From Mechanically Interlocked Structures to Host–Guest Chemistry Based on Twisted Dimeric Architectures by Adjusting Space Constraints
2021; Chinese Chemical Society; Volume: 4; Issue: 6 Linguagem: Inglês
10.31635/ccschem.021.202100948
ISSN2096-5745
AutoresXin Jiang, Hao Yu, Junjuan Shi, Qixia Bai, Yaping Xu, Zhe Zhang, Xin‐Qi Hao, Bao Li, Pingshan Wang, Lixin Wu, Ming Wang,
Tópico(s)Luminescence and Fluorescent Materials
ResumoOpen AccessCCS ChemistryRESEARCH ARTICLE6 Jun 2022From Mechanically Interlocked Structures to Host–Guest Chemistry Based on Twisted Dimeric Architectures by Adjusting Space Constraints Xin Jiang, Hao Yu, Junjuan Shi, Qixia Bai, Yaping Xu, Zhe Zhang, Xin-Qi Hao, Bao Li, Pingshan Wang, Lixin Wu and Ming Wang Xin Jiang State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, Jilin 130012 , Hao Yu State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, Jilin 130012 , Junjuan Shi State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, Jilin 130012 , Qixia Bai Institute of Environmental Research at Greater Bay Area, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou Key Laboratory for Clean Energy and Materials, Guangzhou University, Guangzhou, Guangdong 510006 , Yaping Xu State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, Jilin 130012 , Zhe Zhang Institute of Environmental Research at Greater Bay Area, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou Key Laboratory for Clean Energy and Materials, Guangzhou University, Guangzhou, Guangdong 510006 , Xin-Qi Hao College of Chemistry and Green Catalysis Center, Zhengzhou University, Zhengzhou, Henan 450002 , Bao Li State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, Jilin 130012 , Pingshan Wang Institute of Environmental Research at Greater Bay Area, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou Key Laboratory for Clean Energy and Materials, Guangzhou University, Guangzhou, Guangdong 510006 , Lixin Wu State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, Jilin 130012 and Ming Wang *Corresponding author: E-mail Address: [email protected] State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, Jilin 130012 https://doi.org/10.31635/ccschem.021.202100948 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Mechanically interlocked molecules (MIMs) and host–guest chemistry have received great attention in the past few decades. However, it remains challenging to design architectures with mechanically interlocked features and construct cavities for guest molecule recognition using similar building blocks. In this study, we designed and constructed a series of novel twisted supramolecular structures by assembling various multitopic terpyridine (tpy) ligands with the same diameter and Zn(II) ions. The obtained complexes exhibited evolutional architectures and showed distinctively different space-constraint effects. Specifically, the assembled dimer SA, SB, and SBH displayed mechanically interlocked phenomena, including [2]catenane and [3]catenane, with an increase in concentration. However, no interlocked structures were observed in complexes SC and SCH constructed by hexatopic tpy ligands due to the significant space constraints. The single-crystal data of complex SCH further proved significant space constraints and illustrated the formation of a relatively closed cavity, which showed excellent host–guest properties for different calixarenes, especially high affinity for calix[6]arene. Download figure Download PowerPoint Introduction Inspired by the self-assembly phenomena and functional expressions of natural molecules, such as DNA formation, protein folding or recognition, and enzyme catalysis,1–6 noncovalent molecular interactions, including metal–ligand coordination, hydrogen bonding, π–π interactions, and so on,7–9 have been extensively applied to construct numerous discrete architectures.10–12 Based on the discrete structures, more complex systems formed by intermolecular interactions, such as hierarchical self-assembly,13–15 the mechanically interlocked molecules (MIMs),16–19 and host–guest systems,20–24 have received considerable attention over the past few decades. As widespread structures playing a unique role in living organisms, complex systems inspire the fabrication of aesthetic molecular structures and provide impetus to the development of molecular machines and smart materials.25–30 Coordination-driven self-assembly has served as one of the most effective approaches to construct complex and exquisite discrete architectures, due to the feature of dynamic reversibility and coordination geometry.31–37 In recent years, by employing discrete metallosupramolecular structures, a variety of interlocked architectures have been extensively reported, including rotaxanes,38–40 catenanes,41–44 and knots.45–48 In contrast, many discrete metallosupramolecules have been widely employed in the fabrication of functional host–guest systems, such as catalysis,49,50 molecular binding,51 and drug delivery.52,53 For interlocked and host–guest molecular systems, an appropriate cavity with predesigned interactions and space constraints is the most critical factor for fabricating the interlocked structures and guest encapsulation. Although many types of cavities have been created for complex molecular systems, developing a suitable system to transform interlocked to host–guest structures by simply adjusting space constraints remains a great challenge. 2,2′:6′,2″-Terpyridine derivatives have been widely used to construct numerous novel supramolecular structures54–59 with special applications in diverse fields, including catalysts,60,61 medicines,62 sensors,63,64 smart materials,65,66 and optoelectronic devices.67–69 However, the octahedral coordination geometry of the tpy-M(II)-tpy complex can cause significant steric hindrance, which limits the application in the formation of coordination-directed, instead of templating-directed, mechanically interlocked structures .70–73 On the contrary, the high steric hindrance of tpy-M(II)-tpy is more advantageous to construct a tighter closed cavity for the encapsulation of guest molecules. Herein, we designed and synthesized five ortho-tpy ligands with the same diameter (Scheme 1), denoted as ditopic LA, tritopic LB and LBH, and hexatopic LC and LCH. To reduce the steric congestion of the pseudo-octahedral tpy-M(II)-tpy connection, tpy units were located in the center of the final structures. The corresponding complexes with twisted dimeric structures were successfully constructed through assembling these ligands with Zn(II) ions. The obtained complexes exhibited different space constraints and showed significantly different interlocking or host–guest properties. For metal complexes SA, SB, and SBH, assembled by ditopic ligand LA, and tritopic ligands LB and LBH (without alkyl chains), the obvious self-interlocked phenomena were observed upon increasing the concentration of these complexes, due to their lower space constraints and suitable cavity. However, with further increasing space constraints, the complexes SC and SCH, based on the hexatopic ligands, could only form monomeric twisted prisms, and no interlocking phenomena were observed. Because of the significant space restriction effect, SCH served as a well-sealed cavity for the host–guest properties and efficiently encapsulated the calixarene-type species, especially showing a high affinity for calix[6]arene, with a more complex conformation. Scheme 1 | The self-assembly of twisted dimeric architectures, mechanically interlocked structures, and guest recognition. Conditions: (1) CHCl3/MeOH (1∶3. v/v), 50 °C, 8 h. Download figure Download PowerPoint Experimental Methods All reagents were purchased from Sigma-Aldrich (Chaoyang District, Beijing, China), Acros (Shanghai, China), and Aladdin (Shanghai, China) and used without further purification. Compounds 1,74 2,75 4,76 5,73 7,77 and 878 were synthesized per the literature as reported in Supporting Information Scheme S1. NMR data were recorded at 25 °C on Bruker 500 MHz and 600 MHz (Bruker switzerland AG, Fällanden, Zurich, Switzerland) nuclear magnetic resonance instruments using CDCl3 and CD3CN with tetramethylsilane (TMS) as the solvents. Electrospray ionization mass spectrometry (ESI-MS) and traveling-wave ion mobility mass spectrometry (TWIM-MS) were recorded with a Waters Synapt G2 tandem mass spectrometer (Waters Corporation, Milford, MA, USA). Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) was performed on a Bruker Autoflex III (Bruker Corporation, Billerica, MA, USA) using trans-2-[3-(4-tert-butylphenyl)-2-methyl-2-2-propenyli-dene]malononitrile (DCTB) as a matrix. Crystal data were collected from the BL17B beamline of National Facility for Protein Science in Shanghai (NFPS) at Shanghai Synchrotron Radiation Facility. Synthesis of ligand LA Compound 6 (0.9 g, 1.14 mmol), 4,4″-dibromo-p-terphenyl (186.4 mg, 0.48 mmol), Pd(PPh3)2Cl2 (40 mg, 0.058 mmol), and sodium carbonate (1.59 g, 15.0 mmol) were added into a 100 ml Schlenk flask. Toluene (30 mL), H2O (15 mL), and tert-butyl alcohol (6 mL) were added under N2. The mixture was stirred at 85 °C for 24 h. After cooling to room temperature, the solvent was removed under vacuum, and the residue was extracted with CHCl3. The combined organic layer was washed with brine, dried over anhydrous Na2SO4, and then concentrated in vacuo. The crude product was purified by column chromatography on silica gel with dichloromethane: ethanol (100∶2) as eluent to afford the product as a white solid (0.49 g, 65%). 1H NMR (500 MHz, CDCl3, 298 K, δ): 8.73 (s, 4H, tpy-H3′,5′), 8.72–8.69 (m, 4H, tpy-H6,6″), 8.66 (d, J = 7.9 Hz, 4H, tpy-H3,3″), 7.87 (td, J = 7.7, 1.8 Hz, 4H, tpy-H4,4″), 7.80 (d, J = 8.2 Hz, 4H, Ph-Hj), 7.70 (d, J = 4.6 Hz, 12H, Ph-Hm, Ph-Ho, and Ph-Hn), 7.55 (d, J = 8.0 Hz, 4H, Ph-Hl), 7.36–7.31 (m, 8H, tpy-H5,5″ and Ph-Hi), 7.27 (m, 4H, Ph-Hk), 7.03 (d, J = 2.2 Hz, 4H, Ph-Ha and Ph-Hb), 4.11 (td, J = 6.6, 3.9 Hz, 8H, Alkyl-Hc′ and Alkyl-Hc′), 1.93–1.88 (m, 8H, Alkyl-Hd and Alkyl-Hd′), 1.52 (8H, Alkyl-He and Alkyl-He′), 1.38 (m, 16H, Alkyl-Hf, Alkyl-Hg, Alkyl-Hf′, and Alkyl-Hg′), 0.96–0.89 (m, 12H, Alkyl-Hh and Alkyl-Hh′). 13C NMR (125 MHz, CDCl3, 298 K, δ): 156.40, 156.00, 150.04, 149.24, 148.78, 148.65, 142.60, 140.64, 139.77, 139.51, 138.53, 137.01, 136.25, 132.86, 132.51, 130.66, 130.54, 127.55, 127.50, 127.42, 127.06, 126.72, 123.95, 121.48, 118.83, 116.20, 31.77, 29.45, 25.90, 22.81, 14.23, 0.16. MALDI-TOF-MS (m/z): calcd for [C108H104N6O4]+, 1548.8; found, 1548.8. Synthesis of ligand LB Compound 6 (1.0 g, 1.27 mmol), 1,3,5-tris(4-bromophenyl)benzene (178 mg, 0.33 mmol), Pd(PPh3)2Cl2 (44 mg, 0.064 mmol), and sodium carbonate (1.06 g, 10.0 mmol) were added into a 100 ml Schlenk flask. Toluene (25 mL), H2O (10 ml), and tert-butyl alcohol (3 mL) were added under N2. The mixture was stirred at 85 °C for 3 days. After cooling to room temperature, the solvent was removed under vacuum, and the residue was extracted with CHCl3. The combined organic layer was washed with brine, dried over anhydrous Na2SO4, and then concentrated in vacuo. The crude product was purified by column chromatography on silica gel with dichloromethane: ethanol (100∶2.5) as eluent to afford the product as a white solid (0.51 g, 68%). 1H NMR (500 MHz, CDCl3, 298 K, δ): 8.73 (s, 6H, tpy-H3′,5′), 8.71–8.68 (m, 6H, tpy-H6,6″), 8.65 (dd, J = 7.9, 1.1 Hz, 6H, tpy-H3,3″), 7.86–7.83 (m, 9H, tpy-H4,4″, Ph-Ho), 7.82–7.78 (m, 6H, Ph-Hj), 7.77–7.71 (m, 12H, Ph-Hn and Ph-Hm), 7.58–7.52 (m, 6H, Ph-Hl), 7.35–7.30 (m, 12H, Ph-Hi and tpy-H5,5″), 7.27 (m, 6H, Ph-Hk), 7.03 (d, J = 1.4 Hz, 6H, Ph-Ha and Ph-Hb), 4.12 (td, J = 6.6, 4.4 Hz, 12H, Alkyl-Hc and Alkyl-Hc′), 1.88 (m, 12H, Alkyl-Hd and Alkyl-Hd′), 1.52 (m, 12H, Alkyl-He and Alkyl-He′), 1.38 (m, 24H, Alkyl-Hf, Alkyl-Hg, Alkyl-Hf′, and Alkyl-Hg′), 0.95–0.89 (m, 18H, Alkyl-Hh and Alkyl-Hh′). 13C NMR (125 MHz, CDCl3, 298 K, δ): 156.35, 155.98, 150.01, 149.22, 148.76, 148.63, 142.58, 142.08, 140.67, 139.99, 138.50, 137.00, 136.23, 132.83, 132.48, 130.65, 130.54, 127.78, 127.58, 127.05, 126.75, 125.03, 123.95, 121.46, 118.81, 116.18, 31.76, 29.44, 25.89, 22.80, 14.22. MALDI-TOF-MS (m/z): calcd for [C159H153N9O6+H]+, 2285.2; found, 2285.2. Synthesis of ligand LBH Compound 3 (1.2 g, 2.0 mmol), 1,3,5-tris(4-bromophenyl)benzene (0.31 g, 0.57 mmol), Pd(PPh3)2Cl2 (70 mg, 0.1 mmol), and sodium carbonate (1.59 g, 15 mmol) were added into a 100 mL Schlenk flask. Toluene (30 mL), H2O (15 mL), and tert-butyl alcohol (5 mL) were added under N2. The mixture was stirred at 85 °C for 3 days. After cooling to room temperature, the solvent was removed under vacuum, and the residue was extracted with CHCl3. The combined organic layer was washed with brine, dried over anhydrous Na2SO4, and then concentrated in vacuo. The crude product was purified by column chromatography on silica gel with dichloromethane: ethanol (100∶2.5) as eluent to afford the product as a white solid (0.62 g, 65%). 1H NMR (500 MHz, CDCl3, 298 K, δ): 8.73 (s, 6H, tpy-H3′,5′), 8.69 (dd, J = 4.9, 1.7 Hz, 6H, tpy-H6,6″), 8.65 (d, J = 7.9 Hz, 6H tpy-H3,3″), 7.87–7.79 (m, 15H, tpy-H4,4″, Ph-Hk and Ph-Ha), 7.75 (m, 12H, Ph-Hj and Ph-Hi), 7.57 (d, J = 8.0 Hz, 6H, Ph-Hh), 7.54–7.52 (m, 6H, Ph-Hd and Ph-Hc), 7.51–7.46 (m, 6H, Ph-Hf and Ph-He), 7.35 (d, J = 8.2 Hz, 6H, Ph-Hb), 7.30 (m, 12H, tpy-H5,5″ and Ph-Hg). 13C NMR (125 MHz, CDCl3, δ): 156.38, 156.02, 149.99, 149.23, 142.55, 142.09, 140.61, 140.31, 140.05, 138.85, 136.98, 136.61, 130.86, 130.59, 130.49, 127.97, 127.79, 127.60, 127.10, 126.78, 125.04, 123.94, 121.47, 118.87, 77.42, 77.16, 76.91. MALDI-TOF-MS (m/z): calcd for [C123H81N9]+, 1683.7; found, 1683.7. Synthesis of ligand LC Compound 6 (1.0 g, 1.27 mmol), hexa(4-bromophenyl)-benzene (163 mg, 0.16 mmol), Pd(PPh3)4 (72 mg, 0.064 mmol), and sodium carbonate (1.59 g, 15 mmol) were added into a 100 mL Schlenk flask. Toluene (30 mL), H2O (15 mL), and tert-butyl alcohol (5 mL) were added under N2. The mixture was stirred at 85 °C for 6 days. After cooling to room temperature, the solvent was removed under vacuum, and the residue was extracted with CHCl3. The combined organic layer was washed with brine, dried over anhydrous Na2SO4, and then concentrated in vacuo. The crude product was purified by column chromatography on silica gel with dichloromethane: ethanol (100∶3.5) as eluent to afford the product as a white solid (251 mg, 35%). 1H NMR (500 MHz, CDCl3, 298 K, δ): 8.60 (s, 12H, tpy-H3′,5′), 8.56 (d, J = 4.8 Hz, 12H, tpy-H6,6″), 8.52 (d, J = 8.0 Hz, 12H, tpy-H3,3″), 7.74 (td, J = 7.8, 1.8 Hz, 12H, tpy-H4,4″), 7.63 (d, J = 7.9 Hz, 12H, Ph-Hj), 7.28 (m, 12H, Ph-Hn), 7.16 (m, 36H, tpy-H5,5″, Ph-Hi and Ph-Hl), 7.00 (d, J = 8.2 Hz, 12H, Ph-Hm), 6.93 (s, 6H, Ph-Ha), 6.89–6.83 (m, 18H, Ph-Hk and Ph-Hb), 4.08–3.96 (m, 24H, Alkyl-Hc and Alkyl-Hc′), 1.87–1.77 (m, 24H, Alkyl-Hd and Alkyl-Hd′), 1.51–1.42 (m, 24H, Alkyl-He and Alkyl-He′), 1.39–1.29 (m, 48H, Alkyl-Hf, Alkyl-Hg, Alkyl-Hf′, and Alkyl-Hg′), 0.92–0.83 (m, 36H, Alkyl-Hh and Alkyl-Hh′). 13C NMR (125 MHz, CDCl3, δ): 156.16, 155.70, 149.55, 148.95, 148.61, 148.35, 142.32, 139.88, 138.53, 136.68, 135.78, 132.81, 131.83, 130.35, 130.00, 129.45, 126.74, 126.34, 125.23, 125.22, 123.64, 121.21, 118.50, 116.25, 116.24, 115.63, 31.59, 29.28, 25.73, 22.61, 14.03. MALDI-TOF-MS (m/z): calcd for [C312H300N18O12+H]+, 4491.3; found, 4491.3. Synthesis of ligand LCH Compound 3 (1.5 g, 2.6 mmol), hexa(4-bromophenyl)-benzene (328 mg, 0.33 mmol), Pd(PPh3)4 (150 mg, 0.13 mmol), and sodium carbonate (1.59 g, 15 mmol) were added into a 100 mL Schlenk flask. Toluene (30 mL), H2O (15 mL), and tert-butyl alcohol (4 mL) were added under N2. The mixture was stirred at 85 °C for 6 days. After cooling to room temperature, the solvent was removed under vacuum, and the residue was extracted with CHCl3. The combined organic layer was washed with brine, dried over anhydrous Na2SO4, and then concentrated in vacuo. The crude product was purified by column chromatography on silica gel with dichloromethane: ethanol (100∶3.5) as eluent to afford the product as a white solid (0.47 g, 43%). 1H NMR (500 MHz, CDCl3, 298 K, δ): 8.59 (s, 12H, tpy-H3′,5′), 8.58–8.55 (m, 12H, tpy-H6,6″), 8.51 (d, J = 8.0 Hz, 12H, tpy-H3,3″), 7.74 (td, J = 7.7, 1.8 Hz, 12H, tpy-H4,4″), 7.64 (d, J = 8.1 Hz, 12H, Ph-Ha), 7.43–7.34 (m, 18H, Ph-Hc, Ph-Hd, and Ph-He), 7.30 (d, J = 7.4 Hz, 6H, Ph-Hf), 7.29 (s, 12H, Ph-Hj), 7.19 (ddd, J = 7.5, 4.7, 1.2 Hz, 12H, tpy-H5,5″), 7.15 (d, J = 8.0 Hz, 12H, Ph-Hb), 7.11 (d, J = 8.0 Hz, 12H, Ph-Hh), 6.99 (d, J = 8.1 Hz, 12H, Ph-Hi), 6.86 (d, J = 8.0 Hz, 12H, Ph-Hg). 13C NMR (125 MHz, CDCl3, δ): 156.26, 155.82, 149.66, 149.09, 142.44, 140.36, 140.25, 139.90, 139.83, 138.97, 137.07, 136.84, 136.24, 131.96, 130.94, 130.78, 130.41, 130.08, 127.82, 127.10, 126.92, 126.50, 125.41, 123.80, 121.38, 118.68. MALDI-TOF-MS (m/z): calcd. for [C240H156N18]+, 3289.3; found, 3289.3 Synthesis of complex SA To a solution of ligand LA (10.0 mg, 6.5 μmol) in CHCl3 (3 mL), a solution of Zn(NO3)2·6H2O (1.9 mg, 6.4 μmol) in MeOH (9 mL) was added. The mixture was stirred at 50 °C for 8 h and then cooled to room temperature. Upon addition of NH4PF6 (100 mg), a precipitate was formed and washed with water to give a white product (10.6 mg). 1H NMR (500 MHz, CD3CN, 298 K, δ): 8.95 (s, 8H, tpy-H3′,5′), 8.68 (d, J = 8.1 Hz, 8H, tpy-H3,3″), 8.10–8.14 (m, 16H, tpy-H4,4″, Ph-Hj), 7.79 (m, 32H, tpy-H6,6″, Ph-Hm, Ph-Hn, and Ph-Ho), 7.65 (d, J = 8.0 Hz, 8H, Ph-Hl), 7.57 (d, J = 8.1 Hz, 8H, Ph-Hi), 7.36 (m, 16H, Ph-Hk and tpy-H5,5″), 7.13 (s, 4H, Ph-Ha), 7.10 (s, 4H, Ph-Hb), 4.14 (q, J = 6.9 Hz, 16H, Alkyl-Hc and Alkyl-Hc′), 1.84 (m, 16H, Alkyl-Hd and Alkyl-Hd′), 1.53 (m, 16H, Alkyl-He and Alkyl-He′), 1.42–1.36 (m, 32H, Alkyl-Hf, Alkyl-Hg, Alkyl-Hf′, and Alkyl-Hg′), 0.98–0.90 (m, 24H, Alkyl-Hh and Alkyl-Hh′). 13C NMR (125 MHz, CD3CN, 298 K, δ) 155.50, 149.77, 149.05, 148.62, 147.94, 147.84, 144.94, 141.63, 141.14, 140.79, 139.64, 139.57, 138.16, 133.55, 132.72, 131.60, 131.25, 130.69, 127.84, 127.48, 127.43, 127.22, 126.43, 124.66, 123.16, 120.99, 116.11, 31.34, 29.13, 25.53, 22.40, 13.36. ESI-MS (m/z): 1760.3 [M-2PF6−]2+ (calcd: 1760.3), 1125.0 [M-3PF6−]3+ (calcd: 1125.0), 807.5 [M-4PF6−]4+ (calcd: 807.5). Synthesis of complex SB To a solution of ligand LB (8.0 mg, 3.5 μmol) in CHCl3 (3 mL), a solution of Zn(NO3)2·6H2O (1.6 mg, 5.4 μmol) in MeOH (9 mL) was added. The mixture was stirred at 50 °C for 8 h and then cooled to room temperature. Upon addition of NH4PF6 (100 mg), a precipitate was formed and washed with water to give a white product (9.1 mg). 1H NMR (500 MHz, CD3CN, 298 K, δ): 8.94 (s, 12H, tpy-H3′,5′), 8.67 (d, J = 8.1 Hz, 12H, tpy-H3,3″), 8.11 (d, J = 7.8 Hz, 24H, tpy-H4,4″ and Ph-Hj), 7.98–7.86 (m, 18H, Ph-Ho and Ph-Hn), 7.78 (m, 24H, Ph-Hm and Ph-Hl), 7.63 (d, J = 7.7 Hz, 12H, tpy-H6,6″), 7.56 (d, J = 8.0 Hz, 12H, Ph-Hi), 7.34 (m, 24H, Ph-Hk and tpy-H5,5″), 7.14 (s, 6H, Ph-Ha), 7.09 (s, 6H, Ph-Hb), 4.19–4.06 (m, 24H, Alkyl-Hc and Alkyl-Hc′), 1.84 (s, 24H, Alkyl-Hd and Alkyl-Hd′), 1.53 (s, 24H, Alkyl-He and Alkyl-He′), 1.42–1.36 (m, 48H, Alkyl-Hf, Alkyl-Hg, Alkyl-Hf′ and Alkyl-Hg′), 0.96–0.90 (m, 36H, Alkyl-Hh and Alkyl-Hh′). ESI-MS (m/z): 1734.1 [M-3PF6−]3+ (calcd: 1734.1), 1264.5 [M-4PF6−]4+ (calcd: 1264.5), 982.4 [M-5PF6−]5+ (calcd: 982.4), 794.5 [M-6PF6−]6+ (calcd: 794.5). Synthesis of complex SBH To a solution of ligand LBH (10.0 mg, 5.9 μmol) in CHCl3 (3 mL), a solution of Zn(NO3)2·6H2O (2.6 mg, 8.9 μmol) in MeOH (9 mL) was added. The mixture was stirred at 50 °C for 8 h and then cooled to room temperature. Upon addition of NH4PF6 (100 mg), a precipitate was formed and washed with water to give a white product (11.8 mg). 1H NMR (500 MHz, CD3CN, 298 K, δ): 8.95 (s, 12H, tpy-H3′,5′), 8.67 (d, J = 8.1 Hz, 12H, tpy-H3,3″), 8.15–8.06 (m, 24H, Ph-Ha and tpy-H4,4″), 7.96 (s, 6H, Ph-Hk), 7.90 (d, J = 8.0 Hz, 12H, Ph-Hj), 7.78 (m, 24H, tpy-H6,6″ and Ph-Hi), 7.66 (d, J = 8.0 Hz, 12H, Ph-Hh), 7.63–7.56 (m, 36H, Ph-Hd, Ph-Hc, Ph-He, Ph-Hb, and Ph-Hf), 7.38 (d, J = 8.0 Hz, 12H, Ph-Hg), 7.34 (dd, J = 7.7, 5.2 Hz, 12H, tpy-H5,5″). 13C NMR (125 MHz, CD3CN, 298 K, δ) 149.79, 147.96, 144.92, 141.62, 141.16, 140.77, 140.04, 139.24, 138.49, 136.69, 135.19, 134.83, 134.01, 133.67, 131.14, 130.70, 130.58, 128.53, 128.07, 127.84, 127.58, 127.44, 127.26, 126.49, 124.67, 123.17, 121.11. ESI-MS (m/z): 1333.6 [M-3PF6−]3+ (calcd: 1333.6), 963.7 [M-4PF6−]4+ (calcd: 963.7), 742.0 [M-5PF6−]5+ (calcd: 742.0), 594.1 [M-6PF6−]6+ (calcd: 594.1). Synthesis of complex SC To a solution of ligand LC (6.0 mg, 1.34 μmol) in CHCl3 (2 mL), a solution of Zn(NO3)2·6H2O (1.2 mg, 4.0 μmol) in MeOH (6 mL) was added. The mixture was stirred at 50 °C for 8 h and then cooled to room temperature. Upon addition of NH4PF6 (80 mg), a precipitate was formed and washed with water to give a white product (6.8 mg, 92%). 1H NMR (500 MHz, CD3CN, 298 K, δ): 8.74 (s, 24H, tpy-H3′,5′), 8.59 (d, J = 8.0 Hz, 24H, tpy-H3,3″), 8.04 (t, J = 7.6 Hz, 24H, tpy-H4,4″), 7.70 (d, J = 5.0 Hz, 24H, tpy-H6,6″), 7.61 (d, J = 7.8 Hz, 24H, Ph-Hj), 7.44–7.39 (m, 48H, Ph-Hn and Ph-Hl), 7.30–7.21 (m, 72H, Ph-Hk, Ph-Hi, and tpy-H5,5″), 7.15 (d, J = 7.9 Hz, 24H, Ph-Hm), 6.97 (m, 24H, Ph-Ha and Ph-Hb), 4.05 (s, 48H, Alkyl-Hc and Alkyl-Hc′), 1.77 (d, J = 8.7 Hz, 48H, Alkyl-Hd and Alkyl-Hd′), 1.46 (s, 48H, Alkyl-He and Alkyl-He′), 1.33 (s, 96H, Alkyl-Hf, Alkyl-Hg, Alkyl-Hf′, and Alkyl-Hg′), 0.88 (s, 72H, Alkyl-Hh and Alkyl-Hh′). 13C NMR (125 MHz, CD3CN, 298 K, δ) 156.28, 155.59, 154.36, 148.69, 147.74, 140.82, 140.33, 140.28, 137.96, 135.66, 135.08, 132.48, 130.42, 129.12, 127.34, 127.22, 126.96, 126.00, 125.76, 122.80, 31.33, 29.16, 25.53, 25.30, 13.16. ESI-MS (m/z): 2079.1 [M-5PF6−]5+ (calcd: 2079.1), 1708.2 [M-6PF6−]6+ (calcd: 1708.2), 1443.6 [M-7PF6−]7+ (calcd: 1443.6), 1244.9 [M-8PF6−]8+ (calcd: 1244.9), 1090.6 [M-9PF6−]9+ (calcd: 1090.6), 966.8 [M-10PF6−]10+ (calcd: 966.8). Synthesis of complex SCH To a solution of ligand LCH (6.0 mg, 1.82 μmol) in CHCl3 (2 mL), a solution of Zn(NO3)2·6H2O (1.6 mg, 5.4 μmol) in MeOH (6 mL) was added. The mixture was stirred at 50 °C for 8 h and then cooled to room temperature. Upon addition of NH4PF6 (80 mg), a precipitate was formed and washed with water to give a white product (7.1 mg, 90%). 1H NMR (500 MHz, CD3CN, 298 K, δ): 8.75 (s, 24H, tpy-H3′,5′), 8.60 (d, J = 8.1 Hz, 24H, tpy-H3,3″), 8.05 (td, J = 7.7, 1.6 Hz, 24H, tpy-H4,4″), 7.70 (d, J = 4.8 Hz, 24H, tpy-H6,6″), 7.59 (d, J = 7.9 Hz, 24H, Ph-Ha), 7.47 (m, 72H, Ph-Hj, Ph-Hi, and Ph-Hh), 7.41 (dd, J = 8.4, 1.9 Hz, 12H, Ph-Hc), 7.31 (dd, J = 8.3, 1.9 Hz, 12H, Ph-He), 7.28–7.25 (m, 36H, Ph-Hd and Ph-Hb), 7.23 (dd, J = 7.4, 5.2 Hz, 24H, tpy-H5,5″), 7.16 (m, 36H, Ph-Hg and Ph-Hf). 13C NMR (125 MHz, CD3CN, 298 K, δ) 155.91, 149.70, 147.94, 147.72, 144.17, 141.10, 140.25, 139.42, 138.54, 138.29, 136.82, 135.71, 134.17, 131.84, 131.83, 130.98, 130.76, 130.42, 128.53, 128.15, 127.65, 127.52, 126.07, 125.03, 124.84, 122.99, 121.31. ESI-MS (m/z): 1597.9 [M-5PF6−]5+ (calcd: 1597.9), 1307.6 [M-6PF6−]6+ (calcd: 1307.6), 1099.8 [M-7PF6−]7+ (calcd: 1099.8), 944.4 [M-8PF6−]8+ (calcd: 944.4), 823.4 [M-9PF6−]9+ (calcd: 823.4). Results and Discussion Synthesis, characterization, and interlocking study of complex SA The attempt to synthesis ligand LAH (without alkyl chain) was unsuccessful because of the poor solubility of LAH. To improve the solubility, alkyl chains were introduced into ligand LA. The 1H NMR spectra of ligand LA and corresponding complex SA exhibited one set of signals (Figures 1a and 1b, Supporting Information Figures S17 and S22), indicating the formation of a highly symmetrical structure.79 Compared with ligand LA, the 3′,5′-tpy protons of SA were shifted downfield due to the lower electron density after complexation,80 while the protons at the 6,6″ position of tpy were significantly shifted upfield (∼0.92 ppm) based on the electron shielding effect.64 The full assignments of 1H NMR were confirmed by detailed two-dimensional (2D) COSY (correlation spectroscopy). All NMR (1H, 13C, and COSY) and MALDI-TOF data of ligand LA and complex SA were shown in Supporting Information Figures S17–28. Figure 1 | 1H NMR (a–g) spectra (500 MHz, 298 K) of (a) LA in CDCl3, (b) SA-0.5 mg/mL, (c) SA-1.5 mg/mL, (d) SA-2.5 mg/mL, (e) SA-3.5 mg/mL, (f) SA-4.5 mg/mL, and (g) SA-5.5 mg/mL in CD3CN. Download figure Download PowerPoint Interestingly, the 1H NMR spectra changed significantly upon increasing the concentration of SA. Specifically, all protons on tpy gradually shifted upfield with increasing concentration from 0.5 to 5.5 mg/mL (Figures 1b–1g, and Supporting Information Figures S23 and S24), and a set of mixed signals appeared during this process (Figures 1d and 1e). Notably, the protons of the phenyl moieties on the LA axis (Hk, Hl, Hm, Hn, and Ho) exhibited a significant upfield shift compared with the other protons. Moreover, the protons on the corner phenyl group displayed an opposite trend: Hb gradually shifted upfield, while Ha moved downfield. Meanwhile, Hc′ and Hc presented a similar trend compared with Ha and Hb. These phenomena indicated that as the concentration increased, there existed obvious interactions between SA that influenced the electron cloud density. Furthermore, the diffusion-ordered NMR spectroscopy (DOSY) experiment was employed to measure the trend of the size change as further evidence; we observed a single band (log D = −9.38) at a lower concentration and another band (log D = −9.47) at a higher concentration. The experimental hydrodynamic radii (rH) calculated via the Stokes–Einstein equation were 1.4 nm at 0.5 mg/mL and 1.8 nm at 5.5 mg/mL ( Supporting Information Figures S29 and S30 and Table S2),81 suggesting an interlocked structure formed by two or more SA (Scheme 1) at high concentration. In addition, considering the steric hindrance of tpy, it is reasonable to speculate that the phenyl rings on the axis were stacked through π–π interaction to form interlocked structures, instead of the ring-in-ring assemblies. ESI-MS was used to detect the detailed molecular compositions of SA. In Figure 2a, only one prominent set of peaks with different charge states from 2+ to 4+ was observed at a concentration of 0.5 mg/mL due to the successive loss of a different number of PF6−. The isotope pattern of each peak matched well with the simulated isotope pattern of SA (Figure 2a and Supporting Information Figure S1) for the desired dimer with a molecular weight of 3805.3 Da. Upon concentrating SA (>0.5 mg/mL), a new peak at m/z 1379.1 for 5+ was observed (Figure 2b), which was exactly twice the molecular weight of SA, confirming the formation of [2]catenane ( SA-2). At a higher concentration, the appearance of the peak at m/z of 2141.2 for 5+ further confirmed the formation of [3]catenane ( SA-3) (Figure 2c and Supporting Information Figure S2). Figure 2 | (a) ESI-MS spectrum of complex SA at a concentration of 0.5 mg/mL. Calculated (top) and measured (bottom) isotope patterns for (b) [2]catenane (SA-2) and (c) [3]catenane (SA-3) at high concentration (PF6− as counterion). Download figure Download PowerPoint Synthesis, characterization, and interlocking study of complexes SB and SBH To further explore the effects of space constraints on the structure and function of the supramolecules, complex SB, based on tritopic ligand LB, was obtained through the same synthetic method as shown in Supporting Information Scheme S2. The 1H NMR spectrum of SB also showed one set of signals with similar chemical shifts to SA ( Supporting Information Figure S36). The protons at tpy-6,6″ shifted upfield (∼1.06 ppm) characteristically upon complexation because of the electron shielding effect, while almost all other peaks were shifted downfield. The assignments of other proton peaks were confirmed through the 2D COSY experiment. All NMR (1H, 13C, and COSY) and MALDI-TOF data of ligand LB and corresponding complex SB were shown in Supporting Information Figures S31–S41. The ESI-MS spectrum of complex SB displayed a series of continuous charge states from 3+ to 6+ ( Supporting Information Figure S3). The experimental m/z values and isotope patterns agreed well with the simulated results of SB with a molecular weight of 5637.2 Da. To detect the possible presence of overlapping isomers or conformers, TWIM-MS was introduced as an advanced level of MS analysis. As shown in Supporting Information Figure S14, each charge state showed a narrow drift time distribution, indicating no conformers or overlapping isomers of the assembly existed in this complex. We further investigated the concentration dependence of SB by using 1H NMR spe
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