A molecular shuttle that operates inside a metal–organic framework


A ‘molecular shuttle’ is an interlocked molecular assembly in which a macrocyclic ring is able to move back and forth between two recognition sites. This large-amplitude translational motion was first characterized in solution in 1991. Since that report, many mechanically interlocked molecules (MIMs) have been designed, synthesized and shown to mimic the complex functions of macroscopic switches and machines. Here, we show that this fundamental concept—the translational motion of a molecular shuttle—can be organized, initiated and made to operate inside a crystalline, solid-state material. A metal–organic framework (MOF) designated UWDM-4 was prepared that contains a rigid linker that is a molecular shuttle. It was demonstrated by variable-temperature 1H-13C cross-polarization/magic-angle spinning (CP/MAS) and 13C 2D exchange correlation spectroscopy (EXSY) solid-state NMR at 21.1 T on a 13C-enriched sample that the macrocyclic ring undergoes rapid shuttling along the rigid axle built between struts of the framework.

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Figure 1: Stoddart's original molecular shuttle operating in acetone solution.
Figure 2: MOF materials are commonly constructed from a combination of rigid linking struts (green) and metal nodes (brown).
Figure 3: Synthesis and X-ray structural characterization of a molecular shuttle linker.
Figure 4: Structure of UWDM-4·HBF4 determined by single-crystal X-ray diffraction.
Figure 5: UWDM-4·HBF4 can be efficiently converted to UWDM-4 without loss of crystallinity.
Figure 6: 13C SSNMR studies verify that the designed molecular shuttle can undergo translational motion (molecular shuttling) inside the lattice of the MOF.


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This work was supported by the Natural Sciences and Engineering Research Council (NSERC) of Canada through Discovery Grants and Accelerator Supplements to S.J.L. and R.W.S. and a Canada Research Chair award to S.J.L. R.W.S. and S.J.L. acknowledge support from NSERC, the Canadian Foundation for Innovation, the Ontario Innovation Trust and the University of Windsor, for the development and maintenance of the SSNMR and X-ray diffraction centres. V.N.V. acknowledges financial support provided by NSERC through an Alexander Graham Bell Canada Graduate Doctoral Scholarship and by the International Center for Diffraction Data for a Ludo Frevel Crystallography Scholarship. The authors thank M. Revington for technical assistance with solution NMR spectroscopy experiments, V. Terskikh for collecting the 21.1 T SSNMR data and J. Auld for recording electrospray mass spectrometry data. Access to the 900 MHz NMR spectrometer was provided by the National Ultrahigh-Field NMR Facility for Solids (Ottawa, Canada; http://www.uwindsor.ca).

Author information

S.J.L. supervised the project. K.Z. designed the experiments with help from V.N.V. and C.O. K.Z. performed all the synthetic experiments. K.Z. and V.N.V. collected and analysed the PXRD, TGA and SCXRD data with assistance from S.J.L. C.O. collected and analysed the SSNMR data. R.W.S supervised all SSNMR data collection, analysis and interpretation. S.J.L. and K.Z. wrote the manuscript with input from V.N.V., C.O. and R.W.S.

Correspondence to Robert W. Schurko or Stephen J. Loeb.

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Crystallographic data for compound 2. (CIF 1490 kb)

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Crystallographic data for compound UWDM-4•HBF4. (CIF 4846 kb)

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Zhu, K., O'Keefe, C., Vukotic, V. et al. A molecular shuttle that operates inside a metal–organic framework. Nature Chem 7, 514–519 (2015) doi:10.1038/nchem.2258

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