Synchrotron Radiation for Structural Chemistry—Endohedral Natures of Metallofullerenes Found by Synchrotron Radiation Powder Method

The recent progress of the structural studies of endohedral metallofullerenes by the synchrotron radiation (SR) powder diffraction utilizing the maximum entropy method (MEM) is reviewed. Results of the endohedral metallofullerenes (Y@C₈₂, La@C₈₂, Sc@C₈₂, Sc₂@C₈₄, Sc₃@C₈₂, Sc₂@C₆₆, La₂@C₈₀ and Sc₂C₂@C₈₄) are given. The precise MEM charge densities of metallofullerenes presents the direct image of endohedral nature of metallofullerenes indicating the charge transfer from metal atoms to carbon cage, which governs the stability of the unique endohedral structures. The MEM/Rietveld method and SR powder method using imaging plate (IP), which are the crucial methods for data analysis and measurement in order to determine structure of fulleride, are also mentioned in some detail.