La2@Cs(17 490)‐C76: A New Non‐IPR Dimetallic Metallofullerene Featuring Unexpectedly Weak Metal–Pentalene Interactions |
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| Authors: | Dr. Mitsuaki Suzuki Dr. Naomi Mizorogi Tao Yang Prof. Dr. Filip Uhlik Prof. Dr. Zdenek Slanina Prof. Dr. Xiang Zhao Prof. Dr. Michio Yamada Prof. Dr. Yutaka Maeda Prof. Dr. Tadashi Hasegawa Prof. Dr. Shigeru Nagase Prof. Dr. Xing Lu Prof. Dr. Takeshi Akasaka |
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| Affiliation: | 1. Foundation for Advancement of International Science (FAIS), Tsukuba, Ibaraki 305‐0821 (Japan);2. Department of Chemistry, Tokyo Gakugei University, Koganei, Tokyo 184‐8501 (Japan);3. Life Science Center of Tsukuba Advanced Research Alliance (TARA), University of Tsukuba, Tsukuba, Ibaraki 305‐8577 (Japan);4. Institute for Chemical Physics and Department of Chemistry, Xi'an Jiaotong University, Xi'an 710049 (P.R. China);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, ROC);7. Fukui Institute for Fundamental Chemistry (FIFC), Kyoto University, Kyoto 606‐8103 (Japan);8. School of Materials Science and Engineering, Huazhong University of Science and Technology (HUST), Wuhan 430074 (P. R. China) |
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| Abstract: | Although all the pure‐carbon fullerene isomers above C60 reported to date comply with the isolated pentagon rule (IPR), non‐IPR structures, which are expected to have different properties from those of IPR species, are obtainable either by exohedral modification or by endohedral atom doping. This report describes the isolation and characterization of a new endohedral metallofullerene (EMF), La2@C76, which has a non‐IPR fullerene cage. The X‐ray crystallographic result for the La2@C76/[NiII(OEP)] (OEP=octaethylporphyrin) cocrystal unambiguously elucidated the Cs(17 490)‐C76 cage structure, which contains two adjacent pentagon pairs. Surprisingly, multiple metal sites were distinguished from the X‐ray data, which implies dynamic behavior for the two La3+ cations inside the cage. This dynamic behavior was also corroborated by variable‐temperature 139 La NMR spectroscopy. This phenomenon conflicts with the widely accepted idea that the metal cations in non‐IPR EMFs invariably coordinate strongly with the negatively charged fused‐pentagon carbons, thereby providing new insights into modern coordination chemistry. Furthermore, our electrochemical and computational studies reveal that La2@Cs(17 490)‐C76 has a larger HOMO–LUMO gap than other dilanthanum‐EMFs with IPR cage structures, such as La2@D3h(5)‐C78 and La2@Ih(7)‐C80, which implies that IPR is no longer a strict rule for EMFs. |
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| Keywords: | cocrystallization density functional calculations isolated pentagon rule metallofullerenes X‐ray diffraction |
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