A supramolecular complex was constructed by encapsulation of a 3 O2 molecule inside an open-cage C60 derivative. Its single-crystal X-ray diffraction analysis revealed the presence of the 3 O2 at the center of the fullerene cage. The CV measurements suggested that unprecedented dehydrogenation was promoted by the encapsulated 3 O2 after two-electron reduction. The ESR measurements displayed the triplet character as well as the anisotropy of the 3 O2 . 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 1 O2 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.
Keywords: EPR spectroscopy; open-cage C60; oxygen; structure elucidation; supramolecular chemistry.
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