Endohedral hydrogen fullerene

This chemical compound has a potential application in molecular electronics and was synthesized in 2005 at Kyoto University by the group of Koichi Komatsu.

In silico calculations show that the electrons in the HOMO reside primarily in the double bonds of the butadiene part of the ring and indeed singlet oxygen reacts at these positions through the dioxetane intermediate 6 with alkene cleavage to diketone 7 (only one isomer shown).

Elemental sulfur S8 is inserted into the single bond of the diene group leading to the extension of the ring to 13 atoms (structures 8 and 9 are identical).

The reverse cycloadditions take place at 340 °C in a vacuum splitting of 2-cyanopyridine and diphenylacetylene resulting in the formation of H2@C60 at a 40% chemical yield starting from pristine fullerene.

Filling cracked-open fullerene now takes 8 hours at 190 °C at 760 atmospheres (77 MPa) of hydrogen and release between 150 °C and 180 °C is three times as fast compared to the sulfur analogue.

[3] There is evidence that hydrogen in the fullerene cage is not completely shielded from the outside world as one study found that H2@C60 is more efficient at quenching singlet oxygen than empty C60.