Synthesis and properties of open fullerenes encapsulating ammonia and methane

Bloodworth, Sally; Gr�svik, John; Alom, Shamim; Kouril,, Karel; Elliott, Stuart J.; Wells, Neil J.; Horsewill, Anthony J.; Mamone, Salvatore; Jimenez-Ruiz, Monica; Rols, St�phane; Nagel, Urmas; Room, Toomas; Levitt, Malcolm H.; Whitby, Richard J.

Abstract

We describe the synthesis and characterisation of open fullerene (1) and its reduced form (2) in which CH₄ and NH₃ are encapsulated, respectively. The ¹H NMR resonance of endohedral NH₃ is broadened by scalar coupling to the quadrupolar ¹⁴N nucleus, which relaxes rapidly. This broadening is absent for small satellite peaks, which are attributed to natural abundance ¹⁵N. The influence of the scalar relaxation mechanism on the linewidth of the ¹H ammonia resonance is probed by variable temperature NMR. A rotational correlation time of τc= 1.5 ps. is determined for endohedral NH₃, and of τc=57±5 ps. for the open fullerene, indicating free rotation of the encapsulated molecule. IR spectroscopy of NH3@2 at 5 K identifies three vibrations of NH₃ (ν₁, ν₃ and ν₄) redshifted in comparison with free NH₃, and temperature dependence of the IR peak intensity indicates the presence of a large number of excited translational/ rotational states. Variable temperature ¹H NMR spectra indicate that endohedral CH4 is also able to rotate freely at 223 K, on the NMR timescale. Inelastic neutron scattering (INS) spectra of CH₄@1 show both rotational and translational modes of CH₄. Energy of the first excited rotational state (J=1) of CH₄@1 is significantly lower than that of free CH₄.

Citation

Bloodworth, S., Gräsvik, J., Alom, S., Kouril,, K., Elliott, S. J., Wells, N. J., Horsewill, A. J., Mamone, S., Jimenez-Ruiz, M., Rols, S., Nagel, U., Room, T., Levitt, M. H., & Whitby, R. J. (2018). Synthesis and properties of open fullerenes encapsulating ammonia and methane. ChemPhysChem, 19(3), https://doi.org/10.1002/cphc.201701212

• Journal Article Type: Article
• Acceptance Date: Nov 13, 2017
• Online Publication Date: Jan 4, 2018
• Publication Date: Feb 5, 2018
• Deposit Date: Feb 27, 2018
• Publicly Available Date: Feb 27, 2018
• Journal: ChemPhysChem
• Print ISSN: 1439-4235
• Electronic ISSN: 1439-7641
• Publisher: Wiley
• Peer Reviewed: Peer Reviewed
• Volume: 19
• Issue: 3
• DOI: https://doi.org/10.1002/cphc.201701212
• Keywords: endofullerenes; inelastic neutron scattering spectroscopy; infra-red spectroscopy; NMR spectroscopy; SpinDynamica
• Public URL: https://nottingham-repository.worktribe.com/output/909912
• Publisher URL: http://onlinelibrary.wiley.com/doi/10.1002/cphc.201701212/full
• Contract Date: Feb 27, 2018