Squeezing formaldehyde into C60 fullerene
Vijyesh K. Vyas, George R. Bacanu, Murari Soundararajan, Elizabeth S. Marsden, Tanzeeha Jafari, Anna Shugai, Mark E. Light, U. Nagel, T. Rõõm, Malcolm H. Levitt, Richard J. Whitby
Abstract
Abstract The cavity inside fullerene C 60 provides a highly symmetric and inert environment for housing atoms and small molecules. Here we report the encapsulation of formaldehyde inside C 60 by molecular surgery, yielding the supermolecular complex CH 2 O@C 60 , despite the 4.4 Å van der Waals length of CH 2 O exceeding the 3.7 Å internal diameter of C 60 . The presence of CH 2 O significantly reduces the cage HOMO-LUMO gap. Nuclear spin-spin couplings are observed between the fullerene host and the formaldehyde guest. The rapid spin-lattice relaxation of the formaldehyde 13 C nuclei is attributed to a dominant spin-rotation mechanism. Despite being squeezed so tightly, the encapsulated formaldehyde molecules rotate freely about their long axes even at cryogenic temperatures, allowing observation of the ortho-to-para spin isomer conversion by infrared spectroscopy. The particle in a box nature of the system is demonstrated by the observation of two quantised translational modes in the cryogenic THz spectra.