Detection of a Family of Gadolinium-Containing Endohedral Fullerenes and the Isolation and Crystallographic Characterization of One Member as a Metal−Carbide Encapsulated inside a Large Fullerene Cage

A series of di-gadolinium endohedrals that extends from Gd2C90 to Gd2C124 has been detected by mass spectrometry of the o-dichlorobenzene extract of the carbon soot produced by direct current arcing of graphite rods filled with a mixture of Gd2O3 and graphite powder. Chromatographic separation has led to the isolation of pure samples of two isomers of Gd2C94 and the complete series from Gd2C96 to Gd2C106. Endohedral fullerenes of the type M2C2n can exist as the conventional endohedral, M2@C2n, or as the carbide-containing endohedral, M2C2@C2n−2. Crystallographic characterization of the more rapidly eluting isomer of Gd2C94 reveals that it possesses the carbide structure, Gd2C2@D3(85)-C92. Computational studies suggest that the more slowly eluting isomer of Gd2C94 may be a conventional endohedral, Gd2@C2(121)-C94

Detection of a Family of Gadolinium-Containing Endohedral Fullerenes and the Isolation and Crystallographic Characterization of One Member as a Metal−Carbide Encapsulated inside a Large Fullerene Cage

A series of di-gadolinium endohedrals that extends from Gd2C90 to Gd2C124 has been detected by mass spectrometry of the o-dichlorobenzene extract of the carbon soot produced by direct current arcing of graphite rods filled with a mixture of Gd2O3 and graphite powder. Chromatographic separation has led to the isolation of pure samples of two isomers of Gd2C94 and the complete series from Gd2C96 to Gd2C106. Endohedral fullerenes of the type M2C2n can exist as the conventional endohedral, M2@C2n, or as the carbide-containing endohedral, M2C2@C2n−2. Crystallographic characterization of the more rapidly eluting isomer of Gd2C94 reveals that it possesses the carbide structure, Gd2C2@D3(85)-C92. Computational studies suggest that the more slowly eluting isomer of Gd2C94 may be a conventional endohedral, Gd2@C2(121)-C94

Single Samarium Atoms in Large Fullerene Cages. Characterization of Two Isomers of Sm@C₉₂ and Four Isomers of Sm@C₉₄ with the X-ray Crystallographic Identification of Sm@<i>C</i>₁(42)-C₉₂, Sm@<i>C</i>_<i>s</i>(24)-C₉₂, and Sm@<i>C</i>_3<i>v</i>(134)-C₉₄

Two isomers of Sm@C₉₂ and four isomers of Sm@C₉₄ were isolated from carbon soot obtained by electric arc vaporization of carbon rods doped with Sm₂O₃. Analysis of the structures by single-crystal X-ray diffraction on cocrystals formed with Ni^II(octaethylporphyrin) reveals the identities of two of the Sm@C₉₂ isomers: Sm@C₉₂(I), which is the more abundant isomer, is Sm@<i>C</i>₁(42)-C₉₂, and Sm@C₉₂(II) is Sm@<i>C</i>_<i>s</i>(24)-C₉₂. The structure of the most abundant form of the four isomers of Sm@C₉₄, Sm@C₉₄(I), is Sm@<i>C</i>_3<i>v</i>(134)-C₉₄, which utilizes the same cage isomer as the previously known Ca@<i>C</i>_3<i>v</i>(134)-C₉₄ and Tm@<i>C</i>_3<i>v</i>(134)-C₉₄. All of the structurally characterized isomers obey the isolated pentagon rule. While the four Sm@C₉₀ and five isomers of Sm@C₈₄ belong to common isomerization maps that allow these isomers to be interconverted through Stone–Wales transformations, Sm@<i>C</i>₁(42)-C₉₂ and Sm@<i>C</i>_<i>s</i>(24)-C₉₂ are not related to each other by any set of Stone–Wales transformations. UV–vis–NIR spectroscopy and computational studies indicate that Sm@<i>C</i>₁(42)-C₉₂ is more stable than Sm@<i>C</i>_<i>s</i>(24)-C₉₂ but possesses a smaller HOMO–LUMO gap. While the electronic structures of these endohedrals can be formally described as Sm²⁺@C_2<i>n</i>^2–, the net charge transferred to the cage is less than two due to some back-donation of electrons from π orbitals of the cage to the metal ion

Fabrication of Mesoporous Co₃O₄ from LP-FDU-12 via Nanocasting Route and Effect of Wall/Pore Size on Their Magnetic Properties

Highly ordered mesoporous Co₃O₄ nanostructures were prepared using LP-FDU-12 as hard templates. By changing the hydrothermal temperature or by the acid treatment of the LP-FDU-12 template, Co₃O₄ replicas with different cell parameters and wall thicknesses have been obtained. The structure and textural characteristics of both LP-FDU-12 and Co₃O₄ replicas were investigated by X-ray diffraction, transmission electron microscopy, and N₂ adsorption–desorption isotherm analysis. The cell parameter and wall thickness of a mesoporous Co₃O₄ have been varied systematically within the ranges 30.4–33.9 and 24.8–18.2 nm, respectively, and the materials exhibit surface areas in the 29.6–52.9 m² g^–1 range, while preserving a highly ordered 3D pore structure and highly crystalline walls. Most importantly, magnetic studies show that the factors which affect the magnetic behavior in the Co₃O₄ nanosphere system are not only the sphere size but also the space-filled parameter at the nanoscale

Single Samarium Atoms in Large Fullerene Cages. Characterization of Two Isomers of Sm@C₉₂ and Four Isomers of Sm@C₉₄ with the X-ray Crystallographic Identification of Sm@<i>C</i>₁(42)-C₉₂, Sm@<i>C</i>_<i>s</i>(24)-C₉₂, and Sm@<i>C</i>_3<i>v</i>(134)-C₉₄

Two isomers of Sm@C₉₂ and four isomers of Sm@C₉₄ were isolated from carbon soot obtained by electric arc vaporization of carbon rods doped with Sm₂O₃. Analysis of the structures by single-crystal X-ray diffraction on cocrystals formed with Ni^II(octaethylporphyrin) reveals the identities of two of the Sm@C₉₂ isomers: Sm@C₉₂(I), which is the more abundant isomer, is Sm@<i>C</i>₁(42)-C₉₂, and Sm@C₉₂(II) is Sm@<i>C</i>_<i>s</i>(24)-C₉₂. The structure of the most abundant form of the four isomers of Sm@C₉₄, Sm@C₉₄(I), is Sm@<i>C</i>_3<i>v</i>(134)-C₉₄, which utilizes the same cage isomer as the previously known Ca@<i>C</i>_3<i>v</i>(134)-C₉₄ and Tm@<i>C</i>_3<i>v</i>(134)-C₉₄. All of the structurally characterized isomers obey the isolated pentagon rule. While the four Sm@C₉₀ and five isomers of Sm@C₈₄ belong to common isomerization maps that allow these isomers to be interconverted through Stone–Wales transformations, Sm@<i>C</i>₁(42)-C₉₂ and Sm@<i>C</i>_<i>s</i>(24)-C₉₂ are not related to each other by any set of Stone–Wales transformations. UV–vis–NIR spectroscopy and computational studies indicate that Sm@<i>C</i>₁(42)-C₉₂ is more stable than Sm@<i>C</i>_<i>s</i>(24)-C₉₂ but possesses a smaller HOMO–LUMO gap. While the electronic structures of these endohedrals can be formally described as Sm²⁺@C_2<i>n</i>^2–, the net charge transferred to the cage is less than two due to some back-donation of electrons from π orbitals of the cage to the metal ion

Single Samarium Atoms in Large Fullerene Cages. Characterization of Two Isomers of Sm@C₉₂ and Four Isomers of Sm@C₉₄ with the X-ray Crystallographic Identification of Sm@<i>C</i>₁(42)-C₉₂, Sm@<i>C</i>_<i>s</i>(24)-C₉₂, and Sm@<i>C</i>_3<i>v</i>(134)-C₉₄

Two isomers of Sm@C₉₂ and four isomers of Sm@C₉₄ were isolated from carbon soot obtained by electric arc vaporization of carbon rods doped with Sm₂O₃. Analysis of the structures by single-crystal X-ray diffraction on cocrystals formed with Ni^II(octaethylporphyrin) reveals the identities of two of the Sm@C₉₂ isomers: Sm@C₉₂(I), which is the more abundant isomer, is Sm@<i>C</i>₁(42)-C₉₂, and Sm@C₉₂(II) is Sm@<i>C</i>_<i>s</i>(24)-C₉₂. The structure of the most abundant form of the four isomers of Sm@C₉₄, Sm@C₉₄(I), is Sm@<i>C</i>_3<i>v</i>(134)-C₉₄, which utilizes the same cage isomer as the previously known Ca@<i>C</i>_3<i>v</i>(134)-C₉₄ and Tm@<i>C</i>_3<i>v</i>(134)-C₉₄. All of the structurally characterized isomers obey the isolated pentagon rule. While the four Sm@C₉₀ and five isomers of Sm@C₈₄ belong to common isomerization maps that allow these isomers to be interconverted through Stone–Wales transformations, Sm@<i>C</i>₁(42)-C₉₂ and Sm@<i>C</i>_<i>s</i>(24)-C₉₂ are not related to each other by any set of Stone–Wales transformations. UV–vis–NIR spectroscopy and computational studies indicate that Sm@<i>C</i>₁(42)-C₉₂ is more stable than Sm@<i>C</i>_<i>s</i>(24)-C₉₂ but possesses a smaller HOMO–LUMO gap. While the electronic structures of these endohedrals can be formally described as Sm²⁺@C_2<i>n</i>^2–, the net charge transferred to the cage is less than two due to some back-donation of electrons from π orbitals of the cage to the metal ion

Single Samarium Atoms in Large Fullerene Cages. Characterization of Two Isomers of Sm@C₉₂ and Four Isomers of Sm@C₉₄ with the X-ray Crystallographic Identification of Sm@<i>C</i>₁(42)-C₉₂, Sm@<i>C</i>_<i>s</i>(24)-C₉₂, and Sm@<i>C</i>_3<i>v</i>(134)-C₉₄

Two isomers of Sm@C₉₂ and four isomers of Sm@C₉₄ were isolated from carbon soot obtained by electric arc vaporization of carbon rods doped with Sm₂O₃. Analysis of the structures by single-crystal X-ray diffraction on cocrystals formed with Ni^II(octaethylporphyrin) reveals the identities of two of the Sm@C₉₂ isomers: Sm@C₉₂(I), which is the more abundant isomer, is Sm@<i>C</i>₁(42)-C₉₂, and Sm@C₉₂(II) is Sm@<i>C</i>_<i>s</i>(24)-C₉₂. The structure of the most abundant form of the four isomers of Sm@C₉₄, Sm@C₉₄(I), is Sm@<i>C</i>_3<i>v</i>(134)-C₉₄, which utilizes the same cage isomer as the previously known Ca@<i>C</i>_3<i>v</i>(134)-C₉₄ and Tm@<i>C</i>_3<i>v</i>(134)-C₉₄. All of the structurally characterized isomers obey the isolated pentagon rule. While the four Sm@C₉₀ and five isomers of Sm@C₈₄ belong to common isomerization maps that allow these isomers to be interconverted through Stone–Wales transformations, Sm@<i>C</i>₁(42)-C₉₂ and Sm@<i>C</i>_<i>s</i>(24)-C₉₂ are not related to each other by any set of Stone–Wales transformations. UV–vis–NIR spectroscopy and computational studies indicate that Sm@<i>C</i>₁(42)-C₉₂ is more stable than Sm@<i>C</i>_<i>s</i>(24)-C₉₂ but possesses a smaller HOMO–LUMO gap. While the electronic structures of these endohedrals can be formally described as Sm²⁺@C_2<i>n</i>^2–, the net charge transferred to the cage is less than two due to some back-donation of electrons from π orbitals of the cage to the metal ion

Isolation of Three Isomers of Sm@C₈₄ and X-ray Crystallographic Characterization of Sm@<i>D</i>_3<i>d</i>(19)-C₈₄ and Sm@<i>C</i>₂(13)-C₈₄

Three isomers with the composition Sm@C₈₄ were isolated from carbon soot obtained by electric arc vaporization of carbon rods doped with Sm₂O₃. These isomers were labeled Sm@C₈₄(I), Sm@C₈₄(II), and Sm@C₈₄(III) in order of their elution times during chromatography on a Buckyprep column with toluene as the eluent. Analysis of the structures by single-crystal X-ray diffraction on cocrystals formed with Ni^II(octaethylporphyrin) reveals the identities of two of the isomers: Sm@C₈₄(I) is Sm@<i>C</i>₂(13)-C₈₄, and Sm@C₈₄(III) is Sm@ <i>D</i>_3<i>d</i>(19)-C₈₄. Sm@C₈₄(II) can be identified as Sm@<i>C</i>₂(11)-C₈₄ on the basis of the similarity of its UV/vis/NIR spectrum with that of Yb@<i>C</i>₂(11)-C₈₄, whose carbon cage has been characterized by ¹³C NMR spectroscopy. Comparison of the three Sm@C₈₄ isomers identified in this project with two prior reports of the preparation and isolation of isomers of Sm@C₈₄ indicate that five different Sm@C₈₄ isomers have been found and that the source of samarium used for the generation of fullerene soot is important in determining which of these isomers form

Isolation of Three Isomers of Sm@C₈₄ and X-ray Crystallographic Characterization of Sm@<i>D</i>_3<i>d</i>(19)-C₈₄ and Sm@<i>C</i>₂(13)-C₈₄

Three isomers with the composition Sm@C₈₄ were isolated from carbon soot obtained by electric arc vaporization of carbon rods doped with Sm₂O₃. These isomers were labeled Sm@C₈₄(I), Sm@C₈₄(II), and Sm@C₈₄(III) in order of their elution times during chromatography on a Buckyprep column with toluene as the eluent. Analysis of the structures by single-crystal X-ray diffraction on cocrystals formed with Ni^II(octaethylporphyrin) reveals the identities of two of the isomers: Sm@C₈₄(I) is Sm@<i>C</i>₂(13)-C₈₄, and Sm@C₈₄(III) is Sm@ <i>D</i>_3<i>d</i>(19)-C₈₄. Sm@C₈₄(II) can be identified as Sm@<i>C</i>₂(11)-C₈₄ on the basis of the similarity of its UV/vis/NIR spectrum with that of Yb@<i>C</i>₂(11)-C₈₄, whose carbon cage has been characterized by ¹³C NMR spectroscopy. Comparison of the three Sm@C₈₄ isomers identified in this project with two prior reports of the preparation and isolation of isomers of Sm@C₈₄ indicate that five different Sm@C₈₄ isomers have been found and that the source of samarium used for the generation of fullerene soot is important in determining which of these isomers form

Isolation of Three Isomers of Sm@C₈₄ and X-ray Crystallographic Characterization of Sm@<i>D</i>_3<i>d</i>(19)-C₈₄ and Sm@<i>C</i>₂(13)-C₈₄

Three isomers with the composition Sm@C₈₄ were isolated from carbon soot obtained by electric arc vaporization of carbon rods doped with Sm₂O₃. These isomers were labeled Sm@C₈₄(I), Sm@C₈₄(II), and Sm@C₈₄(III) in order of their elution times during chromatography on a Buckyprep column with toluene as the eluent. Analysis of the structures by single-crystal X-ray diffraction on cocrystals formed with Ni^II(octaethylporphyrin) reveals the identities of two of the isomers: Sm@C₈₄(I) is Sm@<i>C</i>₂(13)-C₈₄, and Sm@C₈₄(III) is Sm@ <i>D</i>_3<i>d</i>(19)-C₈₄. Sm@C₈₄(II) can be identified as Sm@<i>C</i>₂(11)-C₈₄ on the basis of the similarity of its UV/vis/NIR spectrum with that of Yb@<i>C</i>₂(11)-C₈₄, whose carbon cage has been characterized by ¹³C NMR spectroscopy. Comparison of the three Sm@C₈₄ isomers identified in this project with two prior reports of the preparation and isolation of isomers of Sm@C₈₄ indicate that five different Sm@C₈₄ isomers have been found and that the source of samarium used for the generation of fullerene soot is important in determining which of these isomers form