Synthesis, Separation, Structure And Derivation Of Sm-endohedral Metallofullerenes

Arc discharging synthesis, o-dichlorobenzene extraction aided withultrasonication, and multi-step HPLC isolation were implied to Sm endohedralfullerenes. Complete Sm containing metallofullerene series Sm@C_2n (n = 40-42, 44-47) and Sm₂@C_2n (2n = 88, 92, 104) were obtained, and each individual product hasbeen characterized by LDI-TOF-MS and UV-Vis-NIR spectroscopy. Sm₂@C₁₀₄(â… )was successfully grown cocrystalizing with Ni(OEP), and X-ray diffraction studieswere performed on Sm₂@C₁₀₄(â… )·Ni(OEP) single crystal. Density functional theorycalculations have been carried out on the neutral and tetraanion forms of the D_3d(822)-C₁₀₄ iosmer. Reactivities of some Sm endohedral fullerenes were also studied.There are 8 new mono-metallofullerenes among the endohedral fullerenessynthesized, which are Sm@C₈₂(â… ), Sm@C₈₈, Sm@C₉₀(â… -â…£), Sm@C₉₂, Sm@C₉₄. It isinteresting that the UV-Vis-NIR spectrum of Sm@C₉₀(â…¢) are different from those ofall the divalent mono- metallofullerenes encapsulated Ca, Eu, Yb reported, indicatingits unique carbon cage. UV-Vis-NIR spectra of other new metallofullerenes resembleto M@C_2n (M = Ca, Eu, Yb) respectively.Di-metallofullerenes Sm₂@C₈₈, Sm₂@C₉₂ and Sm₂@C₁₀₄(â… -â…¢) were obtained。All UV-Vis-NIR spectra of Sm₂C_2n were also made careful comparison withcorresponding dimetallofullerenes, carbide and TNT metallofullerenes reported.Those of Sm₂C_2n (2n=88, 92, 104) resemble the relevant ones of M₂C_2n+2 (M=Er, Dy,Gd). The comparability indicate that these Sm₂C_2n are Sm₂@C_2n but not Sm₂C₂@C_2n,and Sm is divalent.Crystallographical studies of Sm₂C₁₀₄(â… )·2Ni(OEP) single crystal revealed thatSm₂@C₁₀₄(â… ) utilized a D_3d(822)-C₁₀₄ isomer. In this flat carbon cage, the two primarysamarium atoms are located near the threefold axis of the cage and are separated by5.8322(7) (?). D_3d(822)-C₁₀₄ will be produced by cutting perpendicular to the C₃ axesof I_h-C₈₀ the molecule, addition of 24 carbon atoms. Sm₂@C₁₀₄(â… ) is a nanocaosule.DFT B3LYP level calculation was successively adopted to find out HOMO-LUMO band gaps of D_3d(822)-C₁₀₄ and D_3d(822)-C₁₀₄^4-. Band gap of D_3d(822)-C₁₀₄ istoo small to form the neutral fullerene, but band gap D_3d(822)-C₁₀₄^4- is big enough toform Sm₂@D_3d(822)-C₁₀₄ Reactivity of Sm@C₈₄, Sm@C₈₈, Sm@C₉₀(â…£), Sm@C₉₄ were studied throughreaction of endohedral fullerenes with dimethyl acetylenedicarboxylate andtriphenylphosphine. Four major products have been separated by HPLC andcharacterized by LDI-TOF-MS and UV-Vis-NIR spectra. The major products aremonoadducts. Difference between derivative of Sm@C₈₄ and Sm@C₈₈ with motherendohedral fullerenes suggest that these adducts possess a "closed" cyclopropylstructure, whereas similarity between derivative of Sm@C₉₀(â…£) and Sm@C₉₄ withmother metallofullerenes indicate these adducts have ring-opened type structure.