Size-Selective Recognition by a Tubular Assembly of Phenylene

Sep 16, 2015 - Daiki Suzuki , Hajime Abe , and Masahiko Inouye ... Daiki Suzuki , Hajime Abe , Takaya Minami , Shinya Matsumoto , Masahiko Inouye...
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Size-Selective Recognition by a Tubular Assembly of Phenylene– Pyrimidinylene Alternated Macrocycle through Hydrogen-Bonding Interactions Duoduo Xiao, Dengqing Zhang, Beihua Chen, Dahai Xie, Yunjie Xiang, Xianying Li, and Wusong Jin Langmuir, Just Accepted Manuscript • DOI: 10.1021/acs.langmuir.5b02273 • Publication Date (Web): 16 Sep 2015 Downloaded from http://pubs.acs.org on September 22, 2015

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Size-Selective Recognition by a Tubular Assembly of Phenylene–Pyrimidinylene Alternated Macrocycle through Hydrogen-Bonding Interactions †











Duoduo Xiao, Dengqing Zhang, Beihua Chen, Dahai Xie, Yunjie Xiang, Xianying Li, *, and Wusong Jin*, †



State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of

Chemistry, Chemical Engineering and Biotechnology, Donghua University, 2999 North Renmin Road, Songjiang, Shanghai 201620, P. R. China. ‡

School of Environmental Science and Engineering, Donghua University, 2999 North Renmin

Road, Songjiang, Shanghai 201620, P. R. China. ABSTRACT. Study of artificial tubular assemblies as a useful host scaffold for size-selective recognition and release of guest molecules is an important subject in host–guest chemistry. We describe well-defined self-assembled nanotubes (NT6mer) formed from π-conjugated mphenylene–pyrimidinylene alternated macrocycle 16mer that exhibit size-selective recognition towards a specific aromatic acid. In a series of guest molecules, a size-matched trimesic acid (G3) gives inclusion complexes (NT6mer⊃G3) in dichloromethane resulting in an enhanced and red-shifted fluorescence. 1H NMR titration experiments indicated that the complex was formed

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in a 1:1 molar ratio. DFT calculations and the binding constant value (K = 1.499 × 105 M−1) of NT6mer with G3 suggested that the complex involved triple hydrogen-bonding interactions. The encapsulated guest G3 molecules can be readily released from the tubular channel through the dissociation of hydrogen bonding by the addition of a polar solvent such as DMSO. In contrast, 16mer could not form self-assembled nanotubes in CHCl3 or THF solution, leading to weak or no size-selective recognizability, respectively. INTRODUCTION Natural nanotubular assemblies display significant biological activities in vivo with high selectivity for ions and water.1–4 Inspired by such natural phenomena, the development of artificial size-selective recognizable channels using well-defined one-dimensional (1D) selfassembled nanotubes has become an important topic both for fundamental research and potential applications.5–14 The main challenge in synthetic tubular assemblies lies in their capability to selectively trap and rapidly release appointed guest molecules under specific conditions. From a fundamental point of view, shape-persistent and fully π-conjugated macrocycles possess structural superiority because they not only supply an intrinsic inner cavity for the guest molecules but also form 1D tubular objects through an intermolecular π–π interaction. Consequently, a variety of fully π-conjugated macrocyclic derivatives with different skeletons and cavities have been developed as efficient artificial building blocks.15–43 So far, by precision molecular design, fully π-conjugated macrocycles composed of porphine,30–32 pyridine,33–35 thiophene,21,25 carbazole,17,20,23,24,28 and other moieties with various internal cavities have been synthesized to respond to an external stimulus by means of well-known host–guest chemistry.36– 39

Most of these macrocycles show excellent self-assembly properties in solution forming various

nano-objects such as nanowires,18–21 spherical structures,40–42 tubular objects,43–45 as well as two-

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dimensional sheets. Therein, nanotubes possessing structural fascination with a uniform inner diameter and large 1D hollow channels are used in many applications including transporting materials, encapsulation of guest molecules, and as soft templates. Lyophilized nanotubes can encapsulate small-size guests in solution by capillary attraction to form inclusion complexes.46,47 However, systematic studies on precise size-selective recognition of the guest by self-assembled nanotubes with specific interactions is still limited. The pyrimidine ring, which possesses a high electron-affinity classic aromaticity, is basic, and has proton acceptor properties, is the most promising candidate for incorporation in functional molecules. Herein, a series of pyrimidinebased π-conjugated macrocycles, serving as building block to investigate their self-assembling behaviors, were synthesized for the first time. Among these macrocycles, 16mer (Scheme 1) can self-assemble into well-defined 1D nanotubes (NT6mer) in CH2Cl2. Interestingly, the NT6mer exhibits an unexpected size-selective recognition of trimesic acid (G3) and forms inclusion complexes (NT6mer⊃G3) through the intermolecular hydrogen-bonding interactions. The entrapped G3 can be readily released from the NT6mer channel through the addition of a drop of DMSO (Figure 1). EXPERIMENTAL SECTION Materials. Unless otherwise noted, all commercial reagents were used as received. Methallyl dichloride (98%, GC) was purchased from TCI (Tokyo Chemical Industry). 3,5-Dibromophenol was prepared according to a reported procedure.48 Tetrahydrofuran (THF) was refluxed over a mixture of Na and benzophenone under argon and distilled just before use. DMF was dried over CaH2 under argon and freshly distilled prior to use. CH2Cl2 was dried over CaH2 under argon and freshly distilled prior to use. CHCl3 was dried over molecular sieves and freshly distilled under argon before use.

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Synthesis and Purification of the Macrocyclic Derivatives. The Suzuki-coupling reaction between monomer 2 and 3 was carried out in THF/toluene under an argon atmosphere. The resulting mixture was extracted with chloroform. The organic phase was washed with water, dried over anhydrous MgSO4 and evaporated to dryness. The residue was subjected to column chromatography on silica gel (eluent: PE/EA = 3/1), giving the crude product as a white solid. The crude solid was purified using recycling preparative gel permeation chromatography (GPC, CHCl3 as eluent solution) to obtain macrocyclic derivatives 16mer, 18mer, 110mer, 112mer, and 114mer as white solids after six cycles (Figure S1), at a yield of 12%, 9%, 8%, 7%, and 5%, respectively. Self-assembly of 1. Compound 1 (1 mg) was dissolved in 2.8 mL of solvent (CH2Cl2, CHCl3 or THF) at room temperature. The resulting colorless transparent solution was kept at 25 °C for 24 h. The characterization of the self-assembled nanostructures was carried out using highresolution transmission electron microscopy (HR-TEM). The TEM samples were prepared by drop-casting the diluted solutions on a carbon-coated copper grid. TEM was recorded on a JEOL model JEM-2100 electron microscope operating at 200 kV. Atomic force microscopy (AFM) was performed on a SII Nanonavi E-Sweep microscope. Size-selective Recognition. Size-selective recognition by the NT6mer towards guests was detected by electronic absorption and fluorescence spectrometric titration. The concentration of the pre-prepared guests was 1 × 10−2 mol/L. Guests were added into the CH2Cl2 solutions of NT6mer (5 × 10−6 mol/L, 2 mL) by a gradual increase in the equivalence concentration. Electronic absorption spectra were recorded on a Persee model TU-1901 spectrophotometer, using a quartz cell (1-cm path length). Fluorescence spectroscopy was conducted using a quartz cell (1-cm path length) on a HORIBA model Fluoromax-4 spectrophotometer. Infrared (IR) spectra were recorded on a Varian 640 FT-IR spectrometer.

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Density Functional Theory (DFT) Calculations. All geometry optimizations of model compounds were performed with Gaussian 09 (Rev. D. 01) by DFT method using B3LYP functional and the 6-31G basis set.49 RESULTS AND DISCUSSION Synthesis of the Macrocycles. The one-pot Suzuki cross-coupling reaction between 2 and 3 (Scheme S1) simultaneously gave a series of m-phenylene–pyrimidinylene macrocyclic derivatives 16mer–114mer (Scheme 1). The 1H NMR spectrum of 16mer in CDCl3 (25 °C) displayed five highly resolved singlet signals in the aromatic region corresponding to the skeleton protons (Figure 2a(i) and Figure S20) indicative of a symmetric proton environment and assigned to a cyclic structure of 16mer. The other macrocycles derivatives were also unambiguously characterized by 1H NMR spectroscopy (Figure S24–S31) and MALDI-TOF mass spectrometry (Figure S2). Self-assembly of 1. Shape-persistent and fully π-conjugated macrocycles tend to form 1D nanotubes through an intermolecular π-π interaction.44–46 The electronic absorption spectrum of 16mer in CH2Cl2 even at a dilute concentration (1 × 10−6 mol/L) at 25 °C showed a structureless peak around 297 nm and a peak with a slight shoulder near 350 nm (Figure 2c). Without a further distinct blue- or red-shift, the absorption intensity enhanced as the concentration of 16mer increased from 1 × 10−6 to 1 × 10−5 mol/L (Figure 2c). Macrocycle 16mer has weak dark blue fluorescence in a dilute CH2Cl2 solution (5 × 10−6 mol/L) with an emission maximum centered at 372 nm (Figure 2d). The 1H NMR spectrum of 16mer in CD2Cl2 (1 × 10−3 mol/L) at 25 °C displayed a broadening of the aromatic proton signals (Figure 2a(iii) and Figure S21), and concentration-dependent 1H NMR spectra of NT6mer in CD2Cl2 showed chemical-shift variations with increasing concentration of 16mer (from 0.6 × 10−3 to 3 × 10−3 mol/L) at room temperature

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(Figure S3), which proved the existence of strong intermolecular interactions between the macrocycles. The TEM micrograph suggested that 16mer could self-assemble into well-defined nanotubular structures (NT6mer) in CH2Cl2 with a few hundred nanometers in length and uniform diameters of 1.5–1.6 nm (Figure 2b). Furthermore, from the AFM image of NT6mer (Figure S4), we observed bundled and crossed nanotubes. The height of the nanotubes measured by AFM was ~1.6 nm. DFT calculations indicated that 16mer most likely adopts a slightly twisted saddleshaped structure. The diameter of the nanotubes is slightly smaller than the calculated value (1.7 nm, Figure S18) probably because of this skeletal distortion. Notably, the self-assembly behavior of macrocycle 16mer is strongly dependent on the solvent because 16mer is composed of hydrophobic segments, which are sensitive to the polarity changes of solvents. For example, CH2Cl2 and CHCl3 are halogenated solvents with different polarity, leading to different self-assembly behavior of 16mer. There are five resolved signals displayed in the 1H NMR spectra of 16mer in CDCl3 (1 × 10−3 mol/L) at 25 °C (Figure 2a(i)), which indicated that macrocycle 16mer is highly dispersed in CHCl3. TEM measurement confirmed that no nanoobjects were formed in CHCl3 (Figure S5a). Although slightly broadened signals appeared in the 1

H NMR spectrum in THF-d8 (1 × 10−3 mol/L) at 25 °C (Figure 2a(ii) and Figure S22), the TEM

micrograph of an air-dried sample (5 × 10−6 mol/L) showed formation of amorphous aggregates rather than ordered aggregates (Figure S5b). For the other macrocycles (18mer, 110mer, 112mer, and 114mer), which have a different polarity to 16mer owing to the increased macrocyclic skeleton and side chains, we did not observe assembly of nanotubes in CH2Cl2 (Figure S6), probably because the polarity of CH2Cl2 might not be suitable for the formation of nanotubes from these macrocycles.

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Size-selective recognition properties of NT6mer. Because of the essential basic character of the nitrogen atoms of the pyrimidine ring, pyrimidine derivatives often act as an excellent protonacceptor and easily combine with various proton-donating groups such as carboxylic acids and amino groups through hydrogen bonds.50−51 Here, the self-assembled nanotubes are composed of numerous, highly ordered pyrimidine units, and are expected to incorporate proton-donors to form inclusion complexes through hydrogen-bonding interactions. For the complexation studies of self-assembled nanotube NT6mer, we chose some aromatic carboxylic acid derivatives as potential proton-donors (Figure 1a). When a small-size G1 (benzoic acid) was added to NT6mer in CH2Cl2, the 1H NMR spectrum in CD2Cl2 solution (2 × 10−3 mol/L) corresponding to aromatic proton signal of the pyrimidine ring at 9.10 ppm slightly decreased with increasing amounts of G1 from 0 to 50 equivalents (Figure 3e). In contrast, the fluorescence spectra showed little change (Figure S7). These results suggest negligible interaction between NT6mer and G1. A similar result was obtained for G2 (isophthalic acid) (Figure S8). To our surprise, when G3 (trimesic acid, 1 × 10−2 mol/L in THF) was mixed with NT6mer in CH2Cl2, significant spectral changes were observed, which indicated that G3 interacts with NT6mer. Because of the insolubility of G3 in CH2Cl2, we pre-prepared a THF solution of G3. When 0−2 µL (0−2 equiv.) G3 THF solution was titrated into a 2 mL CH2Cl2 solution of NT6mer (5 × 10−6 M), the electronic absorption showed a stepwise red-shift in response to increased G3 concentration from 0.25 to 1 equivalents with an isosbestic point at 312 nm (Figure 4a). The electronic absorption no longer changed after the addition of more than 1 equivalent of G3. Meanwhile, the fluorescence emission band at 372 nm gradually red-shifted to 445 nm upon

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addition of G3 from 0.25 to 1 equivalents, and bright blue fluorescence was visible under ultraviolet irradiation at 356 nm (Figure 4b). The fluorescence intensity was saturated at 1 equivalent of G3, and no further spectral change was found even at 2 equivalents of G3. The TEM micrograph of an air-dried sample of CH2Cl2 solution of NT6mer in the presence of G3 displayed a tubular structure with an identical diameter to that of the original NT6mer (Figure 3b). Moreover, there was no dramatic interference for the interaction of NT6mer with G3 even in the presence of a large amount of G1 (600 equiv) (Figure S9). When a bulkier sized G5 (4,4'biphenyldicarboxylic acid) and G6 (4,4',4''-benzene-1,3,5-triyltribenzoic acid) were used as proton-donors, no such spectral changes were observed (Figure S10 and S11). These observations indicated that the complexation of NT6mer with various proton-donors is sizeselective. The diameter size of G3 is about ~8.4 Å,52 which matched well with the inner cavity size of ~1.4 nm for 16mer (Figure 1b). The incorporated G3 molecules in the macrocycle interacted with the nitrogen atoms of the pyrimidine rings to form an inclusion complex (NT6mer⊃G3). Compared with G3, the size of G2 mismatched with the size of the channel of NT6mer. The smaller G2 did not combine with NT6mer to form a stable system, which implies that the size effect played an important role in the formation of complex system. Furthermore, the fluorescence spectra was virtually unchanged when G4 (trimethyl benzene1,3,5-tricarboxylate), an esterification product of G3, was used (Figure 3f). The contrasting observations indicated that the complexation between NT6mer and G3 most probably results from the formation of multiple hydrogen bonds (Figure 5). This conclusion was further supported by the following experimental result. When a drop of DMSO, a strongly competing solvent for hydrogen bonding,53-55 was added to the NT6mer in CH2Cl2 solution, there was no complexation

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between NT6mer and G3 (Figure S12) and the nanotube structure of NT6mer was not destroyed after adding DMSO. In sharp contrast, when G3 was added into a CHCl3 solution of 16mer, a weak force between the highly dispersed 16mer and G3 was demonstrated by the unremarkable changes of fluorescent (Figure 4c) and 1H NMR spectra (Figure 3c). Furthermore, no distinct spectral changes in THF (Figure 4d) indicated irregular aggregates of 16mer did not exhibit size-selective recognition of G3. Using other macrocycles 18mer, 110mer, 112mer and 114mer as hosts, size-selective recognition was not observed in the solvents mentioned above (Figure S13). To determine the stoichiometry of the complexation, 1H NMR spectrometric titration of NT6mer with G3 was conducted in CD2Cl2 (3 × 10-3 mol/L) at 25 °C (Figure 3a). The NT6mer showed stepwise spectral changes in response to [G3]/[16mer] at 0-1.25 equiv. The proton signal of the pyrimidine ring around 9.10 ppm was significantly stepwise decreased and slightly shifted downfield upon addition of G3. At 1.25 equivalents of G3, this signal completely disappeared, and the spectrum no longer changed even with addition of up to 2 equivalents of G3. Considering the dynamic nature of self-assembly as well as the fact that the cavity of 16mer is only big enough to accommodate one molecule of G3, we conclude that the rational inclusion complex (NT6mer⊃G3) is formed according to a 16mer/G3 ratio of 1:1 (Figure 5). Formation of the 1: 1 complex was further confirmed by the linear Benesi-Hildebrand equation.56 The measured absorbance [1/(A-A0)] at 297 nm showed a linear relationship with a change of 16mer /[G3], and the association constant value was found to be (1.499 ± 0.255) × 105 M-1 (Figure S14), which might be expected for a complex that contains multiple hydrogen-bond interactions.57 The infrared spectra are shown in Figure S15. The O-H vibrations of G3 in the range of 3200 to 2500 cm-1 in the infrared spectrum disappeared indicated hydrogen bonding

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interactions. Together with red-shifting of the C=O vibration from 1718 to 1710 cm-1, we can conclude that G3 was encapsulated into the cavity of NT6mer through hydrogen bonding. According to the DFT calculations (Figure S19), G3 can insert into the cavity of macrocycle 16mer through triple hydrogen bonding between carboxyl groups and nitrogen atoms of pyrimidine. The entrapped G3 can be completely released from the inclusion complex through dissociation of the hydrogen bond (Figure 5). Typically, when a drop of DMSO was added into NT6mer⊃G3, the bright blue emission disappeared, and the fluorescence emission band at 445 nm immediately changed back to the initial value of 372 nm (Figure S16). This implied that the hydrogen bonds between NT6mer and G3 dissociated. As shown in Figure 3a, the proton signals corresponding to the pyrimidine rings appeared again, and the chemical shift value slightly shifted slightly upfield to 9.05 ppm. Meanwhile, a new proton signal at 8.81 ppm appeared, which was assigned to the aromatic proton of free G3 in the presence of DMSO according to the control experiment (Figure 3a). The TEM micrograph of the resulting material showed that the addition of DMSO did not destroy the nanotubular structure of NT6mer after the release of G3 (Figure S17). CONCLUSIONS A series of shape-persistent and fully π-conjugated m-phenylene−pyrimidinylene alternated macrocycles have been successfully synthesized by a one-pot Suzuki-coupling reaction. We obtained well-defined, self-assembled nanotubes NT6mer using 16mer as a building block in CH2Cl2. The basic channel of the NT6mer could size-selectively recognize the size-matched trimesic acid (G3) to form the inclusion complexes NT6mer⊃G3 through multiple hydrogen bonds. The entrapped G3 could be released by simple disassociation of the hydrogen bonds. The

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unique size-selective feature of the NT6mer makes it attractive as a scaffold for post modifications with functional guest molecules to construct stimuli-responsive materials. ASSOCIATED CONTENT Supporting Information. Details of synthesis and characterization of macrocycles 1, MALDITOF mass, NMR, IR and fluorescence spectra, TEM micrographs, AFM images and DFT profiles. This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author [email protected], [email protected] Notes The authors declare no completing financial interest ACKNOWLEDGMENT This work was supported by National Foundation of Natural Science in China (No. 21172035), Research Fund for the Doctoral Program of Higher Education of China (No.2012007511001), Chinese Universities Scientific Fund (No.CUSF-DH-D-201437) and The Science and Technology Commission of Shanghai Municipality (No.12JC1400200). REFERENCES (1) Eisenberg, B. Ionic Channels in Biological Membranes: Natural Nanotubes. Acc. Chem. Res. 1998, 31, 117-123. (2) Montenegro, J.; Ghadiri, M. R.; Granja, J. R. Ion Channel Models Based on SelfAssembling Cyclic Peptide Nanotubes. Acc. Chem. Res. 2013, 46, 2955-2965.

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(12) Shimizu, T.; Masuda, M.; Minamikawa, H. Supramolecular Nanotube Architectures Based on Amphiphilic Molecules. Chem. Rev. 2005, 105, 1401-1443. (13) Ajayaghosh, A.; Praveen, V. K. π-Organogels of Self-Assembled p-Phenylenevinylenes: Soft Materials with Distinct Size, Shape, and Functions. Acc. Chem. Res. 2007, 40, 644-656. (14) Kim, Y.; Shin, S.; Lee, M. Development of Toroidal Nanostructures by Self-Assembly: Rational Designs and Applications. Acc. Chem. Res. 2013, 46, 2888-2897. (15) Höger, S. Shape-Persistent Macrocycles: From Molecules to Materials. Chem. Eur. J. 2004, 10. 1320-1329. (16) Dsouza, R. N.; Pischel, U.; Nau, W. M. Fluorescent Dyes and Their Supramolecular Host/Guest Complexes with Macrocycles in Aqueous Solution. Chem. Rev. 2011, 111, 79417980. (17) Zang, L.; Che, Y.; Moore, J. S. One-Dimensional Self-Assembly of Planar π-Conjugated Molecules: Adaptable Building Blocks for Organic Nanodevices. Acc. Chem. Res. 2008, 41, 1596-1608. (18) Zhang, W.; Moore, J. S. Shape-Persistent Macrocycles: Structures and Synthetic Approaches from Arylene and Ethynylene Building Blocks. Angew. Chem., Int. Ed. 2006, 45, 4416-4439. (19) Iyoda, M.; Yamakawa, J.; Rahman, M. J. Conjugated Macrocycles: Concepts and Applications. Angew. Chem., Int. Ed. 2011, 50, 10522-10554. (20) Jin, Y.; Wang, Q.; Taynton, P.; Zhang, W. Dynamic Covalent Chemistry Approaches Toward Macrocycles, Molecular Cages, and Polymers. Acc. Chem. Res. 2014, 47, 1575-1586. (21) Morrison, D. L.; Höger, S. Shape-persistent macrocyclic amphiphiles: molecular reversible coats. Chem. Commun.1996, 2313-2314.

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(22) Kakao, K.; Nishimura, M.; Tamachi, T.; Kuwatani, Y.; Miyasaka, H.; Nishinaga, T.; Iyoda, M. Giant Macrocycles Composed of Thiophene, Acetylene, and Ethylene Building Blocks. J. Am. Chem. Soc. 2006, 28, 16740-16747. (23) Schmaltz, B.; Rouhanipour, A.; Räder, H. J.; Pisula, W.; Müllen, K. Filling the Cavity of Conjugated Carbazole Macrocycles with Graphene Molecules: Monolayers Formed by Physisorption Serve as a Surface for Pulsed Laser Deposition. Angew. Chem., Int. Ed. 2009, 48, 720-724. (24) Finke, A. D.; Gross, D. E.; Moore, J. S. Engineering Solid-State Morphologies in Carbazole_Ethynylene Macrocycles. J. Am. Chem. Soc. 2011, 133, 14063-14070. (25) O’Sullivan, M. C.; Sprafke, J. K.; Kondratuk, D. V.; Rinfray, C.; Claridge, T. D. W.; Saywell, A.; Blunt, M. O.; O’Shea, J. N.; Beton, P. H.; Malfois, M.; Anderson, H. L. Vernier templating and synthesis of a 12-porphyrin nano-ring. Nature 2011, 469, 72-75. (26) Iyoda, K.; Tanaka, K.; Shimizu, H.; Hasegawa, M.; Nishinaga, T.; Nishiuchi, T.; Kunugi, Y.; Ishida, T.; Otani, H.; Sato, H.; Inukai, K.; Tahara, K.; Tobe, Y. Multifunctional π-Expanded Macrocyclic Oligothiophene 6-Mers and Related Macrocyclic Oligomers. J. Am. Chem. Soc. 2014, 136, 2389-2396. (27) Lee, S.; Chen, C.-H.; Flood, A. H. A pentagonal cyanostar macrocycle with cyanostilbene CH donors binds anions and forms dialkylphosphate [3]rotaxanes Nature Chem. 2013, 5, 704-710. (28) Aggarwal, A. V.; Thiessen, A.; Idelson, A.; Kalle, D.; Würsch, D.; Stangl, T.; Steiner, F.; Jester, S.-S.; Vogelsang, J.; Höger, S.; Lupton, J. M. Fluctuating exciton localization in giant πconjugated spoked-wheel macrocycles Nature Chem. 2013, 5, 964-970.

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(29) Li, S.; Huang, J.; Zhou, F.; Cook, T. R.; Yan, X.; Ye, Y.; Zhu, B.; Zheng, B.; Stang, P. J. Self-Assembly of Triangular and Hexagonal Molecular Necklaces. J. Am. Chem. Soc. 2014, 136, 5908-5911. (30) Sugiura, K.-i.; Fujimoto, Y.; Sakata, Y. A porphyrin square: synthesis of a square-shaped π-conjugated porphyrin tetramer connected by diacetylene linkages. Chem. Commun. 2000,11051106. (31) Kato, A.; Sugiura, K.; Miyasaka, H.; Tanaka, H.; Kawai, T.; Sugimoto, M.; Yamashita, M. A Square Cyclic Porphyrin Dodecamer: Synthesis and Single-Molecule Characterization. Chem. Lett. 2004, 33, 578-579. (32) Song, J.; Aratani, N.; Shinokubo, H.; Osuka, A. A Porphyrin Nanobarrel That Encapsulates C60. J. Am. Chem. Soc. 2010, 132, 16356-16357. (33) Tobe, Y.; Nagano, A.; Kawabata, K.; Sonoda, M.; Naemura, K. Synthesis and Association Behavior of Butadiyne-Bridged [44](2,6)Pyridinophane and [46](2,6)Pyridinophane Derivatives. Org. Lett. 2000, 2, 3265-3268. (34) Kobayashi, S.; Yamaguchi, Y.; Wakamiya, T.; Matsubara, Y.; 
Sugimoto, K.; Yoshida, Z.-i.

Shape-persistent

cyclyne-type

azamacrocycles:

synthesis,

unusual

light-emitting

characteristics, and specific recognition
of the Sb(V) ion. Tetrahedron Lett. 2003, 44, 14691472. (35) Yamaguchi, Y.; Kobayashi, S.; Miyamura, S.; Okamoto, Y.; Wakamiya, T.; Matsubara, Y.; Yoshida, Z.-i. Synthesis and Light-Emitting Characteristics of Doughnut-Shaped p-Electron Systems. Angew. Chem., Int. Ed. 2004, 43, 366-369. (36) Hara, K.; Hasegawa, M.; Kuwatani, Y.; Enozawa, H.; Iyoda, M. Mono- and bis(tetrathiafulvaleno)hexadehydro[12]annulenes. Chem. Commun. 2004, 2042-2043.

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(37) Iyoda, M.; Enozawa, H.; Miyake, Y. Bis(tetrathiafulvaleno)octadehydro[20]annulene with Multi-functionality. Chem. Lett. 2004, 33, 1098-1099. (38) Chen, G.; Wang, L.; Thompson, D. W.; Zhao, Y. Highly π-Extended TTF Analogues with a Conjugated Macrocyclic Enyne Core. Org. Lett. 2008, 10, 657-660. (39) Chen, G.; Dawe, L.; Wang, L.; Zhao, Y. Planar Acetylene-Expanded TTFAQ Analogues. Org. Lett. 
2009, 11, 2736-2739. (40) Seo, S. H.; Chang, J. Y.; Tew, G. N. Self-Assembled Vesicles from an Amphiphilic orthoPhenylene Ethynylene Macrocycle. Angew. Chem., Int. Ed., 2006, 45, 7526-7530. (41) Kim, J. K.; Lee, E.; Kim, M. C.; Sim, E.; Lee, M. Reversible Transformation of Helical Coils and Straight Rods in Cylindrical Assembly of Elliptical Macrocycles. J. Am. Chem. Soc. 2009, 131, 17768-17770. (42) Wang, D.; Hsu, J. F.; Bagui, M.; Dusevich, V.; Wang, Y.; Liu, Y.; Holder, A. J.; Peng, Z. Synthesis and self-assembly of a triphenylene-containing amphiphilic conjugated Macrocycle. Tetrahedron Lett. 2009, 50, 2147-2149. (43) Tobe, Y.; Utsumi, N.; Kawabata, K.; Nagano, A.; Adachi, K.; Araki, S.; Sonoda, M.; Hirose, K.; Naemura, K. m-Diethynylbenzene Macrocycles: Syntheses and Self-Association Behavior in Solution. J. Am. Chem. Soc. 2002, 124, 5350-5364. (44) He, Z.; Xu, X.; Zheng, X.; Ming, T.; Miao, Q. Conjugated macrocycles of phenanthrene: a new segment of [6,6]-carbon nanotube and solution- processed organic semiconductors. Chem. Sci. 2013, 4, 4525-4531. (45) Kline, M. A.; Wei, X.; Horner, I.; Liu, J. R.; Chen, S.; Chen, S.; Yung, K. Y.; Yamato, K.; Cai, Z.; Bright, F. V.; Zeng, X. C.; Gong, B. Extremely strong tubular stacking of aromatic oligoamide macrocycles. Chem. Sci. 2015, 6, 152-157.

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(46) Shimizu, T. Self-Assembled Lipid Nanotube Hosts: The Dimension Control for Encapsulation of Nanometer-Scale
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(55) González-Rodriguez, D.; van Dongen, J. L. J.; Lutz, M.; Spek, A. L.; Schenning, A. P. H. J.; Meijer, E. W. G-quadruplex self-assembly regulated by Coulombic interactions. Nature Chem. 2009, 1, 151-155. (56) Benesi, H. A.; Hildebrand, J. H. A Spectrophotometric Investigation of the Interaction of Iodine with Aromatic Hydrocarbons. J. Am. Chem. Soc. 1949, 71, 2703-2707. (57) Zimmerman, S. C.; Wendland, M. S.; Rakow, N. A.; Zharov, I.; Suslick, K. S. Synthetic hosts by monomolecular imprinting inside dendrimers. Nature 2002, 418, 399-403.

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Scheme 1. Synthesis of macrocycles 16mer-114mer.

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(a)

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O OH

O OH

O OH

O OH

O OH

O OH

G1

HO

G2

O OH

O

G3

O OMe MeO

O OMe

O

G4

HO

O

HO

O OH

O

G5

G6

(b) ~0.9 nm

CH 2Cl 2 1.4 nm

(G3)

~1.7 nm

1 6mer

DMSO

NT 6mer

(G3)

NT 6mer

Figure 1. (a) Molecular structures of guest G1-G6. (b) Schematic representation of the complexation of self-assembled nanotube NT6mer with guest G3.

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Figure 2. (a) 1H NMR (400 MHz) spectra of 16mer in aromatic region in (i) CDCl3, (ii) THF-d8 and (iii) CD2Cl2 at 25 °C. (b) TEM micrograph of an air-dried CH2Cl2 solution of tubularly assembled 16mer. (c) Electronic absorption and (d) fluorescence spectra of 16mer in CH2Cl2 at 25 °C. (inset) A photograph of a CH2Cl2 solution of 16mer under UV irradiation at 356 nm.

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Figure 3. (a) 1H NMR (400 MHz) spectral changes of NT6mer in CD2Cl2 at 25 °C in aromatic region upon titration with G3. (b) TEM micrograph of an air-dried CH2Cl2 solution of NT6mer⊃G3. (c) 1H NMR (400 MHz) spectral changes of 16mer in CDCl3 at 25 °C in aromatic region upon titration with G3. (d) 1H NMR (400 MHz) spectral changes of 16mer in THF-d8 at 25 °C in aromatic region upon titration with G3. (e) 1H NMR (400 MHz) spectral changes of NT6mer in CD2Cl2 at 25 °C in aromatic region upon titration with G1. (f) Fluorescence spectral changes of NT6mer in CH2Cl2 at 25 °C upon titration with G4.

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Figure 4. (a) Electronic absorption spectral changes of NT6mer (5 × 10-6 mol/L) upon titration with G3 in CH2Cl2 at 25 °C, [G3] = 0, 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75 and 2 equiv. (b) Fluorescence spectral changes of NT6mer (5 x 10-6 mol/L) upon titration with G3 in CH2Cl2 at 25 °C, [G3] = 0, 0.25, 0.5, 0.75, 1, 1.25, 1.5, 1.75 and 2 equiv. (inset) Photograph of a CH2Cl2 solution of NT6mer⊃G3 under UV irradiation at 356 nm. (c) Fluorescence spectral changes of 16mer (5 × 10-6 mol/L) upon titration with G3 in CHCl3 at 25 °C, [G3] = 0, 0.5, 1, 2, 3 and 4 equiv. (inset) Photograph of a CHCl3 solution of 16mer after adding G3 under UV irradiation at 356 nm. (d) Fluorescence spectral changes of 16mer (5 x 10-6 mol/L) upon titration with G3 in THF at 25 °C, [G3] = 0-30 equiv. (inset) Photograph of a THF solution of 16mer after adding G3 under UV irradiation at 356 nm.

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Figure 5. Schematic representation of released G3 from tubular channel by the addition of DMSO.

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TOC GRAPHIC

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