Structures, Properties, and Growth Process of Endohedral Metallofullerenes

1.面内金属富勒烯的结构、电子态和成键特征通过理论预测和实验的密切结合，揭示了单金属富勒烯M@C_&lt；82&gt；(M=Ca，Sc.Y.La，Ce，Pr，Nd，Eu，Gd，Yb和Lu)和双金属富勒烯SC_2@C_&lt；84&gt；和La_2@C_&lt；80&gt；的面内结构。此外，还对电子密度及其拉普拉斯量进行了拓扑分析，揭示了金属富勒烯中化学键的一般特征。三金属富勒烯Sc_3@C_&lt；82&gt；的结构和成键研究仍在进行中。被包裹金属原子的动力学行为从La_2@C_&lt；80&gt；的变温~(13)CNMR测量首次发现，即使在室温下，两个La原子仍以3电荷在圆形C_t；80&gt；笼内循环。变温~(139)La核磁共振测量和理论计算也证实了这一发现。金属富勒烯的非常规笼形结构在生长和热处理过程中，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含有七角环(从而不符合富勒烯的传统定义)的非常规结构。作为代表性的例子，这体现在Ca@C&lt；72&gt；和SC_2@C&lt；74&gt；。用一个氮原子取代La@C&lt；82&gt；和La_2中的一个笼状碳，制备了La@C_&lt；81&gt；N和La_2@C_&lt；79&gt；N。值得注意的是，与C&lt；81&gt；N和C&lt；79&gt；N.5不同，这些La掺杂的杂富勒烯在笼子上没有明显的自由基性质。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，因为金属笼子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面体结构。

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.