Determining addition pathways and stable isomers for CF3 functionalization of endohedral Gd@C60

Using density functional theory approaches, we follow the sequential addition of CF3 functional groups to the surface of the metallic endofullerene species Gd@C60. The presence of gadolinium in the interior of the cage strongly influences the addition sequence. The calculations are able to successfully identify end points in the addition sequence at Gd@C60(CF3)n, n = 3 and two isomers at n = 5, in predictive agreement with experiment. Inverting the algorithm to determine the most labile groups also identifies the correct positively charged Gd@C60(CF3)4+ isomer, as confirmed by experimental mass spectra. The importance of surface mobility, notably at later stage addition, is discussed.