Concise Synthesis of Open-Cage Fullerenes for Oxygen Delivery

Open-cage fullerenes with a 19-membered orifice were prepared in three steps from C₆₀ . The key step for cage-opening is aniline mediated ring expansion of a fullerene-mixed peroxide with a ketolactone moiety on the orifice. Release of ring strain on the spherical fullerene cage served as the main driving force for the efficient cage-opening sequence. Encapsulation of oxygen could be achieved at room temperature under moderate pressure (50 atm) and the encapsulated oxygen could be released slowly under ambient conditions. The activation energy of the oxygen-releasing process is 18.8 kcal mol^-1 and the half-life at 37 °C was 73 min, which makes this open-cage fullerene derivative a potential oxygen-delivery material.