Synthesis, Isolation,Characterization And Functionalization Of Scandium-based Endohedral Fullerenes And Higher Fullerenes

Fullerenes have been attracting extensive attention and developed rapidly from the beginning of their discovery due to their perfect molecular structures and special physical/chemical properties. Endohedral fullerenes represent a special type of fullerenes with such species as atoms, ions or cluster encapsulated in the hollow inner space. Endohedral fullerenes not only bear the properties of both the encaged metals and carbon cage, but also may possess new properties due to the charge transfer from the encaged metals to the carbon cage. Exploring the novel endohedral fullerenes leads to further extending the family of endohedral fullerenes toward their potential applications in variable fields. Besides, chemical functionalization of fullerene can help to understand the chemical property of fullerenes and to expand their physical/chemical properties related to novel functions, thus becomes an important research topic in the field of fullerenes. In this dissertation, we focus on synthesis, isolation, characterization and properties of scandium-based novel endohedral fullerenes as well as the functionalization of endohedral fullerenes and higher empty fullerenes, and have carried out the following works:1) Using scandium (Sc) and dysprosium (Dy) as metal sources, we synthesized a series of mixed metal nitride clusterfullerenes with various cage sizes DyxSc3-xN@C2n (x=1,2,2n=68,70,76-86)-via the modified arc-discharge method, which were isolated by HPLC. Their electronic properties and molecular structures have been characterized by UV-vis-NIR and FTIR vibrational spectra in combination with DFT computations. Moreover, the influence of radius of the metal ion on the yield and cage size distribution of endohedral fullerenes has been deeply discussed.2) The "missing" fullerene-Sc3N@Cs2-was for the first time synthesized by using the modified arc-discharge method with optimized synthesis condition. Isomerically pure Sc3N@Cs2was isolated by multi-step HPLC, and its molecular structure was unambiguously determined by X-ray single crystal diffraction to be Sc3N@C82-C2v(9) with an isolated pentagon rule (IPR) carbon cage, which is obviously different from the reported Cs2-based metal nitride clusterfullerenes (NCFs) with other lanthanide metals encaged, indicating the effect of encapsulated metal ion on the structure of the carbon cage. UV-vis-NIR absorption spectroscopic study reveals that Sc3N@Cs2-C2v(9) is low optical band-gap structure with low kinetic stability. Sc3N@Cg2-C2v(9) also exhibits special electrochemical property compared with other M3N@C82, which can be reasonably explained by their different molecular structures.3) Several higher empty fullerenes, including C96, C102and C104, were successfully synthesized by conventional arc-discharge method and isolated by multi-step HPLC. Their halogenations with VCl4and SbCl5afforded a series of chlorinated derivatives including C96Cl22,24, C102CI20and C104Cl22,24.Single crystal X-ray diffraction revealed that C102CI20was a non-IPR product with a pair of pentagons, thus the structure rearrangement of C102can be inferred in the process of chlorination. For C104, two new isomers were successfully determined to be C104(812) and C104(258) by chlorination and followed by X-ray single crystal diffraction characterization, and the former one is the most stable isomers of C104. For C96, four isomers were characterized including C96(145), C96(144), C96(176), C96(183), and the later three isomers were reported for the first time.4) Various fractions of C96and C86were synthesized and isolated, followed by chlorination with a mixture of VCl4and SbCl5at high temperature. Single crystal X-ray diffraction resulted in identification a variety of derivative products. For C96, three IPR isomers were obtained, among them chlorides of two new isomers,C96(114) and C96(80) undergo cage shrinkages affording C94(NCl)Cl28and C92(NC2)Cl32with non classical (NC) carbon cages. These two NC chlorides contain, respectively, one and two heptagons flanked by pairs of fused pentagons and are stabilized by chlorine attachment to the emerging pentagon-pentagon junctions. Similarly, C2-and C4-losses have also been detected in chloride of C86, leading to the formation of C84CI30and C82Cl30containing one and two heptagons, respectively. Noteworthy, the intermediate compounds was captured and identified in the process of skeletal transformation of C86promoted by chlorination, and this will be helpful to better understand the formation mechanism of NC fullerenes.5) Two isomers of Sc3N@C80(Ih, D5h) were trifluoromethylated with CF3I at high temperature, affording a variety of multi-adducts. X-ray single crystal diffraction study revealed that the derivative of Sc3N@C80-D5h (Sc3N@D5h-C80-(CF3)16) was the precursor of reported Sc3N@D5h-C80-(CF3)18. Several isomers of Sc3N@C80-Ih derivatives were also identified, among them two new isomers were detected and determined by X-ray single crystal diffraction, which enables to detailed study the adduct site and molecular configuration, thus one of these two new isomers was the precursor of known Sc3N@Ih-C80(CF3)i6can be concluded.