Henry Rzepa's Blog

The annual “Molecules of the Year” selections are available for the year 2025. A theme was elemental allotropes and one such was carbon in the form of C₄₈ stabilised by formation of a catenane C₄₈.M3 (M = red ligand below)[1] – it was not possible however to crystallise C₄₈.M3. When “unmasked” by removal of the M ligand, the true allotrope C₄₈ had a solution half-life of about 1 hour at 20°C. This follows the reports from 2019 onwards of a series of smaller cyclo[n]carbon allotropes, (n=6,10,12,13,14,16,18,20,26)[2],[3] which were only characterised on a solid surface and not in solution.

(more…)

References

1. Y. Gao, P. Gupta, I. Rončević, C. Mycroft, P.J. Gates, A.W. Parker, and H.L. Anderson, "Solution-phase stabilization of a cyclocarbon by catenane formation", Science, vol. 389, pp. 708-710, 2025. https://doi.org/10.1126/science.ady6054
2. K. Kaiser, L.M. Scriven, F. Schulz, P. Gawel, L. Gross, and H.L. Anderson, "An sp-hybridized molecular carbon allotrope, cyclo[18]carbon", Science, vol. 365, pp. 1299-1301, 2019. https://doi.org/10.1126/science.aay1914
3. H. Rzepa, "Cyclo[18]carbon: The Kekulé vibration calculated and hence a mystery!", 2019. https://doi.org/10.59350/jdy16-7rv58