Stereoselective Self-Assembly of Chiral Metalla[2]Catenanes and Lemniscular Macrocycles

Abstract

Open AccessCCS ChemistryRESEARCH ARTICLES11 Jan 2024Stereoselective Self-Assembly of Chiral Metalla[2]Catenanes and Lemniscular Macrocycles Shu-Jin Bao, Hai-Ning Zhang and Guo-Xin Jin Shu-Jin Bao , Hai-Ning Zhang and Guo-Xin Jin *Corresponding author: E-mail Address: [email protected] https://doi.org/10.31635/ccschem.024.202303525 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Designing and stereoselectively constructing chiral mechanically interlocked molecules (MIMs) is a goal that many chemists are pursuing due to their potential in the development of functional molecular machines involved in catalysis, sensing, and chiroptical switching. However, the synthesis of enantiopure supramolecular entities with crystallographic structures remains challenging. Herein, the stereoselective self-assembly of chiral metalla[2]catenanes interlocked by two D-shaped macrocycles was realized by combining long binuclear half-sandwich organometallic Cp*RhIII (Cp* = η5-pentamethylcyclopentadienyl) clip and ditopic monodentate ligand incorporating l-leucine residues. The resulting metalla[2]catenane displayed unique co-conformational mechanical helical chirality characteristics arising from the chirality transfer of the chiral ligand. Furthermore, decreasing the length of the binuclear Cp*RhIII clip and adjusting the steric hindrance of the amino-acid side chains (l-alanine and l-phenylalanine) in the ligands resulted in two lemniscular macrocycles with left-handed (M)-twisted conformational chirality. To the best of our knowledge, the synthesized macrocycles are the first family of homochiral abnormal lemniscate-shaped organometallic macrocycles featuring figure-eight geometries. Metalla[2]catenanes and macrocycles with opposite chirality were also generated by employing corresponding d-amino acid ligands, as evidenced by single-crystal X-ray diffraction, nuclear magnetic resonance, mass, and circular dichroism spectroscopies. Our present study demonstrates that homochiral MIMs can be accessed readily using amino acid–containing ligands through rational molecular design. Download figure Download PowerPoint Introduction Abundant and impressive chiral mechanically interlocked molecules (MIMs), such as lasso peptides, circular deoxyribonucleic acid (DNA) catenanes, and so on, have been identified in living organisms and in real-world settings that are essential to daily life.1–4 In recent years, significant advancements in the enantioselective synthesis of chiral MIMs, including chiral rotaxanes, [2]catenanes, trefoil knots, Solomon links, and so on, have been developed, which spurs the creation of intricate molecular machines with potential uses in stereoselective catalysis,5,6 sensing,7–9 and chiroptical switching.10–12 Building blocks that are enantiomerically pure are often used to manipulate the mechanical and/or other covalent chirality of the MIMs by chirality transfer, leading to the construction of artificial chiral MIMs.13–17 As one of the most important chirality sources, the structurally varied and reasonably priced amino-acid family, has been widely employed in creating chiral MIMs.18–24 Chiral [2]catenanes, one of the most common chiral MIMs, have been successfully synthesized via covalent-directed and noncovalent-template strategies.25–35 However, chiral [2]catenanes in enantiopure forms frequently necessitate preparative chiral stationary phase high-performance liquid chromatography (CSP–HPLC) purification of the final product or chiral subunits, which is expensive and hinders more thorough research of their applications.36–40 Therefore, although challenging, developing convenient and efficient stereoselective methods to synthesize enantiopure chiral [2]catenanes is extremely important. Coordination-driven self-assembly, which takes advantage of various noncovalent contacts and allows spontaneous error correction to guide intermolecular/intramolecular entanglement, has become a powerful tool for the bottom-up building of complicated MIMs in a single step.41,42 To date, the number of enantiomeric co-conformational mechanical helically chiral [2]catenanes with unambiguous crystallographic structures has been very limited and the synthesis of such [2]catenanes remains an exciting but daunting task. Herein, we describe the synthesis of a homochiral metalla[2]catenane, (MMH,S4)- Rh-1 ( Rh-1S, MMH, and S represent co-conformational mechanical helical chirality and point chirality, respectively, and the superscript 4 represents four chiral stereogenic centers. Coordination-driven self-assembly of the point-chiral ligand, (S,S)- L 1 ( Supporting Information Figures S1, S14–S17, S76, and S79), bearing two l-leucine residues and the binuclear half-sandwich organometallic clip [Cp*2Rh2(TPPHZ)(OTf)2](OTf)2 ( E1, Cp* = η5-pentamethylcyclopentadienyl; TPPHZ = tetrapyrido[3,2-a:2′,3′c:3″,2″-h:2‴,3‴-j]phenazine; OTf = trifluoromethanesulfonate anion) was performed in a single step (Scheme 1). Notably, the inter-ring interlocking exhibited a single co-conformational mechanical helical chirality, ascribed to the chirality transfer of chiral ligand. Furthermore, two chiral ligands, (S,S)- L 2 ( Supporting Information Figures S22–S25, S77, and S80) and (S,S)- L 3 ( Supporting Information Figures S30–S33, S78, and S81), carrying l-phenylalanine and l-alanine residues, respectively, led to the left-handed (M)-twisted chiral lemniscular macrocycles, (M,S4)- Rh-2 ( Rh-2S) and (M,S4)- Rh-3 ( Rh-3S), via self-assembly with the much shorter binuclear half-sandwich organometallic unit [Cp*2Rh2(BiBzlm)(OTf)2] ( E2, BiBzlm = 2,2′-bisbenzimidazole). As expected, [2]catenane (PMH,R4)- Rh-1 ( Rh-1R), the enantiomer of Rh-1S, was formed via self-assembly with E1 utilizing the ligand bearing the identical d-leucine residues. Likewise, the right-handed (P)-twisted enantiomers of Rh-2S and Rh-3S, macrocycles (P,R4)- Rh-2 ( Rh-2R) and (P,R4)- Rh-3 ( Rh-3R), respectively, were formed via self-assembly with E2 employing corresponding d-amino acid ligands. Single-crystal X-ray diffraction (SCXRD), nuclear magnetic resonance (NMR), electrospray ionization mass spectrometry (ESI-MS), and circular dichroism (CD) spectroscopy were employed to confirm the stereoselective synthesis of Rh-1S/R, Rh-2S/R, and Rh-3S/R. Scheme 1 | Diagrammatic depiction of the stereoselective self-assembly of chiral metalla[2]catenanes and lemniscular organometallic macrocycles by varying the binuclear Cp*Rh clip lengths and a succession of point-chiral ligands carrying amino-acid residues. Download figure Download PowerPoint Experimental Methods General procedure for preparation of chiral metalla[2]catenanes Rh-1S/R Ligand (S,S)- L 1 (12.9 mg, 0.02 mmol) and E1 (29.2 mg, 0.02 mmol) were agitated in 10 mL methanol (MeOH) at room temperature for 24 h. After the reacting orange solution was filtered through a membrane filter, the resulting filtrate was reduced to ∼3 mL by rotational evaporation. Orange crystals of Rh-1S were obtained using isopropyl ether diffusion into the reactive solution, washed with diethyl ether, and vacuum-dried. The synthesis method of Rh-1R was consistent with that of Rh-1S, in which Rh-1R was obtained by substituting ligand (S,S)- L 1 for (R,R)- L 1 ( Supporting Information Figures S18–S21). General procedure for the preparation of chiral lemniscular macrocycles Rh-2S/R and Rh-3S/R Ligand (S,S)- L 2 (14.3 mg, 0.02 mmol) and E2 (20.1 mg, 0.02 mmol) were agitated in an N,N-dimethylformamide (DMF)/MeOH (5 mL/1.5 mL) solution at room temperature for 24 h. Orange crystals of Rh-2S were obtained by isopropyl ether diffusion, following the filtration of the reacted orange solution via a membrane filter. The crystals obtained were washed with diethyl ether and vacuum-dried. Rh-2R and Rh-3S/R were synthesized following the same procedure as Rh-2S, except that (S,S)- L 2 was replaced with (R,R)- L 2 ( Supporting Information Figures S26–S29) (14.3 mg, 0.02 mmol), (S,S)- L 3 (11.3 mg, 0.02 mmol) and (R,R)- L 3 ( Supporting Information Figures S34–S37) (11.3 mg, 0.02 mmol), respectively. X-ray crystal structure determination and crystallographic data Using Ga Kα radiation (λ = 1.34138 Å) at 173 K, a Bruker APEX-II CCD diffractometer (Bruker Corporation, Karlsruhe, Germany) was used to measure all of the data for the crystal structures of Rh-1S/R, Rh-2S/R, and Rh-3S/R. Their structures were determined using direct methods and refined using the full-matrix least-squares techniques on Fo2 using the single crystal structure refinement program, SHELXL (https://shelx.uni-goettingen.de/) through the OLEX2 interface. The X-ray crystallographic data for Rh-1S/R, Rh-2S/R, and Rh-3S/R are shown in Supporting Information Tables S1–S3. Cambridge Crystallographic Data Centre (CCDC) numbers: 2298276 ( Rh-1S), 2298277 ( Rh-1R), 2298274 ( Rh-2S), 2298275 ( Rh-2R), 2298272 ( Rh-3S), and 2298273 ( Rh-3R). Results and Discussion Stereoselective synthesis of chiral metalla[2]catenanes Rh-1S/R Our group has conducted numerous studies in recent years demonstrating that interlocked molecules could be created readily using half-sandwich Cp*M (M = IrIII/RhIII) building blocks as metal corners.43–47 Furthermore, utilizing the binuclear Cp*M organometallic fragment of the appropriate length, coordination-driven self-assembly enabled the synthesis of chiral MIMs with excellent stereoselectivity.13,18–20 In this context, we selected the binuclear Cp*Rh organometallic fragment, E1, with a long Rh–Rh nonbonding length of 12.87 Å as the stiff capping units. Moreover, the chiral semirigid ligand (S,S)- L 1 bearing two l-leucine residues was synthesized, to which a large π-conjugated fluorene moiety, comprising a keto functional group and four amide bonds capable of forming hydrogen bonds were introduced. Orange crystals of Rh-1S were generated in 83% yield when ligand (S,S)- L 1 and E1 interacted in MeOH and were subsequently diffused with isopropyl ether (Figure 1). The crystal structure of Rh-1S was precisely determined using SCXRD analysis. Owing to the two D-shaped macrocycles latching together, Rh-1S was fabricated as a chiral metalla[2]catenane with two crossings (Figure 2a), crystallizing in the chiral monoclinic space group P21. This result demonstrated that one-step self-assembly accelerated the generation of the Rh-1S hierarchical structure. Figure 1 | Stereoselective synthesis of the metalla[2]catenanes enantiomers Rh-1S/R. Download figure Download PowerPoint Chiral stereogenic elements were present in the structure of metalla[2]catenane Rh-1S. A slight angle between the two D-shaped molecular loops in Rh-1S inevitably created a single co-conformational mechanical helical chirality (MMH, Figure 2a), indicating effective chirality transfer from the chiral ligands via noncovalent interactions happened during the self-assembly. Close inspection of the structure of Rh-1S revealed that the C atoms in the fluorene groups established rather close contact with the C and N atoms in the TPPHZ moieties of E1, developing inter-ring multiple π–π stacking interactions in the range of 3.31–3.50 Å (Figure 2b). The H atoms of the amide bonds in the ligand (S,S)- L 1 established four directional intra-ring N–H···O contacts with the O atoms of the other amide bonds (2.70–3.08 Å) (Figure 2c, yellow dotted lines). The H atoms of l-leucine residues in (S,S)- L 1 developed intra-ring C–H···O interactions with the O atoms of the amide bonds in the range of 2.15–2.44 Å (Figure 2c, magenta dotted lines). Inter-ring C–H···O hydrogen bonds (Figure 2c, green dotted lines) and CH···π interactions ( Supporting Information Figure S2) were also observed in [2]catenane Rh-1S, with primary distance ranges of 2.50–2.69 Å and 3.07–3.38 Å, respectively. Thus, it is likely that the integration of these noncovalent interactions not only facilitated the effective chirality transfer of the ligand but also stabilized the chiral metalla[2]catenane Rh-1S, which can be considered as the driving forces that propelled the generation of Rh-1S's interlocked topology. Figure 2 | (a) The structures of the metalla[2]catenane enantiomers Rh-1S/R, and their simplified topological representations, exhibiting single co-conformational mechanical helical chirality (M/PMH). (b) The π–π stacking interactions between the fluorene groups and the TPPHZ moieties in Rh-1S. (c) The N–H···O and C–H···O hydrogen bonding interactions present in Rh-1S. (d) The dimensions of metalla[2]catenane Rh-1S fitted by D (2.67 × 10−6 cm2 s−1) according to the prolate spheroidal model. Counteranions and solvent molecules are omitted for clarity. Color code: C, gray; H, pink; N, blue; O, red; Rh, turquoise. Download figure Download PowerPoint The existence of chiral metalla[2]catenane Rh-1S was further confirmed by NMR spectroscopic and ESI-MS tests in MeOH. In Rh-1S, all 1H NMR signal assignments were supported by 1H–1H correlated spectroscopy NMR data ( Supporting Information Figures S38 and S39). All of the Cp*-based proton, aromatic, and aliphatic signals (excluding solvent signals) in the diffusion-ordered spectroscopy (DOSY) NMR spectrum of Rh-1S were ascribed to a single species, with a diffusion constant (D) of 2.67 × 10−6 cm2 s−1 ( Supporting Information Figure S40). Furthermore, the dimensions (radius length × half height length, 14.3 Å × 12.0 Å) of the structure of Rh-1S were in agreement with the experimental dimensions (semimajor axis length × semiminor axis length, 15.7 Å × 12.6 Å) fitted by D (2.67 × 10−6 cm2 s−1) via the modified Stocks–Einstein equation modeled as a prolate spheroid (Figure 2d).48,49 Subsequently, concentration gradient studies were carried out, varying concentration values from 0.05 to 3.0 mM with respect to Cp*RhIII. As shown in Supporting Information Figure S41, neither the chemical shift nor the peak shape showed detectable changes, indicating that the structural transformation of Rh-1S did not occur in MeOH-d4. The ESI-MS analysis revealed two signals at m/z = 1253.2186 and 1954.3048, assigned to [ Rh-1S – 3 OTf−]3+ and [ Rh-1S – 2 OTf−]2+, respectively, with the correct isotope distribution patterns ( Supporting Information Figures S58–S60). These results demonstrate the excellent stability of chiral metalla[2]catenane Rh-1S in MeOH. To verify the stereoselective preparation of chiral [2]catenanes, we performed the identical self-assembly employing the corresponding d-leucine acid ligand (R,R)- L 1 instead of (S,S)- L 1. As anticipated, Rh-1R ( Supporting Information Figures S42–S45 and S61–S63), the enantiomer of Rh-1S, was successfully synthesized, which exhibited opposite co-conformational mechanical helical chirality (PMH). Similar noncovalent interactions observed in Rh-1S were also found in Rh-1R ( Supporting Information Figures S3–S5). Stereoselective synthesis of chiral lemniscular macrocycles Rh-2S/R and Rh-3S/R Conceptually, two chiral D-shaped macrocyclic rings might be interlocked to create chiral [2]catenanes. By selecting an appropriate pyridine ligand to combine with the binuclear Cp*Rh organometallic fragment, we anticipated that chiral D-shaped macrocycles could be easily synthesized. To verify this assumption, we further synthesized ligand (S,S)- L 2 with greater steric hindrance in amino-acid side chains than ligand (S,S)- L 1. This ligand was intended to combine with the binuclear Cp*Rh clip E2, which was considerably shorter than E1 and had a Rh–Rh nonbonding distance of 5.65 Å. Unexpectedly, the reaction of ligand (S,S)- L 2 with E2 in a mixed DMF/MeOH solution yielded a chiral lemniscular organometallic macrocycle, Rh-2S, with an intramolecular M-twisted conformation in a high yield of 89% (Figure 3). Figure 3 | Stereoselective synthesis of the lemniscular organometallic macrocycle enantiomers Rh-2S/R, Rh-3S/R. Download figure Download PowerPoint Figure 4a depicts the crystal structure of the organometallic macrocycle Rh-2S. It crystallized in the chiral orthorhombic space group P212121, and a pyridyl N atom from ligand (S,S)- L 2 completed the tetrahedral geometry of each Rh(III) center in E2. Intriguingly, the two (S,S)- L 2 ligands were arranged in an alternating pattern rather than in parallel. Therefore, Rh-2S lacked the normal shape of most rectangles and appeared to be folded into a figure-eight conformation. The figure-eight geometry of Rh-2S was accurately approximated with a Booth lemniscate.50,51 Figure 4 | (a) The structures of the lemniscular macrocycle enantiomers Rh-2S/R, and their simplified topological representations with M/P-twisted conformations. (b) The π–π stacking interactions between the two fluorene groups in Rh-2S. (c) The N–H···O, C–H···O, and C–H···N hydrogen bonding interactions present in Rh-2S. (d) The dimensions of macrocycle Rh-2S fitted by D (2.47 × 10−6 cm2 s−1) according to the prolate spheroidal model. Counteranions and solvent molecules are omitted for clarity. Color code: C, gray; H, pink; N, blue; O, red; Rh, turquoise. Download figure Download PowerPoint Rich π–π stacking interactions between the fluorene groups were found in the range of 3.42–3.47 Å (Figure 4b). Furthermore, distinct hydrogen bonding interactions were involved in which the O atoms on the amide bonds were in contact with the neighboring H atoms from the amide bonds and phenylalanine residues in another (S,S)- L 2, creating directional N–H···O (2.00 and 2.17 Å) and C–H···O (2.96–3.18 Å) interactions. The fluorene moiety containing a carbonyl group also established C–H···O (3.38 and 3.49 Å) and C–H···N (3.36 and 3.46 Å) contacts with another fluorene moiety and the adjacent N atoms of amide bonds in another (S,S)- L 2 (Figure 4c). In addition, the structure of Rh-2S exhibited plenty of C–H···π interactions between the two fluorene moieties, with the primary distances being 3.29–3.50 Å ( Supporting Information Figure S6). The aforementioned close-contact analysis of macrocycle Rh-2S further demonstrated that these noncovalent interactions possibly facilitated the assembly of the binuclear fragment E2 and ligand (S,S)- L 2, and effectively stabilized its macrocycle skeleton. The high purity of Rh-2S was demonstrated by the NMR data ( Supporting Information Figures S46–S48). The 1H DOSY NMR analysis in MeOH yielded a single D value of 2.46 × 10−6 cm2 s−1, indicating that macrocycle Rh-2S remained intact in solution ( Supporting Information Figure S48). The experimental dimensions (19.2 Å × 10.1 Å) calculated from D (2.46 × 10−6 cm2 s−1) in the 1H DOSY NMR spectrum were consistent with the size (19.4 Å × 10.2 Å) determined from its solid state structure (Figure 4d, radius length × half height length). The ESI-MS spectrum displayed two signals at m/z = 711.4340 and 998.2290, with the appropriate isotope distribution patterns being assigned to [ Rh-2S – 4 OTf−]4+ and [ Rh-2S – 3 OTf−]3+, respectively ( Supporting Information Figures S64–S66). Given the substantial steric hindrance of l-phenylalanine residues in the ligand (S,S)- L 2, reducing the steric hindrance of the amino-acid residues may result in the formation of different topological structures. To verify this speculation, we synthesized ligand (S,S)- L 3 bearing two l-alanine residues, which was less sterically inhibited than (S,S)- L 2. However, chiral M-twisted conformational macrocycle Rh-3S ( Supporting Information Figures S52–S54 and S70–S72) was isomorphic to macrocycle Rh-2S, produced by the combination of ligand (S,S)- L 3 and E2 (Figures 3 and 5a). There were favorable π–π stacking interactions (3.39–3.50 Å) between the two fluorene groups (Figure 5b), C–H···π interactions (3.31–3.55 Å, Supporting Information Figure S10), as well as two N–H···O (both 2.19 Å) and numerous C–H···O (3.01–3.11 Å) hydrogen bonds in Rh-3S (Figure 5c). Additionally, both P-twisted macrocycles, Rh-2R ( Supporting Information Figures S7–S9, S49–S51 and S67–S69) and Rh-3R ( Supporting Information Figures S11–S13, S55–S57, and S73–S75), were stereoselectively synthesized via self-assembly employing ligands (R,R)- L 2 and (R,R)- L 3 bearing corresponding d-amino acid residues. To the best of our knowledge, our newly synthesized homochiral lemniscate-shaped organometallic macrocycles with a figure-eight geometry are the first to be reported. The aforementioned findings exemplify the ability to control the assembled structure simply by varying the binuclear Cp*Rh organometallic clip lengths and the intrinsic nature of the organic linkers with various amino-acid residues, thus influencing the conformation and geometry of the resulting chiral assemblies. Figure 5 | (a) The structures of the lemniscular macrocycle enantiomers Rh-3S/R, and their simplified topological representations with M/P-twisted conformations. (b) The π–π stacking interactions between the two fluorene groups in Rh-3S. (c) The N–H···O and C–H···O hydrogen bonding interactions present in Rh-3S. Counteranions and solvent molecules are omitted for clarity. Color code: C, gray; H, pink; N, blue; O, red; Rh, turquoise. Download figure Download PowerPoint The UV–visible (UV–vis) absorption spectra (Figure 6a) clearly showed an energy absorption band spanning from 200 to 450 nm for metalla[2]catenanes Rh-1S/R and lemniscular macrocycles Rh-2S/R, Rh-3S/R. The chirality of Rh-1S/R, Rh-2S/R, and Rh-3S/R was further examined using CD spectroscopy in the UV–vis absorption region. Metalla[2]catenane Rh-1S displayed positive-to-negative-to-positive-to-negative-to-positive cotton bands, while Rh-1R exhibited the exact opposite Cotton effects from Rh-1S (Figure 6b). Additionally, due to the differences in amino-acid side chains, the lemniscular macrocycles Rh-2S and Rh-3S presented distinct CD signals, in which Rh-2S displayed cotton bands oscillating from negative to positive to negative to positive (Figure 6c), whereas Rh-3S revealed positive to negative to positive cotton bands (Figure 6d). Both enantiomers displayed perfect mirror-image symmetry relations, validating their enantiomeric nature with opposite conformational chirality. Figure 6 | (a) Normalized UV–vis absorption spectra of metalla[2]catenanes Rh-1S/R (3.64 × 10−5 M), lemniscular macrocycles Rh-2S/R (2.91 × 10−6 M) and Rh-3S/R (7.97 × 10−6 M) in MeOH. CD spectra of the enantiomers of (b) Rh-1S/R, (c) Rh-2S/R, and (d) Rh-3S/R in MeOH at room temperature. Download figure Download PowerPoint Conclusion This study demonstrates the stereoselective synthesis of chiral metalla[2]catenanes by self-assembly between ditopic monodentate pyridine ligands incorporating l/d-leucine residues and a long binuclear Cp*Rh clip. Owing to the inherent mechanical bonds and the point chirality of the ligands, the synthesized [2]catenanes exhibited unique co-conformational mechanical helical chirality. By sharply reducing the length of the binuclear Cp*Rh clip and adjusting the steric hindrance of the amino-acid side chains in the ligands, the first family of chiral M/P-twisted lemniscular organometallic macrocycles with figure-eight conformations were synthesized. A variety of noncovalent interactions, including hydrogen bonding and π–π stacking interactions, were essential for the development of chiral [2]catenanes and macrocyclic structures, which facilitated the efficient chirality transfer of point-chiral ligands. This study provides a strong foundation for the directed synthesis of homochiral interlocked molecules and molecular machines in the future. Supporting Information Supporting Information is available and includes synthetic and experimental procedures, X-ray crystallographic data, ESI-time-of-flight (TOF) MS spectra, NMR spectra, absorption spectra, and CD spectra. Conflict of Interest There is no conflict of interest to report. Funding Information This research was made possible as a result of a generous grant from the National Science Foundation of China (grant nos. 22031003 and 21720102004), the Shanghai Science Technology Committee, China (grant no. 19DZ2270100), and the Shanghai Post-doctoral Excellence Program, China (grant no. 2022009). References 1. Forgan R. S.; Sauvage J.-P.; Stoddart J. F.Chemical Topology: Complex Molecular Knots, Links, and Entanglements.Chem. Rev.2011, 111, 5434–5464. Google 2. of and to to Google S.; Molecular Google Zhang with and Google Google of a Chiral Ligand for Google of and Molecular in Stereoselective and Google S.; from of and and of Google J. by Chiral Google of Chiral Google J. Google of of Using Chiral as Chiral Google Jin of a Chiral Solomon Google J. in a Molecular Google J. J. J. the and of an Molecular Google J. Chiral for the of Chiral Google Sauvage of a Chiral The Google Jin Self-Assembly of Complex Chiral Using Building Google Jin of a Molecular by Google Jin of Chiral and Google Zhang Zhang Zhang of a Molecular Google and Google from Google J. by of two Google in and Google to the of Google of a Chiral Google Chiral Google of Chiral and the of Their Google J. Chiral from Google Chiral [2]catenane on Google J. R. of and of Google J. of Google Stoddart J. in Google the of the of Google S.; with a Google Molecular Information Google Molecular Information Google Zhang S.; Chiral for the Stereoselective of Chiral and Google J. R. for the of Chiral Google Jin of Molecular Google S.; Self-Assembly of Molecular Google Zhang Jin of 6 1 3 and 6 2 3 Google Zhang Jin and of a and Google Jin and of Google Jin of Google Zhang Jin of and Molecular for J. Google NMR as a for the of and for the of of Google Zhang R. Zhang Self-Assembly and of Google Zhang of an in Google J. A Google Information residues

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