Anisotropic Magnetic Behavior of Anionic Ce@C<sub>82</sub> Carbene Adducts

Takano, Yuta; Aoyagi, Motoki; Yamada, Michio; Nikawa, Hidefumi; Slanina, Zdenêk; Mizorogi, Naomi; Ishitsuka, Midori O.; Tsuchiya, Takahiro; Maeda, Yutaka; Akasaka, Takeshi; Kato, Tatsuhisa; Nagase, Shigeru

doi:10.1021/ja902106a

Cited by 61 publications

(75 citation statements)

References 67 publications

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“…Furthermore, Ce@C 2v -C 82 reacts with Ad carbene regioselectively to yield only two regioisomers: C 1 symmetric Ce@C 2v -C 82 (Ad)-I and C s symmetric Ce@C 2v -C 82 (Ad)-II (Scheme 1) [23]. In both cases, the C-C bonds on the addition sites were cleaved by adding the electrophilic carbenes to form the [6,6]-open structures.…”

Section: Carbene Adductsmentioning

confidence: 99%

In-depth understanding of π-electron systems: New vistas in fullerene endohedrals

Yamada

Tsuchiya

Akasaka

et al. 2010

Pure and Applied Chemistry

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The synthesis and characterization of various endohedral metallofullerenes and their derivatives are described. The encapsulated metal atoms' positions and movements were determined using NMR study, X-ray crystallographic analysis, and theoretical calculations. The results of electrochemical investigations clarified the relation between the electronic properties and the π-electron systems of the fullerene endohedrals.the positions and movements of untouchable metal atoms inside spherical π-spaces, along with some insights into their electronic properties. EXPERIMENTALEndohedral metallofullerenes are synthesized in a modified Krätschmer-Huffman generator. A composite rod containing graphite and metal oxide was subjected to an arc discharge as an anode. After annealing, the rod was vaporized in a helium atmosphere by arc discharge. We optimized the arc-discharge conditions (arc current = 256 A, arc voltage = 35 V, and He pressure = 150 Torr) to improve the yields. Carbonaceous soot containing empty fullerenes and endohedral metallofullerenes was obtained. From among the components, soluble fullerene species were extracted from the soot by refluxing in an organic solvent such as N,N-dimethylformamide (DMF). Then the extracts were subjected to high-performance liquid chromatography (HPLC) to isolate endohedral metallofullerenes. RESULTS AND DISCUSSION Molecular structure of Ce@C 2v -C 82It is noteworthy that c pc includes geometrical information (r and θ) related to the encapsulated Ce atoms. We conducted variable-temperature (VT) 13 C NMR measurements of Ce@C 2v -C 82 anion to obtain the experimental c pc values. Use of the least-squares method revealed the distance between Ce and the center of the hexagonal ring along the C 2 axis to be 2.1-2.8 Å. This metal position corresponds to M. YAMADA et al.

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Section: Carbene Adductsmentioning

confidence: 99%

In-depth understanding of π-electron systems: New vistas in fullerene endohedrals

Yamada

Tsuchiya

Akasaka

et al. 2010

Pure and Applied Chemistry

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“…14 Recently, our group reported anisotropic magnetism in an endohedral metallofullerene (EMF) Ce@C 2v -C 82 (hereafter denoted as Ce@C 82 , "C 2v " and "@" indicate the molecular symmetry of the fullerene cage and encapsulation, respectively) in both the pristine form 15,16 and the chemically functionalized form. 17 Remarkably, the observed magnetic anisotropy in NMR measurements was weakly influenced by the addition of a carbene. Moreover, the absolute positions of the hydrogen atoms of the addend could be assigned by analyzing the effective distance in the anisotropic magnetism, which decreases with the cube of the distance between the Ce and hydrogen atoms.…”

Section: ■ Introductionmentioning

confidence: 97%

Molecular Location Sensing Approach by Anisotropic Magnetism of an Endohedral Metallofullerene

et al. 2016

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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 (1)H 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 (1)H 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.

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“…It would be convenient to use DFT calculations to delineate such structures, and even obtain further independent predictions of new structures. [13,19,20] But the DFT calculations are strongly dependent on the functionals used when dealing with hZ-EMFs. Just for the controversy system uranium endohedral metallofullerenes U@C 28 , configuration-interaction (CI) method would bring wrong conclusions in studying such a complex carbon-based hZ-EMF.…”

Section: Introductionmentioning

confidence: 99%

The Reliability of the Density‐Functional Theory in Actinide Endohedral Systems

Wang

Xie

Jiang

et al. 2019

Advcd Theory and Sims

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Density-functional theory (DFT) has shown obvious violation to the Jacob's ladder in predicting the geometric and electronic structures of carbon-based high-Z elements endohedral metallofullerenes (hZ-EMFs). This has aroused long-term discussion in both theoretical and experimental fields, because this is related to whether the computationally efficient DFT can be the substitution to post-HF. In this work, the violation to the Jacob's ladder emerges again on the boron based uranium endohedral structure U@B 40 . The proper choice of functionals has been a significant factor to predict both geometric and electronic structures of U@B 40 . Pure generalized gradient approximations (GGA) functionals give a high symmetrical singlet ground state of D 2d , while a slightly tortured C 2v triplet state is more stable when hybrid GGAs are used. Compared to pure GGAs triplet state, the spin density accumulates more obviously on its B 40 cage in hybrid GGAs triplet state. The qualitative difference originates in the proportion of exact exchange energy that can exert a tremendous influence on energy splitting between electronic states of U@B 40 . This controversial calculation is an ideal model to reestimate the role of exchange functionals in studying hZ-EMFs. Therefore, these findings will provide important references to the benchmark experiments and future theoretical predictions.

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Anisotropic Magnetic Behavior of Anionic Ce@C₈₂ Carbene Adducts

Cited by 61 publications

References 67 publications

In-depth understanding of π-electron systems: New vistas in fullerene endohedrals

In-depth understanding of π-electron systems: New vistas in fullerene endohedrals

Molecular Location Sensing Approach by Anisotropic Magnetism of an Endohedral Metallofullerene

The Reliability of the Density‐Functional Theory in Actinide Endohedral Systems

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Anisotropic Magnetic Behavior of Anionic Ce@C82 Carbene Adducts

Cited by 61 publications

References 67 publications

In-depth understanding of π-electron systems: New vistas in fullerene endohedrals

In-depth understanding of π-electron systems: New vistas in fullerene endohedrals

Molecular Location Sensing Approach by Anisotropic Magnetism of an Endohedral Metallofullerene

The Reliability of the Density‐Functional Theory in Actinide Endohedral Systems

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Anisotropic Magnetic Behavior of Anionic Ce@C₈₂ Carbene Adducts