Much of the work presented in this thesis deals with the efficient preparation of endohedral metallofullerenes. The correlation among relative yield of endohedral lanthanide metallofullerenes, relative retention times and the third ionization potentials of lanthanide elements was found for the first time by a novel design of arc discharge and subsequent HPLC and DCI-MS analysis. This was further correlated to the formation mechanism of metallofullerene in arc plasma region, which involves charge transfer and formation of metal-carbon clusters as metallofullerene precursors. Based on these findings, the yield of the lanthanide metallofullerenes was enhanced by more than one order of magnitude through arc re-discharging. Plenty of carbon-coated lanthanide carbide was found in the soot. Th...[ Read more ]

Much of the work presented in this thesis deals with the efficient preparation of endohedral metallofullerenes. The correlation among relative yield of endohedral lanthanide metallofullerenes, relative retention times and the third ionization potentials of lanthanide elements was found for the first time by a novel design of arc discharge and subsequent HPLC and DCI-MS analysis. This was further correlated to the formation mechanism of metallofullerene in arc plasma region, which involves charge transfer and formation of metal-carbon clusters as metallofullerene precursors. Based on these findings, the yield of the lanthanide metallofullerenes was enhanced by more than one order of magnitude through arc re-discharging. Plenty of carbon-coated lanthanide carbide was found in the soot. The absence of oxygen from the carbon-coated carbides and the nano-scale mixing of metal and carbon are believed to be the reasons for the enhanced yield. In addition, an ultrasonic Soxhlet extractor was successfully set up for the first time to extract metallofullerene in a more efficient way.

The characterizations of metallofullerenes and higher fullerenes include nonlinear optical properties and magnetic properties. The second hyperpolarizability of the empty fullerenes were measured to be on the order of 10^-31 to 10^-30 esu at 532 nm, in which exists a trend that higher fullerenes show larger γ₁₁₁₁. The second hyperpolarizabilities of the metallofullerenes Nd@C₈₂ and Dy@C₈₂ were also determined, which show over one order of magnitude larger than that of C₆₀ and also significantly larger than those of higher neighboring fullerenes such as C₈₄ and C₈₆. The magnetic properties (temperature-dependant magnetization and isothermal magnetization) of the metallofullerenes M@C₈₂ (M = Gd, Tb, Dy, Er, Ho) were measured systemically for the first time. The isothermal magnetization curves of the metallofullerenes follow Brillouin function above a certain temperature, which depends on the metal species inside. These temperatures as well as the fitting results were found to be related to the orbital angular momentum of the lanthanide ions. In addition, the effective magnetic moments of the metallofullerenes obtained from both Curie-Weiss law and Brillouin function are significantly smaller than those of their corresponding free ions, but with a different extent of reduction for different metallofullerenes.

Finally, Langmuir-Blodgett films of the endohedral metallofullerenes Dy@C₈₂ and La@C₈₂ have been successfully constructed at air/water and Ar/water interfaces for the first time. Short range ordered and layered metallofullerene particle assemblies were clearly observed by HRTEM. Blue-shifted UV-Vis absorption peaks for the LB film deposited in air were identified and attributed to the oxidation of the metallofullerene particles. For the LB film formed at the Ar/water interface, however, red-shifted absorption peaks were found and ascribed to the strong interaction of the pristine metallofullerene particles. The quality of the transferred LB film prepared at the Ar/water interface was found to be much better than that prepared at the air/water interface in terms of both the morphology uniformity and the persistency of the films in air.