Structures And Chemical Properties Of Metal Cyanaide Endohedral Fullerens And Empty Fullerenes Based On Higher Carbon Cages

Ever since fullerenes were discovered,they have been attracting extensive attention due to their unique molecular structure and excellent physical and chemical properties.Fullerenes are molecules with definite structure compared to other carbon allotrope,and it is characteristic in bearing a hollow interior and the sp2-hybridization of the carbon atoms,which render the endohedral and exohedral functionalization.Upon entrapping metal ions or clusters which are able to transfer electrons to the outer fullerene cage,the as-formed endohedral metallofullerenes demonstrate extra physical properties that are inaccessible by empty fullerenes.Fullerene derivatives were formed when fullerene cage is exohedrally functionalized by different groups,the exohedral functionalization facilitate the steering of energy level and physical properties of fullerenes,thus expanding the potential applications of fullerenes materials.In particular,the chemical properties of empty fullerenes based on higher carbon cage are relatively less studied,since their more ? electrons and lower structural symmetry.In our dissertation,we focus on the structures and chemical properties of metal cyanaide endohedral fullerens(CYCFs)and empty fullerenes based on higher carbon cages,the intramolecular metal-cage interactions of C84-based CYCFs were investigated,the novel fullerene structures were characterized by high-temperature chlorination reaction of C₉₂ isomers.The following three works have been carried out:(1)MCN@C2(13)-C84(M=Y,Dy,Tb)were successfully synthesized by DC arc discharge method,and their molecular structures were determined unambiguously by single crystal X-ray diffraction.The X-ray structure of MCN@C2(13)-C84(M=Y,Dy,Tb)enabling a systematic study on the influence of the encapsulated metals on their metal-cage interactions.Upon varying the encapsulated metal with only slight difference on the ionic radius(0.90,0.91 and 0.92 A for Y3+,Dy3+and Tb3+respectively),obvious change on the intramolecular metal-cage interactions within MCN@C2(13)-C84 is found.It was demonstrated that the intramolecular metal-cage interactions of CYCFs can be steered internally by changing the encapsulated metal.We further carried out UV-vis-NIR spectroscopic and CV characterization to investigate the electronic properties of MCN@C2(13)-C84(M=Y,Dy,Tb),the electronic configuration of[M3+(CN)-]2+@[C84]2-can be proposed by comparing with divalent metal-based mono-metallofullerenes M@C2(13)-C84(M=Sm,Eu,Yb).(2)We have synthesized,isolated and characterized novel CYCFs DyCN@C2v(17)-C84 based on C84 carbon cage.C2v(17)-C84 isomer has lower relative energy than several isolated C84 isomers but never been isolated,which defined as"missing fullerene".We fulfill the first identification of the missing C2v(17)-C84 isomer,which is derived from the smaller relative energy when the electroneutral C84 becomes dianion C842-.There is structural connectivity of the C2(13)-C84 and C2v(17)-C84 isomers,C2(13)-C84 isomer can be interconverted to C2v(17)-C84 via two Stone-Wales Rotation steps(SWR).Thus,it is no wonder that both DyCN@C2(13)-C84 and DyCN@C2v(17)-C84 can be produced simultaneously.Furthermore,by comparing the metal-cage interactions of DyCN@C2v(17)-C84 with DyCN@C2(13)-C84,it was demonstrated that the intramolecular metal-cage interactions of CYCFs can be also steered by changing the isomeric cage.(3)Four fullerenes fractions of C₉₂ isomers were obtained by high-performance liquid chromatography(HPLC),and treated by high-temperature chlorination reaction,resulting in the respective chloro derivatives including C₉₂(38)Cl18/22,C₉₂(26)Cl24,C90(NC)Cl22 and#86239C90C126.Among them,#86239C90Cl26 bears two pairs of fused pentagons and C90(NC)Cl22 contains one heptagon and two pairs of fused pentagons.The topological reconstruction revealed that C₉₂(50)cage could be interconverted to C90(NC)cage by one step of C2 loss,and four-step skeletal transformations including C2 loss and SWR are necessary to accomplish the chlorination-promoted cage transformation from C₉₂(23)cage to#86239C90.DFT calculations reveal that the formation energy of C₉₂(50)and C₉₂(23)isomers are higher than that of C₉₂(38)and C₉₂(26)isomers,which account for the skeleton transformation of C₉₂(50)and C₉₂(23)isomers.We demonstrate the existence of C₉₂(38),C₉₂(26),C₉₂(50),and C₉₂(23)isomers in fullerene soot,the presence of C₉₂(26),C₉₂(50),and C₉₂(23)isomers have never been reported before.