Highly Regioselective Derivatization of Trimetallic Nitride Templated Endohedral Metallofullerenes via a Facile Photochemical Reaction

Photochemically generated benzyl radicals react with Sc3N@C80-Ih to produce a dibenzyl adduct [Sc3N@C80(CH2C6H5)2] in 82% yield and high regioselectivity. The adduct’s 1H spectrum revealed high symmetry: only one AB pattern was observed for the methylene protons. The 13C NMR spectrum suggested a C2-symmetrical structure. DFT calculations reveal that a 1,4-adduct is more favorable than a 1,2-adduct by >10 kcal/mol. The 1,4-structure on [566] ring junctions was unambiguously confirmed by X-ray crystallographic analysis. UV−vis spectra revealed that the removal of two p orbitals from the π system of the cage together with the benzylic substituents change the electronic properties of the metallofullerene in a manner similar to those reported for disilirane and trifluoromethyl moieties. Under the same conditions from Lu3N@C80-Ih we prepared (63% yield) Lu3N@C80(CH2C6H5)2, which demonstrated properties similar to the 1,4-dibenzyl adduct of Sc3N@C80-Ih.