Structures, Properties, and Growth Process of Endohedral Metallofullerenes

1.内嵌金属富勒烯的结构、电子态和成键特征通过理论预测和实验的密切联系，揭示了单金属富勒烯M@C_<82>（M=Ca，Sc，Y，La，Ce，Pr，Nd，Eu，Gd，Yb，Lu）和双金属富勒烯Sc_2@C_<84>和La_2@C_<80>的内嵌结构。此外，电子密度及其拉普拉斯算子的拓扑分析已经进行了揭示的一般特征的化学键在金属富勒烯。三金属富勒烯Sc_3@C_的结构和成键研究<82>仍在进行中.本文首次用变温~（13）CNMR测量了La_2@C_2的动态行为<80>，发现即使在室温下，两个La原子也带着+3电荷在圆形的C_2笼中循环<80>。这一发现也得到了变温139 La NMR测量和理论计算的证实.内嵌金属富勒烯的非常规笼状结构在生长和退火过程中，金属原子可以稳定违反富勒烯化学中建立的孤立五边形规则并包含七边形环（从而不遵守富勒烯的传统定义）的非常规结构。作为代表性实例，这已经针对Ca@C_<72>和Sc_2@C_示出<74>。内金属掺杂的杂富勒烯。<82>已经进行了用一个氮原子取代La@C_ N和La_2中的一个笼状碳以制备La@C_<81>N和La_2@C_<79>N.it的实验尝试，值得注意的是，这些La掺杂的杂富勒烯与C_ N和C_N不同，在笼上没有显著的自由基特征<81><79>。金属富勒烯的笼状结构不一定与最稳定的富勒烯异构体的笼状结构一致，因为从金属到碳笼的电子转移很大。最有可能的是，在退火过程中形成了内晶结构。

1. Structures, Electronic States, and Bonding Features of Endohedral MetallofullerenesThe endohedral structures of monometallofullerenes M@C_<82>(M=Ca, Sc.Y.La, Ce, Pr, Nd, Eu, Gd, Yb, and Lu) and dimetallofullerenes Sc_2@C_<84> and La_2@C_<80> have been disclosed through a close interplay between theoretical prediction and experiment. In addition, a topological analysis of electron density and its Laplacian has been carried out to reveal the general features of chemical bonding in metallofullerenes. The structural and bonding study of the trimetallfullerene Sc_3@C_<82> is still in progress.2. The Dynamic Behaviors of Encapsulated Metal AtomsFrom the variable-temperature 13CNMR measurement of La_2@C_<80>, it has been for the first time found that the two La atoms circulate with +3 charge inside the round C_<80> cage even at room temperature. This finding has been also confirmed by the variab1e-temperature 139La NMR measurement and theoretical calculations.3. Unconventional Cage Structures of Endohedral MetallofullerenesMetal atoms can stabilize unconventional structures which violate the isolated pentagon rule established in fullerene chemistry and contain heptagonal rings (thereby not obeying the traditional definition of fullerenes), during growth and annealing processes. This has been shown for Ca@C_<72> and Sc_2@C_<74>, as representative examples.4. Endohedrallly Metal-Doped Heterofullerenes.An experimental attempt to substitute one cage carbon in La@C_<82> and La_2 by one nitrogen atom has been performed to prepare La@C_<81>N and La_2@C_<79>N.it is noteworthy that these La-doped heterofullerenes have no significant radical character on the cages, unlike C_<81>N and C_<79>N.5. SummaryThe cage structures of metallofullerenes do not necessary coincide with those of the most stable fullerene isomers, because of significant electron transfer from metal to carbon cages. Most Probably, endohedral structures are formed during the annealing process.