Studying Buckminsterfullerene Using High-Resolution Infrared Absorption Spectroscopy

Buckminsterfullerene is a molecule that has fascinated researchers. Known for containing 60 carbon atoms (C₆₀), buckminsterfullerene is known for its physical properties (1). Because of its unique structure, researchers have taken a special interest in examining the molecule to learn more about its physical properties, including what they can tell us about other fullerene molecules.

Buckminsterfullerene was named after architect Buckminster Fuller, who had popularized geodesic domes (2). The molecule, because it closely resembles the shape of a geodesic dome, was colloquially referred to as “buckyballs” for this reason (2). Geodesic domes have a curved appearance and are comprised of equilateral triangles; they are designed to sustain their own weight (2). The geodesic dome, apart from being a distinctive architectural style, is often noted for its similarity to the soccer ball (2).

A study published in Science examined buckminsterfullerene using high-resolution infrared (IR) absorption spectroscopy (1). The research team, led by P. Bryan Changala, Marissa L. Weichman, and Jun Ye, used total quantum state-resolved spectroscopy to study the isolated buckminsterfullerene molecules.

Despite decades of interest, observing total quantum state–resolved spectroscopy of isolated C₆₀ molecules has proven challenging, primarily because of difficulties in preparing cold, gas-phase C₆₀ in high densities (1). However, the team's approach utilizing cryogenic buffer-gas cooling and cavity-enhanced direct frequency comb spectroscopy enabled the observation of quantum state–resolved rovibrational transitions in buckminsterfullerene (1).

By using high-resolution infrared absorption spectroscopy, conducted in the 8.5-µm (1176.47 cm^–1) spectral region, revealed characteristic nuclear spin statistical intensity patterns that confirm the indistinguishability of the carbon-12 atoms within the molecule (1). Additionally, the rovibrational fine structure provided further insight into the rare icosahedral symmetry of buckminsterfullerene.

This achievement not only sheds light on the fundamental properties of buckminsterfullerene, but it also opens up new avenues for future research in fullerene science. The success of buffer-gas cooling paves the way for similar studies on larger fullerenes like C₇₀, as well as endofullerenes, where an atom or small molecule is enclosed within the fullerene cage (1).

Fullerene research has shifted over the decades. At first, fullerenes were studied for where they could exist in nature. Researchers discovered that fullerenes have been observed in soot and in outer space, for example (2). Once research in this field shifted to studying its physical properties, researchers discovered that unlike other carbon allotropes, the molecule is soluble in nonoxygenated organic solvents such as toluene (2).

This study conducted by the research team shows how precision spectroscopy techniques demonstrate the initial steps toward single quantum state preparation and control of large molecular systems (1). Such capabilities could have far-reaching implications across various fields, from quantum computing to materials science (1).

The findings reported by Changala, Weichman, Ye, and their team not only deepen our understanding of how they can alter molecular quantum states, but they discovered more about the physical properties of buckminsterfullerene (1). Despite chemists Harold W. Kroto at the University of Sussex, Richard E. Smalley at Rice University, and Robert F. Curl Jr., also of Rice University discovering the molecule in 1985, there is still a lot researchers do not know about this molecule’s physical properties (2). This study advances work into fullerene research, exploring how these molecules can be properly utilized in nanotechnology and other applications.

References

(1) Changala, P. B.; Weichman, M. L.; Lee, K. F.; et al. Rovibrational Quantum State Resolution of the C60 Fullerene. Science 2019, 363 (6422), 49–54. DOI: 10.1126/science.aav2616

(2) American Chemical Society, Molecule of the Week Archive: Buckminsterfullerene. Available at: https://www.acs.org/molecule-of-the-week/archive/b/buckminsterfullerene.html (accessed 2024-04-30).