Endohedral hydrogen fullerene
Endohedral hydrogen fullerene (
endohedral fullerene containing molecular hydrogen. This chemical compound has a potential application in molecular electronics and was synthesized in 2005 at Kyoto University by the group of Koichi Komatsu.[1][2] Ordinarily the payload of endohedral fullerenes are inserted at the time of the synthesis of the fullerene itself or is introduced to the fullerene at very low yields at high temperatures and high pressure. This particular fullerene was synthesised in an unusual way in three steps starting from pristine C60 fullerene: cracking open the carbon framework, insert hydrogen gas and zipping up by organic synthesis
methods.
Organic synthesis
Scheme 1 presents an overview of the first step, the creation of a 13 membered ring orifice on the fullerene surface. A
Diels-Alder reaction at high temperature and for an extended reaction time. In this reaction nitrogen is expulsed and an 8-membered ring is formed (3). This orifice is further extended by reaction with singlet oxygen in carbon tetrachloride which causes one of the ring alkene groups to oxidize to a ketone. The 12-ring is extended to a 13-ring by reaction with elemental sulfur in presence of tetrakis(dimethylamino)ethylene
.
The proposed
one-electron reduction
or by complexation.
From
chemical yield
starting from pristine fullerene.
Properties
H2@C60 is found to be a stable molecule. it survives 10 minutes at 500 °C and shows the same chemical reactivity as empty C60. The electronic properties are also largely unaffected.
The process of hydrogen introduction and release can be facilitated by increasing the size of the orifice. This can be done by replacing sulfur by
kJ/mol).[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.[4]