Squeezing formaldehyde into C<sub>60</sub> fullerene.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 38514674.
- Also identified by DOI 10.1038/s41467-024-46886-5 and PMC identifier 10957948.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
The cavity inside fullerene C<sub>60</sub> provides a highly symmetric and inert environment for housing atoms and small molecules. Here we report the encapsulation of formaldehyde inside C<sub>60</sub> by molecular surgery, yielding the supermolecular complex CH<sub>2</sub>O@C<sub>60</sub>, despite the 4.4 Å van der Waals length of CH<sub>2</sub>O exceeding the 3.7 Å internal diameter of C<sub>60</sub>. The presence of CH<sub>2</sub>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 <sup>13</sup>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.