Synthesis, Isolation And Characterization Of Novel Endohedral Cluster Fullerenes

Endohedral fullerenes, with encapsulation of variable atoms or clusters in the hollow sphere of carbon cage, have attracted much interest in the field of fullerenes research. Until now, many cluster fullerenes, including carbide, nitride, sulfide, carbonnitride, hydrocarbide and oxide cluster fullerenes, have been synthesized and characterized. One of amazing characters of endohedral fullerenes is the fact that their physical and chemical properties as well as structures can be adjusted by the various species encapsulated inside fullerene cages. These compounds have shown great potential in the field of photoelectric materials, nano materials, biomedicines and so on. In this thesis, we reported the synthesis, isolation and characterization of four novel cluster fullerenes, i.e., Sc2O@C2v(5)-C80, Sc2O@C3v(8)-C82, Sc3O@C80 and Sc2C2@C74.1. A novel oxide cluster fullerene, Sc2O@C2v(5)-C80, has been synthesized, isolated and characterized by high performance liquid chromatography, matrix-assisted laser desorption/ ionization time of flight mass spectrometry, UV-vis-NIR absorption spectroscopy, 45 Sc NMR, cyclic voltammetry, single crystal X-ray diffraction and DFT calculations. The crystallographic analysis unambiguously elucidated that the cage is C2v(5)-C80 and the Sc2 O unit is ordered inside the cage. The Sc-O-Sc angle of Sc2O@C2v(5)-C80 is much larger than that of Sc2O@Td(19151)-C76 but almost comparable to that of Sc2O@Cs(6)-C82. It suggest that the Sc2 O unit is flexible and can exhibit large variation in the Sc-O-Sc angle, which decides by the size and shape of the cage. DFT calculations show that four electrons are transferred from the Sc2 O unit to the C80 cage, i.e.,(Sc2O)4+@(C80)4- and the frontier molecular orbitals are mainly localized on the C80 framework. Contrastive research between Sc2C2@C2v(5)-C80 and Sc2O@C2v(5)-C80 uncover that the clusters have a significant impact on their electronic structures in spite of their close structural resemblance.2. By using CO2 as the oxygen source during the arcing process,a new isomer of Sc2O@C82, i.e., Sc2O@C3v(8)-C82, was discovered and characterized by high performance liquid chromatography, mass spectrometry, UV-vis-NIR absorptionspectroscopy, 45 Sc NMR, cyclic voltammetry, DFT calculations and single crystal X-ray diffraction. The crystallographic analysis unambiguously elucidated that the cage is C3v(8)-C82 and the Sc2 O unit is disordered inside the cage. Contrastive research between Sc2O@C3v(8)-C82 and Sc2S@C3v(8)-C82 reveal that the Sc-O-Sc angles of dimetallic clusters are flexible inside the cages. The cyclic voltammetry studies reveal that the electrochemical gap of Sc2O@C3v(8)-C82 is the largest among those of the oxide cluster fullerenes reported so far. Additionally, the electrochemical studies show that both of the cage structures and the dimetallic clusters have significant impact on the electronic structures of the cluster fullerenes. DFT calculations show that the Sc2 O of Sc2O@C3v(8)-C82 can rotate and change its Sc-O-Sc angle easily at rather low temperature.3. Sc2C76, has been synthesized and fully characterized by high performance liquid chromatography, mass spectrometry, UV-vis-NIR absorption spectroscopy, 45 Sc NMR, cyclic voltammetry, differential pulse voltammetry, and DFT calculations. A combined study of spectroscopic characterization, cyclic voltammetry, differential pulse voltammetry and DFT calculation might assigned the cage structure to C2(13333)-C74, which is the first non-IPR isomer and the first cluster fullerene of C74. DFT calculation confirms that there is a formal transfer of four electrons from the Sc2C2 unit to the C74 cage, i.e.,(Sc2C2)4+@C744-. The HOMO and LUMO are mainly localized on the C74 framework, so the oxidation and reduction take place in the cage. Furthermore, we also compared the electrochemical properties of this molecule to the previously reported scandium carbide cluster fullerenes. The results show that the different cage of the scandium carbide fullerenes present a dramatic influence on their electronic structures.4. The trimetallic oxide cluster fullerene Sc3O@C80 radical has been detected, isolated and purified with very low yields. The tiny amount of product obtained made only possible characterization by UV-vis-NIR spectroscopy. DFT computations predict Sc3O@Ih(7)-C80 to be the isolated isomer and provide further information about the electronic structure and other(magnetic and electrochemical) properties of this fullerene. Significant spin density on the endohedral Sc ions and in cavea redox processes are themain characteristics of Sc3O@Ih(7)-C80, which is isoelectronic to the anion of the prototypical nitride Sc3N@Ih(7)-C80.