Supramolecular Fullerene Sponges as Catalytic Masks for Regioselective Functionalization of C60

Isomer-pure poly-functionalized fullerenes are required to boost the development of fullerene chemistry in all fields. On a general basis, multi-adduct mixtures with uncontrolled regioselectivity are obtained, and the use of chromatographic purification is prohibitively costly and time consuming, especially in the production of solar cells. Single-isomer poly-functionalized fullerenes are only accessible via stoichiometric, multistep paths entailing protecting-unprotecting sequences. Herein, a nanocapsule is used as a supramolecular tetragonal prismatic mask to exert full control on the reactivity and the equatorial regioselectivity of Bingel-Hirsch cyclopropanation reactions of a confined C60 guest. Thus, equatorial bis-, tris-, and tetrakis-C60 homo-adducts are exclusively obtained in a stepwise manner. Furthermore, isomer-pure equatorial hetero-tetrakis-adducts or hetero-Th-hexakis-adducts are synthesized at will in one-pot synthesis for the first time. The supramolecular mask protocol is a significant step forward for the regioselective functionalization of fullerenes. The exquisite ability to form pureisomer poly-functionalized C60 adducts, overcoming tedious and non-practical chromatographic separations, allows for their direct testing in solar cell prototypes. Furthermore, the supramolecular mask strategy can be applied to C70 or higher fullerenes, opening a plethora of poly-functionalized fullerene derivatives to be synthesized and tested. Moreover, apart from the nucleophilic cyclopropanations reported herein, the protocol is currently being expanded to Diels-Alder (DA), 1,3-dipolar cycloadditions and PC60BM-type cyclopropanations, thus enabling a variety of regioselective functionalization reactions. This supramolecular mask strategy can help the discovery of the next generation of improved solar cells (organic or perovskite based) or new drug candidates.

This paper was recently published in Chem:

C. Fuertes-Espinosa, C. García-Simón, M. Pujals, M. Garcia-Borràs, L. Gómez, T. Parella, J. Juanhuix, I. Imaz, D. Maspoch, M. Costas, and X. Ribas
“Supramolecular Fullerene Sponges as Catalytic Masks for Regioselective Functionalization of C60”
Chem., 2019, ASAP [abstract]