Regioselective access to orthogonal Diels-Alder C60 bis-adducts and tris-heteroadducts via avant-garde supramolecular mask strategy

The regioselective poly-functionalization of highly symmetric spherical Ih-C60 is extremely challenging and usually leads to the formation of regio-isomeric mixtures not amenable for HPLC purification. Recently, we have pioneered the regioselective functionalization of C60 fullerene under a supramolecular mask strategy, using tetragonal prismatic nanocapsules to encapsulate C60 and performing the Bingel tetrakis-cyclopropanation at the exposed fullerene surface through the four windows of the nanocapsule. Here, we describe an extension of the supramolecular mask strategy for the selective Diels-Alder (DA) functionalization of Ih-C60 using acenes. The supramolecular mask allows the chemo- and regioselective synthesis of e,e-bis-anthracene-C60 (functionalization at 90o) or the synthesis of trans-1-bis-pentacene-C60 (functionalization at 180o), only by changing the acene length. Moreover, the mask strategy allows to obtain unprecedented equatorial hetero-tris-functionalized-C60 adducts combining Diels-Alder with Bingel mask regiofunctionalization. Computational modelling revealed significant differences in the host-guest interactions and equilibrium established between the firstly formed anthracene- and pentacene-based monoadducts with the nanocapsule, respectively, which finally determine the observed orthogonal regioselectivity. The combination of Molecular Dynamics (MD) simulations and analysis of Frontier Molecular Orbital (FMO) involved in the Diels-Alder cycloadditions provide crucial insights to rationalize the regioselective control exerted by the supramolecular mask.