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Shape-Persistent Macrocycles New Platforms for Cluster Compounds?

This research explores the use of shape-persistent macrocycles as precursors for molecule-based nanotubes. The self-assembly of these nanotubes is achieved through non-covalent interactions, such as hydrogen bonding. The resulting nanotubes have potential applications in AFM tips, nanoelectronics, sensors, hydrogen storage, and more. However, challenges include scaling up production, purification, and limited compositions.

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Shape-Persistent Macrocycles New Platforms for Cluster Compounds?

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  1. Shape-Persistent MacrocyclesNew Platforms for Cluster Compounds? Shape-Persistent Precursors for Molecule-Based Nanotubes Mark MacLachlan Department of Chemistry University of British Columbia

  2. Nanotubes curl • AFM tips • nanoelectronics • sensors • host for nanomaterials • hydrogen storage • space elevator? • difficult to scale up • difficult to purify • polydisperse widths • mixture of electronic properties • limited to few compositions

  3. Nature’s Way – Self-Assembly Can we use non-covalent interactions to assemble stable nanotubes? Self-assembly Nature uses hydrogen bonding to assemble its materials: DNA (storage) and proteins (processors).

  4. Molecule-Based NanotubesHydrogen-Bonding • ion channel mimics Reza Ghadiri, Scripp’s Institute

  5. Molecule-Based Nanotubesp-Stacking • driven by p-p interactions at high concentrations • can also occur in polar solvents Jeffrey Moore, Sigurd Höger

  6. Coordination Chemistry Rigid, shaped metal-containing molecules can be organized using chemistry. … … 1-D nanowires

  7. Molecular Nanotubes • monodisperse channels • tunable design with organic chemistry Channel! = • ion channels • templates for nanomaterials • molecular size / shape selective sensors and catalysts

  8. = Disc Shaped Molecules for Stacking • covalent ring – stability • conjugated – properties

  9. Assembly Reaction amine aldehyde imine

  10. Precursors Yield: ~50% 20 g scale 50 g scale Yield: ~50%

  11. Assembly [3+3] Schiff Base Condensation 1H NMR Spectrum R = C6H13 (300 MHz, CDCl3) 75-80% yield CH N=CH OCH2 OH

  12. Structure (R = C2H5) • not flat • strong OH---N bonding

  13. A crown ether? Assembly [3+3] Schiff Base Condensation 1H NMR Spectrum R = C6H13 (300 MHz, CDCl3) 75-80% yield CH N=CH OCH2 OH

  14. Addition of Metal Ions 10-4 M CH2Cl2 + NaBPh4 + KBPh4 + RbBPh4 + CsBPh4 + NH4BPh4 • Addition of alkali metal or NH4+ results in a dramatic colour change

  15. Electrospray MS 3 (R = C6H13)

  16. UV-Visible Spectroscopy 3 + NaBPh4 3 + CsBPh4 • changes in spectra with addition of alkali metal • change for Na+ > K+ > Rb+ > Cs+ • no clear isosbestic point – many species 3 (R = C6H13)

  17. 1H NMR Spectroscopy – Na+ OCH2 N=CH CH OH + = BPh4-

  18. 1H NMR Spectroscopy – Cs+ “[3]2Cs+”

  19. Na+ Cs+ (NH4+) vs. Key Points Oligomers observed in MS Colour change is dependent on cation Large upfield shifts of peaks on periphery of macrocycle (1H NMR) Shifts depend on the size of the cation (1H NMR, UV-vis) Final ratio of 1:1 [3]:M+ Influence of adjacent ring currents Greater shift with Na+

  20. Proposed Model • the macrocycles can be assembled into 1-D “polymers” by alkali metals in solution Gallant, Angew. Chem. Int. Ed. Engl.2003.

  21. What about other metals?

  22. Reaction With Excess Zinc 1H NMR Spectrum (300 MHz, CDCl3) Loss of OH peak Zn+ macrocycle macrocycle

  23. SCXRD Structure • heptanuclear zinc complex • 4, 5, and 6-coordinate Zn atoms

  24. Structure

  25. Zn7 Structure – Side Cluster-capped cone • 4, 5, and 6-coordinate Zn atoms • no plane of symmetry in macrocycle • C3v symmetry

  26. Cluster Formation Mechanism Two possibilities: • Macrocycle scoops up pre-formed [Zn4O]6+ cluster in solution • Macrocycle templates formation of cluster in its interior

  27. An Intermediate The cluster is templated by the macrocycle.

  28. Zn7 Structure – Bottom There is space in the bottom.

  29. Coordination Capsules? New metallohosts for supramolecular chemistry

  30. Expanding the Macrocycles 68% yield 2.3 nm C=N: d CH ~ 8.58 ppm nC=N: 1607 cm-1 (IR) nC≡C: 2208 cm-1 (Raman)

  31. MALDI-TOF Spectrum 1617 M+ = 1616 (R = C6H13)

  32. (Further) Expanding the Macrocycles 8.8 Å 13.2 Å 8.6 Å 6.7 Å 2.5 nm 2.9 nm 62% yield 40% yield • We can tune the size, shape, and properties of the macrocycles Dimensions from semi-empirical (PM3) calculations

  33. Wavelength (nm) Fluorescent Macrocycles

  34. Zn3 Macrocycle in THF/DCM • In DCM: • redshift (~ 50 nm) • broad

  35. NMR Study DCM-d2:THF-d8 0:1 1:3 1:1 3:1 1:0

  36. Aggregation Model CH2Cl2 THF Assembly may be driven by Zn---O interactions

  37. A Turn-On Sensor + Base Deaggregation

  38. DCM DCM THF

  39. Diamond-Shaped Macrocycles

  40. Wavelength (nm) Recap Precursors for new magnetic materials?

  41. Acknowledgements Cecily • Amanda Gallant • Cecily Ma • Jonathan Chong • Marc Sauer • Alfred Leung • Joseph Hui • Ago Pietrangelo • Britta Boden • Amir Abdolmaleki • Charles Yeung Amanda • UBC Mass Spectrometry Facility (Yun Ling, Marshall Lapawa) • UBC, NSERC, and CFI for Funding

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