Revisiting the Preparation of La@C82 (I and II) and La2@C80: Efficient Production of the “Minor” Isomer La@C82 (II)

Current status and future developments of endohedral metallofullerenes

Endohedral metallofullerenes (EMFs), a new class of hybrid molecules formed by encapsulation of metallic species inside fullerene cages, exhibit unique properties that differ distinctly from those of empty fullerenes because of the presence of metals and their hybridization effects via electron transfer. This critical review provides a balanced but not an exhaustive summary regarding almost all aspects of EMFs, including the history, the classification, current progress in the synthesis, extraction, isolation, and characterization of EMFs, as well as their physiochemical properties and applications in fields such as electronics, photovoltaics, biomedicine, and materials science. Emphasis is assigned to experimentally obtained results, especially the X-ray crystallographic characterizations of EMFs and their derivatives, rather than theoretical calculations, although the latter has indeed enhanced our knowledge of metal-cage interactions. Finally, perspectives related to future developments and challenges in the research of EMFs are proposed. (381 references).

Studies on Metallofullerene (Dy@C82) Embedded in a DDAB Film in Aqueous Solution

The electrochemical behavior of metallofullerene (Dy@C82) in didodecyldimethylammonium bromide (DDAB) films deposited on glassy carbon, quartz crystal microbalance (QCM) gold crystals, and indium tin oxide (ITO) electrodes in aqueous solution was investigated in detail. Four pairs of reversible redox peaks were observed, and for the first time, these peaks were characterized by vis/NIR spectroscopy. Different from previous fullerene/cationic lipid modified electrodes, one oxidation and three reduction processes were observed. The stability of Dy@C82 and its ions in the film toward air was detected by measuring its cyclic voltammogram after holding the potentials for 10 s, followed by introducing 10 microL of air to the solution. Dy@C82 and its first three anions are stable toward air and water, while some chemical reactions take place when the third anion is further reduced in the film. Dy@C82+ is less stable than Dy@C82- toward water and air. The electrochemical processes were measured in different electrolytes, which showed pronounced anionic dependence on either its cation or anions. The electrochemical processes were also monitored using electrochemical quartz crystal microbalance (EQCM), and from the result a possible electron-transfer mechanism of a Dy@C82/DDAB electrode in aqueous solution was presented. It showed that the anions of Dy@C82 were bound to the DDA+ cation in the film, while the anions of electrolyte diffused into the film to compensate the positive charges when a cation of Dy@C82 was generated.

A Large Family of Dysprosium-based Trimetallic Nitride Endohedral Fullerenes: Dy3N@C2n (39 ≤ n ≤ 44)

Dysprosium-based trimetallic nitride endohedral fullerenes (clusterfullerenes)-the Dy(3)N@C(2)(n) (38 </= n </= 49) family-have been produced at overwhelming yields compared to the empty fullerenes for the first time. The Dy(3)N@C(2)(n) family represents the largest clusterfullerene family explored up to now, even in comparison with the Tm(3)N@C(2)(n) (38 </= n </= 44) family which was discovered very recently. A series of 10 Dy(3)N@C(2)(n) clusterfullerenes (39 </= n </= 44, 1-9) have been isolated successfully and characterized by HPLC, mass spectrometry, and UV-vis-NIR spectroscopy. The study on the HPLC elution behavior reveals that there are two isomers for Dy(3)N@C(78) and Dy(3)N@C(84). Furthermore, a third isomer of Dy(3)N@C(80) is isolated for the first time. The optimum production conditions (Dy:C = 1:15, NH(3) pressure = 20 mbar) have been determined by investigating the effects of the Dy:C ratio and NH(3) pressure on the yields of the Dy(3)N@C(2)(n) clusterfullerenes. UV-vis-NIR spectroscopic study indicates that the Dy(3)N@C(2)(n) clusterfullerenes with small cages (n = 39-41) are large band-gap (1.38 approximately 1.51 eV) materials, while the band-gaps for those with larger cages (n = 42-44) are significantly smaller (0.80 approximately 0.84 eV).