Electronic state and molecular rotation infullerene solid and related compounds

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Fullerene molecules are expected to show large amplitude molecular rotation in solid. Such molecular rotation is able to affect the electronic states and lead to variety phase transitions in solid. The aim of the present study is to clarify the molecular dynamics of fullerene in solids by NMR technique. The main results are summarized as follows.1.The molecular dynamics and phase transition in solid C60, C70, and C76 were studied by NMR.Especially, we found that solid C76 shows a transition around 135-170 K related to C76 molecular rotation. This temperature is much lower than those of solid C60 and C70.2.Superconductors, Na2AC60 (A=K,Rb, Cs), were studied by NMR to obtain information on both the electronic state and C60 molecular dynamics. We found that Na2AC60 is metallic plastic crystal above room temperature. In the plastic phase, very large 13C-NMR spin lattice relaxation rate was observed, suggesting an anomalous metallic state.3.C60 polymer and hard carbon prepared by heating under high pressure were studied by 13C-NMR,which clarify the presence of sp2 and sp3 carbons and C60 molecular rotation in crystal.4.Ammoniated C60 superconductors were studied by NMR to clarify the C60 and NH3 molecular rotation in crystal and its effect on the electronic state.