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ABSTRACT: Photochemical reactions of Lu(3)N@I(h)-C(80) with disiliranes 1 and 2 produce several isomeric adducts. Spectroscopic analyses characterize the most stable isomers as 1,4(AA) adducts, which consist of paired twist conformers at rt. The electrochemical and theoretical studies reveal that the HOMO-LUMO energy gaps of the 1,4(AA) adducts are smaller than that of Lu(3)N@I(h)-C(80) because the electron-donating groups effectively raise the HOMO levels.
Organic Letters 11/2012; · 5.86 Impact Factor
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ABSTRACT: Introducing substituents onto SWNT sidewalls increases their solubility and tunes their properties. Controlling the degree of functionalization is important because the addition of numerous functional groups on the sidewall degrades their intrinsic useful electronic properties. We examined the synthesis and characterization of sidewall-functionalized SWNTs in this study. The functionalized SWNTs ((1)R-SWNTs-(2)R) were prepared in a one-pot reaction of SWNTs with alkyllithium ((1)RLi) followed by alkyl bromide ((2)RBr). The functionalized SWNTs were characterized by the absorption and Raman spectroscopy and thermogravimetric analysis. Not only the total number of functional groups introduced on the SWNT sidewall (formula mass: (1)R = (2)R) but also the ratio of (2)R to (1)R in the functionalized SWNTs (formula mass: (1)R ≠ (2)R) having two different substituents were clarified using the relation between results of Raman spectroscopy and thermogravimetric analysis. Results show that the degree of functionalization of (2)R to (1)R in (1)R-SWNTs-(2)R can be well controlled by the bulkiness of the alkyl groups of (1)RLi and (2)RBr. Moreover, substituent effects of reductive alkylation and reductive silylation of SWNTs via Birch reduction were investigated.
Journal of the American Chemical Society 10/2012; · 9.91 Impact Factor
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ABSTRACT: Functionalization of endohedral metallofullerenes has been shown to differ depending on photochemical or thermal pathways. We report that Lu(3)N@I(h)-C(80) reacts with thermally generated bis(2,6-diethylphenyl)silylene with high selectivity and forms monosilylated derivative 1b. Unexpectedly, 1b undergoes photochemical conversion to afford isomer 1a under ambient light. These adducts were characterized using NMR, visible-near-IR spectroscopy, and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. Single-crystal X-ray structure determination of 1a reveals a rare example of an open 1,2-adduct at the [5,6]-ring junction of the I(h)-C(80) cage. The electrochemical study reveals that the redox potentials of 1a and 1b are shifted cathodically compared to those of pristine Lu(3)N@I(h)-C(80) and that monosilylation is effective to fine-tune the electronic properties of endohedral metallofullerenes as well as empty fullerenes. Density functional theory calculations were also performed, which provide a theoretical basis for the structures and the behavior of the encapsulated Lu(3)N cluster.
Journal of the American Chemical Society 09/2012; 134(38):16033-9. · 9.91 Impact Factor
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ABSTRACT: Thermal carbosilylation of endohedral dimetallofullerene La(2)@I(h)-C(80) with silirane (silacyclopropane) is reported herein for the first time. Two diastereomers of the carbosilylated La(2)@I(h)-C(80) have been isolated and characterized. The fascinating molecular structure of one diastereomer of the carbosilylated derivatives has been determined unambiguously using X-ray crystallographic analysis. Detailed characteristics of the molecular structures including their metal atom movements have also been revealed using NMR spectroscopic studies and computational calculations. Results revealed that two La atoms move dynamically inside the carbon sphere. Furthermore, electrochemical study has demonstrated that carbosilylation is effective to fine-tune the La(2)@I(h)-C(80) electronic properties.
Journal of the American Chemical Society 12/2010; 132(50):17953-60. · 9.91 Impact Factor
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ABSTRACT: Thermal carbosilylation of endohedral dimetallofullerene La2@Ih-C80 with silirane (silacyclopropane) is reported herein for the first time. Two diastereomers of the carbosilylated La2@Ih-C80 have been isolated and characterized. The fascinating molecular structure of one diastereomer of the carbosilylated derivatives has been determined unambiguously using X-ray crystallographic analysis. Detailed characteristics of the molecular structures including their metal atom movements have also been revealed using NMR spectroscopic studies and computational calculations. Results revealed that two La atoms move dynamically inside the carbon sphere. Furthermore, electrochemical study has demonstrated that carbosilylation is effective to fine-tune the La2@Ih-C80 electronic properties.
11/2010;
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Junko Nagatsuka,
Sachie Sugitani, Masahiro Kako,
Tsukasa Nakahodo,
Naomi Mizorogi,
Midori O Ishitsuka,
Yutaka Maeda,
Takahiro Tsuchiya,
Takeshi Akasaka,
Xingfa Gao,
Shigeru Nagase
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ABSTRACT: Photochemical reactions of C(60) with siliranes (1a-d) afford adducts of four types (2a-5b) as carbosilylated and hydrosilylated C(60) derivatives. Characterization of these adducts was conducted using MS, UV, NMR spectroscopy, and single-crystal X-ray analyses. In particular, the first example of the crystal structure of a closed 1,2-adduct at the 5,6-ring junction of the C(60) cage is provided by single-crystal X-ray analysis of 3b. Electrochemical analyses also revealed unique redox properties of the products 2b-5b, which depend on the regiochemistry of the functionality, in addition to the substituents on the C(60) cage. Theoretical calculations offer bases for the experimentally observed redox properties and relative stabilities of the silylated products.
Journal of the American Chemical Society 09/2010; 132(34):12106-20. · 9.91 Impact Factor
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ABSTRACT: A two-step alkylation of single-walled carbon nanotubes was investigated. The functionalized SWNTs were characterized with vis-NIR and Raman spectrometers, scanning electron microscope, and thermogravimetric analysis. This one-pot alkylation of SWNTs with alkyllithium followed by alkyl halide is useful for the sidewall functionalization of SWNTs. This reaction shows significant substituent effects on the degree of functionalization of SWNTs. The degree of functionalization on SWNTs sidewall upon SWNTs may influence their characteristic properties on SWNTs sidewall by the substituent effects.
Organic Letters 03/2010; 12(5):996-9. · 5.86 Impact Factor
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ABSTRACT: Dimetallofullerene Ce(2)@C(78) and its bis-silylated derivative (1) were successfully prepared and fully characterized.
Chemical Communications 03/2008; · 6.17 Impact Factor
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Takatsugu Wakahara,
Michio Yamada,
Satomi Takahashi,
Tsukasa Nakahodo,
Takahiro Tsuchiya,
Yutaka Maeda,
Takeshi Akasaka, Masahiro Kako,
Kenji Yoza,
Ernst Horn,
Naomi Mizorogi,
Shigeru Nagase
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ABSTRACT: The (139)La NMR study of the exohedrally functionalized derivatives of La(2)@C(80) metallofullerene, La(2)@C(80)(Ar(2)Si)(2)CH(2) (: Ar = Mes, Mes = mesityl, : Ar = Dep, Dep = 2,6-diethylphenyl), reveal that the two La atoms hop between two sites along the equator of the C(80) cage.
Chemical Communications 08/2007; · 6.17 Impact Factor
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Takatsugu Wakahara,
Yuko Iiduka,
Ozora Ikenaga,
Tsukasa Nakahodo,
Akihiro Sakuraba,
Takahiro Tsuchiya,
Yutaka Maeda, Masahiro Kako,
Takeshi Akasaka,
Kenji Yoza,
Ernst Horn,
Naomi Mizorogi,
Shigeru Nagase
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ABSTRACT: The photochemical reaction of Sc(3)N@C(80) with 1,1,2,2-tetramesityl-1,2-disilirane affords the adduct as a bis-silylated product. The adduct was characterized by NMR spectroscopy and single-crystal X-ray structure analysis. The dynamic behavior of the disilirane moiety and the encapsulated Sc(3)N cluster were also investigated. The unique redox property of the adduct is reported by means of CV and DPV. Experimental results were confirmed by density functional calculations.
Journal of the American Chemical Society 09/2006; 128(30):9919-25. · 9.91 Impact Factor
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Yutaka Maeda,
Yoshinori Sato, Masahiro Kako,
Takatsugu Wakahara,
Takeshi Akasaka,
Jing Lu,
Shigeru Nagase,
Yumiko Kobori,
Tadashi Hasegawa,
Kenichi Motomiya,
Kazuyuki Tohji,
Atsuo Kasuya,
Dan Wang,
Dapeng Yu,
Zhengxiang Gao,
Rushan Han,
Hengqiang Ye
08/2006;
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Michio Yamada,
Tsukasa Nakahodo,
Takatsugu Wakahara,
Takahiro Tsuchiya,
Yutaka Maeda,
Takeshi Akasaka, Masahiro Kako,
Kenji Yoza,
Ernst Horn,
Naomi Mizorogi,
Kaoru Kobayashi,
Shigeru Nagase
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ABSTRACT: The exohedrally functionalized derivative of endohedral metallofullerene, Ce2@C80(Mes2SiCH2SiMes2), was successfully synthesized and fully characterized. X-ray crystallographic and NMR spectroscopic analyses reveal that the free random motion of two metal atoms in Ce2@C80 is controlled inside the cage by exohedral chemical functionalization.
Journal of the American Chemical Society 11/2005; 127(42):14570-1. · 9.91 Impact Factor
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Yuko Iiduka,
Ozora Ikenaga,
Akihiro Sakuraba,
Takatsugu Wakahara,
Takahiro Tsuchiya,
Yutaka Maeda,
Tsukasa Nakahodo,
Takeshi Akasaka, Masahiro Kako,
Naomi Mizorogi,
Shigeru Nagase
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ABSTRACT: Sc3N@C80 has a lower thermal reactivity than La2@C80, although Sc3N@C80 has the same carbon cage (Ih) and oxidation state (C806-) as La2@C80. This result is attributed to the difference in the energy level and distribution of LUMO between Sc3N@C80 and La2@C80.
Journal of the American Chemical Society 08/2005; 127(28):9956-7. · 9.91 Impact Factor
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Michio Yamada,
Lai Feng,
Takatsugu Wakahara,
Takahiro Tsuchiya,
Yutaka Maeda,
Yongfu Lian, Masahiro Kako,
Takeshi Akasaka,
Tatsuhisa Kato,
Kaoru Kobayashi,
Shigeru Nagase
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ABSTRACT: The silylation of endohedral mono-metallofullerenes (Y@C(82) and La@C(82)) and isolation of the corresponding adducts by HPLC separation have been accomplished. The redox properties of the silylated mono-metallofullerene were first clarified by CV and DPV measurements, indicating that the bis-silylated mono-metallofullerenes have lower oxidation and higher reduction potentials than the parent mono-metallofullerenes. These results reveal that bis-silylation is very effective for producing the electronegatively mono-metallofullerene derivatives as well as empty fullerenes.
The Journal of Physical Chemistry B 05/2005; 109(13):6049-51. · 3.70 Impact Factor
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Yutaka Maeda,
Jun Miyashita,
Tadashi Hasegawa,
Takatsugu Wakahara,
Takahiro Tsuchiya,
Lai Feng,
Yongfu Lian,
Takeshi Akasaka,
Kaoru Kobayashi,
Shigeru Nagase, Masahiro Kako,
Kazunori Yamamoto,
Karl M Kadish
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ABSTRACT: The chemical reduction and oxidation of M@C82 (M = Y, La, and Ce) afford the corresponding anion and cation, respectively, which show unique and interesting chemical reactivities. It is found that the successful reversible gain or loss of electrons by ionization is useful for controlling the stability and reactivity of M@C82 toward both nucleophiles and electrophiles.
Journal of the American Chemical Society 03/2005; 127(7):2143-6. · 9.91 Impact Factor
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Takatsugu Wakahara,
Jun-ichi Kobayashi,
Michio Yamada,
Yutaka Maeda,
Takahiro Tsuchiya,
Mutsuo Okamura,
Takeshi Akasaka,
Markus Waelchli,
Kaoru Kobayashi,
Shigeru Nagase,
Tatsuhisa Kato, Masahiro Kako,
Kazunori Yamamoto,
Karl M Kadish
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ABSTRACT: Ce@C(82) is isolated by high-performance liquid chromatography (HPLC) and the cage symmetry is determined as C(2)(v)() by measuring the (13)C NMR spectra of its anion. The (13)C NMR peaks of [Ce@C(82)](-) show temperature-dependent shifts ascribed to the f electron remaining on the Ce atom. Both Ce@C(82) and [Ce@C(82)](-) are silent in electron spin resonance spectroscopy (ESR) because of the highly anisotropic g matrix as well as of the fast relaxation process originating from the orbital angular momentum of the f electron. This is the complementary relationship to the observation of the paramagnetic shift in (13)C NMR. [Ce@C(82)](-) has lower stability in air than [La@C(82)](-).
Journal of the American Chemical Society 05/2004; 126(15):4883-7. · 9.91 Impact Factor
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Takatsugu Wakahara,
Yoichiro Matsunaga,
Akira Katayama,
Yutaka Maeda, Masahiro Kako,
Takeshi Akasaka,
Mutsuo Okamura,
Tatsuhisa Kato,
Yoong-Kee Choe,
Kaoru Kobayashi,
Shigeru Nagase,
Houjin Huang,
Masafumi Ata
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ABSTRACT: N@C60 has a lower photochemical reactivity toward disilirane than C60, although N@C60 does not differ from C60 in its thermal reactivity; theoretical calculations reveal that N@C60 and C60 have the same orbital levels and that N@3C60* has a shorter lifetime than 3C60*.
Chemical Communications 01/2004; · 6.17 Impact Factor
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ABSTRACT: A photochemical reaction of C(60) with disilane in a 2:3 ratio affords the isomer mixture of the tetrakis-adduct of C(60)((t)BuPh(2)Si)(4) as the major product. The use of a three-stage HPLC separation system isolated three of their isomers. Their structural assignments were based on FAB mass, UV-vis, NMR, and cyclic voltammetry (CV) measurements. The CV analysis showed that the terakis-adduct has lower oxidation and higher reduction potentials than the bis-adduct C(60)((t)BuPh(2)Si)(2) and the parent C(60).
The Journal of Organic Chemistry 09/2003; 68(17):6791-4. · 4.45 Impact Factor
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