Open-Cage Fullerene Derivatives Suitable for the Encapsulation of a Hydrogen Molecule

• Published in: Journal of organic chemistry Vol. 70; no. 12; pp. 4820 - 4825
• Main Authors: Iwamatsu, Sho-ichi, Murata, Shizuaki, Andoh, Yukihiro, Minoura, Masayuki, Kobayashi, Kaoru, Mizorogi, Naomi, Nagase, Shigeru
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 10-06-2005
• Subjects: Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Fullerenes and related materials; diamonds, graphite; Materials science; Physics; Specific materials; Encapsulation; Cage compound; Hydrogen; Fullerenes; Mass spectroscopy; NMR spectroscopy; Activation energy
• ISSN: 0022-3263; 1520-6904
• DOI: 10.1021/jo050251w

The encapsulation of molecular hydrogen into an open-cage fullerene having a 16-membered ring orifice has been investigated. It is achieved by the pressurization of H2 at 0.6−13.5 MPa to afford endohedral hydrogen complexes of open-cage fullerenes in up to 83% yield. The efficiency of encapsulation is dominantly dependent on both H2 pressure and temperature. Hydrogen molecules inside the C60 cage are observed in the range of −7.3 to −7.5 ppm in 1H NMR spectra, and the formations of hydrogen complexes are further confirmed by mass spectrometry. The trapped hydrogen is released by heating. The activation energy barriers for this process are determined to be 22−24 kcal/mol. The DSC measurement of the endohedral H2 complex reveals that the escape of H2 from the C60 cage corresponds to an exothermic process, indicating that encapsulated H2 destabilizes the fullerene.