Metallofullerenes lanthanide

Edelmann F T 1995 Filled buckyballs—recent developments from the endohedral metallofullerenes of lanthanides Angew. Chem. Int. Edn. Engl. 34 981-5... 

In addition to group 3 (Sc, Y, La) and the lanthanide metallofullerenes, group 2 metal atoms (Ca, Sr, Ba) were also found to form endohedral metallofullerenes, and have been produced and isolated in milligram quantity (Dennis and Shinohara, 1997a,b, 1998 Dennis et al., 1998 Wan et al., 1997, 1998 Xu et al., 1996). These metal atoms have been encaged not only by Cs2 and Cs4 but also by such smaller fullerenes as C72, C74, and Cso- Furthermore, group 4 metallofullerenes (Ti, Zr, Hf) were s)mthesized and isolated (Gao et al., 2001, 2002). 

The CV measurements indicate that the oxidation state of the yttrium atom in Y Cs2 (Suzuki et al., 1996) was close to that of La Cs2, probably 3-i. The electrochemistry of Y Cs2 is almost identical to that of La Cs2 (Anderson et al., 1997a Suzuki et al., 1996). Other mono-metallofullerenes such as Y Cs2, Ce Cs2 and Gd Cs2 have a similar tendency in their redox properties (Suzuki et al., 1996). Anderson et al. (1997b) reported CV data on Sc3C2 Cso- CV measurements were also taken on other lanthanide fullerenes such as Pr Cs2, Nd Cs2, Tb Cs2, E)y C82, Ho C82, Er C82 and Lu C82 by Wang et al. (1997). The first reduction potentials of all seven M C82 were found to locate within a close vicinity... 

Akiyama et al. (2001) s)mthesized and isolated some light actinide metallofullerenes such as U C82, Np Cg2/ and Am C82 and foimd the valency of U atom in C82 cage is 3-I-, showing almost exactly the same UV-Vis-NIR absorption spectrum as that of the bivalent lanthanide C82 metallofullerenes such as La Cs2 and Gd C82-... 

Lanthanide metallofullerenes are novel forms of fullerene-related materials which were first obtained in their purified form in January 1993 (Shinohara et al., 1993a). Since then, as detailed in this paper, numerous investigations into various aspects of metallofullerenes have been intensively carried out by various research groups. These studies have revealed unique structural and novel electronic properties of the metallofullerenes. 

The metallofullerenes were purified by CS2 extraction and toluene HPLC elution. The dominant products identified for neptunium and americium were An C82. Two uranium-containing metallofullerenes were identified, U C82 and U2 C8o. Based upon comparison with the optical spectra of lanthanide analogs, it was suggested that the oxidation state in these complexes might best be regarded as +3. 

For mono-metallofullerenes with rare earth metals, three electrons are donated from the encaged metal to the fullerene cage, such as Y and most lanthanides (La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, andLu) [2, 108, 109]. However, Sc, Sm [110], Eu [111], Tm [112], and Yb [113] are found to donate only two electrons and prefer to take the valence of +2. Consequently, the EMEs containing rare earth metals are classifiable into two categories according to the electronic state of the encaged metal(s) trivalent EMFs and divalent EMFs. Eor example, La Cs2 should be expressed as La + Cg2. whereas Yb Cs2 has the formula of Yb + CgJ. These two types of EME differ markedly from each other in their structures and properties, (i) When three electrons are transferred to the carbon cage, the resultant -type EMFs... 

Huang, H.J. and Yang, S.H. (1998) Relative yields of endohedral lanthanide metallofullerenes by arc synthesis and their correlation with the elution behavior. Journal of Physical Chemistry B, 102, 10196—10200. 

Molecular structures of the non-IPR endohedral metallofullerenes. Carbon cages are shown in grey except for the adjacent pentagon pairs, which are shown in black. In MsN Cts, M N C82/ and M N C84, M can be Y, Gd, Dy, Tm, Tb, and possibly some other lanthanides... 

The steady-state absorption spectra of La Cg2 show the absorption bands at 1412, 1002, and 636 nm, which are characteristic of the lanthanide metal-encapsulated 32-fullerenes. Since it has been reported that the change of central metal does not affect the positions of absorption maxima, the electronic transitions take place within the Cg2 . The absorption spectrum of La2 Cgg shows a broad band around 900 nm and a relatively sharp shoulder at 400-450 nm, which are characteristic bands of endohedral metallofullerenes. 

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