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1.
Sci Adv ; 5(8): eaaw0982, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31467971

RESUMO

Carboncones, a special family of all-carbon allotropes, are predicted to have unique properties that distinguish them from fullerenes, carbon nanotubes, and graphenes. Owing to the absence of methods to synthesize atomically well-defined carboncones, however, experimental insight into the nature of pure carboncones has been inaccessible. Herein, we describe a facile synthesis of an atomically well-defined carboncone[1,2] (C70H20) and its soluble penta-mesityl derivative. Identified by x-ray crystallography, the carbon skeleton is a carboncone with the largest possible apex angle. Much of the structural strain is overcome in the final step of converting the bowl-shaped precursor into the rigid carboncone under mild reaction conditions. This work provides a research opportunity for investigations of atomically precise single-layered carboncones having even higher cone walls and/or smaller apex angles.

2.
J Org Chem ; 2019 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-31315398

RESUMO

A general one-step synthesis of symmetrical or unsymmetrical 1,4-di(organo)fullerenes from organo(hydro)fullerenes (RC60H) is realized by direct oxidative arylation. The new combination of catalytic trifluoromethanesulfonic acid (TfOH) and stoichiometric o-chloranil is the first to be used to directly generate an R-C60+ intermediate from common RC60H. Unexpectedly, the in situ generated R-C60+ intermediate is shown to be quite stable in whole 13C NMR spectroscopy characterization in the absence of cation quenching reagents. Because the direct oxidation of common RC60H to form the corresponding R-C60+ has never been realized, the present combination of TfOH and o-chloranil solves the challenges associated with the formation of stable RC60+ cations from common RC60H without any coordination of an R group.

3.
Artigo em Inglês | MEDLINE | ID: mdl-31237012

RESUMO

All previously reported C70 isomers have positive curvature and contain 12 pentagons in addition to hexagons. Herein, we report a new C70 species with two negatively curved heptagon moieties and 14 pentagons. This unconventional heptafullerene[70] containing two symmetric heptagons, referred to as dihept-C70 , grows in the carbon arc by a theoretically supported pathway in which the carbon cluster of a previously reported C66 species undergoes successive C2 insertion via a known heptafullerene[68] intermediate with low energy barriers. As identified by X-ray crystallography, the occurrence of heptagons facilitates a reduction in the angle of the π-orbital axis vector in the fused pentagons to stabilize dihept-C70 . Chlorination at the intersection of a heptagon and two adjacent pentagons can greatly enlarge the HOMO-LUMO gap, which makes dihept-C70 Cl6 isolable by chromatography. The synthesis of dihept-C70 Cl6 offers precious clues with respect to the fullerene formation mechanism in the carbon-clustering process.

4.
J Am Chem Soc ; 141(16): 6651-6657, 2019 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-30879294

RESUMO

The combustion has long been applied for industrial synthesis of carbon materials such as fullerenes as well as carbon particles (known as carbon black), but the components and structures of the carbon soot are far from being clarified. Herein, we retrieve an unprecedented hydrofullerene C66H4 from a soot of a low-pressure combustion of benzene-acetylene-oxygen. Unambiguously characterized by single-crystal X-ray diffraction, the C66H4 renders a nonclassical geometry incorporating two heptagons and two pairs of fused pentagons in a C2 v symmetry. The common vertexes of the fused pentagons are bonded with four hydrogen atoms to convert the hydrogen-linking carbon atoms from sp2 to sp3 hybridization, which together with the adjacent heptagons essentially releases the sp2-bond strains on the abutting-pentagon sites of the diheptagonal fused pentagon C66 (dihept-C66). DFT computations suggest the possibility for an in situ hydrogenation process leading to stabilization of the dihept-C66. In addition, the experiments have been carried out to study heptagon-dependent properties of dihept-C66H4, indicating the key responsibility of the heptagon for changing hydrocarbon activity and electronic properties. The present work with the unprecedented double-heptagon-containing hydrofullerene successfully isolated and identified as one of the low-pressure combustion products shows that the heptagon is a new building block for constructing fullerene products in addition to pentagons and hexagons in low-pressure combustion systems.

5.
Nat Commun ; 10(1): 485, 2019 01 30.
Artigo em Inglês | MEDLINE | ID: mdl-30700716

RESUMO

The assembly of spherical fullerenes, or buckyballs, into single crystals for crystallographic identification often suffers from disordered arrangement. Here we show a chiral configuration of decapyrrylcorannulene that has a concave 'palm' of corannulene and ten flexible electron-rich pyrryl group 'fingers' to mimic the smart molecular 'hands' for self-adaptably cradling various buckyballs in a (+)hand-ball-hand(-) mode. As exemplified by crystallographic identification of 15 buckyball structures representing pristine, exohedral, endohedral, dimeric and hetero-derivatization, the pyrryl groups twist with varying dihedral angles to adjust the interaction between decapyrrylcorannulene and fullerene. The self-adaptable electron-rich pyrryl groups, susceptible to methylation, are theoretically revealed to contribute more than the bowl-shaped palm of the corannulene in holding buckyball structures. The generality of the present decapyrrylcorannulene host with flexible pyrryl groups facilitates the visualization of numerous unknown/unsolved fullerenes by crystallography and the assembly of the otherwise close-packed spherical fullerenes into two-dimensional layered structures by intercalation.

6.
Angew Chem Int Ed Engl ; 55(42): 13047-13051, 2016 10 10.
Artigo em Inglês | MEDLINE | ID: mdl-27650894

RESUMO

Buckybowls are fascinating components of supramolecular assemblies owing to their unique bowl-shaped π-surfaces. Herein we present a protocol for the functionalization of a sulfur-doped buckybowl, trithiasumanene, via a brominated intermediate, from which thiolated trithiasumanenes were derived. The curved surface and electron-donating properties of thiolated trithiasumanenes promote their ready assembly with fullerenes to form concave-convex complexes. The supramolecular assembly behavior in solution was investigated by NMR analysis. The structures of supramolecular complexes were unambiguously characterized by crystallography. The crystals of the concave-convex complexes showed high thermal stability and photoconductivity.

7.
J Am Chem Soc ; 138(30): 9629-33, 2016 08 03.
Artigo em Inglês | MEDLINE | ID: mdl-27377559

RESUMO

Curvature prevalently exists in the world of carbon materials (e.g., fullerenes, buckyl bowls, carbon nanotubes, and onions), but traditional C2-addition mechanisms fail to elucidate the mechanism responsible for the formation of carbon curvature starting from a pentagonal carbon ring in currently available chemical-physical processes such as combustion. Here, we show a complete series of nascent pentagon-incorporating C5-C18 that are online produced in the flame of acetylene-cyclopentadiene-oxygen and in situ captured by C60 or trapped as polycyclic aromatic hydrocarbons for clarifying the growth of the curved subunit of C20H10. A mechanism regarding C1-substitution and C2-addition has been proposed for understanding the formation of curvature in carbon materials, as exemplified by the typical curved molecule containing a single pentagon completely surrounded by five hexagons. The present mechanism, supported by the intermediates characterized by X-ray crystallography as well as NMR, has been experimentally validated for the rational synthesis of curved molecule in the commercially useful combustion process.

8.
Angew Chem Int Ed Engl ; 53(30): 7853-5, 2014 Jul 21.
Artigo em Inglês | MEDLINE | ID: mdl-24827119

RESUMO

Previously reported fused-pentagon fullerenes stabilized by exohedral derivatization do not share the same cage with those stabilized by endohedral encapsulation. Herein we report the crystallographic identification of (#4348)C66Cl10, which has the same cage as that of previously reported Sc2@C66. According to the geometrical data of (#4348)C66Cl10, both strain relief (at the fused pentagons) and local aromaticity (on the remaining sp(2)-hybrided carbon framework) contribute to the exohedral stabilization of this long-sought 66 carbon atom cage.

9.
Nat Chem ; 5(9): 739-44, 2013 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-23965674

RESUMO

Graphite, the most stable form of elemental carbon, consists of pure carbon sheets stacked upon one another like reams of paper. Individual sheets, known as graphene, prefer planar geometries as a consequence of the hexagonal honeycomb-like arrangements of trigonal carbon atoms that comprise their two-dimensional networks. Defects in the form of non-hexagonal rings in such networks cause distortions away from planarity. Herein we report an extreme example of this phenomenon. A 26-ring C80H30 nanographene that incorporates five seven-membered rings and one five-membered ring embedded in a hexagonal lattice was synthesized by stepwise chemical methods, isolated, purified and fully characterized spectroscopically. Its grossly warped structure was revealed by single-crystal X-ray crystallography. An independent synthetic route to a freely soluble derivative of this new type of 'nanocarbon' is also reported. Experimental data reveal how the properties of such a large graphene subunit are affected by multiple odd-membered-ring defects.


Assuntos
Grafite/química , Nanoestruturas/química , Cristalografia por Raios X , Grafite/síntese química , Conformação Molecular
10.
J Am Chem Soc ; 134(38): 15664-7, 2012 Sep 26.
Artigo em Inglês | MEDLINE | ID: mdl-22978569

RESUMO

All 10 C-H positions on the rim of corannulene can be arylated by repetitive palladium-catalyzed C-H activation. To relieve congestion among the 10 tightly packed aryl substituents in the product, the central corannulene adopts a nearly planar geometry.

11.
Org Lett ; 14(15): 4002-5, 2012 Aug 03.
Artigo em Inglês | MEDLINE | ID: mdl-22831400

RESUMO

Open-cage fullerene derivative 2, C(59)(O)(4)(NAr)(2) (Ar = p-tBuC(6)H(4)), was prepared from 1, C(60)(O)(4)(OH)(2)(NAr)(2), through processes involving decarbonylation and elimination of the two hydroxyl groups. The phenyl groups in compound 2 act as chelating ligands for the fullerene cage and induce partial dimerization of 2 in solution. The single crystal X-ray structure of 2 shows strong intradimer π-π interactions and also weaker interdimer CH-π and π-π interactions.

12.
J Am Chem Soc ; 134(1): 107-10, 2012 Jan 11.
Artigo em Inglês | MEDLINE | ID: mdl-22133011

RESUMO

The inaccessibility of uniform-diameter, single-chirality carbon nanotubes (CNTs) in pure form continues to thwart efforts by scientists to use these ultrathin materials in innovative applications that could revolutionize nanoscale electronics. Stimulated by the challenge to address this long-standing problem, we and other organic chemists have envisioned a new production strategy involving the controlled elongation of small hydrocarbon templates, such as hemispherical nanotube end-caps, prepared by bottom-up chemical synthesis; the diameter and rim structure encoded in the template would dictate the diameter and chirality of the resulting CNT. Toward that objective, a short [5,5] CNT has now been synthesized by stepwise chemical methods. This C(50)H(10) geodesic polyarene has been isolated, purified, crystallized, and fully characterized by NMR spectroscopy, UV-vis absorption spectroscopy, high resolution mass spectrometry, and X-ray crystallography.

13.
J Org Chem ; 76(16): 6743-8, 2011 Aug 19.
Artigo em Inglês | MEDLINE | ID: mdl-21728381

RESUMO

[60]Fullerene mixed peroxide C(60) (OH)(Cl)(OOtBu) reacts with PhMe(2)SiH/B(C(6)F(5))(3) to give oxahomofullerene. Mechanistic investigation indicates that the hydroxyl group in the central pentagon ring is essential to convert the tert-butylperoxo group into a ketal moiety. Migration of the silyl group and transformation of the siloxy group into a phenyl group are observed in the deprotection of the fullerene bound siloxy group. A 12-membered open-cage fullerendione was obtained through oxidation of a [6,6]-fullerendiol. This orifice could be closed to form ketal/hemiketal moieties by BF(3)-catalyzed reaction with methanol. All of the new fullerene derivatives were characterized by spectroscopic data, and structure of the open-cage fullerendione was also confirmed by single-crystal X-ray analysis.

15.
Adv Mater ; 22(13): 1498-507, 2010 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-20437499

RESUMO

Open-cage fullerenes can act as hosts for small molecules such as water, nitrogen, or hydrogen, forming endohedral fullerenes. Following a brief summary of carbon, nitrogen, and oxygen insertion in the fullerene framework to form homofullerenes, methods of creating a hole in the fullerene surface are surveyed. Techniques of hole enlargement and the insertion of atoms or molecules through the orifice to form endohedral fullerenes are described. Finally, the possibility of subsequent closure of the hole is considered.


Assuntos
Fulerenos/química , Carbono/química , Nitrogênio/química , Oxirredução , Oxigênio/química
16.
Org Lett ; 11(13): 2772-4, 2009 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-19492837

RESUMO

Cage-opened fullerenes with 18-membered-ring orifices have been prepared starting from fullerene-mixed peroxides. The key transformation involves a cascade sequence including a deketalization, a S(N)2' epoxide opening reaction, and a formal 3,3-sigma rearrangement. The 18-membered-ring orifice is big enough for water encapsulation under mild conditions. Single crystal X-ray structures were obtained for both the empty and water-encapsulated fullerene derivatives.

17.
J Org Chem ; 73(7): 2518-26, 2008 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-18336040

RESUMO

The epoxide moiety in the fullerene-mixed peroxide C60(O)(OOtBu)4 1 reacts readily with aryl isocyanates ArNCS (Ar = Ph, Naph) to form both the thiirane derivative C60(S)(OOtBu)4 and fullerene-fused tetrahydrothiazolidin-2-one. The reaction of 1 with trimethylsilyl isothiocyanate TMSNCS yields the isothiocyanate derivative C60(NCS)(OH)(OOtBu)4, the isothiocyanate and hydroxyl moieties of which could be converted to a fullerene-fused tetrahydrothiazolidin-2-one ring with alumina quantitatively. Treating 1 with BF3.Et2O yields the fullerene-fused [1,3,2]-dioxoborolane derivative C60(O2BOH)(OOtBu)4. In the presence of aldehyde or acetone, BF3.Et2O catalyzes the conversion of epoxide to fullerene-fused 1,3-dioxolane derivatives. The products are characterized by spectroscopic data. Two of the compounds are also characterized by single-crystal X-ray analysis.


Assuntos
Dioxolanos/síntese química , Compostos de Epóxi/química , Fulerenos/química , Sulfetos/síntese química , Tiazolidinas/síntese química , Cristalografia por Raios X , Dioxolanos/química , Modelos Moleculares , Conformação Molecular , Estereoisomerismo , Sulfetos/química , Tiazolidinas/química
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