Iwamoto Takahiro, Slanina Zdenek, Mizorogi Naomi, Guo Jingdong, Akasaka Takeshi, Nagase Shigeru, Takaya Hikaru, Yasuda Nobuhiro, Kato Tatsuhisa, Yamago Shigeru
Institute for Chemical Research, Kyoto University, Uji 611-0011 (Japan).
Chemistry. 2014 Oct 27;20(44):14403-9. doi: 10.1002/chem.201403879. Epub 2014 Sep 15.
[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]CPP(δ+) , 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.
[11]环对亚苯基（[11]CPP）在溶液和固态中都能选择性地包裹La@C82，形成可能最短的金属富勒烯 - 碳纳米管（CNT）豆荚结构，即La@C82⊂[11]CPP。溶液中的络合作用受溶剂极性影响，在极性溶剂硝基苯中比在非极性溶剂1,2 - 二氯苯中强16倍。电化学分析表明，与游离的La@C82相比，络合后La@C82的氧化还原电位发生负向偏移。此外，氧化还原电位的偏移随溶剂极性增加。这些结果与通过从[11]CPP到La@C82的部分电子转移形成极性络合物（La@C82）(δ-)⊂[11]CPP(δ+)一致。这是首次观察到富勒烯豌豆与CPP豆荚之间存在这种电子相互作用。理论计算也支持从[11]CPP到La@C82的部分电荷转移（0.07）。通过X射线晶体学分析明确确定了该络合物的结构，结果表明La原子位于[11]CPP外围附近的C82内部。La@C82的偶极矩朝向CPP豌豆，几乎垂直于CPP轴。La@C82⊂[11]CPP中La原子的位置和偶极矩方向与La@C82⊂CNT中观察到的显著不同，这表明富勒烯 - CPP和富勒烯 - CNT豆荚结构中富勒烯豌豆的取向存在差异。这些结果突出了豌豆 - 豌豆相互作用在确定金属富勒烯 - CNT豆荚结构中金属富勒烯取向方面的重要性。
