Intrinsic properties of endohedral metallofullerenes

Endohedral metallofullerenes (EMFs) have been attracting wide interest all over the world over the past two decades [1]. To date, a wealth of EMFs have been synthesized and isolated, including conventional EMFs (M_x@C_2n, x = 1–3) and several different types of cluster fullerenes such as nitride cluster fullerenes (NCFs) [2], carbide cluster fullerenes (CCFs) [1], oxide cluster fullerenes (OCFs) [1], sulfide cluster fullerenes (SCFs) [1], hydrocarbide cluster fullerenes [1], carbonitride cluster fullerenes [1], and cyanide cluster fullerenes [1]. EMFs exhibit unique properties resulting from the electron transfer from the encapsulated species (metal ions or clusters) to the carbon cage. Therefore, EMFs not only inherit the properties of the carbon cage and the encapsulated species but also exhibit intriguing properties which are derived from the intramolecular interaction between the carbon cage and the encapsulated species [1,3].