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Investigating structural alterations in pyrogallol[4]arene-pyrene nanotubular frameworks
Harshita Kumari1, Steven R Kline, Wei G Wycoff
1Department of Chemistry, University of Missouri-Columbia, 601 S. College Avenue, Columbia, MO 65211, USA.
Small (Weinheim an Der Bergstrasse, Germany)
|August 14, 2012
Summary
Hydrogen-bonded pyrogallol[4]arene nanotubes transform into spherical structures in acetone. This study reveals solvent-induced structural changes in these nanoassemblies, favoring stable nanocapsules over nanotubes.
Area of Science:
- Supramolecular Chemistry
- Materials Science
- Nanotechnology
Background:
- Hydrogen-bonded pyrogallol[4]arene (PgC6) form nanotubular frameworks in the solid state.
- Investigating the solution-phase stability and geometry of these assemblies is crucial for understanding their applications.
Purpose of the Study:
- To investigate the structural stability and geometry of pyrene-guest-containing C-hexylpyrogallol[4]arene (PgC6-pyrene) nanotubular frameworks in solution.
- To explore the influence of different solvents on the self-assembly of PgC6-pyrene.
Main Methods:
- Small-angle neutron scattering (SANS) to analyze the structure of PgC6-pyrene assemblies.
- Diffusion Nuclear Magnetic Resonance (NMR) spectroscopy to study molecular mobility and structural rearrangements.
Main Results:
- In acetone, PgC6-pyrene assemblies rearrange from nanotubes to dimeric spheres, with no pyrene guest observed.
- Individual PgC6 spheres exhibit a radius of approximately 8.6 Å and a diffusion coefficient of 9.12 × 10⁻¹⁰ m²/s in acetone.
- Solvent type (acetone, methanol, acetonitrile/D2O) significantly influences the structural differences in PgC6 nanoassemblies.
Conclusions:
- This work presents the first example of a structural transformation of pyrogallol[4]arene nanotubes (guest-exo) in solution.
- The observed solution-phase structural alteration provides evidence for the enhanced stability of pyrogallol[4]arene nanocapsules compared to nanotubes.
- Diffusion NMR offers new insights into solvent-governed structural variations in these supramolecular nanoassemblies.
