Preparation?Characterization And Property Studies Of Endohedral Metallofullerenes Or Clusterfullerenes

Since their discovery,fullerenes have attracted extensive attentions due to their unique structures and properties.Endohedral fullerenes are formed by trapping atoms,molecules,and clusters inside fullerene cage.Hollow fullerenes are closed polyhedral structures composed of pentagons and hexagons,and each pentagon are separated by hexagons.Due to charge transfer occuring between the embedded materials and carbon cage,the carbon cage can be stably present even having fused pentagons.In addition,the presence of embedded materials and their interaction with carbon cages may possess unique properties that are different from those of empty fullerenes.This thesis focuses on the preparations,structural characterizations,optoelectronic and magnetic properties of endohedral metallofullerenes.This thesis is aiming to better understand the structure and properties of some of novel metallofullerenes and clusterfullerenes.The main topics are as follows:(1)Sm@C76 sample has been synthesized by DC arc discharge method,and then been separated and purified to get pure Sm@C76 by high performance liquid chromatography.A combined study of single-crystal X-ray diffraction and DFT calculations not only elucidates the non-IPR cage structure of C2v(19138)-C76 but also suggests that the endohedral Sm'+ion prefers to reside along the C2 cage axis and close to the fused pentagon unit in the cage framework,indicative of a significant metal-cage interaction,which alone can stabilize the non-IPR cage.Furthermore,electrochemical studies reveal the fully reversible redox behaviors and small electrochemical gap of Sm@C2v(19138)-C76,which are comparable to those of IPR species Sm@D3h-C74.(2)The Sc2O@C2n(n=35-47)samples have been synthesized by DC arc discharge method with CO2 as the oxygen source,and then separated and purified to get pure Sc2O@C78 isomers.The results of single crystal XRD analysis indicate that the carbon cage structures of the isomers were C2v(3)-C78 and D3h(5)-C78,respectively,which are closely related via a single-step Stone-Wales(SW)transformation.Additional characterizations demonstrate that these Sc2O@C78 isomers feature different energy bandgaps and electrochemical behaviors,indicating the impact of SW defects on the energetic and electrochemical characteristics of metallofullerenes.More importantly,these novel Sc2O@C78 isomers represent the key links in a well-defined formation pathway for the Sc2O@C2n(n=3 8-41),providing molecular structural evidence for the less confirmed fullerene formation mechanism.(3)Fullerene/S8 micro/nano-structures have been prepare with a liquid-liquid interfacial deposition method(LLIP)by adjusting the concentration of fullerene and the ratio of solvent.The morphology was characterized by Scanning Electron Microscope(SEM),Transmission Electron Microscopic(TEM)and High-Resolution-TEM(HR-TEM).The results of C70/S8 and Lu3N@C80/S8 micro/nano-structures show rectangular and hexagonal nanosheets,respectively.It shows that fullerenes have an important effect on the morphology of nanostructures.The absorption spectroscopy characterization shows that Lu3N@C80/S8 nanosheets have obvious charge transfer compared with Lu3N@C80,while C70/S8 nanosheets do not.Finally,the photoelectric properties of the two samples were tested.The measured photocurrents of Lu3N@C80/S8 nanosheets are much larger than those of C70/S8 nanosheets at bias voltages of 0 V and 0.2 V,highlighting the importance of charge transfer.(4)Nitride clusters fullerene DyY2N@C80 and Dy2YN@C80 were prepared by DC arc discharge method and purified by high performance liquid chromatography.The magnetic properties of the powder samples were studyed by SQUID magnetometry.The results show that DyY2N@C80 has a higher blocking temperature of magnetization(TB=8.4 K)than the reported of DySc2N@C80 in the literature(TB=7 K)under the same conditions.It shows the regulation of the magnetic properties of metal fullerenes by non-magnetic metal ions.In addition,the magnetic test results show that Dy2YN@C80 has a lower blocking temperature of magnetization(TB=4.65 K),indicating that the number and arrangement of Dy3+ions in the embedded clusters have an effect on the magnetic properties of metallofullerenes.