Novel Terbium-Based Endohedral Clusterfullerenes: Synthesis, Isolation and Characterization

Fupin Liu¹, Tao Wei¹, Song Wang¹, Jian Guan¹, Xing Lu², and Shangfeng Yang¹* 

¹ Hefei National Laboratory for Physical Sciences at Microscale, CAS Key Laboratory of Materials for Energy Conversion & Department of Materials Science and Engineering, University of Science and Technology of China (USTC), Hefei 230026, China

Email: sfyang@ustc.edu.cn

² State Key Laboratory of Materials Processing and Die & Mould Technology, College of Materials Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan 430074, China

Clusterfullerenes as a special branch of endohedral fullerenes are characteristic in the encapsulation of an unstable metal cluster by a robust fullerene cage.^[1,2] We present here several novel Tb-based endohedral clusterfullerenes isolated successfully recently. Tb₂C₈₄ was isolated by multistep HPLC. According to the UV-vis-NIR spectroscopic characterization and comparison with the reported analogous M2C84 (M = Sc, Y) metallofullerenes, the molecular structure of Tb₂C₈₄ is proposed to be Tb₂C₂@C_s(6)-C₈₂ featuring a metal carbide clusterfullerene (CCF) structure, which is unambiguously confirmed by X-ray crystallographic study. A detailed analysis of the crystal structure of a cocrystal of Tb₂C₂@C_s(6)-C₈₂·Ni^II(OEP)·2C₆H₆ (Ni^II(OEP) = nickel (II) octaethylporphyrin) reveals  that a bent Tb₂C₂ carbide cluster is encaged rigidly inside a C_s(6)-C₈₂ cage.^[3] More recently we also successfully isolated the first Tb-based monometallic cyanide clusterfullerene (CYCF), TbCN@C₈₂. The UV-vis-NIR spectrum and cyclic voltammetry of TbCN@C₈₂ show high resemblance to those of the recently reported analogous CYCF YCN@C_s(6)-C₈₂,^[4] suggesting that TbCN@C₈₂ has the same monometallic cyanide clusterfullerene structure and C_s(6)-C₈₂ isomeric cage, and the electronic property of monometallic cyanide clusterfullerene MCN@C₈₂is insensitive on the encapsulated metal. 

REFERENCES 

1. a) S. F. Yang, F. P. Liu, C. B. Chen, M. Z. Jiao, T. Wei, Chem. Commun. 2011, 47, 11822-11839. b) X. Lu, L. Feng, T. Akasaka, S. Nagase, Chem. Soc. Rev. 2012, 41, 7723-7760.
2. a) A. A. Popov, S. F. Yang, L. Dunsch, Chem. Rev. 2013, 113, 5989-6113; d) S. F. Yang, C. R. Wang (eds), “Endohedral Fullerenes: From Fundamentals to Applications”, World Scientific Publishing Co., Singapore, 2013 (ISBN: 978-9814489836); c) S. F. Yang, Curr. Org. Chem. 2012, 16, 1079-1094; d) A. Rodriguez-Fortea, A. L. Balch, J. M. Poblet, Chem. Soc. Rev. 2011, 40, 3551-3563.
3. F. P. Liu, T. Wei, S. Wang, J. Guan, X. Lu, S. F. Yang, Fullerenes, Nanotubes and Carbon Nanostructures 2013, 21, in press (DOI: 10.1080/1536383X.2013.801839).
4. S. F. Yang, C. B. Chen, F. P. Liu, Y. P. Xie, F. Y. Li, M. Z. Jiao, M. Suzuki, T. Wei, S. Wang, Z. F. Chen, X. Lu, T. Akasaka, Sci. Rep. 2013, 3, 1487.