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1.
Beilstein J Org Chem ; 20: 1179-1188, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38887572

RESUMO

The addition reaction of C60 with silylene 1, a silicon analog of carbene, yielded the corresponding bis-adduct 3. The structure of 3 was determined by single-crystal X-ray structure analysis, representing the first example of a crystal structure of a silirane (silacyclopropane) derivative of fullerenes. Electrochemical measurements confirmed that the redox potentials of 3 are shifted cathodically compared to those of the parent mono-adduct 2. Density functional theory (DFT) calculations provided the basis for the electronic properties of compound 3.

2.
Molecules ; 22(7)2017 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-28708116

RESUMO

Exohedral derivatization of endohedral metallofullerenes (EMFs) has been exploited as a useful method for characterizing the structural and chemical properties of EMFs, and for functionalizing them for potential applications. The introduction of heteroatoms, such as electropositive silicon atoms, to fullerene cages is a novel functionalization method that remarkably affects the electronic characteristics of fullerenes. This review comprehensively describes the results of the reactions of monometallofullerene, dimetallofullerene, and trimetallic nitride template EMFs with disilirane, silirane, silylene, and digermirane, which afforded the corresponding silylated and germylated fullerenes. Several examples emphasize that exohedral functionalization regulates the dynamic behaviors of the encapsulated metal atoms and clusters in the fullerene cages. The electronic effects of silyl and germyl groups are represented by comparing the redox properties of silylated and germylated EMFs with those of other EMFs derivatized with carbon-atom-based functional groups.


Assuntos
Carbono/química , Fulerenos/química , Germânio/química , Metais/química , Silício/química , Cinética , Nanopartículas Metálicas/química , Estrutura Molecular , Oxirredução , Relação Estrutura-Atividade
3.
Molecules ; 22(5)2017 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-28531116

RESUMO

Photochemical carbosilylation of Lu3N@Ih-C80 was performed using siliranes (silacyclopropanes) to afford the corresponding [5,6]- and [6,6]-adducts. Electrochemical studies indicated that the redox potentials of the carbosilylated derivatives were shifted cathodically in comparison with those of the [5,6]-pyrrolidino adducts. The electronic effect of the silirane addends on Lu3N@Ih-C80 was verified on the basis of density functional theory calculations.


Assuntos
Ciclopropanos/química , Elétrons , Fulerenos/química , Silanos/química , Técnicas Eletroquímicas , Luz , Estrutura Molecular , Oxirredução , Processos Fotoquímicos , Pirrolidinas/química
4.
Chem Asian J ; 12(12): 1391-1399, 2017 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-28452140

RESUMO

Photochemical carbosilylation of Sc3 N@Ih -C80 with silirane 1 afforded two corresponding [5,6]-adducts, 2 and 3, and a [6,6]-adduct, 4. The structural and electronic properties of these products were characterized by means of spectroscopic, electrochemical, and theoretical methods. The structure of 2 was disclosed by means of single-crystal X-ray crystallographic analysis. Thermal isomerization of 3 to 2 was observed, whereas that of 2 to 3 proceeded less efficiently at 100 °C. Upon heating under the same conditions, adduct 4 underwent facile decomposition to afford Sc3 N@Ih -C80 , or isomerized into small amounts of 2 and 3. The relative stabilities of 2, 3, and 4 were rationalized through the results of theoretical calculations. In contrast, adducts 2, 3, and 4 were stable under the photolytic conditions employed for carbosilylation. The photochemical functionalization of Sc3 N@Ih -C80 represents a convenient synthetic method to obtain thermally labile fullerene-based products.

5.
Chemistry ; 21(46): 16411-20, 2015 Nov 09.
Artigo em Inglês | MEDLINE | ID: mdl-26439980

RESUMO

Bis-silylated and bis-germylated derivatives of Lu3 N@Ih -C80 (3, 4, 5) were successfully synthesized by the photochemical addition of disiliranes 1 a, 1 b or digermirane 2, and fully characterized by spectroscopic, electrochemical, and theoretical studies. Interestingly, digermirane 2 reacts more efficiently than disiliranes 1 a and 1 b because of its good electron-donor properties and lower steric hindrance around the Ge-Ge bond. The 1,4-adduct structures of 3, 4, 5 were unequivocally established by single-crystal X-ray crystallographic analyses. The electrochemical and theoretical studies reveal that the energy gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of the 1,4-adducts are remarkably smaller than those of Lu3 N@Ih -C80 , because the electron-donating groups effectively raise the HOMO levels. It is also observed that germyl groups are slightly more electron-donating than the silyl groups on the basis of the redox properties and the HOMO-LUMO energies of 4 and 5. Bis-silylation and bis-germylation are effective and versatile methods for tuning the electronic characteristics of endohedral metallofullerenes.

7.
Org Lett ; 14(23): 5908-11, 2012 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-23145910

RESUMO

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.

8.
J Am Chem Soc ; 134(43): 18101-8, 2012 Oct 31.
Artigo em Inglês | MEDLINE | ID: mdl-23057606

RESUMO

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.

9.
J Am Chem Soc ; 134(38): 16033-9, 2012 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-22947031

RESUMO

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.


Assuntos
Fulerenos/química , Cromatografia Líquida de Alta Pressão , Cristalografia por Raios X , Espectroscopia de Ressonância Magnética , Espectrometria de Massas , Modelos Moleculares , Espectroscopia de Luz Próxima ao Infravermelho
10.
J Am Chem Soc ; 132(50): 17953-60, 2010 Dec 22.
Artigo em Inglês | MEDLINE | ID: mdl-21105663

RESUMO

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.

11.
J Am Chem Soc ; 132(34): 12106-20, 2010 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-20695641

RESUMO

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.


Assuntos
Fulerenos/química , Silanos/química , Silanos/síntese química , Estrutura Molecular , Fotoquímica , Estereoisomerismo
12.
Org Lett ; 12(5): 996-9, 2010 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-20131815

RESUMO

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.

13.
Chem Commun (Camb) ; (5): 558-60, 2008 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-18209788

RESUMO

Dimetallofullerene Ce(2)@C(78) and its bis-silylated derivative (1) were successfully prepared and fully characterized.

14.
Chem Commun (Camb) ; (26): 2680-2, 2007 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-17594018

RESUMO

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.

15.
J Am Chem Soc ; 128(30): 9919-25, 2006 Aug 02.
Artigo em Inglês | MEDLINE | ID: mdl-16866551

RESUMO

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.

16.
J Am Chem Soc ; 127(42): 14570-1, 2005 Oct 26.
Artigo em Inglês | MEDLINE | ID: mdl-16231899

RESUMO

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.


Assuntos
Cério/química , Fulerenos/química , Compostos Organometálicos/síntese química , Isótopos de Carbono , Espectroscopia de Ressonância Magnética/métodos , Espectroscopia de Ressonância Magnética/normas , Modelos Moleculares , Compostos Organometálicos/química , Padrões de Referência
17.
J Am Chem Soc ; 127(28): 9956-7, 2005 Jul 20.
Artigo em Inglês | MEDLINE | ID: mdl-16011332

RESUMO

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.

18.
J Am Chem Soc ; 127(7): 2143-6, 2005 Feb 23.
Artigo em Inglês | MEDLINE | ID: mdl-15713091

RESUMO

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.

19.
J Phys Chem B ; 109(13): 6049-51, 2005 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-16851664

RESUMO

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.


Assuntos
Fulerenos/química , Lantânio/química , Compostos Organometálicos/síntese química , Silício/química , Ítrio/química , Compostos Organometálicos/química
20.
J Am Chem Soc ; 126(15): 4883-7, 2004 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-15080693

RESUMO

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)](-).

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