset face-to-face aromatic stacking interactions existing between the naphthyl and phenazinyl planes within 3.39–3.77 Å and the tilted T-shaped edge-to-face aromatic interactions existing between the hydrogen atoms in the naphthyl group at 66°–89° to the surrounding pyridyl planes of ligand 2 , and the perpendicular distances were found to vary between 2.94 and 3.20 Å. Subsequently, the behaviour of 4 in solution was further investigated using NMR spectroscopy. The variable concentration (0.1–6.0 mM) 1 H NMR spectra in acetonitrile- d 3 revealed that the chemical shifts and number of peaks do not vary with the concentration, while the intensity of the peaks does, indicating that the structure of 4 does not undergo structural transformation in the acetonitrile solution (Figure S6). Together with the 1 H NMR spectra of 2 (Fig. 4 A) and 3 (Fig. 4 B) as well as the 1 H- 1 H correlated spectroscopy (COSY) and 1 H diffusion-ordered spectroscopy (DOSY) NMR spectra of 4 (Figures S7 and S8), the peak signals in the 1 H NMR spectrum of 4 can be well attributed (Fig. 4 C and Figure S9) and are consistent with the characterization of the BL structure. The chemical shifts H a and H b for the pyridyl group both shift to lower fields, whereas H c and H d for the alkenyl group as well as H e , H f and H g for the naphthyl group shift to higher fields due to shielding by the phenazinyl plane. H 1 , H 2 and H 3 of building unit 3 split into two sets of peak signals, and H 4 attributed to η 5 -pentamethycyclopentadiene (Cp*) shifts to a lower field. Furthermore, the 13 C{ 1 H} NMR spectrum of 4 in acetonitrile- d 3 was also obtained using NMR (Figure S10). The abovementioned peak signals were found to have the same diffusion coefficient (D) of 2.78 × 10 − 10 m 2 s − 1 in the 1 H DOSY NMR spectrum (Figure S8). The cationic structure of 4 in the solid state can be imagined as a prolate spheroid with major and minor axes of 20.1 and 14.2 Å (Fig. 4 D), respectively. Using the modified Stokes–Einstein equation based on a prolate spheroid model 30,31 , the corresponding dimensions were simulated as 20.7 and 14.2 Å for the major ( a ) and minor axes ( b ), respectively, which are similar to the molecular structural dimensions of 4 in the solid state (Fig. 4 E and S42). Further evidence for the existence of 4 was provided by the ESI-TOF/MS spectrum, which showed peaks at m/z 3433.2812 and 2537.7571 assigned to [4–3OTf] 3+ and [4–4OTf] 4+ , respectively (Figures S11–S13). Synthesis and Characterization of Molecular Borromean Links 8 and 10. After the successful construction of a BL using metalla-rectangles, we explored the possibility of constructing BL s using metalla-cuboids. To achieve this goal, we analysed the structure of the target model (Fig. 5 A). The factor that should be considered when constructing BL s consisting of monocycles is the size matching between the length and width (Fig. 2 A). However, in addition to this factor, another factor that needs to be considered when selecting building units for constructing BL s based on cages is the height. Therefore, the size matching among the length, width, and height must be considered when selecting the building unit (Fig. 5 B– 5 E). Based on previous research on metallocages 32 , we used a bimetallic building block together with a tetrapyridyl ligand to fabricate the target structure (Fig. 5 D). Considering the distance ( ca. 3.5 Å) of π···π stacking interactions, tetrapyridyl ligand 6 based on dibenzo-18-crown-6 was designed and synthesized (Scheme S3), and compound 7 was selected as the bimetallic building unit. The detailed synthesis method of ligand 6 from precursor 5 and the detailed characterization of 6 can be found in the Supplementary Information (Figures S14–S21). As shown in Fig. 5 F, a mixture of 6 , 7 and NaOTf at a stoichiometric ratio of 1:2:1 was stirred in a mixed solvent of methanol/nitromethane ( v / v = 6/1) for 24 h at room temperature to obtain a dark red solution. The solvent was removed, and the mixture was washed with diethyl ether and dried to obtain a brown crystalline solid of 8 in 89% yield (Scheme S4). Under ambient conditions, the slow diffusion of diisopropyl ether into a methanol/nitromethane ( v / v = 6/1) solution of 8 for several days provided dark-red cubic crystals suitable for SCXRD. According to the X-ray crystallographic analysis results (Fig. 6 A and 6 B), complex 8 crystallized in the cubic space group \(\:{Pa}_{3}^{-}\) with four molecules in the unit and was discovered to have a BL topology, in which three chemically independent cages are locked such that no two of the three cages are linked with each other (Fig. 6 C). The overall structure contains a nearly spheroid cationic part ( r = 16.6 Å), and every octanuclear metallocage consists of two tetrapyridyl ligands, four naphthalenediimide (NDI)-based ligands, two Na + ions and eight Cp*Rh III metal corners; additionally, the metallocage exhibits a somewhat distorted cuboid shape with length ( l ), width ( w ) and height ( h ) dimensions of 24.2000(38), 12.2591(37) and 18.3915(66) Å (the length and width are the Rh···Rh distances, and the height is the Na···Na distance, Fig. 6 D). To reveal the presence of noncovalent forces in the structure of 8 , IGM analysis based on the crystal structure 26–28 was conducted, and together with the VMD program 29 , twelve large green isosurfaces between the phenyl and NDI planes and twenty-four small green isosurfaces between the hydrogen atoms of Cp* and the nearby oxygen atoms of NDI were found, which confirmed the existence of π···π stacking interactions and weak C-H···O interactions (Figure S22). Combined with the X-ray crystallographic analysis results, the distance range of the offset face-to-face aromatic stacking interactions in this structure was found to be 3.5–3.7 Å, whereas the distance range of weak C-H···O hydrogen bonding interactions was found to be 2.7–3.2 Å (Fig. 6 E). This result further demonstrates that the abovementioned noncovalent interactions play a crucial role in stabilizing this cage-based BL structure. Then, the behaviour of 8 in solution was investigated in depth using NMR via an approach similar to that used in the study of 4 , and a variable concentration experiment with methanol- d 4 /nitromethane- d 3 ( v / v = 6/1) as the solvent was used to explore the behaviour at different concentrations from 0.1 to 5.0 mM. The different concentrations of methanol- d 4 /nitromethane- d 3 ( v / v = 6/1) led to the same results in terms of the number and chemical shifts of the peaks in the 1 H NMR spectra, which suggested that the concentration of 8 in the methanol/nitromethane mixture ( v / v = 6/1) had no effect on the BL topology (Figure S23). As seen by comparing the 1 H NMR spectra of ligand 6 (Fig. 7 A) and building unit 7 (Fig. 7 B), the majority of the peaks in the 1 H NMR spectrum of 8 show slight changes in the chemical shift, but there is no significant splitting of the peaks (Fig. 7 C). Using the evidence provided by the 1 H- 1 H COSY and 1 H DOSY NMR spectra (Figures S24 and S25), the peaks in the 1 H NMR spectrum of 8 were assigned to the BL structure (Figure S26). As a result of the shielding effect of the NDI planes, the chemical shifts H a , H b , H c , H d and H e for the pyridyl, alkenyl, and phenyl groups in 6 are shifted to higher fields, whereas the chemical shifts H f and H g for the dibenzo-18-crown-6-based group remain almost unchanged without any shielding effect. The chemical shifts H 1 and H 2 for the NDI-based group and Cp* remain almost unchanged, but their peaks split into two sets of signals (Fig. 7 C). Moreover, the 1 H{ 13 C} NMR spectrum of 8 in methanol- d 4 /nitromethane- d 3 was also obtained to characterize the BL structure (Figure S27). As mentioned in the crystallographic analysis results, the cationic portion of 8 can be approximated as a sphere with a radius of 16.6 Å. With the obtained diffusion coefficient D (2.43 × 10 − 10 m 2 s − 1 , Fig. 7 D and S43), the radial dimension of 8 in solution for the spheroid can be calculated as 16.5 Å by directly using the Stokes–Einstein Eq. 3 0 , which is similar to that in the solid state, thus providing further evidence of the BL structure in solution (Fig. 7 E). Additionally, the ESI-TOF/MS spectra confirm the existence of 8 based on the peaks at m/z 2936.9528 and 2165.4436, which are consistent with the calculated isotopic distributions of [ 8–6 OTf] 6+ and [ 8–8 OTf] 8+ with peaks at m/z 2936.8992 and 2165.4377, respectively (Figures S28–S30). To investigate the effect of the central ion in the metal corner on this cage-based BL structure, Ir III was chosen to replace Rh III in the coordination-driven self-assembly process. As shown in Fig. 5 F, the conditions were kept the same as those used for the synthesis of 8 except that the bimetallic building block was changed from 7 to 9 , and compound 10 was finally obtained in a yield of 92%. Despite many attempts, the quality of the single-crystal sample of 10 still did not satisfy the crystallographic requirements for structural determination, but based on the currently resolved structure, it appears to have a BL topology similar to that of 8 (Figure S31). In terms of the NMR characterization of 10 , the relevant spectra of 10 provided evidence for the existence of a BL structure in solution, and in particular, the 1 H and 1 H{ 13 C} NMR spectra of 10 were similar to the relevant spectra of 8 (Figures S32–S38). And the size simulation based on 1 H DOSY NMR also confirmed its dimension in solution (Figure S44). In addition, the ESI-TOF/MS spectrum provided clear evidence confirming the presence of the BL structure (Figures S39–S41). Conclusion In summary, based on the construction of the molecular ring-based Borromean metalla-link 4 , we propose a strategy for the rational design and controlled synthesis of cage-based Borromean links. Following this strategy, dibenzo-18-crown-6-based tetrapyridyl ligand 6 and two binuclear building units 7 and 9 were tactically selected to fabricate two molecular Borromean links comprising three identical decanuclear metallocages in nearly quantitative yield. Together with IGM analysis, SCXRD analysis revealed that noncovalent interactions between components (e.g., π···π stacking interactions and weak C-H···O interactions) play a significant role in maintaining the cage-based Borromean links. Evidence from detailed NMR, ESI-TOF/MS and elemental analysis further confirmed the existence of the Borromean links. The strategy employed in this work enables the construction of a new generation of molecular Borromean links, which we hope will serve as a useful reference for fabricating more sophisticated topologies in the future. Method Synthesis: The ligands 2 and 6 were synthesized using conditions of Heck coupling reaction and the specific method and characterization of 2 and 6 are provided in Supplementary Information. The Borromean metalla-links 4 , 8 and 10 were synthesized using ligands 2 and 6 and binuclear building units 3 , 7 and 9 , respectively, and the detailed method and characterization of 4 , 8 and 10 are provided in Supplementary Information. X-ray Crystallography: Single crystals of 4 and 8 suitable for X-ray diffraction were obtained at room temperature. X-ray intensity data were collected at 170 K on a Bruker D8 VENTURE system and used Ga K α radiation ( λ = 1.34139 Å). Using Olex2 33 , the structures of 4 and 8 were solved with the SHELXS-1997 34,35 structure solution program using direct methods and refined with the SHELXL 36 refinement package using least-squares minimization. With these data, the disordered solvent molecules that could not be restrained properly were removed using the SQUEEZE method. The details of the crystal data collection and refinement are summarized in Table S1 and S2 . Computational details: Independent gradient model (IGM) analysis of promolecular density was performed for 4 and 8 . The calculation models were established by extracting molecules from the crystal structures. The cubic files (.cub) for IGM analysis 27-28 were generated by the wavefunction software Multiwfn 3.8 26 , and the IGM inter surfaces were visualized and analysed using the Visual Molecular Dynamics program (VMD 1.93) 29 . Declarations Data availability Crystallographic data for the structures reported in this work are available from the Cambridge Crystallographic Data Centre with the following codes: 4 (CCDC 2363098) and 8 (CCDC 2363099). CIFs are available free of charge at http://www.ccdc.cam.ac.uk/data_request/cif. Other data that support the findings of this study are available in the Supplementary Information. Acknowledgements This work was supported by the National Science Foundation of China (22031003, 21720102004 and 22301040), the Shanghai Science Technology Committee (19DZ2270100), the China National Postdoctoral Program for Innovative Talents (BX20220092) and the Shanghai Postdoctoral Excellence Program (2022736). G.-X.J thanks the Alexander von Humboldt Foundation for a Humbold Research Award. Author contributions H.-N.Z. and G.-X.J. designed the experimental protocol. H.-N.Z. performed the synthesis and characterization studies, solved the crystal structure and wrote the manuscript. 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Acta Crystallogr. Sect. A 46 , 467-473 (1990). Sheldrick, G. A short history of SHELX. Acta Crystallogr. Sect. A 64 , 112-122 (2008). Sheldrick, G. SHELXT - Integrated space-group and crystal-structure determination. Acta Crystallogr. Sect. A 71 , 3-8 (2015). Additional Declarations There is NO Competing Interest. Supplementary Files DataS1.cif CIF data for S1 DataS2.cif CIF data for S2 SupplementaryInformation.docx Cite Share Download PDF Status: Published Journal Publication published 14 Jan, 2025 Read the published version in Nature Synthesis → Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4824942","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":336216611,"identity":"e6aa3d23-7f1a-401f-8fa6-a9a6f767128d","order_by":0,"name":"Guo-Xin Jin","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA1ElEQVRIiWNgGAWjYHCChAMMFXIMDAdAbDaitZwxJk0LAwNjGyla5CMSHh4unGeQ2Hf87AGGD2WHGfhnN+DXYnjmQMLhmdsMEmeeyUtgnHHuMIPEnQMEtLQ3JBzm3fYnccOBHANm3rbDDAYSCQS0NDMAtcwxSNxw/o0B819itMizg2xpAGq5AbSFkRgtBjxAv/AcMzCeeeONwcGec+k8EjcI2TIjJ/kzT42BbN/5HMMHP8qs5fhnELLlAA9CxQEg5sGvHmRLA/sBgopGwSgYBaNghAMA6exKaxpBeSYAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0002-7149-5413","institution":"Fudan University","correspondingAuthor":true,"submittingAuthor":false,"prefix":"","firstName":"Guo-Xin","middleName":"","lastName":"Jin","suffix":""},{"id":336216612,"identity":"d1aa4d46-557b-451c-ac21-8ea6e4b2eac7","order_by":1,"name":"Hai-Ning Zhang","email":"","orcid":"","institution":"Fudan University","correspondingAuthor":false,"submittingAuthor":false,"prefix":"","firstName":"Hai-Ning","middleName":"","lastName":"Zhang","suffix":""}],"badges":[],"createdAt":"2024-07-30 01:45:24","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4824942/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4824942/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1038/s44160-024-00720-4","type":"published","date":"2025-01-14T05:00:00+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":61944980,"identity":"5b263922-a782-41c2-a3e4-26d10661fe47","added_by":"auto","created_at":"2024-08-07 11:16:40","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":244420,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eOrthogonal arrangement of Borromean link and building units in this work.\u003c/strong\u003e Representation of ring-based (A) and cage-based Borromean link (B). (C) Selected building units \u003cstrong\u003e2\u003c/strong\u003e, [\u003cstrong\u003e6\u003c/strong\u003e·Na]\u003csup\u003e+\u003c/sup\u003e \u003cstrong\u003e3\u003c/strong\u003e\u003csup\u003e4+\u003c/sup\u003e, \u003cstrong\u003e7\u003c/strong\u003e\u003csup\u003e2+\u003c/sup\u003e and \u003cstrong\u003e9\u003c/strong\u003e\u003csup\u003e2+\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4824942/v1/e57415f2523e38f85382c844.png"},{"id":61944392,"identity":"976d6a8d-b87d-4510-a14a-9be5dc6a39be","added_by":"auto","created_at":"2024-08-07 11:08:40","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":399340,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDesign and synthesis of a metallacycle-based Borromean link.\u003c/strong\u003e (A) Rational conditions for constructing metalla-rectangle-based Borromean links. (B) Synthetic route to Borromean link \u003cstrong\u003e4\u003c/strong\u003e: i) 4-vinylpyridine, K\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e, PdCl\u003csub\u003e2\u003c/sub\u003e(PPh\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, DMF, 393 K, 48 h; ii) MeCN, rt, 24 h.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4824942/v1/ed4fce9e05358321f692f9a6.png"},{"id":61944400,"identity":"238cd505-424b-4562-b3c3-ba879d0e6ff3","added_by":"auto","created_at":"2024-08-07 11:08:41","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":724890,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eX-ray crystallographic analysis of 4.\u003c/strong\u003e(A) Chemical structure representation of \u003cstrong\u003eBL\u003c/strong\u003e \u003cstrong\u003e4\u003c/strong\u003e. (B) Cationic molecular structure of \u003cstrong\u003e4\u003c/strong\u003e in the ball-and-stick representation. (C) Reduced representation of the \u003cstrong\u003eBL\u003c/strong\u003e \u003cstrong\u003e4\u003c/strong\u003e and \u003cstrong\u003eBL\u003c/strong\u003e topologies. (D) Dimensions (length and width) of one metalla-rectangle making up \u003cstrong\u003e4\u003c/strong\u003e. (E) Partial structures highlighting the intermolecular forces in the structure of \u003cstrong\u003e4\u003c/strong\u003e. Colour code: C, grey; H, light blue; N, navy blue; Rh, violet.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-4824942/v1/db0c1da89bfc78b5ef5cfea8.png"},{"id":61944393,"identity":"d72b2a1a-e8a7-46da-9300-2b8dce6cff2e","added_by":"auto","created_at":"2024-08-07 11:08:40","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":508788,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDetailed NMR analysis of 4.\u003c/strong\u003e Partial \u003csup\u003e1\u003c/sup\u003eH NMR spectra: ligand \u003cstrong\u003e2\u003c/strong\u003e (A), binuclear building unit \u003cstrong\u003e3\u003c/strong\u003e (B), and Borromean link \u003cstrong\u003e4\u003c/strong\u003e, \u003cem\u003ec\u003c/em\u003e = 6.0 mM (C). (D) Molecular structure dimensions measured by SCXRD analysis of \u003cstrong\u003e4\u003c/strong\u003e. (E) DOSY-derived dimensions (major axis: \u003cem\u003ea\u003c/em\u003e =20.7 Å, minor axis: \u003cem\u003eb\u003c/em\u003e = 14.2 Å) fitted using the diffusion constant \u003cem\u003eD\u003c/em\u003e = 2.78 × 10\u003csup\u003e-10\u003c/sup\u003e m\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e-1\u003c/sup\u003e.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4824942/v1/4c649056bc55f15346c80f76.png"},{"id":61944396,"identity":"02db8f63-c1f4-40ad-91a0-240471611b24","added_by":"auto","created_at":"2024-08-07 11:08:40","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":1274778,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDesign and synthesis of two metallocage-based Borromean links.\u003c/strong\u003e (A) Representation of a cage-based \u003cstrong\u003eBL\u003c/strong\u003e. (B) The speculated structure of a cage-based \u003cstrong\u003eBL\u003c/strong\u003e. (C) Relationships among the length, width, and height of the metallocage. \u003cem\u003ed\u003c/em\u003e\u003csub\u003e1\u003c/sub\u003e, \u003cem\u003ed\u003c/em\u003e\u003csub\u003e4\u003c/sub\u003e, \u003cem\u003ed\u003c/em\u003e\u003csub\u003e5\u003c/sub\u003e, \u003cem\u003ed\u003c/em\u003e\u003csub\u003e8\u003c/sub\u003e ≈ 3.5 Å (π···π interactions), \u003cem\u003ed\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e, \u003cem\u003ed\u003c/em\u003e\u003csub\u003e3\u003c/sub\u003e,\u003csub\u003e \u003c/sub\u003e\u003cem\u003ed\u003c/em\u003e\u003csub\u003e6\u003c/sub\u003e,\u003csub\u003e \u003c/sub\u003e\u003cem\u003ed\u003c/em\u003e\u003csub\u003e7\u003c/sub\u003e ≥ 2.45 Å (CH···π interactions), \u003cem\u003eL\u003c/em\u003e – \u003cem\u003eW\u003c/em\u003e ≥ 11.9 Å, \u003cem\u003eH –\u003c/em\u003e \u003cem\u003eW\u003c/em\u003e ≥ 4.9 Å, \u003cem\u003eL\u003c/em\u003e \u003cem\u003e–\u003c/em\u003e \u003cem\u003eH\u003c/em\u003e = \u003cem\u003ed\u003c/em\u003e\u003csub\u003e5\u003c/sub\u003e + \u003cem\u003ed\u003c/em\u003e\u003csub\u003e8\u003c/sub\u003e ≈ 7 Å, and \u003cem\u003eL\u003c/em\u003e \u003cem\u003e+\u003c/em\u003e \u003cem\u003eH\u003c/em\u003e \u003cem\u003e–\u003c/em\u003e 2\u003cem\u003eW\u003c/em\u003e ≥ 16.8 Å. (D) Selected metalla-ligand [\u003cstrong\u003e6\u003c/strong\u003e•Na]\u003csup\u003e+\u003c/sup\u003e and binuclear building units \u003cstrong\u003e7\u003c/strong\u003e and \u003cstrong\u003e9\u003c/strong\u003e. (E) One cage of the target cage-based \u003cstrong\u003eBL\u003c/strong\u003e and its chemical structure representation. (F) Synthetic route to Borromean links \u003cstrong\u003e8/10\u003c/strong\u003e: i) 4-vinylpyridine, K\u003csub\u003e2\u003c/sub\u003eCO\u003csub\u003e3\u003c/sub\u003e, PdCl\u003csub\u003e2\u003c/sub\u003e(PPh\u003csub\u003e3\u003c/sub\u003e)\u003csub\u003e2\u003c/sub\u003e, DMF, 393 K, 48 h; ii) NaOTf, MeOH/MeNO\u003csub\u003e3\u003c/sub\u003e (v/v = 6/1), rt, 24 h.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-4824942/v1/8bc1e648477fd167db21a8e9.png"},{"id":61944402,"identity":"f123188c-d959-47ef-b0dc-da2ea059d838","added_by":"auto","created_at":"2024-08-07 11:08:41","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":947914,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eX-ray crystallographic analysis of 8.\u003c/strong\u003e (A) Chemical structure representation of \u003cstrong\u003eBL\u003c/strong\u003e \u003cstrong\u003e8\u003c/strong\u003e. (B) Cationic molecular structure of \u003cstrong\u003e8\u003c/strong\u003e in the ball-and-stick representation. (C) Reduced representation of \u003cstrong\u003eBL\u003c/strong\u003e \u003cstrong\u003e8\u003c/strong\u003e. (D) Dimensions (length, width and height) of one metallocage comprising \u003cstrong\u003e8\u003c/strong\u003e. (E) Partial structures highlighting the intermolecular forces in the structure of \u003cstrong\u003e8\u003c/strong\u003e. Colour code: C, grey; H, light blue; N, navy blue; O, red; Rh, violet, Na, cerise.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-4824942/v1/75c6dcb07df189c6780880a8.png"},{"id":61944982,"identity":"8e18ce85-06bd-46f7-b7b5-720cb69a9f92","added_by":"auto","created_at":"2024-08-07 11:16:40","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":836298,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eDetailed NMR analysis of 8.\u003c/strong\u003e Partial \u003csup\u003e1\u003c/sup\u003eH NMR spectra of (A) ligand \u003cstrong\u003e6\u003c/strong\u003e, (B) binuclear building unit \u003cstrong\u003e7\u003c/strong\u003e, and (C) metallocage-based Borromean link \u003cstrong\u003e8\u003c/strong\u003e, \u003cem\u003ec\u003c/em\u003e = 5.0 mM. (D) Partial \u003csup\u003e1\u003c/sup\u003eH DOSY NMR spectrum (400 MHz, 298.15 K, \u003cem\u003ec\u003c/em\u003e = 5.0 mM, \u003cem\u003eD\u003c/em\u003e = 2.43 × 10\u003csup\u003e-10\u003c/sup\u003e m\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e-1\u003c/sup\u003e) of \u003cstrong\u003e8\u003c/strong\u003e in methanol-\u003cem\u003ed\u003c/em\u003e\u003csub\u003e4\u003c/sub\u003e/nitromethane-\u003cem\u003ed\u003c/em\u003e\u003csub\u003e3\u003c/sub\u003e (v/v = 6/1). (E) Molecular cationic structure dimensions measured by X-ray crystallographic analysis of \u003cstrong\u003e8\u003c/strong\u003e.\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-4824942/v1/a0b07bb86624207c9272931f.png"},{"id":73839542,"identity":"b1a1fc24-dbd7-44b3-8657-54ea49f6fed9","added_by":"auto","created_at":"2025-01-15 08:07:34","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6241414,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4824942/v1/a0ebe00a-847a-4659-b03c-b7237bfa4f78.pdf"},{"id":61945400,"identity":"eaf21907-a8b9-4b3a-ba9e-47a295d52075","added_by":"auto","created_at":"2024-08-07 11:24:40","extension":"cif","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":5663068,"visible":true,"origin":"","legend":"CIF data for S1","description":"","filename":"DataS1.cif","url":"https://assets-eu.researchsquare.com/files/rs-4824942/v1/9ae52746ae0478d675d64212.cif"},{"id":61944983,"identity":"4eaaad95-0dbf-4043-88c3-8b4a295b1317","added_by":"auto","created_at":"2024-08-07 11:16:41","extension":"cif","order_by":2,"title":"","display":"","copyAsset":false,"role":"supplement","size":12323075,"visible":true,"origin":"","legend":"\u003cp\u003eCIF data for S2\u003c/p\u003e","description":"","filename":"DataS2.cif","url":"https://assets-eu.researchsquare.com/files/rs-4824942/v1/cc145374edc699c6f52c3dba.cif"},{"id":61944399,"identity":"b68c6491-e250-49fe-a1dc-e1ac1dd1b58f","added_by":"auto","created_at":"2024-08-07 11:08:41","extension":"docx","order_by":3,"title":"","display":"","copyAsset":false,"role":"supplement","size":21870501,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cbr\u003e\u003c/p\u003e","description":"","filename":"SupplementaryInformation.docx","url":"https://assets-eu.researchsquare.com/files/rs-4824942/v1/ac5a24995a4c508b921e6c25.docx"}],"financialInterests":"There is \u003cb\u003eNO\u003c/b\u003e Competing Interest.","formattedTitle":"Molecular Borromean links based on metallocages","fulltext":[{"header":"Introduction","content":"\u003cp\u003eAs the most familiar example of\u0026nbsp;a\u0026nbsp;Brunnian link,\u0026nbsp;the\u0026nbsp;Borromean link\u003csup\u003e1-4\u003c/sup\u003e is a prime link and generally refers to a topology consisting of three relatively independent but interlocked rings, with no interlocking between any two of them (Figure 1A). This structural feature means that disconnection of one of the rings results in complete separation of the remaining two rings\u003csup\u003e5\u003c/sup\u003e. The construction of topological structures with structural integrity and aesthetics at the molecular level has long been regarded as a challenge in synthetic chemistry\u003csup\u003e2\u003c/sup\u003e, and the pioneering work by Seeman\u0026rsquo;s group on the first-ever artificial construction of such topologies using specific interactions between different DNA fragments\u0026nbsp;inspired\u0026nbsp;chemists to think about how to rationally construct these structures by means of chemical synthesis\u003csup\u003e6\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eStoddart and\u0026nbsp;coworkers\u0026nbsp;ingeniously utilized\u0026nbsp;the\u0026nbsp;transition metal ion Zn\u003csup\u003eII\u003c/sup\u003e as\u0026nbsp;a\u0026nbsp;template\u0026nbsp;for\u0026nbsp;self-assembly of molecular Borromean link precursors induced by metal\u0026ndash;ligand coordination bonds and achieved the first synthesis of a molecular Borromean link with organic skeletons in a wholly synthetic molecular form after covalent ring closure\u0026nbsp;and\u0026nbsp;removal of the templating agent\u003csup\u003e7\u003c/sup\u003e. Our group\u0026nbsp;first\u0026nbsp;obtained molecular Borromean links with metallo-backbones via\u0026nbsp;the co-driven self-assembly of coordination and noncovalent interactions\u003csup\u003e8,9\u003c/sup\u003e and summarized the design strategy applicable to controlled construction of such molecular Borromean metalla-links\u003csup\u003e10,11\u003c/sup\u003e. Inspired by the above two synthetic strategies, researchers have realized a series of molecular Borromean links through rational design and efficient construction\u003csup\u003e11-13\u003c/sup\u003e.\u003c/p\u003e\n\u003cp\u003eThe first interlocked-cage structures reported by Fujita et al. subsequently inspired synthetic chemists to successfully construct cage-based interlocked structures featuring organo- or metallo-backbones\u003csup\u003e14\u003c/sup\u003e. However, among these reported structures, most of them\u0026nbsp;involve\u0026nbsp;dimeric catenation of cages\u003csup\u003e15-24\u003c/sup\u003e, while trimeric catenation structures are rare. Recently, Mastalerz and coworkers synthesized three interlocked, identical organic cages, but\u0026nbsp;their\u0026nbsp;topology was not a molecular Borromean link\u003csup\u003e25\u003c/sup\u003e.\u0026nbsp;To date, molecular Borromean links are usually formed by three interlocked macrocycles and not by three interlocked cages (Figure 1B). Therefore, we aimed to develop a level-up strategy for constructing\u0026nbsp;a\u0026nbsp;new generation of cage-based molecular Borromean metalla-links.\u003c/p\u003e\n\u003cp\u003eBy following the strategy suitable for fabricating molecular Borromean metalla-links\u003csup\u003e10,11\u003c/sup\u003e, we first obtained\u0026nbsp;the\u0026nbsp;molecular Borromean link \u003cstrong\u003e4\u003c/strong\u003e consisting of six \u003cstrong\u003e2\u003c/strong\u003e ligands and six \u003cstrong\u003e3\u003c/strong\u003e binuclear building units (Figure 1C). Then, accounting for the characteristics of\u0026nbsp;the\u0026nbsp;target structure, the existing strategy for\u0026nbsp;ring-based molecular Borromean links was extended to a suitable\u0026nbsp;strategy\u0026nbsp;for\u0026nbsp;cage-based molecular Borromean links. In line with\u0026nbsp;this\u0026nbsp;upgraded strategy, we designed and synthesized tetrapyridyl ligand \u003cstrong\u003e6\u003c/strong\u003e and selected two binuclear units,\u0026nbsp;\u003cstrong\u003e7\u003c/strong\u003e and \u003cstrong\u003e8\u003c/strong\u003e, to achieve the first synthesis of two cage-based molecular Borromean metalla-links (Figure 1C), as confirmed by X-ray crystallographic analysis, detailed nuclear magnetic resonance (NMR), electrospray ionization-time-of-flight/mass spectrometry (ESI-TOF/MS), and elemental analysis.\u003c/p\u003e"},{"header":"Results and Discussion","content":"\u003cdiv id=\"Sec2\" class=\"Section2\"\u003e \u003ch2\u003eSynthesis and Characterization of Molecular Borromean Link 4\u003c/h2\u003e \u003cp\u003eTo construct a molecular Borromean link (\u003cb\u003eBL\u003c/b\u003e) based on three metalla-rectangles, dipyridyl ligand \u003cb\u003e2\u003c/b\u003e, which features a naphthyl plane, and binuclear building unit \u003cb\u003e3\u003c/b\u003e were strategically selected, and the synthesis of \u003cb\u003e2\u003c/b\u003e from \u003cb\u003e1\u003c/b\u003e as well as its characterization can be found in the Supplementary Information (Scheme S1, Figures \u003cspan refid=\"MOESM1\" class=\"InternalRef\"\u003eS1\u003c/span\u003e\u0026ndash;S4). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA, ligand \u003cb\u003e2\u003c/b\u003e serves as the length side, building unit \u003cb\u003e3\u003c/b\u003e serves as the width side, and the difference between the length and the width is approximately 7 \u0026Aring;, which meets the requirements of the construction strategy considering the bond length of Rh-N (ca. 2.1 \u0026Aring;). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eB, a yellow solution of \u003cb\u003e4\u003c/b\u003e can be obtained by reacting ligand \u003cb\u003e2\u003c/b\u003e with building unit \u003cb\u003e3\u003c/b\u003e in acetonitrile at a stoichiometric ratio of 1:1 for 24 h at room temperature, and then, an orange crystalline solid is obtained in 91% yield by removing the solvent under vacuum.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eWith the slow diffusion of diisopropyl ether into an acetonitrile solution of \u003cb\u003e4\u003c/b\u003e at 298 K over five days, yellow block crystals suitable for single-crystal X-ray diffraction (SCXRD) were obtained. According to X-ray crystallographic analysis, compound \u003cb\u003e4\u003c/b\u003e crystallized in the triclinic space group \u003cem\u003eP\u003c/em\u003eī with one molecule in the unit cell, and its solid-state structure was determined to have a \u003cb\u003eBL\u003c/b\u003e topology, in which three equivalent rings adopted a distorted rectangle-like conformation with average length and width (Rh\u0026middot;\u0026middot;\u0026middot;Rh separations) of 20.7817(\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e) and 12.9129(\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e) \u0026Aring;, respectively (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eA\u0026ndash;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eD).\u003c/p\u003e \u003cp\u003eTo determine the reasons for the stabilization of this topological structure, independent gradient model (IGM) analysis based on the promolecular density\u003csup\u003e26\u0026ndash;28\u003c/sup\u003e was conducted using the wavefunction software Multiwfn 3.8\u003csup\u003e26\u003c/sup\u003e. With the help of the Visual Molecular Dynamics (VMD) program\u003csup\u003e29\u003c/sup\u003e, the analysis revealed six large green isosurfaces between the naphthyl and phenazinyl planes and twelve small green isosurfaces between the hydrogen atoms of the naphthyl group and nearby pyridyl planes, which confirmed the occurrence of CH\u0026middot;\u0026middot;\u0026middot;π and π\u0026middot;\u0026middot;\u0026middot;π interactions in the stacking assembly (Figure S5). Coupled with the X-ray crystallographic analysis results (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003eE), the three chemically nonconnected, distorted rectangles were determined to be held together by the offset face-to-face aromatic stacking interactions existing between the naphthyl and phenazinyl planes within 3.39\u0026ndash;3.77 \u0026Aring; and the tilted T-shaped edge-to-face aromatic interactions existing between the hydrogen atoms in the naphthyl group at 66\u0026deg;\u0026ndash;89\u0026deg; to the surrounding pyridyl planes of ligand \u003cb\u003e2\u003c/b\u003e, and the perpendicular distances were found to vary between 2.94 and 3.20 \u0026Aring;.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eSubsequently, the behaviour of \u003cb\u003e4\u003c/b\u003e in solution was further investigated using NMR spectroscopy. The variable concentration (0.1\u0026ndash;6.0 mM) \u003csup\u003e1\u003c/sup\u003eH NMR spectra in acetonitrile-\u003cem\u003ed\u003c/em\u003e\u003csub\u003e3\u003c/sub\u003e revealed that the chemical shifts and number of peaks do not vary with the concentration, while the intensity of the peaks does, indicating that the structure of \u003cb\u003e4\u003c/b\u003e does not undergo structural transformation in the acetonitrile solution (Figure S6). Together with the \u003csup\u003e1\u003c/sup\u003eH NMR spectra of \u003cb\u003e2\u003c/b\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eA) and \u003cb\u003e3\u003c/b\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eB) as well as the \u003csup\u003e1\u003c/sup\u003eH-\u003csup\u003e1\u003c/sup\u003eH correlated spectroscopy (COSY) and \u003csup\u003e1\u003c/sup\u003eH diffusion-ordered spectroscopy (DOSY) NMR spectra of \u003cb\u003e4\u003c/b\u003e (Figures S7 and S8), the peak signals in the \u003csup\u003e1\u003c/sup\u003eH NMR spectrum of \u003cb\u003e4\u003c/b\u003e can be well attributed (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eC and Figure S9) and are consistent with the characterization of the \u003cb\u003eBL\u003c/b\u003e structure. The chemical shifts H\u003csub\u003ea\u003c/sub\u003e and H\u003csub\u003eb\u003c/sub\u003e for the pyridyl group both shift to lower fields, whereas H\u003csub\u003ec\u003c/sub\u003e and H\u003csub\u003ed\u003c/sub\u003e for the alkenyl group as well as H\u003csub\u003ee\u003c/sub\u003e, H\u003csub\u003ef\u003c/sub\u003e and H\u003csub\u003eg\u003c/sub\u003e for the naphthyl group shift to higher fields due to shielding by the phenazinyl plane. H\u003csub\u003e1\u003c/sub\u003e, H\u003csub\u003e2\u003c/sub\u003e and H\u003csub\u003e3\u003c/sub\u003e of building unit \u003cb\u003e3\u003c/b\u003e split into two sets of peak signals, and H\u003csub\u003e4\u003c/sub\u003e attributed to \u003cem\u003eη\u003c/em\u003e\u003csup\u003e5\u003c/sup\u003e-pentamethycyclopentadiene (Cp*) shifts to a lower field. Furthermore, the \u003csup\u003e13\u003c/sup\u003eC{\u003csup\u003e1\u003c/sup\u003eH} NMR spectrum of \u003cb\u003e4\u003c/b\u003e in acetonitrile-\u003cem\u003ed\u003c/em\u003e\u003csub\u003e3\u003c/sub\u003e was also obtained using NMR (Figure S10).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe abovementioned peak signals were found to have the same diffusion coefficient (D) of 2.78 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;10\u003c/sup\u003e m\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e in the \u003csup\u003e1\u003c/sup\u003eH DOSY NMR spectrum (Figure S8). The cationic structure of \u003cb\u003e4\u003c/b\u003e in the solid state can be imagined as a prolate spheroid with major and minor axes of 20.1 and 14.2 \u0026Aring; (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eD), respectively. Using the modified Stokes\u0026ndash;Einstein equation based on a prolate spheroid model\u003csup\u003e30,31\u003c/sup\u003e, the corresponding dimensions were simulated as 20.7 and 14.2 \u0026Aring; for the major (\u003cem\u003ea\u003c/em\u003e) and minor axes (\u003cem\u003eb\u003c/em\u003e), respectively, which are similar to the molecular structural dimensions of \u003cb\u003e4\u003c/b\u003e in the solid state (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eE and S42). Further evidence for the existence of \u003cb\u003e4\u003c/b\u003e was provided by the ESI-TOF/MS spectrum, which showed peaks at \u003cem\u003em/z\u003c/em\u003e 3433.2812 and 2537.7571 assigned to [4\u0026ndash;3OTf]\u003csup\u003e3+\u003c/sup\u003e and [4\u0026ndash;4OTf]\u003csup\u003e4+\u003c/sup\u003e, respectively (Figures S11\u0026ndash;S13).\u003c/p\u003e \u003cp\u003e \u003cb\u003eSynthesis and Characterization of Molecular Borromean Links 8 and 10.\u003c/b\u003e \u003c/p\u003e \u003cp\u003eAfter the successful construction of a \u003cb\u003eBL\u003c/b\u003e using metalla-rectangles, we explored the possibility of constructing \u003cb\u003eBL\u003c/b\u003es using metalla-cuboids. To achieve this goal, we analysed the structure of the target model (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eA). The factor that should be considered when constructing \u003cb\u003eBL\u003c/b\u003es consisting of\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003emonocycles is the size matching between the length and width (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eA). However, in addition to this factor, another factor that needs to be considered when selecting building units for constructing \u003cb\u003eBL\u003c/b\u003es based on cages is the height. Therefore, the size matching among the length, width, and height must be considered when selecting the building unit (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eB\u0026ndash;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eE). Based on previous research on metallocages\u003csup\u003e32\u003c/sup\u003e, we used a bimetallic building block together with a tetrapyridyl ligand to fabricate the target structure (Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eD).\u003c/p\u003e \u003cp\u003eConsidering the distance (\u003cem\u003eca.\u003c/em\u003e 3.5 \u0026Aring;) of π\u0026middot;\u0026middot;\u0026middot;π stacking interactions, tetrapyridyl ligand \u003cb\u003e6\u003c/b\u003e based on dibenzo-18-crown-6 was designed and synthesized (Scheme S3), and compound \u003cb\u003e7\u003c/b\u003e was selected as the bimetallic building unit. The detailed synthesis method of ligand \u003cb\u003e6\u003c/b\u003e from precursor \u003cb\u003e5\u003c/b\u003e and the detailed characterization of \u003cb\u003e6\u003c/b\u003e can be found in the Supplementary Information (Figures S14\u0026ndash;S21). As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eF, a mixture of \u003cb\u003e6\u003c/b\u003e, \u003cb\u003e7\u003c/b\u003e and NaOTf at a stoichiometric ratio of 1:2:1 was stirred in a mixed solvent of methanol/nitromethane (\u003cem\u003ev\u003c/em\u003e/\u003cem\u003ev\u003c/em\u003e\u0026thinsp;=\u0026thinsp;6/1) for 24 h at room temperature to obtain a dark red solution. The solvent was removed, and the mixture was washed with diethyl ether and dried to obtain a brown crystalline solid of \u003cb\u003e8\u003c/b\u003e in 89% yield (Scheme S4).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eUnder ambient conditions, the slow diffusion of diisopropyl ether into a methanol/nitromethane (\u003cem\u003ev\u003c/em\u003e/\u003cem\u003ev\u003c/em\u003e\u0026thinsp;=\u0026thinsp;6/1) solution of \u003cb\u003e8\u003c/b\u003e for several days provided dark-red cubic crystals suitable for SCXRD. According to the X-ray crystallographic analysis results (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eA and \u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eB), complex \u003cb\u003e8\u003c/b\u003e crystallized in the cubic space group \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\(\\:{Pa}_{3}^{-}\\)\u003c/span\u003e\u003c/span\u003e with four molecules in the unit and was discovered to have a \u003cb\u003eBL\u003c/b\u003e topology, in which three chemically independent cages are locked such that no two of the three cages are linked with each other (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eC). The overall structure contains a nearly spheroid cationic part (\u003cem\u003er\u003c/em\u003e\u0026thinsp;=\u0026thinsp;16.6 \u0026Aring;), and every octanuclear metallocage consists of two tetrapyridyl ligands, four naphthalenediimide (NDI)-based ligands, two Na\u003csup\u003e+\u003c/sup\u003e ions and eight Cp*Rh\u003csup\u003eIII\u003c/sup\u003e metal corners; additionally, the metallocage exhibits a somewhat distorted cuboid shape with length (\u003cem\u003el\u003c/em\u003e), width (\u003cem\u003ew\u003c/em\u003e) and height (\u003cem\u003eh\u003c/em\u003e) dimensions of 24.2000(38), 12.2591(37) and 18.3915(66) \u0026Aring; (the length and width are the Rh\u0026middot;\u0026middot;\u0026middot;Rh distances, and the height is the Na\u0026middot;\u0026middot;\u0026middot;Na distance, Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eD).\u003c/p\u003e \u003cp\u003eTo reveal the presence of noncovalent forces in the structure of \u003cb\u003e8\u003c/b\u003e, IGM analysis based on the crystal structure\u003csup\u003e26\u0026ndash;28\u003c/sup\u003e was conducted, and together with the VMD program\u003csup\u003e29\u003c/sup\u003e, twelve large green isosurfaces between the phenyl and NDI planes and twenty-four small green isosurfaces between the hydrogen atoms of Cp* and the nearby oxygen atoms of NDI were found, which confirmed the existence of π\u0026middot;\u0026middot;\u0026middot;π stacking interactions and weak C-H\u0026middot;\u0026middot;\u0026middot;O interactions (Figure S22). Combined with the X-ray crystallographic analysis results, the distance range of the offset face-to-face aromatic stacking interactions in this structure was found to be 3.5\u0026ndash;3.7 \u0026Aring;, whereas the distance range of weak C-H\u0026middot;\u0026middot;\u0026middot;O hydrogen bonding interactions was found to be 2.7\u0026ndash;3.2 \u0026Aring; (Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e6\u003c/span\u003eE). This result further demonstrates that the abovementioned noncovalent interactions play a crucial role in stabilizing this cage-based \u003cb\u003eBL\u003c/b\u003e structure.\u003c/p\u003e \u003cp\u003eThen, the behaviour of \u003cb\u003e8\u003c/b\u003e in solution was investigated in depth using NMR via an approach similar to that used in the study of \u003cb\u003e4\u003c/b\u003e, and a variable concentration experiment with methanol-\u003cem\u003ed\u003c/em\u003e\u003csub\u003e4\u003c/sub\u003e/nitromethane-\u003cem\u003ed\u003c/em\u003e\u003csub\u003e3\u003c/sub\u003e (\u003cem\u003ev\u003c/em\u003e/\u003cem\u003ev\u003c/em\u003e\u0026thinsp;=\u0026thinsp;6/1) as the solvent was used to explore the behaviour at different concentrations from 0.1 to 5.0 mM. The different concentrations of methanol-\u003cem\u003ed\u003c/em\u003e\u003csub\u003e4\u003c/sub\u003e/nitromethane-\u003cem\u003ed\u003c/em\u003e\u003csub\u003e3\u003c/sub\u003e (\u003cem\u003ev\u003c/em\u003e/\u003cem\u003ev\u003c/em\u003e\u0026thinsp;=\u0026thinsp;6/1) led to the same results in terms of the number and chemical shifts of the peaks in the \u003csup\u003e1\u003c/sup\u003eH NMR spectra, which suggested that the concentration of \u003cb\u003e8\u003c/b\u003e in the methanol/nitromethane mixture (\u003cem\u003ev\u003c/em\u003e/\u003cem\u003ev\u003c/em\u003e\u0026thinsp;=\u0026thinsp;6/1) had no effect on the \u003cb\u003eBL\u003c/b\u003e topology (Figure S23).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eAs seen by comparing the \u003csup\u003e1\u003c/sup\u003eH NMR spectra of ligand \u003cb\u003e6\u003c/b\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eA) and building unit \u003cb\u003e7\u003c/b\u003e (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eB), the majority of the peaks in the \u003csup\u003e1\u003c/sup\u003eH NMR spectrum of \u003cb\u003e8\u003c/b\u003e show slight changes in the chemical shift, but there is no significant splitting of the peaks (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eC). Using the evidence provided by the \u003csup\u003e1\u003c/sup\u003eH-\u003csup\u003e1\u003c/sup\u003eH COSY and \u003csup\u003e1\u003c/sup\u003eH DOSY NMR spectra (Figures S24 and S25), the peaks in the \u003csup\u003e1\u003c/sup\u003eH NMR spectrum of \u003cb\u003e8\u003c/b\u003e were assigned to the \u003cb\u003eBL\u003c/b\u003e structure (Figure S26). As a result of the shielding effect of the NDI planes, the chemical shifts H\u003csub\u003ea\u003c/sub\u003e, H\u003csub\u003eb\u003c/sub\u003e, H\u003csub\u003ec\u003c/sub\u003e, H\u003csub\u003ed\u003c/sub\u003e and H\u003csub\u003ee\u003c/sub\u003e for the pyridyl, alkenyl, and phenyl groups in \u003cb\u003e6\u003c/b\u003e are shifted to higher fields, whereas the chemical shifts H\u003csub\u003ef\u003c/sub\u003e and H\u003csub\u003eg\u003c/sub\u003e for the dibenzo-18-crown-6-based group remain almost unchanged without any shielding effect. The chemical shifts H\u003csub\u003e1\u003c/sub\u003e and H\u003csub\u003e2\u003c/sub\u003e for the NDI-based group and Cp* remain almost unchanged, but their peaks split into two sets of signals (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eC). Moreover, the\u003csup\u003e1\u003c/sup\u003eH{\u003csup\u003e13\u003c/sup\u003eC} NMR spectrum of \u003cb\u003e8\u003c/b\u003e in methanol-\u003cem\u003ed\u003c/em\u003e\u003csub\u003e4\u003c/sub\u003e/nitromethane-\u003cem\u003ed\u003c/em\u003e\u003csub\u003e3\u003c/sub\u003e was also obtained to characterize the \u003cb\u003eBL\u003c/b\u003e structure (Figure S27).\u003c/p\u003e \u003cp\u003eAs mentioned in the crystallographic analysis results, the cationic portion of \u003cb\u003e8\u003c/b\u003e can be approximated as a sphere with a radius of 16.6 \u0026Aring;. With the obtained diffusion coefficient \u003cem\u003eD\u003c/em\u003e (2.43 \u0026times; 10\u003csup\u003e\u0026minus;\u0026thinsp;10\u003c/sup\u003e m\u003csup\u003e2\u003c/sup\u003e s\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e, Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eD and S43), the radial dimension of \u003cb\u003e8\u003c/b\u003e in solution for the spheroid can be calculated as 16.5 \u0026Aring; by directly using the Stokes\u0026ndash;Einstein Eq.\u0026nbsp;3\u003csup\u003e0\u003c/sup\u003e, which is similar to that in the solid state, thus providing further evidence of the \u003cb\u003eBL\u003c/b\u003e structure in solution (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e7\u003c/span\u003eE).\u003c/p\u003e \u003cp\u003eAdditionally, the ESI-TOF/MS spectra confirm the existence of \u003cb\u003e8\u003c/b\u003e based on the peaks at \u003cem\u003em/z\u003c/em\u003e 2936.9528 and 2165.4436, which are consistent with the calculated isotopic distributions of [\u003cb\u003e8\u0026ndash;6\u003c/b\u003eOTf]\u003csup\u003e6+\u003c/sup\u003e and [\u003cb\u003e8\u0026ndash;8\u003c/b\u003eOTf]\u003csup\u003e8+\u003c/sup\u003e with peaks at \u003cem\u003em/z\u003c/em\u003e 2936.8992 and 2165.4377, respectively (Figures S28\u0026ndash;S30).\u003c/p\u003e \u003cp\u003eTo investigate the effect of the central ion in the metal corner on this cage-based \u003cb\u003eBL\u003c/b\u003e structure, Ir\u003csup\u003eIII\u003c/sup\u003e was chosen to replace Rh\u003csup\u003eIII\u003c/sup\u003e in the coordination-driven self-assembly process. As shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e5\u003c/span\u003eF, the conditions were kept the same as those used for the synthesis of \u003cb\u003e8\u003c/b\u003e except that the bimetallic building block was changed from \u003cb\u003e7\u003c/b\u003e to \u003cb\u003e9\u003c/b\u003e, and compound \u003cb\u003e10\u003c/b\u003e was finally obtained in a yield of 92%. Despite many attempts, the quality of the single-crystal sample of \u003cb\u003e10\u003c/b\u003e still did not satisfy the crystallographic requirements for structural determination, but based on the currently resolved structure, it appears to have a \u003cb\u003eBL\u003c/b\u003e topology similar to that of \u003cb\u003e8\u003c/b\u003e (Figure S31). In terms of the NMR characterization of \u003cb\u003e10\u003c/b\u003e, the relevant spectra of \u003cb\u003e10\u003c/b\u003e provided evidence for the existence of a \u003cb\u003eBL\u003c/b\u003e structure in solution, and in particular, the \u003csup\u003e1\u003c/sup\u003eH and \u003csup\u003e1\u003c/sup\u003eH{\u003csup\u003e13\u003c/sup\u003eC} NMR spectra of \u003cb\u003e10\u003c/b\u003e were similar to the relevant spectra of \u003cb\u003e8\u003c/b\u003e (Figures S32\u0026ndash;S38). And the size simulation based on \u003csup\u003e1\u003c/sup\u003eH DOSY NMR also confirmed its dimension in solution (Figure S44). In addition, the ESI-TOF/MS spectrum provided clear evidence confirming the presence of the \u003cb\u003eBL\u003c/b\u003e structure (Figures S39\u0026ndash;S41).\u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eIn summary, based on the construction of the molecular ring-based Borromean metalla-link \u003cb\u003e4\u003c/b\u003e, we propose a strategy for the rational design and controlled synthesis of cage-based Borromean links. Following this strategy, dibenzo-18-crown-6-based tetrapyridyl ligand \u003cb\u003e6\u003c/b\u003e and two binuclear building units \u003cb\u003e7\u003c/b\u003e and \u003cb\u003e9\u003c/b\u003e were tactically selected to fabricate two molecular Borromean links comprising three identical decanuclear metallocages in nearly quantitative yield.\u003c/p\u003e \u003cp\u003eTogether with IGM analysis, SCXRD analysis revealed that noncovalent interactions between components (e.g., π\u0026middot;\u0026middot;\u0026middot;π stacking interactions and weak C-H\u0026middot;\u0026middot;\u0026middot;O interactions) play a significant role in maintaining the cage-based Borromean links. Evidence from detailed NMR, ESI-TOF/MS and elemental analysis further confirmed the existence of the Borromean links. The strategy employed in this work enables the construction of a new generation of molecular Borromean links, which we hope will serve as a useful reference for fabricating more sophisticated topologies in the future.\u003c/p\u003e"},{"header":"Method","content":"\u003cp\u003e\u003cstrong\u003eSynthesis:\u003c/strong\u003e The ligands \u003cstrong\u003e2\u003c/strong\u003e and \u003cstrong\u003e6\u003c/strong\u003e were synthesized using conditions of Heck coupling reaction and the specific method and characterization of \u003cstrong\u003e2\u003c/strong\u003e and \u003cstrong\u003e6\u003c/strong\u003e are provided in Supplementary Information. The Borromean metalla-links \u003cstrong\u003e4\u003c/strong\u003e, \u003cstrong\u003e8\u003c/strong\u003e and \u003cstrong\u003e10\u003c/strong\u003e were synthesized using ligands \u003cstrong\u003e2\u003c/strong\u003e and \u003cstrong\u003e6\u003c/strong\u003e and binuclear building units \u003cstrong\u003e3\u003c/strong\u003e, \u003cstrong\u003e7\u003c/strong\u003e and \u003cstrong\u003e9\u003c/strong\u003e, respectively, and the detailed method and characterization of \u003cstrong\u003e4\u003c/strong\u003e, \u003cstrong\u003e8\u003c/strong\u003e and \u003cstrong\u003e10\u003c/strong\u003e are provided in Supplementary Information.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eX-ray Crystallography:\u003c/strong\u003e Single crystals of \u003cstrong\u003e4\u003c/strong\u003e and \u003cstrong\u003e8\u003c/strong\u003e suitable for X-ray diffraction were obtained at room temperature. X-ray intensity data were collected at 170 K on a Bruker D8 VENTURE system and used Ga\u003cem\u003eK\u003c/em\u003e\u0026alpha; radiation (\u003cem\u003e\u0026lambda;\u003c/em\u003e = 1.34139 \u0026Aring;). Using Olex2\u003csup\u003e33\u003c/sup\u003e, the structures of \u003cstrong\u003e4\u003c/strong\u003e and \u003cstrong\u003e8\u003c/strong\u003e were solved with the SHELXS-1997\u003csup\u003e34,35\u003c/sup\u003e structure solution program using direct methods and refined with the SHELXL\u003csup\u003e36\u003c/sup\u003e refinement package using least-squares minimization. With these data, the disordered solvent molecules that could not be restrained properly were removed using the SQUEEZE method. The details of the crystal data collection and refinement are summarized in \u003cstrong\u003eTable S1\u003c/strong\u003e and \u003cstrong\u003eS2\u003c/strong\u003e.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eComputational details:\u003c/strong\u003e Independent gradient model (IGM) analysis of promolecular density was performed for \u003cstrong\u003e4\u003c/strong\u003e and \u003cstrong\u003e8\u003c/strong\u003e. The calculation models were established by extracting molecules from the crystal structures. The cubic files (.cub) for IGM analysis\u003csup\u003e27-28\u003c/sup\u003e were generated by the wavefunction software Multiwfn 3.8\u003csup\u003e26\u003c/sup\u003e, and the IGM inter surfaces were visualized and analysed using the Visual Molecular Dynamics program (VMD 1.93)\u003csup\u003e29\u003c/sup\u003e.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCrystallographic data for the structures reported in this work are available from the Cambridge Crystallographic Data Centre with the following codes: \u003cstrong\u003e4\u003c/strong\u003e (CCDC 2363098) and \u003cstrong\u003e8\u003c/strong\u003e (CCDC 2363099). CIFs are available free of charge at http://www.ccdc.cam.ac.uk/data_request/cif. Other data that support the findings of this study are available in the Supplementary Information.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the National Science Foundation of China (22031003, 21720102004 and 22301040), the Shanghai Science Technology Committee (19DZ2270100), the China National Postdoctoral Program for Innovative Talents (BX20220092) and the Shanghai\u0026nbsp;Postdoctoral\u0026nbsp;Excellence Program (2022736). G.-X.J thanks the Alexander von Humboldt Foundation for a Humbold Research Award.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eH.-N.Z. and G.-X.J. designed the experimental protocol. H.-N.Z. performed the synthesis and characterization studies, solved the crystal structure and wrote the manuscript. G.-X.J. directed the research. H.-N.Z. and G.-X.J. analysed the experimental results.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAuthors declare that they have no competing interests.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eLiang, C. \u0026amp; Mislow, K. On Borromean links. \u003cem\u003eJ. Math. Chem.\u003c/em\u003e \u003cstrong\u003e16\u003c/strong\u003e, 27-35 (1994).\u003c/li\u003e\n \u003cli\u003eCantrill, S. J., Chichak, K. S., Peters, A. J. \u0026amp; Stoddart, J. F. Nanoscale Borromean Rings. \u003cem\u003eAcc. Chem. Res.\u003c/em\u003e \u003cstrong\u003e38\u003c/strong\u003e, 1-9 (2005).\u003c/li\u003e\n \u003cli\u003eBeves, J. E., Blight, B. A., Campbell, C. J., Leigh, D. A. \u0026amp; McBurney, R. T. Strategies and Tactics for the Metal-Directed Synthesis of Rotaxanes, Knots, Catenanes, and Higher Order Links. \u003cem\u003eAngew. Chem. Int. 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A\u003c/em\u003e \u003cstrong\u003e71\u003c/strong\u003e, 3-8 (2015).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"nature-portfolio","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"","title":"Nature Portfolio","twitterHandle":"","acdcEnabled":false,"dfaEnabled":false,"editorialSystem":"ejp","reportingPortfolio":"","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"","lastPublishedDoi":"10.21203/rs.3.rs-4824942/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4824942/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe Borromean link, which is characterized by structural integrity and aesthetic beauty, represents one of the most intriguing entanglements. However, the vast majority of Borromean links consist of three identical macrocycles, and there are very few examples of links constructed from dimeric cages. Here, facilitated by multiple aromatic stacking interactions between components, we demonstrate that two molecular cage-based Borromean links containing more than 1100 nonhydrogen atoms, especially 24 rhodium(III)/iridium(III) and six sodium(I) ions, can be constructed in high yield through the strategic selection of a tetrapyridyl ligand based on dibenzo-18-crown-6 and two binuclear building units, as demonstrated by X-ray crystallographic analysis, detailed nuclear magnetic resonance (NMR), electrospray ionization-time-of-flight/mass spectrometry (ESI-TOF/MS), and elemental analysis.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e","manuscriptTitle":"Molecular Borromean links based on metallocages","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-08-07 11:08:35","doi":"10.21203/rs.3.rs-4824942/v1","editorialEvents":[],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"nature-synthesis","isNatureJournal":true,"hasQc":false,"allowDirectSubmit":false,"externalIdentity":"natsynth","sideBox":"Learn more about [Nature Synthesis](https://www.nature.com/natsynth/)","snPcode":"","submissionUrl":"https://mts-natsynth.nature.com/cgi-bin/main.plex","title":"Nature Synthesis","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"ejp","reportingPortfolio":"Nature Research","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"ec68a285-0392-452c-8ccb-cc935cbc06d3","owner":[],"postedDate":"August 7th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[{"id":35609282,"name":"Physical sciences/Chemistry/Coordination chemistry/Organometallic chemistry/Ligands"},{"id":35609283,"name":"Physical sciences/Chemistry/Supramolecular chemistry/Self-assembly"}],"tags":[],"updatedAt":"2025-01-15T08:07:26+00:00","versionOfRecord":{"articleIdentity":"rs-4824942","link":"https://doi.org/10.1038/s44160-024-00720-4","journal":{"identity":"nature-synthesis","isVorOnly":false,"title":"Nature Synthesis"},"publishedOn":"2025-01-14 05:00:00","publishedOnDateReadable":"January 14th, 2025"},"versionCreatedAt":"2024-08-07 11:08:35","video":"","vorDoi":"10.1038/s44160-024-00720-4","vorDoiUrl":"https://doi.org/10.1038/s44160-024-00720-4","workflowStages":[]},"version":"v1","identity":"rs-4824942","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4824942","identity":"rs-4824942","version":["v1"]},"buildId":"FbvkV6FR0MCFSLy54lSbu","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}