Precise Spatial Arrangement and Interaction between Two Different Mobile Components in a Metal-Organic Framework

•MOFs containing [2]rotaxane molecular shuttle ligands•Solvent-assisted linker exchange to access highly crystalline MOFs•Co-ligands dictate the translational position of rotaxane macrocycle•2H solid-state NMR reveals interaction two dynamic components Molecular rotors, motors, and mechanically interlocked molecules are all that can be utilized assemble more complex machines. In order do this mimic behavior macroscopic or biological machinery, strategies need developed for arranging so they interact influence each other’s motion. The organization inside metal-organic frameworks (MOFs) is one such approach. periodic nature MOFs provides a high degree control over spatial orientation its building units, while porosity these materials room not only motion individual but also between components. An H-shaped with biphenyl axle 24-crown-8 (24C8) macrocycle was inserted into tetrahedral cavities isostructural fcu PCN-57, UiO-68-d4, UWCM-10. resulting UWDM-8, UWDM-9-d4, UWDM-10 have precise arrangements different mobile components—a rigid rotor (tetramethylphenyl, phenyl-d4, tetrazine) (24C8). mobility units characterized by variable-temperature (VT) nuclear magnetic resonance (SSNMR). VT 13C SSNMR showed macrocyclic wheel along dictated bulk rotational central rotor, 2H demonstrated dynamics influenced presence macrocycle. One major challenges achieving stimuli-responsive solids in science involves cooperativity synchronization among components.1Khuong T.A. Nuñez J.E. Godinez C.E. Garcia-Garibay M.A. Crystalline machines: quest toward function.Acc. Chem. Res. 2006; 39: 413-422Crossref PubMed Scopus (276) Google Scholar, 2Deng H. Olson Stoddart J.F. Yaghi O.M. Robust dynamics.Nat. 2010; 2: 439-443Crossref (198) 3Krause S. Feringa B.L. 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Each contains primary TTDC (tetramethylterphenyl-dicarboxylate), TPDC-d4 (terphenyldicarboxylate-d4), DPCT (diphenyldicarboxy-tetrazine), respectively, plus spanning (see Figures S1–S4). Direct solvothermal synthesis simple starting possible. Therefore, solvent-assisted (SALE)24Dorneles de Mello M. Kumar Tabassum Jain S.K. T.H. Caratzoulas Vlachos D.G. Han Scott S.L. al.Phosphonate-modified Brønsted acid catalyst use Dehydra-Decyclization 2-Methyltetrahydrofuran pentadienes.Angew. 59: 13260-13266Crossref (7) 25Tan Z. Y. Cui Controlled achiral chiral UiO-68 framework.J. 2018; 140: 16229-16236Crossref (88) 26Islamoglu Goswami Howarth Farha O.K. Hupp J.T. Postsynthetic tuning targeted applications.Acc. 50: 805-813Crossref (439) 27Nickerl Senkovska Kaskel Tetrazine functionalized optical sensor oxidizing gases.Chem. Commun. 51: 2280-2282Crossref 28Karagiaridi O. Bury Mondloch Solvent-assisted exchange: alternative novo unattainable frameworks.Angew. 53: 4530-4540Crossref (263) 29Deria Karagiaridi Beyond post-synthesis modification: evolution block replacement.Chem. 43: 5896-5912Crossref 30Kim Cahill Su Prather K.A. Cohen S.M. ligand route functionalization ‘inert’ 3: 126-130Crossref prepare pristine samples PCN-57 UWDM-8; although latter, partial due denticity tetracarboxylate basic crystal structure net, found formula [Zr6(O)4(OH)4(L)6] (L = dicarboxylate linker), depicted Figure 1A. addition UWCM-10, which H2DPCT tetrazine group; details X-ray summarized Supplemental Experimental Procedures Table S1; S5–S7). Although recently prepared synthesis, material (ZrTz-68) single-crystal diffraction.31BIOVIA Dassault Systèmes Materials Studio. Systèmes, San Diego2019Google structures replacing terphenylene give UWDM-10, formulas [Zr6(O)4(OH)4(1)(L)4], precisely spans width cavity (i.e., ca. 16.7 Å). since SALE, (67%) incorporation could accomplished. Powder diffraction (PXRD) thermal gravimetric analysis (TGA) data S8–S11) were consistent being parent UiO-68, 1B–1D show computer generated (Materials Studio,32Vinu Sivasankar Prabu J.-L. Lin C.-H. C.-C. Demel Tetrazine-based scaffolds post-synthetic modification reaction.Eur. Inorg. 2020: 461-466Crossref (9) Forcite) viewed down emphasize 24C8 arrangement linkers. number features apparent: free volume transit axle, benzimidazole recognition site other, requires come close i.e., linker; presents barrier ring; and, perhaps least obvious, limited may prevent unrestricted sites understand how aspects rings might affect ring, enriched at 2-position (50%, labeled ? 2B, 2F, 2J ). direct method distinguish complexed uncomplexed (SSNMR) chemical shift allows identification and/or crossbar; 2 summarizes results experiments. For TTDC, four methyl attached phenyl reasons, positioned perpendicular terminal (Figure 2A). orients directly potential path (Figures 2B 2C). room-temperature spectrum 2D) sharp peaks indictive groups. Since does vary temperature S12), concluded essentially unsurmountable, locked DPCT, prefers reside same plane 2E). away any interactions 2F 2G). 2H) overlapping sets resonances: similar UWDM-8—from SALE—and broader peak observed UWDM-8. fact maximum 67% uptake during SALE process UWDM-10(see S14). Thus, made up combination contain where lock place those enough allow unlock constraints giving rise shift. It should noted favored constraints—in case, imposed corners cavity—or competitive binding reported previously.33Gholami Baggi Schott E. Zarate Influence length rate mechanism shuttling [2]rotaxanes.Chem. 8: 7718-7723Crossref very scenario sites, would produce average shifts increased temperatures—this observed; rather, just some broadening pattern centered 152.6 ppm occurs elevated temperatures S15–S16; S2). case situation complicated because preferred temperature, occupying several low-energy positions relative 2I). presumed unsubstituted unlikely 2K). Indeed, borne out spectrum, broad indicative therefore, unlocked ring. There few possible reasons UWDM-9-d4. On first sight, appears there many minor underlying corresponding positions, never clearly resolved, even 1H–13C CP/MAS spectra no substantial changes shapes S13). Rather, probable distribution result transient, through-space large pliant slightly scales mobilities. further probe hypothesis, UiO-68-d4 UWDM-9-d4 TPDC-d4, deuterium atoms. availability allowed spectroscopy compare materials, without accompanying While numerous investigations MOFs,34Khudozhitkov A.E. Kolokolov D.I. Stepanov A.G. Characterization fast restricted librations terephthalate UiO-66(Zr) spin–lattice relaxation analysis.J. Phys. 122: 12956-12962Crossref best our knowledge, dynamical motions explored other method. date, majority studies rotors 1,4-benzenedicarboxylate (BDC) linkers, IRMOF-1 UiO-66.34Khudozhitkov Scholar,35Kolokolov Guillerm V. Serre Frick Jobic Probing porous Zr neutron scattering.J. 116: 12131-12136Crossref These fragments ?-flips 180° reorientations), barriers ranging 27 52 kJ mol?1.34Khudozhitkov UiO-66(Zr); system most probed co-workers.35Kolokolov fragment undergoes ?-flips, activation 30 mol–1 correlation times, attributed disorder arising variability metal-oxygen lengths. group published later investigation loading benzene guest UiO-66, finding rates flips slow levels.36Khudozhitkov Freude Haase guest-mediated spectroscopy.J. 121: 11593-11600Crossref (15) reveal motional distinct systems date 3A). At -100°C, static; slow-motion limit (SML) fit quadrupolar coupling constant, CQ, 180 kHz, asymmetry parameter ?Q, 0. Motion onset -75°C, observable patterns 100°C (full shown S17). Variable-temperature PXRD (VT-PXRD) confirmed integrity 175°C S6). attempted two-site ?-flip simulations; however, set parameters involving parameters, rates, Euler angles orient C–D vectors electric field gradient (EFG) tensors) yield intermediate regime (IMR) fast-motion (FML) (representative examples two- three-site models S19 S20). Examination four-site phenyl-like particular, similarity powder own high-temperature limits,37Horike Matsuda R. Tanaka Matsubara Mizuno Endo Kitagawa Dynamic coordination polymers.Angew. 45: 7226-7230Crossref (205) 38Yan Da Silva Blake Dailly Manuel Tang C.C. Schröder Porous polyhedral optimal pore geometry methane storage.J. 139: 13349-13360Crossref (60) 39Moreau Easun T.L. Lewis Nowell Lennox M.J. Besley al.Tailoring Octacarboxylate frameworks.Proc. 3056-3061Crossref (48) encouraged us attempt simulating models. Our final model flipping S3 simulation details) C2 axis flanked rings. EFG tensor orientations defined (? 0°; ? 60°, ?? –60°; ? –45°, +45°; ?? +45°, –45°). lower (in SML IMR), three k1, k2, k3, describe through rotations 90°, 180°, respectively 3C; see S21 matrices). k1 “wobble” (1–2 3–4) side lowest energy. IMR rates; Arrhenius plot yields energy, Ea ± mol?1, pre-exponential factor, 1.28 × 10–11 s?1 S22). k2 (2–3 1–4) k3 (2–4 1–3) processes, involve opposite side, remain approximately temperatures; 104 ? 103 s?1). values larger than process, cannot calculated, variation observed, FML reached. Interestingly, unlike aforementioned models, discontinuities increase spacing higher temperatures, indicates gradually increasing [? ±48°, ±48°] temperatures), 84°, 96°, processes FML. Evidence dramatic S23. note best-fit simulated key well; residual signal center (which low intensity signals), co-workers 3E) bear superficial resemblance especially low-temperature (the CQ kHz ?Q 0). Attempts simulate two-, three-, (akin UiO-68-d4) unsuccessful. ?50°C S17), indicating moving quickly, others position; signals observed. Furthermore, spacings sharp, horns temperatures. six-site [? 0°, –45°] fixed constants, simulations match experimental data, 3G; describes “inner ring” 0°) “outer ±45°) flanking 1–2 2–3), less-frequent 90° outer 3–4 1–6; 3G)—no evidenced 1–4, 2–5, 3–6). Even ?25°C, inner axis. As such, weighted contributions static), undergoing dynamic), 107 s?1. Hence, ?75°C, almost static, whereas 125°C above, them exchange. difference absence unusual interpreted indirect We, interpret observation spatially proximate crown ether 1. static/locked dynamic/wobbling temperature-dependent suggests restricts dynamics, tilt, deform, eliminate restrictions conformations characteristic MOFs.15Gholami designed span conventional strategy MOFs. experiments substitution dramatically crossbar. onto end track, sterically benign move track avoiding skeleton. Most importantly, study potentially subtler fashion. validate hypothesis coupled interactions, dependent.