English

• Over the past few decades, N-heterocyclic carbenes (NHCs) have allowed the rapid preparation of variety supramolecular assemblies, including molecular squares and tweezers, molecular cages, cylinder-like structures and organometallic polymers, by featuring only metal–carbon bonds [1-7]. In recent years, researchers have made considerable progress in the development of construction strategies and exploration of the properties of NHC-based cylinders and pillarplexes, e.g., the properties of these structures in terms of host–guest chemistry and catalysis [8-15]. Notably, most of the above-mentioned studies have focused on exploring the individual molecules of NHC-based pillarplexes, whereas studies on pillarplex-based superstructures are rare [2,4,5,16]. We shifted the focus of our study from individual structures to superstructures and explored the effect of building blocks on the properties of superstructures to examine the correlation between superstructures and properties. Given the important role of fluorine atoms in crystal engineering and material modification [17-21], we aimed to introduce fluorine atoms into the design of NHC-based pillarplexes and investigate their effect on the properties of these structures.

  Hierarchical self-assembly, a process wherein multiple components are brought together in a stepwise manner driven by variety noncovalent interactions, including hydrogen bonds, anion–π interactions, and electrostatic contacts, is gaining attention as a crucial factor in the formation of structurally sophisticated and functionally diverse biological structures [22,23]. Chemists have exploited such intricate pathways to obtain multifunctional artificial supramolecular assemblies and materials [24-44]. Recently, researchers have discovered that discrete supramolecular macrocycles or cages can be used as basic units together with anions to construct superstructures with aesthetic beauty and novel functions, wherein the introduction of anions affects intermolecular noncovalent interactions and regulates hierarchical structures and functions [45-53]. Inspired by this phenomenon, we envisioned the possibility of using NHC-based pillarplexes as basic units and adjusting anion type to obtain different superstructures and their properties.

  Our synthesis route for constructing higher-order assemblies (supramolecular gel and supramolecular channel) is illustrated in Fig. 1. The fluorinated pillarplex demonstrates dense packing through multiple noncovalent interactions and self-organizes to form a gel at high concentrations (A). Furthermore, the combination of fluorinated pillarplex cations and monocarboxylic anion components yields supramolecular column (B) and supramolecular channel (C) through anion-induced self-assembly.

  Figure 1

  

  Figure 1.  Schematic representation of fluorinated pillarplex to generate supramolecular gel and supramolecular channel by hierarchical self-assembly in this work.

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  The tetraimidazolium salts H₄-L(PF₆)₄ and H₄-L_H(PF₆)₄ were prepared using an alkylation procedure that started from bisimidazole 1, tetrabutylammonium bromide and the corresponding bridging linker in a molar ratio of 1:1:1 (Scheme S1 in Supporting information) [54,55]. The formation of the tetraimidazolium salts was confirmed through nuclear magnetic resonance (NMR) spectroscopy, electrospray ionization mass spectrometry (ESI-MS) and X-ray crystallographic analysis (Figs. S1-S9 in Supporting information). The X-ray structure of H₄-L(PF₆)₄ confirms its twisted macrocyclic structure, which is formed mainly by four imidazolium groups, two diphenyl ether units, and two tetrafluorobenzene rings.

  Treating ligands H₄-L(PF₆)₄ and H₄-L_H(PF₆)₄ with a slight excess of Ag₂O in acetonitrile at 65 ℃ yielded two poly-NHC-based pillarplexes [Ag₄L₂](PF₆)₄ and [Ag₄(L_H)₂](PF₆)₄, respectively (Scheme 1). For fluorinated pillarplex [Ag₄L₂](PF₆)₄, the ¹H NMR spectrum shows the complete deprotonation of the tetraimidazolium salt and the formation of a silver carbene complex (Figs. 2a and b). Full peak assignments were conducted on ¹³C{¹H}, ¹⁹F, and two-dimensional (2D) NMR spectra (Figs. S10-S14 in Supporting information). The diffusion-ordered spectroscopy (DOSY) NMR spectrum also reveals the formation of a single product with a single diffusion coefficient (D = 1.35 × 10^–10 m²/s, logD = ‒9.87, c = 3.5 mmol/L) for the signals of [Ag₄L₂](PF₆)₄ (Fig. 2c). The ESI-MS spectrum further supports the formation of the pillarplex [Ag₄L₂](PF₆)₄, showing peaks at m/z 827.0251 (calcd. for {[Ag₄L₂](PF₆)}³⁺ 827.0289) and 1313.0232 (calcd. for {[Ag₄L₂](PF₆)₂}²⁺ 1313.0257) (Fig. 2d).

  Scheme 1

  

  Scheme 1.  Synthesis of the poly-NHC-based pillarplexes [Ag₄L₂](PF₆)₄ and [Ag₄(L_H)₂](PF₆)₄.

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  Figure 2

  

  Figure 2.  Partial ¹H NMR spectra (400 MHz, 298 K, CD₃CN) of (a) H₄-L(PF₆)₄, (b) [Ag₄L₂](PF₆)₄ and (c) ¹H DOSY spectrum of [Ag₄L₂](PF₆)₄ in CD₃CN. (d) ESI-MS spectra of [Ag₄L₂](PF₆)₄ with isotope distribution for selected peaks (experimental in blue, calculated in red).

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  The slow diffusion of diethyl ether into an acetonitrile solution of [Ag₄L₂](PF₆)₄ provided X-ray-quality crystals suitable for diffraction analysis. The cationic portion of the pillarplex reveals an irregular cylinder-like configuration (Fig. 3a). Two tetra-NHC ligands coordinated to silver atoms are rotated relative to each other by 180°, forming a head-to-tail arrangement. Fluorine-substituted benzene units are located in a suitable position and toward the inner cavity. In this structure, two isomers of [Ag₄L₂]⁴⁺ assemble into a supramolecular dimer within a unit cell, wherein one molecule adopts the opposite orientation relative to another (secondary structure, Fig. 3b). In addition, these dimers undergo staggered helical packing through C—H···O and C—H···π interactions (tertiary structure, Fig. 3c). Furthermore, the staggered helical packing self-organizes into a 3D quaternary supramolecular structure via multiple noncovalent interactions and forms a staggered structure (quaternary structure, Figs. 3d and 4a, Figs. S15-S17 in Supporting information). In addition, the crystal packing of [Ag₄L₂](PF₆)₄ was visually revealed through Hirshfeld surfaces analysis, which revealed multiple noncovalent interactions among [Ag₄L₂]⁴⁺ cations, PF₆^-, and neighbouring cation molecules (Fig. S18 in Supporting information) [56,57]. The irregular configuration and dense packing of [Ag₄L₂](PF₆)₄ during crystallization are easily understood on the basis of experimental and theoretical evidence.

  Figure 3

  

  Figure 3.  (a) Stick mode of primary structure [Ag₄L₂]⁴⁺. (b) Supramolecular dimer (secondary structure) self-assembled by [Ag₄L₂]⁴⁺ and interacted through C—H···O interactions. (c) Staggered helical packing (tertiary structure) formed by supramolecular dimers. (d) Quaternary structure formed by supramolecular helical packing, viewed along crystallographic a-axis. Color code: Ag, pink; N, blue; C, gray; F, green; O, red; H, white. Counterion and solvent molecules are omitted for clarity.

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  Figure 4

  

  Figure 4.  (a) Packing diagram and the C—H···F interactions in the [Ag₄L₂](PF₆)₄. (b) Photographs of inverted tube test of [Ag₄L₂](PF₆)₄ in CH₃CN (34 mmol/L, T = 298 K). Color code: Ag, pink; N, blue; C, gray; F, green; O, red; H, white. Partial counterions and solvent molecules are omitted for clarity.

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  When fluorine atoms were replaced with hydrogen atoms, the silver carbene complex [Ag₄(L_H)₂](PF₆)₄ was observed (Figs. S19-S28 in Supporting information). The solid-state structure of [Ag₄(L_H)₂](PF₆)₄ was determined by single-crystal X-ray crystallography. Four silver(Ⅰ) ions are sandwiched between the two tetra-NHC ligands and situated in an essentially planar rectangle and form a regular polygon configuration (Fig. S26). The cylinder [Ag₄(L_H)₂](PF₆)₄, perfectly superimposed and interleaved with two PF₆^- anions, is packed into supramolecular columns via multiple C—H···F interactions (Fig. S27). These supramolecular columns can self-organize into the 3D supramolecular structure and interact by π-π stacking and C—H···F interactions (Fig. S28). Along with these interactions between the cylinder cations and the PF₆^- anions, it favors the ordered alignment of all [Ag₄(L_H)₂](PF₆)₄ complexes and maintains its highly symmetric configuration during crystal conformation.

  In biological systems, identical polypeptides can fold through hierarchical self-assembly and perform different functions and activities [58]. The evaporation of a certain amount of acetonitrile from [Ag₄L₂](PF₆)₄ resulted in the formation of the corresponding gel G^F (Fig. 4b). Upon heating, the semisolid gel charged into a fluid sol owing to the weakening of noncovalent interactions at elevated temperatures (Fig. S29 in Supporting information). The gel was recovered after cooling, and the gelation ability of [Ag₄L₂](PF₆)₄ in various solvents was also determined. Samples were prepared by dissolving the silver carbene complex in different solvents (N,N-dimethylformamide or dimethyl sulfoxide), and the corresponding gels were observed at higher concentrations (Figs. S30 and S31 in Supporting information). However, the gelation of H₄-L(PF₆)₄, H₄-L_H(PF₆)₄ and [Ag₄(L_H)₂](PF₆)₄ was not detected under similar processes. This finding confirms that both the presence of fluorine atoms and the high hierarchical structure are essential for the formation of the gel (Figs. S32-S34 in Supporting information).

  Concentration-dependent ¹H and DOSY NMR spectra were used to evaluate the dimensions of the supramolecular aggregates and thus substantiate the formation of the gel G^F (Figs. S35-S38 in Supporting information) [59-61]. As the concentrations of [Ag₄L₂](PF₆)₄ increased from 3.0 mmol/L to 15.0 mmol/L, the measured weight-average diffusion coefficient D decreased from 1.69 × 10^–10 m²/s to 1.38 × 10^–11 m²/s (D_{3.0 mmol/L}/D_{15.0 mmol/L} ≈ 12.2), indicating the formation of a polymeric network (Fig. S39 in Supporting information). Furthermore, the supramolecular gel in acetonitrile was characterized through rheological experiments at 298 K (Fig. S40 in Supporting information). A strain sweep of G^F reveals a linear response (the storage modulus G′ > the loss modulus G′′) before the critical strain zone (γ = 5%). The frequency sweep test of the gel showed that G′ is considerably higher than the corresponding G′′ within the frequency range of 0.1–100 Hz. However, gel formation by similar NHC-based structures has not been reported [2,16]. The scanning electron microscopy of G^F exhibited an extended and interconnected 3D network, which further verified the formation of the supramolecular gel (Fig. S41 in Supporting information).

  With the development of supramolecular chemistry, anion-induced self-assembly has gradually evolved into a highly efficient tool for the construction of complex molecular architectures, such as pseudorataxanes, polymers, hexameric capsules and supramolecular cages [45-53]. As shown in Fig. 5a, a one-pot reaction of [Ag₄L₂](PF₆)₄ with 4.2 equiv. of 1,4-cyclohexane dicarboxylic acid and 4.0 equiv. of triethylamine in acetonitrile led to the formation of an insoluble precipitate [Ag₄L₂](Hchdc)₄. The energy-dispersive X-ray spectroscopy revealed that the product was composed of elements C, N, O, F, and Ag, but did not include element P (Fig. S42 in Supporting information).

  Figure 5

  

  Figure 5.  (a) Preparation of the supramolecular channel between [Ag₄L₂]⁴⁺ and monocarboxylic anions through an anion-induced approach. (b) Self-assembly of the supramolecular column by [Ag₄L₂]⁴⁺ and monocarboxylic anions through C—H···O interactions. (c) The interactions between the monocarboxylic anions and silver ions in the crystalline phase. (d) Supramolecular channel structure formed by supramolecular column, viewed along crystallographic c-axis. Color code: Ag, pink; N, blue; C, gray; F, green; O, red; H, white. Hydrogen atoms or solvent molecules are omitted for clarity.

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  Single crystals of [Ag₄L₂](Hchdc)₄ suitable for X-ray crystallography were obtained by slow diffusion of diethyl ether into a solution of the corresponding complex in N,N-dimethylformamide over the course of a month at room temperature. The structure shows a supramolecular channel comprising [Ag₄L₂]⁴⁺ and monocarboxylic anions, forming regular channels in a 3D arrangement (Figs. 5b–d). Specifically, [Ag₄L₂]⁴⁺ and monocarboxylic anions form a molecular sandwich and align to form a well-structured supramolecular column via C—H···O interactions in an interleaved manner (Fig. 5b). This supramolecular column exhibits a rare example of tetrameric anions, wherein Ag(Ⅰ) ions lock the neighboring monocarboxylate anions and contribute to the C—H···O interactions, thereby minimizing unfavorable electrostatic repulsions (Fig. 5c) [47]. Subsequently, these columns, which serve as secondary building blocks, self-assemble into a highly regular superstructure with intercolumnar channels (Fig. 5d). The supramolecular structure formed by the tetrameric anions investigated in this study was more organized than those of the dimetric species observed in previous studies on pseudorotaxane [45].

  Notable, the twist-boat conformation of the 1,4-cyclohexane dicarboxylic acid adopted an outside binding mode (Fig. S43 in Supporting information). Switching of the stable chair conformation into a twist-boat geometry with a higher energy without any chemical processes has seldom been achieved [62]. However, a high disorder of unassignable solvent densities was observed inside the cavity. Consequently, we could not explicitly specify them solvent densities.

  The crystal layers stack together through noncovalent interactions, building a 1D porous supramolecular channel structure (Figs. S44 and S45 in Supporting information). Compared with [Ag₄L₂](PF₆)₄, the orientation and dimensions of [Ag₄L₂](Hchdc)₄ in the supramolecular channel present a more spacious configuration. In addition, the cavity dimension of [Ag₄L₂](Hchdc)₄ (509 ų) is larger than that [Ag₄L₂](PF₆)₄ (355 ų) (Figs. S46 and S47 in Supporting information).

  In summary, we have demonstrated that fluorine-functionalized pillarplex can be used to create a complicated hierarchical manner for superstructure. By controlling the functional component of the discrete structures during the self-assembly process, we successfully designed and synthesized two poly-NHC-based pillarplexes from macrocyclic ligands. The pillarplex [Ag₄L₂](PF₆)₄ exhibits an adjustable four-level hierarchical superstructure. In this hierarchical self-assembly process, the fluorinated pillarplex [Ag₄L₂](PF₆)₄ can self-assemble into a gel at higher concentrations, whereas other complexes lack this property. Different hierarchical superstructures can be customized by using an anion-induced strategy to form well-organized supramolecular channels, offering precise control over crystal packing and inner cavity dimensions. This approach provides insight into the construction of superstructures based on hierarchical self-assembly and opens new avenues for exploring functionalized metallosupramolecules. Further investigation into using these hierarchical assemblies in host–guest chemistry, proton conductivity, solid electrolyte, and catalysis is an ongoing endeavor within our laboratories.

  Declaration of competing interest

  The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

  CRediT authorship contribution statement

  Ming-Ming Gan: Writing – review & editing, Writing – original draft, Data curation. Zi-En Zhang: Writing – review & editing, Data curation. Xin Li: Writing – review & editing, Data curation. F. Ekkehardt Hahn: Writing – review & editing. Ying-Feng Han: Writing – review & editing, Writing – original draft, Conceptualization.

  Acknowledgments

  The authors gratefully acknowledge financial support from the National Natural Science Fund for Distinguished Young Scholars of China (No. 22025107), Shaanxi Fundamental Science Research Project for Chemistry & Biology (No. 22JHZ003), the Key International Scientific and Technological Cooperation and Exchange Project of Shaanxi Province (No. 2023-GHZD-15), the National Youth Top-notch Talent Support Program of China, and the FM&EM International Joint Laboratory of Northwest University.

  Supplementary materials

  Supplementary material associated with this article can be found, in the online version, at doi:10.1016/j.cclet.2024.110624.

  
  
• 1. [1]

     N. Sinha, F.E. Hahn, Acc. Chem. Res. 50 (2017) 2167–2184. doi: 10.1021/acs.accounts.7b00158

  2. [2]

     M.M. Gan, J.Q. Liu, L. Zhang, et al., Chem. Rev. 118 (2018) 9587–9641. doi: 10.1021/acs.chemrev.8b00119

  3. [3]

     S. Ibáñez, M. Poyatos, E. Peris, Acc. Chem. Res. 53 (2020) 1401–1413. doi: 10.1021/acs.accounts.0c00312

  4. [4]

     Y. Li, J.G. Yu, L.L. Ma, et al., Sci. China Chem. 64 (2021) 701–718. doi: 10.1007/s11426-020-9937-4

  5. [5]

     R. Banerjee, D. Chakraborty, P.S. Mukherjee, J. Am. Chem. Soc. 145 (2023) 7692–7711. doi: 10.1021/jacs.3c01084

  6. [6]

     Q. Chai, L. Duan, Y. Ma, T. Hou, T. Tu, Sci. China Chem. 67 (2024) 1510–1523. doi: 10.1007/s11426-023-1919-2

  7. [7]

     S. Ibáñez, P. Salvà, L.N. Dawe, E. Peris, Angew. Chem. Int. Ed. 63 (2024) e202318829. doi: 10.1002/anie.202318829

  8. [8]

     D. Wang, B. Zhang, C. He, P. Wu, C. Duan, Chem. Commun. 46 (2010) 4728–4730. doi: 10.1039/c000793e

  9. [9]

     P.J. Altmann, A. Pöthig, J. Am. Chem. Soc. 138 (2016) 13171–13174. doi: 10.1021/jacs.6b08571

  10. [10]

      P.J. Altmann, D.T. Weiss, C. Jandl, F. Kühn, Chem. Asian J. 11 (2016) 1597–1605. doi: 10.1002/asia.201600198

  11. [11]

      P.J. Altmann, A. Pöthig, Angew. Chem. Int. Ed. 56 (2017) 15733–15736. doi: 10.1002/anie.201709921

  12. [12]

      K. Hua, X. Li, Y.F. Han, J. Organomet. Chem. 917 (2020) 121250. doi: 10.1016/j.jorganchem.2020.121250

  13. [13]

      T. Liu, S. Bai, L. Zhang, F.E. Hahn, Y.F. Han, Natl. Sci. Rev. 9 (2022) nwac067. doi: 10.1093/nsr/nwac067

  14. [14]

      S. Rupp, P.D. Dutschke, J. Kinas, A. Hepp, F.E. Hahn, Eur. J. Inorg. Chem. 2022 (2022) e202200216.

  15. [15]

      A.A. Heidecker, M. Stasi, A. Spears, J. Boekhoven, A. Pöthig, ChemPlusChem 88 (2023) e202300234. doi: 10.1002/cplu.202300234

  16. [16]

      Y. Wang, J.P. Chang, R. Xu, et al., Chem. Soc. Rev. 50 (2021) 13559–13586. doi: 10.1039/d1cs00296a

  17. [17]

      K. Reichenbächer, H.I. Süss, J. Hulliger, Chem. Soc. Rev. 34 (2005) 22–30. doi: 10.1039/B406892K

  18. [18]

      R. Berger, G. Resnati, P. Metrangolo, E. Weber, J. Hulliger, Chem. Soc. Rev. 40 (2011) 3496–3508. doi: 10.1039/c0cs00221f

  19. [19]

      A.E. Amooghin, H. Sanaeepur, R. Luque, H. Garcia, B. Chen, Chem. Soc. Rev. 51 (2022) 7427–7508. doi: 10.1039/D2CS00442A

  20. [20]

      S. Niu, L.L. Mao, H. Xiao, et al., Chin. Chem. Lett. 33 (2022) 1970–1974. doi: 10.1016/j.cclet.2021.09.090

  21. [21]

      K. Sato, Langmuir 40 (2024) 2809–2814. doi: 10.1021/acs.langmuir.3c03665

  22. [22]

      D.C. Masison, R.B. Wickner, Science 270 (1995) 93–95. doi: 10.1126/science.270.5233.93

  23. [23]

      I.B. Hilton, A.M. D'Ippolito, C.M. Vockley, et al., Nat. Biotechnol. 33 (2015) 510–517. doi: 10.1038/nbt.3199

  24. [24]

      C. Rest, R. Kandanelli, G. Fernández, Chem. Soc. Rev. 44 (2015) 2543–2572. doi: 10.1039/C4CS00497C

  25. [25]

      D.B. Amabilino, D.K. Smith, J.W. Steed, Chem. Soc. Rev. 46 (2017) 2404–2420. doi: 10.1039/C7CS00163K

  26. [26]

      S. Datta, M.L. Saha, P.J. Stang, Acc. Chem. Res. 51 (2018) 2047–2063. doi: 10.1021/acs.accounts.8b00233

  27. [27]

      M.B. Avinash, T. Govindaraju, Acc. Chem. Res. 51 (2018) 414–426. doi: 10.1021/acs.accounts.7b00434

  28. [28]

      S. Chakraborty, G. Newkome, Chem. Soc. Rev. 47 (2018) 3991–4016. doi: 10.1039/c8cs00030a

  29. [29]

      J.M. Cameron, G. Guillemot, T. Galambos, et al., Chem. Soc. Rev. 51 (2022) 293–328. doi: 10.1039/d1cs00832c

  30. [30]

      W. Fang, Y. Zhang, J. Wu, et al., Chem. Asian J. 13 (2018) 712–729. doi: 10.1002/asia.201800017

  31. [31]

      B. Jiang, L.J. Chen, Y. Zhang, et al., Chin. Chem. Lett. 27 (2016) 607–612. doi: 10.1016/j.cclet.2016.03.017

  32. [32]

      Z. Sun, P. Li, S. Xu, et al., J. Am. Chem. Soc. 142 (2020) 10833–10840. doi: 10.1021/jacs.0c03330

  33. [33]

      S.C. Wang, K.Y. Cheng, J.H. Fu, Y.C. Cheng, Y.T. Chan, J. Am. Chem. Soc. 142 (2020) 16661–16667. doi: 10.1021/jacs.0c06618

  34. [34]

      L. He, S.C. Wang, L.T. Lin, et al., J. Am. Chem. Soc. 142 (2020) 7134–7144. doi: 10.1021/jacs.0c01482

  35. [35]

      H. Wang, K. Wang, Y. Xu, et al., J. Am. Chem. Soc. 143 (2021) 5826–5835. doi: 10.1021/jacs.1c00625

  36. [36]

      Z. Yang, N. Zhang, L. Lei, et al., JACS Au 2 (2022) 819–826. doi: 10.1021/jacsau.1c00556

  37. [37]

      G. Wu, F. Li, B. Tang, X. Zhang, J. Am. Chem. Soc. 144 (2022) 14962–14975. doi: 10.1021/jacs.2c02434

  38. [38]

      Y. He, D. Luo, V.M. Lynch, et al., Chem 9 (2023) 93–101. doi: 10.1117/12.3009523

  39. [39]

      Q.S. Mu, X. Gao, Z. Cui, Y.J. Lin, G.X. Jin, Sci. China Chem. 66 (2023) 2885–2891. doi: 10.1007/s11426-023-1675-0

  40. [40]

      Z. Zhang, X. Hu, S. Qiu, et al., J. Am. Chem. Soc. 146 (2024) 11328–11341. doi: 10.1021/acs.jpclett.4c02383

  41. [41]

      Z. Zhang, B. Mu, X. Miao, et al., Chem 10 (2024) 1279–1294. doi: 10.1016/j.chempr.2024.01.026

  42. [42]

      X. Zhang, D. Zhang, C. Wei, et al., Nat. Commun. 15 (2024) 3766. doi: 10.1038/s41467-024-48135-1

  43. [43]

      M. Li, H. Zhu, S. Adorinni, et al., Angew. Chem. Int. Ed. 63 (2024) e202406909. doi: 10.1002/anie.202406909

  44. [44]

      H.N. Zhang, G.X. Jin, Angew. Chem. Int. Ed. 62 (2024) e202313605.

  45. [45]

      H.Y. Gong, B.M. Rambo, E. Karnas, V.M. Lynch, J.L. Sessler, Nat. Chem. 2 (2010) 406–409. doi: 10.1038/nchem.597

  46. [46]

      H.Y. Gong, B.M. Rambo, E. Karnas, et al., J. Am. Chem. Soc. 133 (2011) 1526–1533. doi: 10.1021/ja109102k

  47. [47]

      W. Zhao, A.H. Flood, N.G. White, Chem. Soc. Rev. 49 (2020) 7893–7906. doi: 10.1039/d0cs00486c

  48. [48]

      G.L. Li, Z. Zhuo, B. Wang, et al., J. Am. Chem. Soc. 143 (2021) 10920–10929. doi: 10.1021/jacs.1c01161

  49. [49]

      Y. Huang, R.H. Gao, M. Liu, et al., Angew. Chem. Int. Ed. 60 (2021) 15166–15191. doi: 10.1002/anie.202002666

  50. [50]

      X. Chi, J. Tian, D. Luo, et al., Molecules 26 (2021) 2426. doi: 10.3390/molecules26092426

  51. [51]

      X.Q. Guo, L.P. Zhou, S.J. Hu, et al., J. Am. Chem. Soc. 143 (2021) 6202–6210. doi: 10.1021/jacs.1c01168

  52. [52]

      Y. Gao, J. Zhao, Z. Huang, et al., Angew. Chem. Int. Ed. 61 (2022) e202201793. doi: 10.1002/anie.202201793

  53. [53]

      Q. Bai, Y.M. Guan, T. Wu, et al., Angew. Chem. Int. Ed. 62 (2023) e202309027. doi: 10.1002/anie.202309027

  54. [54]

      Y. Chun, N.J. Singh, I.C. Hwang, et al., Nat. Commun. 4 (2013) 1797. doi: 10.1038/ncomms2758

  55. [55]

      L. Zhang, L.Y. Sun, J.P. Chang, et al., Chin. Chem. Lett. 33 (2022) 4567–4571. doi: 10.1016/j.cclet.2022.01.064

  56. [56]

      F.L. Hirshfeld, Theor. Chim. Acta 44 (1977) 129–138. doi: 10.1007/BF00549096

  57. [57]

      P.R. Spackman, M.J. Turner, J.J. McKinnon, et al., J. Appl. Cryst. 54 (2021) 1006–1011. doi: 10.1107/s1600576721002910

  58. [58]

      B.L. Sibanda, J.M. Thornton, Nature 316 (1985) 170–174. doi: 10.1038/316170a0

  59. [59]

      P. Wei, X. Yan, T.R. Cook, et al., ACS Macro Lett. 5 (2016) 671–675. doi: 10.1021/acsmacrolett.6b00286

  60. [60]

      Z.E. Zhang, Y.F. Zhang, Y.Z. Zhang, et al., J. Am. Chem. Soc. 145 (2023) 7446–7453. doi: 10.1021/jacs.3c00024

  61. [61]

      Z.E. Zhang, Y.Y. An, B. Zheng, J.P. Chang, Y.F. Han, Sci. China Chem. 64 (2021) 1177–1183. doi: 10.1007/s11426-021-9977-5

  62. [62]

      K. Kakhiani, U. Lourderaj, W. Hu, D. Birney, W.L. Hase, J. Phys. Chem. A 113 (2009) 4570–4580. doi: 10.1021/jp811208g

• 

  Figure 1  Schematic representation of fluorinated pillarplex to generate supramolecular gel and supramolecular channel by hierarchical self-assembly in this work.

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  Scheme 1  Synthesis of the poly-NHC-based pillarplexes [Ag₄L₂](PF₆)₄ and [Ag₄(L_H)₂](PF₆)₄.

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  Figure 2  Partial ¹H NMR spectra (400 MHz, 298 K, CD₃CN) of (a) H₄-L(PF₆)₄, (b) [Ag₄L₂](PF₆)₄ and (c) ¹H DOSY spectrum of [Ag₄L₂](PF₆)₄ in CD₃CN. (d) ESI-MS spectra of [Ag₄L₂](PF₆)₄ with isotope distribution for selected peaks (experimental in blue, calculated in red).

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  Figure 3  (a) Stick mode of primary structure [Ag₄L₂]⁴⁺. (b) Supramolecular dimer (secondary structure) self-assembled by [Ag₄L₂]⁴⁺ and interacted through C—H···O interactions. (c) Staggered helical packing (tertiary structure) formed by supramolecular dimers. (d) Quaternary structure formed by supramolecular helical packing, viewed along crystallographic a-axis. Color code: Ag, pink; N, blue; C, gray; F, green; O, red; H, white. Counterion and solvent molecules are omitted for clarity.

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  Figure 4  (a) Packing diagram and the C—H···F interactions in the [Ag₄L₂](PF₆)₄. (b) Photographs of inverted tube test of [Ag₄L₂](PF₆)₄ in CH₃CN (34 mmol/L, T = 298 K). Color code: Ag, pink; N, blue; C, gray; F, green; O, red; H, white. Partial counterions and solvent molecules are omitted for clarity.

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  Figure 5  (a) Preparation of the supramolecular channel between [Ag₄L₂]⁴⁺ and monocarboxylic anions through an anion-induced approach. (b) Self-assembly of the supramolecular column by [Ag₄L₂]⁴⁺ and monocarboxylic anions through C—H···O interactions. (c) The interactions between the monocarboxylic anions and silver ions in the crystalline phase. (d) Supramolecular channel structure formed by supramolecular column, viewed along crystallographic c-axis. Color code: Ag, pink; N, blue; C, gray; F, green; O, red; H, white. Hydrogen atoms or solvent molecules are omitted for clarity.

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