Partial Charge Transfer in the Shortest Possible Metallofullerene Peapod,La@C82⊂[11]Cycloparaphenylene |
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Authors: | Takahiro Iwamoto Dr Zdenek Slanina Dr Naomi Mizorogi Dr Jingdong Guo Prof?Dr Takeshi Akasaka Shigeru Nagase Dr Hikaru Takaya Dr Nobuhiro Yasuda Prof?Dr Tatsuhisa Kato Prof?Dr Shigeru Yamago |
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Institution: | 1. Institute for Chemical Research, Kyoto University, Uji 611‐0011 (Japan);2. Life Science Center of Tsukuba Advanced Research Alliance, University of Tsukuba, Tsukuba 305‐8577 (Japan);3. Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606‐8103 (Japan);4. Japan Synchrotron Radiation Research Institute, 1‐1‐1 Kouto, Sayo‐cho, Sayo‐gun, Hyogo 679‐5198 (Japan);5. Institute for the Promotion of Excellence in Higher Education, Kyoto University, Kyoto 606‐8501 (Japan);6. CREST, Japan Science and Technology Agency, Tokyo 102‐0076 (Japan) |
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Abstract: | 11]Cycloparaphenylene (11]CPP) selectively encapsulates La@C82 to form the shortest possible metallofullerene–carbon nanotube (CNT) peapod, La@C82?11]CPP, in solution and in the solid state. Complexation in solution was affected by the polarity of the solvent and was 16 times stronger in the polar solvent nitrobenzene than in the nonpolar solvent 1,2‐dichlorobenzene. Electrochemical analysis revealed that the redox potentials of La@C82 were negatively shifted upon complexation from free La@C82. Furthermore, the shifts in the redox potentials increased with polarity of the solvent. These results are consistent with formation of a polar complex, (La@C82)δ??11]CPPδ+, by partial electron transfer from 11]CPP to La@C82. This is the first observation of such an electronic interaction between a fullerene pea and CPP pod. Theoretical calculations also supported partial charge transfer (0.07) from 11]CPP to La@C82. The structure of the complex was unambiguously determined by X‐ray crystallographic analysis, which showed the La atom inside the C82 near the periphery of the 11]CPP. The dipole moment of La@C82 was projected toward the CPP pea, nearly perpendicular to the CPP axis. The position of the La atom and the direction of the dipole moment in La@C82?11]CPP were significantly different from those observed in La@C82?CNT, thus indicating a difference in orientation of the fullerene peas between fullerene–CPP and fullerene–CNT peapods. These results highlight the importance of pea–pea interactions in determining the orientation of the metallofullerene in metallofullerene–CNT peapods. |
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Keywords: | carbon encapsulation fullerenes host– guest systems nanotubes supramolecular chemistry |
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