Isomer-pure functionalized fullerenes are required to boost the development of fullerene chemistry in any field, but their multiple functionalization renders a mixture of regioisomers that are very difficult to purify by chromatography. For the specific case of C70, its nonspherical geometry makes its regioselective functionalization more challenging than that of spherical C60. In this work, the supramolecular mask approach is applied for the first time to C70, which is encapsulated in two different nanocapsules to achieve the Bingel bis-cyclopropanation at alpha-bonds of opposite poles. Based on the tetragonal prismatic geometry imposed by the smaller supramolecular mask tested, the obtained major bis-adduct is completely reversed (major 5 o’clock) compared to bare C70 functionalization (major 2 o’clock). Moreover, by further restricting the accessibility of C70 using a three-shell Matryoshka mask and dibenzyl-bromomalonate, a single regiospecific 2 o’clock bis-isomer is obtained, owing to the perfect complementarity of the mask and the addend steric properties. The outcome of the reactions is fully explained at the molecular level employing a thorough molecular dynamics (MD) study of the accessibility of the alpha-bonds to produce the different bis-adducts.

This work has been led by Valentina Iannace, Clara Sabrià and Prof. Xavi Ribas of the QBIS-CAT group and Dr. Ferran Feixas of the TCBioSys group at the Institute of Computational Chemistry and Catalysis (IQCC) of the University of Girona, also in collaboration with Dr. Max von Delius (University of Ulm) and Prof. Daniel Maspoch (Catalan Institute of Nanoscience and Nanotechnology).
It has been recently published open access in Journal of the American Chemical Society:
V. Iannace, C. Sabrià, Y. Xu, M. von Delius, I. Imaz, D. Maspoch, F. Feixas*, and X. Ribas*
Regioswitchable Bingel Bis-Functionalization of Fullerene C70 via Supramolecular Masks
J. Am. Chem. Soc., 2024ASAP
DOI: 10.1021/jacs.3c10808

Girona, February 15, 2024
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