Can CF3-Functionalized La@C60 Be Isolated Experimentally and Become Superconducting?

Superconducting behavior even under harsh ambient conditions is expected to occur in La@C60 if it could be isolated from the primary metallofullerene soot when functionalized by CF3 radicals. We use ab initio density functional theory calculations to compare the stability and electronic structure of C60 and the La@C60 endohedral metallofullerene to their counterparts functionalized by CF3. We found that CF3 radicals favor binding to C60 and La@C60 and have identified the most stable isomers. Structures with an even number m of radicals are energetically preferred for C60 and structures with odd m for La@C60 due to the extra charge on the fullerene. This is consistent with a wide HOMO-LUMO gap in La@C60(CF3)m with odd m, causing extra stabilization in the closed-shell electronic configuration. CF3 radicals are both stabilizing agents and molecular separators in a metallic crystal, which could increase the critical temperature for superconductivity.