The Unanticipated Dimerization of Ce@C2v (9)-C82 upon Co-crystallization with Ni(octaethylporphyrin) and Comparison with Monomeric M@C2v (9)-C82 (M = La, Sc, and Y)

Mitsuaki Suzuki; Michio Yamada; Yutaka Maeda; Satoru Sato; Yuta Takano; Filip Uhlík; Zdenek Slanina; Yongfu Lian; Xing Lu; Shigeru Nagase; Marilyn M Olmstead; Alan L Balch; Takeshi Akasaka

doi:10.1002/chem.201602595

The Unanticipated Dimerization of Ce@C_2v (9)-C₈₂ upon Co-crystallization with Ni(octaethylporphyrin) and Comparison with Monomeric M@C_2v (9)-C₈₂ (M = La, Sc, and Y)

Chemistry. 2016 Dec 12;22(50):18115-18122. doi: 10.1002/chem.201602595. Epub 2016 Oct 28.

Authors

Mitsuaki Suzuki^{1

2}, Michio Yamada², Yutaka Maeda², Satoru Sato³, Yuta Takano⁴, Filip Uhlík⁵, Zdenek Slanina⁶, Yongfu Lian⁷, Xing Lu⁸, Shigeru Nagase⁹, Marilyn M Olmstead¹⁰, Alan L Balch¹⁰, Takeshi Akasaka^{2

3

8

11}

Affiliations

¹ Department of Chemistry, Josai University, Saitama, 350-0295, Japan.
² Department of Chemistry, Tokyo Gakugei University, Tokyo, 184-8501, Japan.
³ Life Science Center of Tsukuba Advanced Research Alliance, University of Tsukuba, Ibaraki, 305-8588, Japan.
⁴ Institute for Integrated Cell-Material Sciences (WPI-iCeMS), Kyoto University, Kyoto, 615-8510, Japan.
⁵ Department of Physical and Macromolecular Chemistry, Charles University in Prague, 128 43, Prague 2, Czech Republic.
⁶ Department of Chemistry and Biochemistry, National Chung-Cheng University, Chia-Yi, 62117, Taiwan R.O.C.
⁷ Key Laboratory of Functional Inorganic Material Chemistry, Ministry of Education, School of Chemistry and Materials Science, Heilongjiang University, Harbin, 150080, P.R. China.
⁸ State Key Laboratory of Materials Processing and Die & Mold Technology, School of Materials Science and Engineering, Huazhong, University of Science and Technology, Wuhan, 430074, P.R. China.
⁹ Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto, 606-8103, Japan.
¹⁰ Department of Chemistry, University of California, Davis, California, 95616, USA.
¹¹ Foundation for Advancement of International Science, Tsukuba, Ibaraki, 305-0821, Japan.

PMID: 27791293
DOI: 10.1002/chem.201602595

Abstract

We report that Ce@C_2v (9)-C₈₂ forms a centrosymmetric dimer when co-crystallized with Ni(OEP) (OEP = octaethylporphyrin dianion). The crystal structure of {Ce@C_2v (9)-C₈₂ }₂ ⋅2[Ni(OEP)]⋅4 C₆ H₆ shows that a new C-C bond with a bond length of 1.605(5) Å connects the two cages. The high spin density of the singly occupied molecular orbital (SOMO) on the cage and the pyramidalization of the cage are factors that favor dimerization. In contrast, the treatment of Ni(OEP) with M@C_2v (9)-C₈₂ (M = La, Sc, and Y) results in crystallization of monomeric endohedral fullerenes. A systematic comparison of the X-ray structures of M@C_2v (9)-C₈₂ (M = Sc, Y, La, Ce, Gd, Yb, and Sm) reveals that the major metal site in each case is located at an off-center position adjacent to a hexagonal ring along the C₂ axis of the C_2v (9)-C₈₂ cage. DFT calculations at the M06-2X level revealed that the positions of the metal centers in these metallofullerenes M@C_2v (9)-C₈₂ (M = Sc, Y, and Ce), as determined by single-crystal X-ray structure studies, correspond to an energy minimum for each compound.

Keywords: cage compounds; crystal growth; dimerization; metallofullerenes; structure elucidation.