物理化学学报

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内嵌金属碳氮化物团簇富勒烯的稳定性与生成机理

施俊杰1, 胡子琦2, 杨逸豪2, 步宇翔1, 施祖进2   

  1. 1 山东大学化学与化工学院, 济南 250100;
    2 北京大学化学与分子工程学院, 稀土材料化学及应用国家重点实验室, 北京分子科学国家研究中心, 北京 100871
  • 收稿日期:2019-07-25 修回日期:2019-08-09 录用日期:2019-08-09 发布日期:2019-08-14
  • 通讯作者: 步宇翔, 施祖进 E-mail:byx@sdu.edu.cn;zjshi@pku.edu.cn
  • 基金资助:
    国家自然科学基金(21875002,21873056)和国家重点基础研究发展计划(2017YFA024901)资助项目

Stability and Formation Mechanism of Endohedral Metal Carbonitride Clusterfullerenes

Junjie Shi1, Ziqi Hu2, Yihao Yang2, Yuxiang Bu1, Zujin Shi2   

  1. 1 School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, P. R. China;
    2 National Laboratory for Molecular Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, P. R. China
  • Received:2019-07-25 Revised:2019-08-09 Accepted:2019-08-09 Published:2019-08-14
  • Contact: Yuxiang Bu, Zujin Shi E-mail:byx@sdu.edu.cn;zjshi@pku.edu.cn
  • Supported by:
    This project was supported by the National Natural Science Foundation of China (21875002, 21873056) and National Basic Research Program of China (2017YFA024901).

摘要: 对新结构富勒烯金属包合物的探索是富勒烯领域中的研究重点。本文从内嵌团簇与富勒烯碳笼尺寸匹配的角度出发,对基于金属碳氮化物团簇的新结构富勒烯金属包合物进行了研究。通过量子化学计算研究了M3NC团簇(M=Y,La,Gd)内嵌在D2(186)-C96D2(35)-C88分子中所形成包合物的稳定性和电子结构,发现富勒烯碳笼接受内嵌团簇转移的六个电子形成了稳定结构。结合文献已报道过的Sc3NC@Ih(7)-C80分子,阐明了M3NC团簇与富勒烯碳笼之间的尺寸匹配效应,并发现D2(186)-C96D2(35)-C88Ih(7)-C80三种富勒烯碳笼均具有五元环均匀分布的结构特点。我们对富勒烯之间的转变路径进行了研究,提出了不含Stone-Wales异构化过程的富勒烯直接生成机理,即可以通过增加碳原子的过程使五元环重排,在保持稳定性结构单元的同时转变为更大碳笼。

关键词: 富勒烯, 金属富勒烯, 密度泛函理论, 电子结构, 稀土元素

Abstract: Fullerene molecules have nano-scale cavities in which various metal or metal clusters of different sizes can be embedded to form metallofullerenes with unique core-shell structures. The physical and chemical properties of metallofullerenes can be modified through the interaction between the encapsulated metals and the fullerene cages. As such, the investigation of metallofullerenes with novel structures has been a principal research focus in the field of fullerenes. In this study, we investigated the size matching effect between encapsulated clusters and fullerene cages for the endohedral metal carbonitride clusterfullerenes in order to discover new metallofullerenes. The stability and electronic structure of the metallofullerenes formed by encapsulating M3NC clusters (M=Y, La, Gd) into D2(186)-C96 and D2(35)-C88 fullerenes were studied using quantum chemical calculations. It was found that the fullerene cages formed stable structures by accepting six electrons transferred from the encapsulated clusters. The change in configuration of the encapsulated clusters was clarified by a comparison with the corresponding M3N@C2n metal nitride clusterfullerenes; the size matching effect between M3NC cluster and fullerene cage was elucidated on the basis of the calculated results and previous studies on Sc3NC@Ih(7)-C80. For the D2(186)-C96 fullerene, the Gd3NC cluster was found to have smaller changes in the configuration as compared with the La3NC cluster, proving that Gd3NC is more suitable than La3NC for encapsulation in the D2(186)-C96 fullerene cage. In addition, it was determined that the La3NC cluster requires a large structural change to maintain its planar configuration. For the D2(35)-C88 fullerene cage, the Y3NC cluster is more suitable than Gd3NC for encapsulation owing to the smaller size of the Y3NC cluster. The spatial distribution of the highest occupied and lowest unoccupied molecular orbitals (HOMO and LUMO) of Gd3NC@D2(186)-C96 were found to be similar to those of Gd3N@D2(186)-C96. However, a unique endohedral cluster-based occupied molecular orbital was found for Gd3NC@D2(186)-C96. This orbital is derived from the interaction between the NC unit and the Gd atoms. The spatial distribution of the HOMO of Y3NC@D2(35)-C88 is similar to that of Y3N@D2(35)-C88, while the LUMO of Y3NC@D2(35)-C88 has a much larger contribution from the endohedral cluster as compared to Y3N@D2(35)-C88. Thus, the addition of a carbon atom in the cluster has a remarkable impact on the electronic structure of the metallofullerenes. With respect to structural characteristics, we found that the three fullerene cages, D2(186)-C96, D2(35)-C88, and Ih(7)-C80, have a uniform distribution of five-membered carbon atom rings; these fullerenes can be greatly stabilized in the form of C2n6- anions. However, the formation mechanism of fullerenes and metallofullerenes, at present, is poorly understood. Based on the structural analysis, we propose a direct mechanism for the formation of fullerenes without the Stone-Wales isomerization, i.e., the rearrangement of five-membered rings through the addition of carbon atoms and the transformation into larger carbon cages while maintaining stable structural units.

Key words: Fullerene, Metallofullerene, Density functional theory, Electronic structure, Rare-earth element

MSC2000: 

  • O641