Guest Exchange through Facilitated Transport in a Seemingly

Sep 28, 2018 - A new inclusion compound consisting of a guanidinium 1,3,5-tri(4-sulfophenyl)benzene (G3TSPHB) host framework containing isophorone ...
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Guest Exchange through Facilitated Transport in a Seemingly Impenetrable Hydrogen-Bonded Framework Yuantao Li,† Marcel Handke,† Yu-Sheng Chen,‡ Alexander G. Shtukenberg,*,† Chunhua T. Hu,*,† and Michael D. Ward*,†

J. Am. Chem. Soc. Downloaded from pubs.acs.org by UNIV OF LOUISIANA AT LAFAYETTE on 09/28/18. For personal use only.

†

Department of Chemistry and Molecular Design Institute, New York University, 100 Washington Square East, Room 1001, New York, New York 10003, United States ‡ ChemMatCARS, Center for Advanced Radiation Sources, The University of Chicago, Lemont, Illinois 60439, United States S Supporting Information *

ABSTRACT: A new inclusion compound consisting of a guanidinium 1,3,5-tri(4sulfophenyl)benzene (G3TSPHB) host framework containing isophorone guests that surround isolated and seemingly inaccessible pockets was amenable to guest exchange with hexafluorobenzene (HFB) through a single crystal−single crystal transformation (SCSCT). Single-crystal X-ray diffraction of intermediate transformation states, from the parent compound G3TSPHB·(isophorone)3.7·(methanol)5.4 to the final state G3TSPHB·(isophorone)3.1·(HFB)2·(methanol)2, indicated a crystal symmetry change from monoclinic to hexagonal prior to full incorporation of HFB. Optical microscopy during the SCSCT revealed the formation of lamellae, which expanded and then coalesced into a single crystal when the phase transformation was complete. In situ Raman microscopy revealed changes in the orientation of isophorone guests during the transformation that suggested a pathway for HFB entry into the host cavities. The SCSCT occurs more rapidly than expected on the basis of simple diffusion, consistent with facilitated transport along the lamellae interfaces and a reduction in the length scale for guest exchange.

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been inferred solely from the initial and final crystal structures. Structural changes in a metal alloy39 and an inorganic salt40 have been explained by diffusional−displacive phase transformations, wherein a macroscopic change of shape and volume of the parent material facilitates guest migration. This behavior has not been explored in molecular crystals, however. Our laboratory has reported a family of molecular frameworks built from two-dimensional quasihexagonal hydrogen-bonded networks of guanidinium (G) and sulfonate (S) groups of organosulfonates (Figure 1A).41−43 The inherent persistence of the 2D GS network, a characteristic owed to its compliant character, permits GS frameworks to adopt a range of architectures, from lamellar to cylindrical, depending on the particular host−guest combination. Herein, we report exchange of hexafluorobenzene (HFB), through a SCSCT, into seemingly impenetrable inclusion cavities within single crystals constructed from the guanidinium 1,3,5-tri(4-sulfophenyl)benzene (G3TSPHB) host framework. The SCSCT was characterized with in situ polarized optical and Raman microscopies and ex situ single-crystal X-ray diffraction. The phase transformation is rapid along directions defined by a lamellar microstructure, consisting of alternating micrometerscale crystalline layers of transformed and untransformed phases, which facilitates diffusion and subsequent exchange of

INTRODUCTION The inclusion of guest molecules in well-defined cavities of molecular frameworks presents an opportunity to design materials for applications ranging from optoelectronics to chemical storage1−4 to separations.5−14 Frameworks with persistent and predictable architectures can enable separation of structure (i.e., the framework) from function introduced by interchangeable guest molecules, facilitating control of solidstate properties.15 While inclusion compounds are often synthesized by direct crystallization from the host and guest components, postsynthetic guest exchange with retention of framework architecture provides an alternative avenue to host−guest combinations not available by direct crystallization.16−22 Postsynthetic guest exchange has been used to coerce solid-state reactions23 and to enable structure determination of guest molecules that otherwise are not amenable to single-crystal structure analysis.24−27 The mechanism for guest exchange or adsorption can be somewhat mystifying when a crystal structure does not reveal any obvious pathway for these processes, particularly when they occur with retention of single crystallinity.28−32 Several examples of guest adsorption, release, and exchange involving seemingly inaccessible voids have invoked lattice flexibility and synchronous motion, some characterized as single crystal− single crystal transformations (SCSCTs).33−37 Although molecular dynamics has been used to explain guest exchange with synchronous motion,38 such mechanisms typically have © XXXX American Chemical Society

Received: July 15, 2018

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DOI: 10.1021/jacs.8b07065 J. Am. Chem. Soc. XXXX, XXX, XXX−XXX

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Figure 1. (A) The quasi-hexagonal guanidinium-sulfonate (GS) hydrogen-bonded sheet. The hinges denote the axis about which the GS sheet can bend. (B) The guanidinium ion (G) and 1,3,5-tri(4sulfophenyl)benzene (TSPHB) connector that comprise the G3TSPHB framework, and the isophorone and hexafluorobenzene guests. (C) Schematic representation of the hydrogen-bond connectivity of the GS cylinder in compounds 1 and 2 obtained by curling the GS sheet about the hinges between GS ribbons depicted in (A). The spheres denote G ions, and the undecorated vertices denote sulfonate nodes.

HFB and the overall SCSCT. The lamellae broadened during the transformation, eventually healing to produce a new single crystal containing ordered HFB molecules within inclusion cavities of the framework. The behavior is consistent with a diffusional−displacive phase transformation.

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Figure 2. (A) Crystal structure of 1, as viewed down the distorted GS cylinders (void A), which coincide with the b-axis in the setting of the P21 space group. (B) Structure of intermediate state crystal 1-8min (exposed to the vapor of 25% v/v HFB/hexane solution for 8 min), as viewed down the b axis (21 axis). The structure still refines best as P21, and the GS cylinders are nearly hexagonal. (C) Structure of crystal 2, as viewed down the hexagonal GS cylinders that coincide with the caxis (63 screw axis). Images of crystals 1, 1-8min, and 2 with indexed faces are depicted at the lower corners of panels A−C, respectively. Scale bars in crystal images: 150 μm. The green circles in panels B and C correspond to randomly disordered guest molecules.

RESULTS AND DISCUSSION Slow evaporation of a methanol solution of guanidinium 1,3,5tri(4-sulfophenyl)benzene (G3 TSPHB) and isophorone yielded needle-shaped crystals of compound 1, G3TSPHB· (isophorone)3.7·(methanol)5.4 (Table S1). Single-crystal X-ray diffraction data collected at 100 K were consistent with the noncentrosymmetric monoclinic space group P21 (a = 23.13 Å, b = 7.48 Å, c = 24.17 Å, β = 117.65°, Table S2). The long axis of the needle-shaped crystals coincided with the crystallographic b axis (Figures 2A and S2−S5) and six-sided cylinders (void A), which were enclosed by six infinite GS ribbons fused along their edges to form the cylinder wall. Each GS cylinder, linked to six others through the TSPHB linker, was distorted from hexagonal symmetry. The external phenyl rings of TSPHB groups adopt a chiral propeller-like configuration. The crystal structure of 1 reveals five unique void spaces. Void A, the distorted hexagonal channel, is partially occupied by isophorone molecules (depicted in Figure 2A as stick style in light blue), with 66% refined occupancy per G3TSPHB. Voids B and C each contain one isophorone guest (depicted in

dark blue, occupancy 99%). Void D contains isophorone (depicted in light blue), refined at 77% occupancy. On the basis of stoichiometry determined by NMR spectroscopy (Table S1, Figure S6), the remaining isophorone must be contained in isolated pockets denoted as void E, but these could not be refined due to severe disorder. Void E is surrounded by isophorone guests and capped on the top and bottom by the central benzene rings of the tritopic TSPHB linkers, which are separated by 7.48 Å. Single crystals of compound 1 lose methanol solvate upon standing, presumably B

DOI: 10.1021/jacs.8b07065 J. Am. Chem. Soc. XXXX, XXX, XXX−XXX

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were 36% and 46%, respectively (Figures 2B, S15−S17, and Table S2). Further exposure for 7 additional minutes produced crystal 1-22min, which refined as the P63 structure, identical to compound 2, but with only 59% HFB occupancy in void E. These results demonstrate that the SCSCT from P21 to P63 occurred when the HFB occupancy in void E exceeds a critical threshold of roughly 50%. Similar experiments performed by exposure to the vapor of 50% v/v HFB/hexane (Figures S18, S19 and Table S2), with single-crystal X-ray data acquired at 7, 10, and 15 min, revealed that exchange was faster at the higher HFB concentration. The formation of compound 2 likely is driven thermodynamically by the well-documented quadrupole−quadrupole interactions47 between the central benzene ring in TSPHB and HFB, resulting in the formation of alternating stacks of TSPHB and HFB. Inspection of the crystal structure of 1 or the final product 2 does not reveal any obvious pathway for the exchange process, however. Raman spectroscopy was able to distinguish between crystals of 1 and 2, particularly through the appearance of the ring-breathing mode of HFB at 556 cm−1 in 2 (Figure S20). Although the HFB peak at 556 cm−1 partially overlapped with an isophorone peak at 554 cm−1, the inclusion of HFB could be assessed quantitatively by normalizing the intensity at 556 cm−1 relative to the isophorone mode at 533 cm−1, which remained unchanged during the transformation. Raman microscopy, with spatial resolution of approximately 1 μm, permitted characterization of the transformation at specific locations in the crystal. After its quality was verified by X-ray diffraction (see the Supporting Information), a single crystal of 1 was inserted partially into a 0.3 mm glass capillary closed on the opposite end and then sealed at the open end with Torr Seal. This isolated the inserted portion of the crystal within the capillary, while the remaining portion of the crystal remained exposed (Figures 3A and S21A). This configuration exposed the open ends of the

from either void A, D, or E, precluding accurate determination of the amount of methanol by NMR. After accounting for the electron density attributable to disordered isophorone (corresponding to the amount determined by NMR), however, Platon/Squeeze44 suggested 5.4 methanol molecules per G3TSPHB distributed among voids A, D, and E. The internal surfaces of void E, visualized by calculating Connolly surfaces (depicted as yellow/brown in Figure 2A)45 using a 1.2 Å probe radius, revealed apertures between the isophorone guests surrounding void E that were no larger than 0.3 Å, creating a seemingly impenetrable barrier to guest exchange (Figures S3−S5 and video S1). Exposure of single crystals of 1 to hexafluorobenzene (HFB) vapor for 1 h produced crystals with the composition G3TSPHB·(isophorone)3.3·(HFB)1.3·(methanol)4.8 (2), as determined by NMR and electron density calculation (Figure S7). The crystal structure of 2 was refined in the P63 space group (a = b = 24.07 Å, c = 7.37 Å, 100 K, Table S2), exhibiting a framework connectivity and architecture identical to that observed in 1 but with perfectly hexagonal cylinders, as required by the P63 symmetry (Figures 2C and S8−S10). Surprisingly, the diffraction intensity increased (Figure S11B,D,F) and the refinement improved after the transformation from R1 = 0.090 for 1 to R1 = 0.047 for 2. Optical microscopy of the single crystal of 2 revealed no obvious loss of the crystal integrity (Figure 2C). These observations were consistent with a single crystal−single crystal transformation. Under the P63 space group symmetry, voids B, C, and D from the original crystal 1 become symmetrically equivalent, each occupied by one isophorone molecule (100% occupancy). The increased occupancy in void D is presumed to be a consequence of migration of disordered isophorone from void E. The HFB guests, refined as 77% occupancy in crystal 2, were sandwiched between the central benzene rings of TSPHB, and reflected displacement of the disordered isophorone and methanol guests in void E of crystal 1. This afforded a stacking motif of alternating HFB guests and TSPHB rings. The interplanar phenyl−HFB spacing is 3.64 Å (Figures S9 and S10, video S2), similar to the typical eclipsed phenyl−HFB distance of 3.53 Å stacking46 and commensurate with one-half of the distance between sulfonate groups along each GS ribbon (c/2 = 3.68 Å). Platon/Squeeze confirmed that the remaining 0.3 isophorone and 0.5 HFB equivalents, as well as the 4.8 equiv of methanol, were located in void A, albeit randomly disordered. Immersion of single crystals of 1 in neat liquid HFB for 24 h afforded G3TSPHB·(isophorone)3.1·(HFB)2·(methanol)2 (2HFB(l)), as determined from 1H NMR (Figure S12) and the calculated electron density. X-ray data collected at 100 K confirmed 100% occupancy of HFB in void E (Figure S11E,F, Table S2). Additional measurements confirmed the crystal structures of 1 were identical at 100 K and ambient temperature, although the latter exhibited dynamic disorder of the isophorone guests (Table S2, Figures S11G,H and S13). To examine the evolution of the exchange and the SCSCT mechanism, X-ray diffraction data sets were acquired at 100 K for a single crystal coated with immersion oil, which mitigated loss of methanol solvate during handling but allowed transport of HFB from HFB vapor supplied by a 25% v/v HFB/hexane for scheduled intervals. The crystal structure of 1 (Figure S14) exposed for 8 min (1-8min), followed by an additional 7 min (1-15min), revealed that the crystal remained in the original P21 space group, even though the HFB occupancies in void E

Figure 3. (A) Schematic representation of a single crystal of compound 1 inserted partially into a closed-end glass capillary and sealed at the open end of the capillary with Torr Seal to isolate the inserted portion of the crystal while leaving the remaining portion exposed to HFB vapor. The long axis of the needle crystal coincides with the crystallographic b direction in P21 symmetry. (B) Relative intensities from Raman microscopy measurements recorded at a spot 50 μm from the crystal tip (blue dot; spot size 5 μm) at the exposed end of the crystal and at a spot inside the capillary (red dot) upon exposure to HFB vapor. The data reveal that only the exposed portion of the crystal incorporates HFB. C

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crystal (video S3). The lamellae propagated from the perimeter along two directions, one nearly parallel to the (100) plane and the other nearly perpendicular to the (100) plane (Figure 4). These lamellae consisted of alternating regions of high and low birefringence, corresponding to the monoclinic parent and hexagonal daughter phases, respectively. In the course of the transformation the number of lamellae increased, broadening and coalescing until the phase transformation was complete throughout the entire volume of the crystal. Quantitative measurements of linear birefringence performed with rotating polarizers in a Metripol microscope (Figure S23)50,51 revealed that during the initial stage of the transformation the birefringence decreased faster in the low-birefringence regions than in the high-birefringence regions of the parent phase. Once initiated on the perimeter of the crystal, the lamellae propagated rapidly at ca. 0.01 mm/s. If the crystal was removed from the HFB vapor prior to complete transformation, the lamellae continued to propagate for nearly 10 min to produce a partially transformed crystal (video S4). This suggests a trace amount of HFB on the internal surfaces of the lamellae that permits continuation of the transformation. Surprisingly, the lamellae heal as the transformation approaches completion, eventually affording a high-quality, completely transformed crystal of 2. Collectively, these observations suggest that the lamellae facilitate efficient transport of HFB along their interfaces, increasing the interfacial area for guest exchange and decreasing the effective diffusion length. This is consistent with a diffusional− displacive transformation that enables a faster SCSCT than that allowed by simple Fickian diffusion, wherein a structural change from monoclinic to hexagonal and motion of isophorone guests is provoked by the incoming HFB molecules, with propagation of the lamellae driven by the stress associated with the lattice mismatch between the interfaces of the parent and the transformed phases. Polarized Raman spectroscopy mapping of the phase transformation was performed using the νC=C stretching mode of isophorone (1629 cm−1), νC=C stretching mode of TSPHB (1600 cm−1), and the ring breathing mode of HFB (556 cm−1) as signatures (Figure S24). These measurements revealed a contrast between the transformed and untransformed regions that mirrored the changes observed by polarized optical microscopy (Figure S25). In a typical example, a {010} slice of 1 was exposed to HFB vapor for 1 min, after which several lamellae were observable under a polarized light microscope. In situ polarized Raman measurements (Figure 5), performed with the same crystal in the presence of vapor of 50% v/v HFB/hexane solution, revealed that the intensity of the 556 cm−1 HFB peak increased gradually, reaching a plateau after approximately 400 s. This was accompanied by a gradual increase in the intensity of the νC=C stretching mode of G3TSPHB (1600 cm−1). The intensity of the isophorone peak at 1629 cm−1, however, increased rapidly during the first 120 s, followed by a decrease to the initial value at 300 s. These events coincided with the appearance of the lamellar microstructure during the initial stage of the transformation following HFB exposure followed by their coalescence when the phase transformation is complete, as viewed through the optical microscope (video S5). These observations are consistent with dynamic motion of the isophorone guests during the phase transformation, enabling entry of HFB into void E, then returning to

GS cylinders at the tips of the crystal. After 17 min of exposure to HFB vapor, the inclusion of HFB was evident from the appearance of the 556 cm−1 signature in the exposed portion of the crystal only. The Raman intensity increased, indicating continuation of the transformation to 2. The portion isolated within the capillary, however, remained unchanged as P21, even after 2 days (X-ray data set 1-internal, Table S2 and Figure S21B,C). Furthermore, another crystal of 1 with its {010} tips blocked with Torr Seal revealed (Figure S21D) HFB exchange within 15 min by Raman spectroscopy and complete transformation to 2 within 1 h (X-ray data set 2capped, Table S2 and Figure S21E,F). These observations indicate that HFB is incorporated by diffusion perpendicular to the b axis rather than along the cylinders aligned with the b axis of 1. Assuming semi-infinite diffusion through the crystal faces parallel to the b axis, the time scale for the transformation corresponded to an apparent diffusion coefficient of D ≈ 1 × 10−8 cm2/s.48 The b-axis of monoclinic crystal 1 coincides with the c-axis of hexagonal crystal 2. Consequently, the SCSCT can be monitored in situ with polarized light microscopy49 of cross sections created by cutting perpendicular to the b-axis of the monoclinic form, as the birefringent section becomes optically isotropic during the transformation. After approximately 10 min of exposure to the vapor of a 20% v/v HFB/hexane solution, thin lamellae were observed, emerging from the crystal perimeter (Figures 4 and S22C), as well as from imperfections on the {010} surfaces introduced by cutting the

Figure 4. Polarized light optical micrographs of the (010) slice of a single crystal of compound 1 during its transformation to a single crystal of 2 upon exposure to HFB vapor. A first-order red retarder is inserted between the sample and the analyzer. (A) A single crystal (Xray data set 1-LB) of compound 1 prior to HFB exposure. (B,C) The appearance of lamellae after exposure to HFB for 19 and 36 min, respectively. Rapid and slowly transformed areas are denoted in (C) by the white and yellow arrows, respectively. (D) Birefringence of the completely transformed crystal is no longer observable after the SCSCT transformation to 2 was complete. The circular features are air bubbles in the immersion oil. D

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graphite crystal and collimated by a MonoCap collimator. The wavelength from the Mo Kα radiation is 0.71073 Å. The crystal temperature (100 K) was controlled by an Oxford Cryosystems 700+ Cooler. Crystals were mounted on a 0.2 mm MicroMount (MiTeGen) with Type B immersion oil (Cargille Laboratories). Crystal 1-synchrotron was measured at 100 K at the ChemMatCARS beamline of the Advanced Photon Source at Argonne National Laboratory, using a Bruker APEX II CCD detector and an Oxford Cryojet Cooler. A double monochromatic incident X-ray beam of 0.2 mm × 0.2 mm in size was used, conditioned using Si(111) and Si(311) monochromators to have an energy of 30 keV (λ = 0.41328 Å). The detector was mounted orthogonal to the beam path with a sample-to-detector distance of 80 mm. Two ϕ scans were performed with an exposure time of 0.2 s per frame. Data were collected and processed using the APEX2 software (version 2013.12) for data reduction, data correction, and cell refinement.55 The structures were solved by SHELXT56 and refined with full-matrix least-squares by SHELXL (Sheldrick 2014).57 Non-hydrogen atoms were refined with anisotropic displacement parameters, and hydrogen atoms were placed in idealized positions and refined with riding models. Platon/ Squeeze program was used to treat the randomly disordered groups in all structures, which could not be modeled from the electron density maps. The selected crystal data of 16 structures were listed in Table S2. Crystallographic data of these structures including cif, fcf, and hkl files have been deposited with the Cambridge Crystallographic Data Centre, and their corresponding deposite numbers are listed in Table S2. Copies of these data can be requested from, free of charge, the CCDC Web site at https://www.ccdc.cam.ac.uk/structures/. Raman Spectra. Raman spectra were collected using a Thermo Scientific DXR Raman microscope with a 5 mW 532 nm excitation laser and high-resolution grating. The measurements were performed at room temperature using a 25 μm slit aperture. The spectral resolution was 2 cm−1. The data were analyzed using the Omnic software package. Polarized Optical Microscopy. Images were collected on a polarized optical microscope equipped with a 10× objective. A firstorder red retarder was inserted between the sample and the analyzer. A 10 μm-thick crystal was sliced from crystal 1-LB along the normal direction of the needle. The crystal slice then was embedded in the apparatus described in Figure S1C,D and exposed to the vapor of a 20% v/v HFB/hexane solution for in situ polarized microscopy characterization. Synthesis of G 3 TSPHB (Guanidinium 1,3,5-Tri(4sulfonphenyl)benzene) Apohost. This procedure is adapted from a previous report.58,59 Concentrated sulfuric acid (ca. 98%, 15 g) was added to 1,3,5-triphenylbenzene (5 g) and heated to 110 °C for 16 h under a nitrogen atmosphere, after which the hot mixture was poured into 100 mL of deionized water. A solution saturated with sodium hydroxide was added until pH = 14, after which 13.6 g of ntetrabutyammonium chloride was added. The mixture was then extracted with dichloromethane, the organic layer was dried with anhydrous MgSO4, and excess solvent was removed. The resulting solid was then passed through a column packed with Amberlyst 36 ion-exchange resin. Guanidinium tetrafluoroborate (4 g) was then added to the eluent. This mixture was then dried in a rotary evaporator, and the resulting solid was washed with acetone several times and then dried in vacuo, affording 8 g of faint yellow G3TSPHB. 1 H NMR (400 M, d6-DMSO): 7.93 (s, 3H), 7.86 (d, 6H), 7.72 (d, 6H), 6.93 (s, 18H). Crystallization of 1 (G3TSPHB·(isophorone)3.7·(methanol)5.4). G3TSPHB apohost (10 mg) and isophorone (0.3 mL) were dissolved in 2 mL of methanol. The solvent was allowed to evaporate at room temperature in a desiccator containing 4 Å molecular sieves for 48 h, affording needle-shaped single crystals. Transformation of 1 to 2 (G3TSPHB·(isophorone)3.3·(hexafluorobenzene)1.3·(methanol)4.8). Single crystals of compound 1 were exposed to the vapor of neat hexafluorobenzene (HFB) (Figure S1A) for approximately 60 min, affording single crystals of compound 2, as confirmed by single-crystal X-ray structural analysis. The composition was further confirmed by 19F NMR analysis of crystals

Figure 5. In situ polarized Raman microscopy data acquired on the (010) face of a single crystal of compound 1 during its transformation to a single crystal of 2 upon exposure to HFB vapor, using signature modes (see text) for HFB (left y axis, blue), G3TSPHB (right y axis, red), and isophorone (left y axis, blue). The isophorone intensity increases initially, then decreases, suggesting reorientation during the phase transformation. Raman spot size = 7 μm.

orientations similar to the parent phase when the transformation is complete.

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CONCLUSIONS In summary, the TSPHB linkers and isophorone guests in compound 1 enclose a seemingly inaccessible void space that readily incorporates HFB through a single crystal−single crystal transformation from P21 to P63. Polarized Raman spectroscopy during the phase transformation is consistent with dynamic motion of the isophorone guests surrounding void E, the final destination of HFB. The transformation from 1 to 2 is triggered by HFB and accompanied by the formation of lamellae originating at the crystal perimeter, facilitating interfacial transport and decreasing the length scale for exchange, a mechanism distinct from that reported for other SCSCT systems, for example, the nontopotactic SCSCTs of glycine52 and the desolvation of a metal−organic framework.53 The appearance and propagation of the lamellae are similar to a recently reported martensitic transformation in a single crystal of an organic semiconductor, although this example did not involve guest exchange.54 The guest exchange is accompanied by only small changes of the unit cell dimensions but dramatic rearrangements of guest molecules. Overall, the results reveal a diffusional−displacive transformation that enables a faster SCSCT than that allowed by simple Fickian diffusion, similar to diffusional−displacive transformations in a Fe/C alloy39 and Sm(C2O4)3·10H2O.40 The results herein, however, suggest a route for rapid phase transformations accompanying guest exchange in molecular crystals as well.

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EXPERIMENTAL SECTION

Materials and Synthetic Procedures. Isophorone was purchased from Tokyo Chemical Industry Co., Ltd. (Tokyo, Japan), and other chemicals were purchased from Sigma-Aldrich (St. Louis, MO). These were used as received. Immersion oil and capillaries were purchased from Hampton Research. Torr Seal was purchased from Kurt J. Lesker Co. Premium cover glass was purchased from Fisher Scientific. Single-Crystal X-ray Data. All single-crystal X-ray diffraction data sets, other than crystal 1-synchrotron, were acquired on a Bruker SMART APEX II diffractometer equipped with a CCD detector. The X-ray beam generated from a sealed Mo tube is monochromated by a E

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Journal of the American Chemical Society dissolved in d6-DMSO to determine the p-fluorotoluene:HFB ratio using p-fluorotoluene as an internal standard. The G3TSPHB:pfluorobenzene ratio was determined by 1H NMR in d6-DMSO, and the G3TSPHB:HFB ratio was obtained from the p-fluorotoluene internal standard. Transformation of 1 to 2-HFB(l) (G3TSPHB·(isophorone)3.1· (hexafluorobenzene)2·(methanol)2). Single crystals of compound 1 were immersed in neat hexafluorobenzene liquid for 24 h to afford single crystals of compound 2-HFB(l). The composition was further confirmed by 19F NMR analysis of crystals dissolved in d6-DMSO to determine the p-fluorotoluene:HFB ratio using p-fluorotoluene as an internal standard. The G3TSPHB:p-fluorobenzene ratio was determined by 1H NMR in d6-DMSO, and the G3TSPHB:HFB ratio was obtained from the p-fluorotoluene internal standard.

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ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/jacs.8b07065. Experimental details and characterization data (PDF) X-ray crystallographic data for compound 1 (CIF) Video S1 (MPG) Video S2 (MPG) Video S3 (MPG) Video S4 (MPG) Video S5 (MPG)

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AUTHOR INFORMATION

Corresponding Authors

*[email protected] *[email protected] *[email protected] ORCID

Alexander G. Shtukenberg: 0000-0002-5590-4758 Chunhua T. Hu: 0000-0002-8172-2202 Michael D. Ward: 0000-0002-2090-781X Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS We acknowledge the support of the Materials Research Science and Engineering Center (MRSEC) Program of the National Science Foundation under award number DMR-1420073, the National Science Foundation through DMR-1308677, and the NSF Chemistry Research Instrumentation and Facilities Program (CHE-0840277). We also are grateful to A. Martin, T. Adachi, and M. Tan (NYU) and M. Olmstead (UC Davis) for helpful comments. Synchrotron X-ray data were collected at the ChemMatCARS Sector 15 at the Advanced Photon Source (APS), which is principally supported by the Divisions of Chemistry (CHE) and Materials Research (DMR), National Science Foundation, under grant number NSF/CHE-1346572. Use of the APS, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science by Argonne National Laboratory, was supported by the U.S. DOE under contract no. DE-AC02-06CH11357.

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