Molecular Location Sensing Approach by Anisotropic Magnetism of an Endohedral Metallofullerene

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• 作者：Yuta Takano ; Ryo Tashita ; Mitsuaki Suzuki ; Shigeru Nagase ; Hiroshi Imahori ; Takeshi Akasaka
• 刊名：Journal of the American Chemical Society
• 出版年：2016
• 出版时间：June 29, 2016
• 年：2016
• 卷：138
• 期：25
• 页码：8000-8006
• 全文大小：417K
• 年卷期：0
• ISSN：1520-5126

文摘

Location recognition at the molecular scale provides valuable information about the nature of functional molecular materials. This study presents a novel location sensing approach based on an endohedral metallofullerene, Ce@C₈₂, using its anisotropic magnetic properties, which lead to temperature-dependent paramagnetic shifts in ¹H NMR spectra. Five site-isomers of Ce@C₈₂CH₂-3,5-C₆H₃Me₂ were synthesized to demonstrate the spatial sensing ability of Ce@C₈₂. Single-crystal structures, absorption spectra, and density functional theory calculations were used to select the plausible addition positions in the radical coupling reaction, which preferentially happens on the carbon atoms with high electron density of the singly occupied molecular orbital (SOMO) and positive charge. Temperature-dependent NMR measurements demonstrated unique paramagnetic shifts of the ¹H peaks, which were derived from the anisotropic magnetism of the f-electron in the Ce atom of the isomers. It was found that the magnetic anisotropy axes can be easily predicted by theoretical calculations using the Gaussian 09 package. Further analysis revealed that the temperature-dependent trend in the shifts is clearly predictable from the distance and relative position of the proton from the Ce atom. Hence, the Ce-encapsulated metallofullerene Ce@C₈₂ can provide spatial location information about nearby atoms through the temperature-dependent paramagnetic shifts of its NMR signals. It can act as a molecular probe for location sensing by utilizing the anisotropic magnetism of the encapsulated Ce atom. The potentially low toxicity and stability of the endohedral fullerene would make Ce@C₈₂ suitable for applications in biology and material science.