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

Abstract

The regioselective polyfunctionalization of highly symmetric spherical Ih-C60 is extremely challenging and usually leads to the formation of regioisomeric mixtures not amenable for high-pressure liquid chromatography (HPLC) purification. Here, we pioneer the use of tetragonal prismatic nanocapsules to perform selective Diels-Alder (DA) functionalization of encapsulated Ih-C60 using acenes. The supramolecular mask allows the regioselective synthesis of either e,e-bis-anthracene-C60 (functionalization at 90°) or the synthesis of trans-1-bis-pentacene-C60 (functionalization at 180°) by changing only the acene length. Moreover, the mask strategy allows one to obtain unprecedented equatorial hetero-tris-functionalized-C60 adducts combining Diels-Alder with Bingel mask regiofunctionalization. Computational modeling provides crucial insights to rationalize the regioselective control exerted by the supramolecular mask on the successive DA cycloadditions. Molecular dynamics (MD) simulations revealed significant differences in the host-guest interactions and equilibrium established between the first-formed anthracene- and pentacene-based mono-adducts with the nanocapsule, which finally determine the observed orthogonal regioselectivity.