HPLC Isolation,Crystallographic Structure And Properties Of Endohedral Tb,Ho-Containing Metallofullerenes

Fullerenes are all-carbon molecules with unique large inner space,and endohedral metallofullerenes（EMFs）form when a variety of metal atoms or metal-nonmetal clusters are encapsulated.Because of the charge transfer from endohedral metal atoms or metal-nonmetal clusters to carbon cages,EMFs are of unique physical and chemical properties and have extensive application potentials in the fields of single molecule magnet,photovoltaic device and biomedicine,etc.Therefore,the characterization of the structure and properties of metallofullerenes is extremely significant for the exploration of novel functional molecular materials.In this thesis,soot-containing terbium and holmium metallofullerenes was prepared by a modified arc discharge method.After organic solvent extraction,multi-staged high-performance liquid chromatography（HPLC）separation was applied to the isolation of Tb,Ho-Containing metallofullerenes,and mono-metallofullerene Tb@C₈₂（I,II）,di-metallofullerene Ho₂@C₈₂（I,II）and O-cluster metallofullerene Ho₂O@C₉₀（I-IV）were successfully isolated.Among which,di-metallofullerene Ho₂@C₈₂（I,II）and O-cluster metallofullerene Ho₂O@C₉₀（I-IV）have not been reported previously.This has greatly enriched the variety of EMFs.The molecular structures of Tb@C₈₂（I）,Tb@C₈₂（II）and Ho₂@C₈₂（I）are determined to be Tb@C_2v（9）-C₈₂,Tb@C_s（6）-C₈₂ and Ho₂@C_3v（8）-C₈₂ respectively,by single crystal X-ray diffraction.In the 1:1 cocrystal of[Tb@C_2v（9）-C₈₂]?[Ni（OEP）]?2（C₆H₆）,Tb@C_2v（9）-C₈₂ arranges diagonally between the Ni（OEP）double layers to form zigzag chains.In the 2:2 cocrystal of 2[Tb@C_s（6）-C₈₂]?2[Ni（OEP）]?1.5（C₆H₆）?2（CS₂）,Tb@C_s（6）-C₈₂ forms centrosymmetric dimers and linearly aligns with Ni（OEP）in a lattice plane.In the 2:1 cocrystal of 2DPC{Ho₂@C_3v（8）-C₈₂}?4C₇H₈,in which Ho₂@C_3v（8）-C₈₂molecules are closely surrounded by four DPC molecules and aggregate in a sinusoidal wave mode along one axis.The results contributed to the characterization of the molecular structure of metallofullerenes by single crystal X-ray diffraction,and the characterization of the structure of metallofullerenes will significantly advance their properties.Moreover,the fluorescence of Tb@C_2v（9）-C₈₂ and Tb@C_s（6）-C₈₂ are initially detected and mainly ascribed to the endohedral Tb³⁺ions,even though the symmetry of carbon cage has some effect on its position and peak shape.The EPR of Tb@C_2v（9）-C₈₂and Tb@C_s（6）-C₈₂ are comprises a carbon cage with unpaired electron spin formers and a hyperfine splitting peak generated by splitting of 4f orbitals of Tb³⁺ions.Therefore,Tb@C₈₂ might be applicable in many fields as novel optical and magnetic materials.According to the UV-vis-NIR absorption spectra of Ho₂O@C₉₀（I-IV）,the carbon cages of Ho₂O@C₉₀（I）,Ho₂O@C₉₀（III）and Ho₂O@C₉₀（IV）are speculated to be C₂（43）-C₉₀,C₂（40）-C₉₀ and C₂（41）-C₉₀,respectively,and the carbon cage of Ho₂O@C₉₀（II）might be one not reported previously.The results of this study play an important role as a reference for oxygen cluster fullerene separation.