| Since the discovery and large scale synthesis of fullerenes, the interaction of the fullerene and fullerene cage with heteroatoms have been extensively studied .These investigations have been indicated that dopant atoms can interact which the fullerene cage to from three kinds of heterofullerenes, as suggested by Branz et al.. The three kind of heterofullerene is,(1)the endohedral fullerenes ,in which the dopant atom trapped inside the hollow fullerene cage. Such as La@C60,Ca@C82 .(2) substitutional fullerenes ,in which the dopant atom incorporated into the fullerene network by replacement of one or more carbon atoms .such as C59N,C59O .(3)exohedral fullerenes with atoms located outside the cage, in which the heteroatoms are usually attached to the fullerene cage via nonbonding interaction, and may be different for different samples. Such as K3C60,Cs6C60. The mostly used methods to produce heterfullerenes are the laser vaporization and arc discharge of graphite-metal composite rod at very high temperature. Exohedrally and endohedrally doped fullerenes have been produced and extensive studied, such as the well-known superconductivity of fullerides .C60-xBx (x<6) were the first synthesized substitutional fullerenes by Smalley et al. by arc discharge of graphite–metal composite rod .As soon as it were discovered ,it have attracted much attention on it because of its unique structural and electronic properties. C59N,C58N2 et al. substitutional fullerenes were discovered soon after the discovery of C60-xBx. The properties of substitutional fullerenes are quite different from C60.The highest occupied molecular orbital (HOMO) of C59N and C59B is strongly localized. C59B can cat as an electron accepter state, yet C59N can cat as an donor state. In the case of substitutional doping, the metal can incorporate into the fullerene cage network too. the cage, Branz et al. reported synthesized metal-substituted fullerenes C59M,M=(Fe,Co,Ni,Rh and Ir) . Qingyu Kong et al. had synthesized C59M, M=(Pt,Sm,Ni,La,Y,Rh)in 2002. The metal-substituted fullerenes were quite different from the nonmetal-substituted fullerenes. Because the metal heteroatom is quite larger than the nonmetal heteroatom, and the electronic structure between them is quite different.Metallofullerenes have been the subject of numerous studies since their discovery, because the incorporation of metal atoms to the fullerene cage will change the structures of the fullerenes that will make their chemical and physical properties vastly different from pristine fullerenes. In order to study the structures, bonding characteristics of these new metallofullerenes, theoretical calculations have been carried out. In this paper, the work is investigated in detail at the BLYP/LAND2DZ (included in Gaussian package) level. As a result, the stable geometries of C59M still keep the fullerene network, and belong to Cs symmetrical point group, lower than that of C60. The C-M band in the C59M is shorter than that of normal C-M, so, the band is stronger. It is noted that a large quantity of charges concentrated on the M atoms. These M atoms may act as active sites in the electrophilic reactions. The calculated energy gap between the highest occupied orbital (HOMO) and the lowest unoccupied orbital (LUMO) is 0.50ev,0.60ev,0.66ev,respectively. The HOMO-2, HOMO-3……,is quite similar to the C60 HOMO,HOMO-1 ……orbitals. |
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