English

• 0.   Introduction

  As the fourth-generation macrocycles after crown ether, cyclodextrin, and calixarene, cucurbit[n]urils (Q[n]s, n=5-8, 10) family is a class of pumpkin-shaped molecules constructed from n glycoluril units bridged by 2n methylene groups^[1-5]. Due to the presence of a rigid hydrophobic cavity and two carbonyl-fringed polar portals, Q[n]s display high affinity for specific guest molecules, especially positively charged organic molecules, and encapsulate them into the cavity of Q[n]s to form diverse supramolecular host-guest complexes through host-guest, charge-dipole, and hydrogen-bonding interactions^[6]. Hence, since the determination of the crystal structure of the first member Q[6], Q[n]s have been extensively investigated as the host molecules to fabricate various host-guest complexes for different applications: catalysis, molecular recognition, drug delivery, and so on^[7-16]. On the other hand, the abundant lone pair electrons on the carbonyl groups of the two portals allow Q[n]s to act as σ-donors to coordinate with metal cations to form coordination complexes or polymers^[17-22]. According to previous studies, Q[n]s possess higher affinity towards alkali and alkaline-earth metal cations but much lower affinity towards transition and lanthanide metal cations^[23]. Thus, Q[n]s could connect with alkali and alkaline-earth metals through direct coordination, while transition and lanthanide metals generally bind with Q[n]s in the form of hydrated cations via supramolecular interactions^[17-18]. Furthermore, theoretical calculations on Q[n]s indicate that the outer surface of Q[n]s is somewhat electrostatically positive, making it a potential site to interact with electrostatic or anionic species to form supramolecular assemblies^[24]. In the past decade, numerous studies have demonstrated that diverse species, such as Q[n]s, aromatic molecules, calixarenes, inorganic complex ions, and polyoxometalates, can form a variety of supramolecular assemblies with Q[n]s via outer-surface interactions^[24-29]. Among these species, aromatic carboxylate molecules can not only form diverse noncovalent interactions, including hydrogen bonds, C—H…π and π…π interactions, but also act as a second ligand to coordinate with the metal cations to form high-dimensional coordination polymers^[30-37]. For example, Zhang and co-workers separately employed a carboxylate ligand containing a disulfide bond (5, 5′-dithiobis(2-nitrobenzoic acid), H₂DTNB), and an amide linkage (bis(3, 5-dicarboxyphenyl)terephthalamide, H₄BDTA) to react with Q[6] under hydrothermal conditions to afford two supramolecular assemblies and 2D coordination polymers^{[32, 36]}.

  In consideration of the practical reaction conditions and the high reactivity of the disulfide bond, the carboxylate ligand H₂DTNB can break the disulfide bond and transform into other ligands to generate more diverse structures with Q[n]s. In this work, we employed H₂DTNB as the second ligand to react with Q[6] and Cd(NO₃)₂, affording three novel supramolecular assemblies. Single-crystal diffraction (SC-XRD) determination revealed that the ligand H₂DTNB is just deprotonated in the form of HDTNB^- to interact with [Cd(H₂O)₄(Q[6])]²⁺ cations to form supramolecular framework in assembly [Cd(H₂O)₄(Q[6])](HDTNB)₂·3H₂O (1), but transforms into 5, 5′-thiobis(2-nitrobenzoic acid) (H₂TNB) and 2-nitro-5-sulfobenzoic acid (H₂NSB) in the form of TNB^2- anion and [Cd(H₂O)₅(NSB)] complex under different conditions to interact with Q[6]/ [Cd(H₂O)]²⁺ and Q[6] to afford different supramolecular architecture: [Cd(H₂O)₆]₂(TNB)₂·Q[6]·4H₂O (2) and [Cd(H₂O)₅(NSB)]₂·Q[6] (3). Structural analysis revealed that the outer-surface interactions between Q[6] and these carboxylate ligands play a vital role in the formation of these three supramolecular assemblies.

  1.   Experimental

  1.1   Materials and methods

  The initial cadmium nitrate tetrahydrate (Cd(NO₃)₂·4H₂O), ammonium hydroxide (NH₃·H₂O, 28%-30%, aq), and ligand H₂DTNB were commercially purchased at least reagent grade and used directly as received without further purification. Q[6]·10H₂O was synthesized according to previously reported methods^[38]. Powder X-ray diffraction (PXRD) data were collected at room temperature on bulk samples with Cu Kα radiation (λ=0.154 059 nm, U=45 kV, I=40 mA, 2θ=5°-50°) on a Bruker D8 Advance X-ray diffractometer. FTIR spectrum was recorded by a Fourier transform infrared spectrometer (IS5, Thermo Fisher USA). Elemental analyses for C, H, and N were performed on a Perkin-Elmer 240C Elemental Analyzer.

  1.2   Synthesis of assembly 1

  A mixture of Q[6]·10H₂O (15 mg, 0.012 5 mmol), H₂DTNB (9.9 mg, 0.025 mmol), and Cd(NO₃)₂·4H₂O (30.8 mg, 0.1 mmol) in deionized water (5 mL) was sealed in a Teflon-lined stainless steel vessel and reacted in an oven at 120 ℃ for 8 h and then 90 ℃ for 8 h. After cooling to room temperature, pale yellow crystals of assembly 1 were collected with a yield of ca. 30%. Anal. Calcd. for C₆₄H₆₄CdN₂₈O₃₅S₄(%): C, 37.94; H, 3.18; N, 19.36; S, 6.33. Found(%): C, 37.46; H, 4.39; N, 19.62; S, 6.43. IR (KBr pellet, cm^-1) 3 482 (m, br), 1 736 (m), 1 601 (m), 1 557 (m), 1 516 (s), 1 475 (m), 1 423 (w), 1 378 (s), 1 339 (w), 1 290 (w), 1 231 (w), 1 193 (w), 1 147 (w), 970 (w), 874 (m), 802 (m), 758 (m).

  1.3   Synthesis of assembly 2

  A mixture of Q[6]·10H₂O (15 mg, 0.012 5 mmol), H₂DTNB (9.9 mg, 0.025 mmol), ammonium hydroxide (NH₃·H₂O, 0.5 mL) and Cd(NO₃)₂·4H₂O (30.8 mg, 0.1 mmol) in deionized water (5 mL) was sealed in a Teflon-lined stainless steel vessel and then reacted in an oven at 120 ℃ for 6 h. After cooling to room temperature, yellow crystals of assembly 2 could be obtained with a yield of about 15%. Anal. Calcd. for C₆₄H₈₀Cd₂N₂₈O₄₄S₂(%): C, 34.40; H, 3.61; N, 17.55; S, 2.87. Found(%): C, 34.62; H, 3.81; N, 17.89; S, 3.03. IR (KBr pellet, cm^-1): 3 478 (m, br), 1 737 (m), 1 667 (m), 1 562 (m), 1 517 (s), 1 472 (m), 1 380 (w), 1 337 (s), 1 239 (w), 1 190 (m), 1 150 (m), 966 (m), 874 (m), 802 (m), 761 (m).

  1.4   Synthesis of assembly 3

  A mixture of Q[6]·10H₂O (15 mg, 0.012 5 mmol), H₂DTNB (14.8 mg, 0.037 5 mmol), and Cd(NO₃)₂·4H₂O (60.2 mg, 0.20 mmol) in deionized water (5 mL) was sealed in a Teflon-lined stainless steel vessel and then reacted in an oven at 160 ℃ for 6 h. After cooling to room temperature, yellowish green crystals of assembly 3 were collected with a yield of ca. 45%. Anal. Calcd. for C₅₀H₆₄Cd₂N₂₆O₃₆S₂(%): C, 31.70; H, 3.41; N, 19.23; S, 3.39. Found(%): C, 31.49; H, 3.96; N, 18.92; S, 3.12. IR (KBr pellet, cm^-1): 3 469 (m, br), 1 741 (m), 1 472 (m), 1 419 (m), 1 378 (s), 1 327 (m), 1 237 (w), 1 190 (s), 1 147 (w), 963 (w), 801 (m), 759 (m).

  1.5   X-ray crystallography

  SC-XRD data of supramolecular assemblies 1-3 were collected on a Bruker D8 Venture diffractometer with graphite-monochromated Mo Kα radiation (λ=0.071 073 nm). The integration of diffraction data and intensity corrections for the Lorentz and polarization effects was performed by using the SAINT program^[39]. Semi-empirical absorption corrections were applied using the SADABS program^[40]. The structures were solved by direct methods with SHELXT-2018, expanded by subsequent Fourier-difference synthesis, and all the non-hydrogen atoms were refined anisotropically on F² using the full-matrix least-squares technique using the SHELXL-2018 crystallographic software package^[41-42]. The free water molecules in the unit cell have been taken into account using the SQUEEZE option of the PLATON program^[43]. The squeezed water molecules are 3, 4, and 0 for assemblies 1-3, respectively. Other hydrogen atoms were introduced at the calculated positions. The reported refinements are of the guest-free structures obtained by the SQUEEZE routine. The details of crystal parameters, data collection, and refinements are listed in Table 1, and the selected bond lengths and angles are given in Table S1 (Supporting information).

  Table 1

  

  Table 1.  Crystal data and structure refinements for assemblies 1-3

  下载: 导出CSV

  Parameter	1	2	3
  Chemical formula	C64H64CdN28O35S4	C64H80Cd2N28O44S2	C50H64Cd2N26O36S2
  Formula weight	2 026.03	2 234.43	1 894.19
  T / K	296(2)	296(2)	296(2)
  Crystal system	Monoclinic	Monoclinic	Triclinic
  Space group	C2/m	C2/m	P1
  a / nm	1.255 07(10)	1.512 0(5)	1.195 87(14)
  b / nm	3.049 5(2)	1.984 4(7)	1.247 43(15)
  c / nm	1.059 97(8)	1.680 3(6)	1.289 58(15)
  α / (°)			94.325(3)
  β / (°)	99.594 0(10)	104.341(10)	98.633(3)
  γ / (°)			94.677(3)
  Volume / nm3	4.000 1(5)	4.884(3)	1.888 1(4)
  Z	2	2	1
  Dc / (g·cm-3)	1.637	1.470	1.666
  μ / mm-1	0.483	0.575	0.727
  F(000)	2 012	2 200	962
  Reflection collected	17 350	16 229	13 368
  Independent reflection	4 754	5 708	8 478
  Data, Nres, Npara	4 754, 71, 316	5 708, 54, 321	8 478, 0, 533
  GOF	0.981	1.076	1.031
  R1b, wR2c [I > 2σ(I)]	0.086 9, 0.260 1	0.070 7, 0.203 4	0.051 3, 0.148 9
  R1, wR2 (all data)	0.097 2, 0.271 3	0.091 3, 0.216 4	0.069 2, 0.159 9
  a Nres=number of restraints, Npar=number of parameters; b R1=∑||Fo|-|Fc||/∑|Fo|; c wR2={∑[w(Fo2-Fc2)2/(Fo2)2]}1/2, where w=1/[∑2(Fo2)+(aP)2+bP], P=(Fo2+2Fc2)/3.

  2.   Results and discussions

  2.1   Structural description of assembly 1

  According to the results of SC-XRD measurement, supramolecular assembly 1 crystallizes in the monoclinic C2/m space group, and the asymmetric unit consists of one-quarter of a [Cd(H₂O)₄(Q[6])]·(HDTNB)₂ unit. As shown in Fig.1a, the central metal ion Cd1 is disordered into four positions, each with a site occupancy of 0.25, and adopts a distorted octahedral coordination geometry surrounded by two carbonyl oxygen atoms (O1, O3) from one Q[6] molecule and four coordinated water molecules (O1W, O2W, O2W#1, O3W). In structure of assembly 1, merely one Q[6] molecules and one Cd²⁺ cation coordinate to each other, forming simple coordination complexes [Cd(H₂O)₄(Q[6])]²⁺ (Fig.1b). Among these complexes, the hydrogen bonds (O…O 0.276 5, 0.283 5, 0.293 2 nm) between the coordinated water molecules and the carbonyl groups of Q[6]s join them into 1D supramolecular chains (Fig.1b and S1a), which is further assembled by π…π interactions (0.322 7 nm) between the carbonyl groups of adjacent Q[6] molecules into cationic 2D supramolecular layers (Fig.1b and S1a). To maintain the charge balance, the carboxylate ligands (H₂DTNB) are partially deprotonated in the form of HDTNB^- anion and interact with each other through the O—H…O/C—H…O hydrogen bonds (H…O 0.259 0 nm, O…O 0.245 8 nm) and π…π interactions (0.375 1 nm) to form 2D anionic supramolecular layers (Fig.S1b). Meanwhile, depart from the electrostatic interactions between the cationic Q[6]-Cd layers and HDTNB^- layers, numerous noncovalent interactions including the C—H…O hydrogen bonds (H…O 0.237 9-0.257 8 nm) between the methylene/methyne groups of Q[6] and the nitro/carboxylate oxygen atoms of HDTNB^-, and C—H…π interactions (0.2981 nm) between the methylene groups of Q[6] and benzene rings of HDTNB^- (Fig.1c), contribute to the formation of the final 3D supramolecular framework (Fig.1d, S1c, and S1d).

  Figure 1

  

  Figure 1.  (a) Coordination environment of Cd²⁺ in assembly 1 with the ellipsoids drawn at the 50% probability level; (b) Structure of the 2D supramolecular Q[6]-; Cd layer; (c) Noncovalent interactions among ligand HDTNB^- and the outer surfaces of Q[6] molecules; (d) Structure of the 3D Q[6]-; Cd-; HDTNB supramolecular framework

  For clarity, the hydrogen atoms are omitted, and the disordered atoms Cd1/water molecules are presented partially; Symmetry codes: #1: 1-x, y, -z; #2: 1-x, y, 1-z.

  下载: 全尺寸图片 幻灯片

  2.2   Structural description of assembly 2

  SC-XRD analysis demonstrated that assembly 2 crystallizes in the monoclinic system with the space group of C2/m and the asymmetric unit contains half of a Cd²⁺ cation, half of a ligand TNB^2-, one-quarter of a Q[6] molecule, and three coordinated water molecules. As exhibited in Fig.2a, the metal ion Cd1 was coordinated with six water molecules (O1W, O1W#1, O2W, O3W, O4W, O5W) in a slightly distorted octahedral geometry. The formed [Cd(H₂O)₆]²⁺ cations are located above the center of the two portal of Q[6] molecules to generate capsule-like supramolecular complexes via the hydrogen bonds (O…O 0.260 2, 0.273 0, 0.303 1, 0.309 6 nm) between the coordinated water molecules and carbonyl groups of Q[6] molecules (Fig.2b), which further interact with each other through the π…π interactions (0.339 5 nm) between the carbonyl groups of adjacent Q[6] molecules to afford 2D supramolecular layers (Fig.2b and S2a). On the other hand, the reactant ligand H₂DTNB transforms into the sulfide product in the anionic form of TNB^2- to maintain the charge balance and interact with each other through C—H…O hydrogen bonds (H…O 0.266 4 nm) and π…π interactions (0.358 6 nm) to form 1D supramolecular chains (Fig.S2b). Similar to assembly 1, electrostatic interactions, O—H…O hydrogen bonds (O…O 0.274 0, 0.308 1, 0.328 1 nm) between the nitro/carboxylate groups of TNB^2- and the coordinated water moelcules, and the C—H…π interactions (0.279 2 nm) between the methylene groups of Q[6] and benzene rings of TNB^2- all contribute to the formation of the final 3D supramolecular architecture of assembly 2 (Fig.2c, 2d, S2c, and S2d).

  Figure 2

  

  Figure 2.  Coordination environment of Cd²⁺ in assembly 2 with the ellipsoids drawn at the 50% probability level; (b) Structure of the 2D supramolecular Q[6]-; Cd layer; (c) Noncovalent interactions among ligand TNB^2-, Cd(H₂O)₆]²⁺, and Q[6]; (d) Structure of the final 3D framework of assembly 2

  The hydrogen atoms are omitted for clarity; Symmetry code: #1: x, -y+1, z.

  下载: 全尺寸图片 幻灯片

  2.3   Structural description of assembly 3

  SC-XRD experimental results revealed that assembly 3 crystallizes in the triclinic P1 space group, and the asymmetric unit is comprised of one Cd²⁺ cation, one NSB^2- ligand, half of a Q[6] molecule, and five coordinated water molecules. Under the hydrothermal conditions, the disulfide linkage in the raw ligand H₂DTNB is broken and oxidized into the sulfonate ligand NSB^2-. As shown in Fig.3a, the metal ion Cd1 adopts a slightly distorted six-coordinated octahedral geometry to coordinate with one carboxylate oxygen atom (O13) from NSB^2- and five coordinated water molecules (O1W, O2W, O3W, O4W, O5W) to form [Cd(H₂O)₅(NSB)], which interacts with each other via π…π interactions (0.368 3 nm) between the benzene rings of NSB^2- and hydrogen bonds (O…O 0.279 8, 0.279 9 nm) between the carboxylate groups of NSB^2- and coordinated water molecules to give 1D Cd-NSB supramolecular chains (Fig.S3a). Moreover, Q[6] molecules are assembled by C—H…O hydrogen bonds (H…O 0.259 7 nm) between the methylene group and carbonyl groups from neighbouring Q[6] molecules, and the π…π interactions (0.366 5 nm) between the carbonyl groups of adjacent Q[6] molecules (Fig.S3b) into 3D supramolecular framework (Fig.3b). Meanwhile, the Cd-NSB chains filled in the pores of 3D Q[6] framework via the C—H…O hydrogen bonds (H…O 0.231 0, 0.245 1, 0.250 0 nm; O…O 0.268 3, 0.274 6, 0.275 6, 0.276 8, 0.281 2, 0.316 8, 0.332 9 nm) between the nitro/sulfonate groups of NSB^2- and the methylene/methyne groups of Q[6]s, O—H…O hydrogen bonds (O…O 0.268 3, 0.274 6, 0.275 6, 0.276 8, 0.281 2, 0.316 8, 0.332 9 nm) between the coordinated water molecules and carbonyl groups of Q[6]s, the π…π interactions (0.339 5 nm) between the carbonyl groups of Q[6] and the benzene rings of NSB^2- (Fig.3c), generating the final 3D supramolecular framework (Fig.3d, S3c, and S3d).

  Figure 3

  

  Figure 3.  (a) Coordination environment of Cd²⁺ in assembly 3 with the ellipsoids drawn at the 50% probability level; (b) Structure of the 3D supramolecular framework constructed from Q[6] molecules; (c) Noncovalent interactions between complex [Cd(H₂O)₅(NSB)] and Q[6]; (d) Structure of the final 3D framework

  The hydrogen atoms are omitted for clarity.

  下载: 全尺寸图片 幻灯片

  As mentioned above, supramolecular assemblies 1-3 displayed significantly distinct frameworks. Due to the unique property of the disulfide bond, the ligand H₂DTNB transforms into TNB^2- or NSB^2- under different reaction conditions to generate distinct interactions between these ligands. In assembly 1, the interactions between HDTNB^- afford 2D supramolecular layers, while the interactions between TNB^2- in assembly 2 give 1D supramolecular chains, and neither HDTNB^- nor TNB^2- are coordinated to Cd²⁺. However, in assembly 3, it may be due to the presence of sulfonate groups that result in the coordination between the carboxylate groups of NSB^2- with Cd²⁺, and the interactions between the obtained complexes [Cd(H₂O)₅(NSB)] generate 1D supramolecular NSB-Cd chains. Meanwhile, the organic ligands HDTNB^-, TNB^2-, and complex [Cd(H₂O)₅(NSB)] also induce significantly different interactions with Q[6] molecules and finally produce the markedly distinct architectures of assemblies 1-3. Furthermore, in order to examine the phase purity and the structural consistency of these prepared assemblies with the crystal structure, PXRD measurements were performed at room temperature. As shown in Fig.S4, the experimental PXRD patterns matched well with the simulated ones obtained from the SC-XRD data, which clearly demonstrated that the prepared crystal samples of assemblies 1-3 are a pure phase with the same crystal structure as that described above.

  3.   Conclusions

  In this work, the reactions between H₂DTNB, Q[6], and Cd(NO₃)₂ afforded three novel supramolecular assemblies 1-3 under different conditions, and the structures of these assemblies were determined by using SC-XRD and PXRD. In assembly 1, ligand H₂DTNB is partially deprotonated to form 2D HDTNB^- supramolecular layers and interacts with [Cd(H₂O)₄ (Q[6])]²⁺ supramolecular layers to form the final 3D supramolecular structure. However, the ligand H₂DTNB in assemblies 2 and 3 is completely deprotonated and transformed into TNB^2- and NSB^2-, respectively. In assembly 2, the formed ligand TNB^2- interacts with each other to form 1D supramolecular chains and further assembles with Q[6] and [Cd(H₂O)₆]²⁺ to afford the final 3D supramolecular framework. In assembly 3, the transformed ligand NSB^2- coordinates with Cd²⁺ to form complex [Cd(H₂O)₅(NSB)], which interacts with each other to give 1D supramolecular chains and Q[6] to afford the final 3D supramolecular architecture. The outer-surface interactions between Q[6] and the ligands played a crucial role in the formation of all three assemblies.

  
  Acknowledgements: This work was financially supported by the Major Project of Basic Science (Natural Science) Research in Higher Education Institutions of Jiangsu Province (Grant No.22KJA150002). Ding Wenya and Gu Jiayu express their gratitude to the NUIST Students′ Platform for Innovation and Entrepreneurship Training Program (Grants No.202410300037Z, 202410300030Z). We are also grateful to Qunjing Technology Co., Ltd. for its assistance in crystal testing and analysis. Supporting information is available at http://www.wjhxxb.cn
  
• 1. [1]

     LIU Z C, NALLURI S K M, STODDART J F. Surveying macrocyclic chemistry: From flexible crown ethers to rigid cyclophanes[J]. Chem. Soc. Rev., 2017, 46(9): 2459-2478 doi: 10.1039/C7CS00185A

  2. [2]

     XIA D Y, WANG P, JI X F, KHASHAB N M, SESSLER J L, HUANG F H. Functional supramolecular polymeric networks: The marriage of covalent polymers and macrocycle-based host-guest interactions[J]. Chem. Rev., 2020, 120(13): 6070-6123 doi: 10.1021/acs.chemrev.9b00839

  3. [3]

     LEE J W, SAMAL S, SELVAPALAM N, KIM H J, KIM K. Cucurbituril homologues and derivatives:   New opportunities in supramolecular chemistry[J]. Accounts Chem. Res., 2003, 36(8): 621-630 doi: 10.1021/ar020254k

  4. [4]

     LAGONA J, MUKHOPADHYAY P, CHAKRABARTI S, ISAACS L. The cucurbit[n]uril family[J]. Angew. Chem. ‒Int. Edit., 2005, 44(31): 4844-4870 doi: 10.1002/anie.200460675

  5. [5]

     ISAACS L. Cucurbit[n]urils: From mechanism to structure and function[J]. Chem. Commun., 2009, (6): 619-629 doi: 10.1039/B814897J

  6. [6]

     MASSON E, LING X X, JOSEPH R, KYEREMEH-MENSAH L, LU X Y. Cucurbituril chemistry: A tale of supramolecular success[J]. RSC Adv., 2012, 2(4): 1213-1247 doi: 10.1039/C1RA00768H

  7. [7]

     FREEMAN W A, MOCK W L, SHIH N Y. Cucurbituril[J]. J. Am. Chem. Soc., 1981, 103(24): 7367-7369 doi: 10.1021/ja00414a070

  8. [8]

     MACARTNEY D H. Encapsulation of drug molecules by cucurbiturils: Effects on their chemical properties in aqueous solution[J]. Isr. J. Chem., 2011, 51(5/6): 600-615

  9. [9]

     LIU Y L, YANG H, WANG Z Q, ZHANG X. Cucurbit[8]uril-based supramolecular polymers[J]. Chem. ‒Asian J., 2013, 8(8): 1626-1632 doi: 10.1002/asia.201300151

  10. [10]

      KAIFER A E. Toward reversible control of cucurbit[n]uril complexes[J]. Accounts Chem. Res., 2014, 47(7): 2160-2167 doi: 10.1021/ar5001204

  11. [11]

      PAZOS E, NOVO P, PEINADOR C, KAIFER A E, GARCÍA M D. Cucurbit[8]uril (CB[8])-based supramolecular switches[J]. Angew. Chem. ‒Int. Edit., 2019, 58(2): 403-416 doi: 10.1002/anie.201806575

  12. [12]

      AMBROSE B, KATHIRESAN M. Viologen-cucurbit[n]uril supramolecular interactions: A comprehensive overview[J]. Chem. Commun., 2025, 61(67): 12467-12490 doi: 10.1039/D5CC03120F

  13. [13]

      ASSAFA K I, NAU W M. Cucurbiturils: From synthesis to high-affinity binding and catalysis[J]. Chem. Soc. Rev., 2015, 44(2): 394-418 doi: 10.1039/C4CS00273C

  14. [14]

      TANG B H, ZHAO J T, XU J F, ZHANG X. Cucurbit[n]urils for supramolecular catalysis[J]. Chem. ‒Eur. J., 2020, 26(67): 15446-15460 doi: 10.1002/chem.202003897

  15. [15]

      BARROW S J, KASERA S, ROWLAND M J, DEL BARRIO J, SCHERMAN O A. Cucurbituril-based molecular recognition[J]. Chem. Rev., 2015, 115(22): 12320-12406 doi: 10.1021/acs.chemrev.5b00341

  16. [16]

      URBACH A R, RAMALINGAM V. Molecular recognition of amino acids, peptides, and proteins by cucurbit[n]uril receptors[J]. Isr. J. Chem., 2011, 51(5/6): 664-678

  17. [17]

      NI X L, XIAO X, CONG H, LIANG L L, CHENG K, CHENG X J, JI N N, ZHU Q J, XUE S F, TAO Z. Cucurbit[n]uril-based coordination chemistry: From simple coordination complexes to novel poly-dimensional coordination polymers[J]. Chem. Soc. Rev., 2013, 42(24): 9480-9508 doi: 10.1039/c3cs60261c

  18. [18]

      LÜ J, LIN J X, CAO M N, CAO R. Cucurbituril: A promising organic building block for the design of coordination compounds and beyond[J]. Coord. Chem. Rev., 2013, 257(7/8): 1334-1356

  19. [19]

      NI X L, XUE S F, TAO Z, ZHU Q J, LINDOY L F, WEI G. Advances in the lanthanide metallosupramolecular chemistry of the cucurbit[n]urils[J]. Coord. Chem. Rev., 2015, 287: 89-113 doi: 10.1016/j.ccr.2014.12.018

  20. [20]

      CONG H, ZHU Q J, XUE S F, TAO Z, WEI G. Direct coordination of metal ions to cucurbit[n]urils[J]. Chin. Sci. Bull., 2010, 55(32): 3633-3640 doi: 10.1007/s11434-010-4146-8

  21. [21]

      SOKOLOV M N, DYBTSEV D N, FEDIN V P. Supramolecular compounds of cucurbituril with molybdenum and tungsten chalcogenide cluster aqua complexes[J]. Russ. Chem. Bull., 2003, 52(5): 1041-1060 doi: 10.1023/A:1024771902420

  22. [22]

      GAO R H, HUANG Y, CHEN K, TAO Z. Cucurbit[n]uril/metal ion complex-based frameworks and their potential applications[J]. Coord. Chem. Rev., 2021, 437: 213741 doi: 10.1016/j.ccr.2020.213741

  23. [23]

      ZHANG S, GRIMM L, MISKOLCZY Z, BICZÓK L, BIEDERMANN F, NAU W M. Binding affinities of cucurbit[n]urils with cations[J]. Chem. Commun., 2019, 55(94): 14131-14134 doi: 10.1039/C9CC07687E

  24. [24]

      NI X L, XIAO X, CONG H, ZHU Q J, XUE S F, TAO Z. Self-assemblies based on the "outer-surface interactions" of cucurbit[n]urils: New opportunities for supramolecular architectures and materials[J]. Accounts Chem. Res., 2014, 47(4): 1386-1395 doi: 10.1021/ar5000133

  25. [25]

      ZHU Q J, XUE S F, TAO Z. Supramolecular coordination polymers based on the outer-surface interaction of cucurbit[n]urils[J]. Prog. Chem., 2015, 27(6): 625-632

  26. [26]

      CHEN K, HUA Z Y, ZHAO J L, REDSHAW C, TAO Z. Construction of cucurbit[n]uril-based supramolecular frameworks via host-guest inclusion and functional properties thereof[J]. Inorg. Chem. Front., 2022, 9(12): 2753-2809 doi: 10.1039/D2QI00513A

  27. [27]

      HUANG Y, GAO R H, LIU M, CHEN L X, NI X L, XIAO X, CONG H, ZHU Q J, CHEN K, TAO Z. Cucurbit[n]uril-based supramolecular frameworks assembled through outer-surface interactions[J]. Angew. Chem. ‒Int. Edit., 2021, 133(28): 15294-15319 doi: 10.1002/ange.202002666

  28. [28]

      ZHANG X D, CHEN K, SUN W Y. Potential applications of cucurbit[n]urils and their derivatives in the capture of hazardous chemicals[J]. Chem. ‒Eur. J., 2021, 27(16): 5107-5119 doi: 10.1002/chem.202004711

  29. [29]

      TIAN F Y, CHENG R X, ZHAO H J, LI C J, CHEN K. Enhanced ternary composite system potassium-cucurbit[6]uril-ruthenium metal-support interactions in a heterogeneous system to facilitate photocatalytic nitrogen activation[J]. Small Methods, 2025, 36(7/8): 224-234

  30. [30]

      THUÉRY P. Coordination polymers and frameworks in uranyl ion complexes with sulfonates and cucurbit[6]uril[J]. Cryst. Growth Des., 2011, 11(2): 5702-5711

  31. [31]

      CHEN K, KANG Y S, ZHAO Y, YANG J M, LU Y, SUN W Y. Cucurbit[6]uril-based supramolecular assemblies: Possible application in radioactive cesium cation capture[J]. J. Am. Chem. Soc., 2014, 136(48): 16744-16747 doi: 10.1021/ja5098836

  32. [32]

      ZHANG X D, ZHAO Y, CHEN K, WANG P, KANG Y S, WU H, SUN W Y. Cucurbit[6]uril-based multifunctional supramolecular assemblies: Synthesis, removal of Ba􀃭 and fluorescence sensing of Fe􀃮[J]. Dalton Trans., 2018, 47(11): 3958-3964 doi: 10.1039/C8DT00182K

  33. [33]

      KOVALENKO E A, NAUMOV D Y, FEDIN V P. Coordination networks and supramolecular assemblies based on barium cation complexes with cucurbit[6]uril[J]. Polyhedron, 2018, 144: 158-165 doi: 10.1016/j.poly.2018.01.021

  34. [34]

      SUN J P, GUO P P, LIU M, LI H. A novel cucurbit[6]uril-based supramolecular coordination assembly as a multi-responsive luminescent sensor for Fe³⁺, Cr₂O₇^2- and isoquinoline antibiotics in aqueous medium[J]. J. Mater. Chem. C, 2019, 7(29): 8992-8999 doi: 10.1039/C9TC02666E

  35. [35]

      AN S W, MEI L, HU K Q, ZHANG Z H, XIA C Q, CHAI Z F, SHI W Q. Noncomplexed cucurbituril-mediated structural evolution of layered uranyl terephthalate compounds[J]. Inorg. Chem., 2020, 59(1): 943-955 doi: 10.1021/acs.inorgchem.9b03215

  36. [36]

      ZHANG X D, FANG F, HUANG M Y, CHEN K. Construction of cucurbit[6]uril-based coordination polymers incorporating multiaromatic ligands with amide linkages and their iodine adsorption properties[J]. Cryst. Growth Des., 2024, 24(11): 4322-4332 doi: 10.1021/acs.cgd.3c01389

  37. [37]

      CAO J, GU J Y, DING W Y, CHEN X R, HUA Z Y, CHEN K. Carboxylate ligand-directed synthesis of cucurbit[5]uril-based coordination polymers for the detection of norfloxacin[J]. Dalton Trans., 2025, 54(40): 15197-15205 doi: 10.1039/D5DT01769F

  38. [38]

      KIM J, JUNG I S, KIM S Y, LEE E, KANG J K, SAKAMOTO S, YAMAGUCHI K, KIM K. New cucurbituril homologues:   Syntheses, isolation, characterization, and X-ray crystal structures of cucurbit[n]uril (n=5, 7, and 8)[J]. J. Am. Chem. Soc., 2000, 122(3): 540-541 doi: 10.1021/ja993376p

  39. [39]

      SAINT. Program for data extraction and reduction[CP]. Bruker AXS, Inc, Madison, WI, 2001.

  40. [40]

      SHELDRICK G M. SADABS, Program for empirical adsorption correction of area detector data[CP]. University of Göttingen, Germany, 2003.

  41. [41]

      SHELDRICK G M. SHELXT-2018, Program for the crystal structure solution[CP]. University of Göttingen, Germany, 2018.

  42. [42]

      SHELDRICK G M. SHELXL-2018, Program for the crystal structure refinement[CP]. University of Göttingen, Germany, 2018.

• 

  Figure 1  (a) Coordination environment of Cd²⁺ in assembly 1 with the ellipsoids drawn at the 50% probability level; (b) Structure of the 2D supramolecular Q[6]-; Cd layer; (c) Noncovalent interactions among ligand HDTNB^- and the outer surfaces of Q[6] molecules; (d) Structure of the 3D Q[6]-; Cd-; HDTNB supramolecular framework

  For clarity, the hydrogen atoms are omitted, and the disordered atoms Cd1/water molecules are presented partially; Symmetry codes: #1: 1-x, y, -z; #2: 1-x, y, 1-z.

  下载: 全尺寸图片 幻灯片
  

  Figure 2  Coordination environment of Cd²⁺ in assembly 2 with the ellipsoids drawn at the 50% probability level; (b) Structure of the 2D supramolecular Q[6]-; Cd layer; (c) Noncovalent interactions among ligand TNB^2-, Cd(H₂O)₆]²⁺, and Q[6]; (d) Structure of the final 3D framework of assembly 2

  The hydrogen atoms are omitted for clarity; Symmetry code: #1: x, -y+1, z.

  下载: 全尺寸图片 幻灯片
  

  Figure 3  (a) Coordination environment of Cd²⁺ in assembly 3 with the ellipsoids drawn at the 50% probability level; (b) Structure of the 3D supramolecular framework constructed from Q[6] molecules; (c) Noncovalent interactions between complex [Cd(H₂O)₅(NSB)] and Q[6]; (d) Structure of the final 3D framework

  The hydrogen atoms are omitted for clarity.

  下载: 全尺寸图片 幻灯片

  Table 1.  Crystal data and structure refinements for assemblies 1-3

  Parameter	1	2	3
  Chemical formula	C64H64CdN28O35S4	C64H80Cd2N28O44S2	C50H64Cd2N26O36S2
  Formula weight	2 026.03	2 234.43	1 894.19
  T / K	296(2)	296(2)	296(2)
  Crystal system	Monoclinic	Monoclinic	Triclinic
  Space group	C2/m	C2/m	P1
  a / nm	1.255 07(10)	1.512 0(5)	1.195 87(14)
  b / nm	3.049 5(2)	1.984 4(7)	1.247 43(15)
  c / nm	1.059 97(8)	1.680 3(6)	1.289 58(15)
  α / (°)			94.325(3)
  β / (°)	99.594 0(10)	104.341(10)	98.633(3)
  γ / (°)			94.677(3)
  Volume / nm3	4.000 1(5)	4.884(3)	1.888 1(4)
  Z	2	2	1
  Dc / (g·cm-3)	1.637	1.470	1.666
  μ / mm-1	0.483	0.575	0.727
  F(000)	2 012	2 200	962
  Reflection collected	17 350	16 229	13 368
  Independent reflection	4 754	5 708	8 478
  Data, Nres, Npara	4 754, 71, 316	5 708, 54, 321	8 478, 0, 533
  GOF	0.981	1.076	1.031
  R1b, wR2c [I > 2σ(I)]	0.086 9, 0.260 1	0.070 7, 0.203 4	0.051 3, 0.148 9
  R1, wR2 (all data)	0.097 2, 0.271 3	0.091 3, 0.216 4	0.069 2, 0.159 9
  a Nres=number of restraints, Npar=number of parameters; b R1=∑||Fo|-|Fc||/∑|Fo|; c wR2={∑[w(Fo2-Fc2)2/(Fo2)2]}1/2, where w=1/[∑2(Fo2)+(aP)2+bP], P=(Fo2+2Fc2)/3.

  下载: 导出CSV
•