The reaction of a tetraketo-open-cage C60 derivative with elemental sulfur in the presence of tetrakis(dimethylamino)ethylene afforded novel open C60 derivatives containing sulfur atom(s) in the rim of the orifice and the first example of an open C59S derivative. The single crystal X-ray analyses clearly determined these structures and demonstrated that a water molecule was encapsulated inside the cages. The orifice sizes and electronic properties of these fullerene derivatives were revealed.

An open-cage C60 tetraketone with a large opening was able to encapsulate N2 and CO2 molecules after its exposure to high pressures of N2 and CO2 gas. A subsequent selective reduction of one of the four carbonyl groups on the rim of the opening induced a contraction of the opening (→2) and trapped the guest molecules inside 2. The thus-obtained host-guest complexes N2@2 and CO2@2 could be isolated by recycling HPLC, and were found to be stable at room temperature. The molecular structures of N2@2 and CO2@2 were determined by single-crystal X-ray diffraction analyses, and revealed a short N≡N triple bond for the encapsulated N2, as well as an unsymmetric molecular structure for the encapsulated molecule of CO2. The IR spectrum of CO2@2 suggested that the rotation of the encapsulated molecule of CO2 is partially restricted, which was supported by DFT calculations.

A supramolecular complex was constructed by encapsulation of a O molecule inside an open-cage C derivative. Its single-crystal X-ray diffraction analysis revealed the presence of the O at the center of the fullerene cage. The CV measurements suggested that unprecedented dehydrogenation was promoted by the encapsulated O after two-electron reduction. The ESR measurements displayed the triplet character as well as the anisotropy of the O . Additionally, the SQUID measurements also demonstrated the paramagnetic behavior above 3 K without an antiferromagnetic transition. Upon photoirradiation with visible light, three phosphorescent bands at the NIR region were observed, arising from the exited O generated by self-sensitization with the outer cage, whose lifetimes were not affected by the environments. These studies confirmed that the complex is a crystalline triplet system with incompatible "high spin density" but "small interspin interaction" properties.