The design of supramolecular capsules with large cavities is attractive because they feature potential advantages as platforms to selectively bind large guests, such as fullerenes and Endohedral Metallofullerenes (EMFs).¹ Generally, the practical applications of EMFs are hampered by their limited availability. Furthermore, their chromatographic purification (HLPC) is very challenging  and in some cases it is not successful. Our group reported a porphyrin-based supramolecular tetragonal prismatic nanocapsule (1),² which features an internal cavity with size complementary and electrostatic relationship specific for a brand new family of Uranium-based EMFs.³ Nanocapsule 1 is able to sequentially and specifically recognize U₂@I_h-C₈₀ and Sc₂UC@I_h-C₈₀ among all those compounds present in the crude, simply by soaking crystals in a solution of the reaction crude. The stepwise and selective encapsulation of U-based EMFs allowed their separation and further purification by solvent-washing, obtaining highly pure fractions of the desired compounds in one step. Follow-up studies with U-based C₇₈ soots indicate that not only the internal clusterelectronics but also the shape of the carbon cages strongly influences the selectivity of the nanocapsule.

Taking advantage of the tight binding of fullerenes in our porphyrin-based supramolecular tetragonal prismatic nanocapsules, these are used as supramolecular shadow masks to tame the over-reactivity of Bingel-Hirsch-type cyclopropanation reactions and, more importantly, to have full control on the equatorial regioselectivity and on the number of additions.⁴ Thus, exclusively equatorial bis-, tris- and tetrakis-C₆₀ adducts using ethyl-bromomalonate are stepwise obtained and fully characterized (NMR, UV-vis and XRD). Furthermore, the regioselectivity control is finely tuned using a three-shell Matryoshka-like assembly towards the synthesis of a single trans-3 bis-Bingel-C₆₀ for the first time.⁵ These results, fully attributed to the confinement control imposed by the capsule’s cavity, represent a novel and unique strategy to infer regio-control to the synthesis of fullerene multi-adducts. We envision that the described protocol will produce a plethora of derivatives for applications such as solar cells.