Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 152
Filtrar
Filtros adicionais











País/Região como assunto
Intervalo de ano
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.
ACS Appl Mater Interfaces ; 11(27): 23982-23989, 2019 Jul 10.
Artigo em Inglês | MEDLINE | ID: mdl-31257863

RESUMO

In regular perovskite solar cells (PSCs), the commonly used electron transport layer (ETL) is titanium oxide (TiO2). Nevertheless, the preparation of a high-quality TiO2 ETL demands an elevated-temperature sintering procedure, unfavorable for fabrication of PSCs on flexible substrates. Besides, TiO2-based devices often suffer from notorious photocurrent hysteresis and serious light soaking instability, limiting their potential commercialization. Herein, a novel pyridine-functionalized fullerene derivative [6,6]-(4-pyridinyl)-C61-ethyl acid ethyl ester (PyCEE) was synthesized and applied as an ETL to replace TiO2 in n-i-p PSCs. PyCEE-based devices achieved a champion power conversion efficiency (PCE) of 18.27% with significantly suppressed hysteresis, superior to that of TiO2-based devices. PyCEE has suitable energy levels and high electron mobility, which facilitate electron extraction/transport. Besides, the pyridine moiety within PyCEE affords coordination interactions with the Pb2+ ion within CH3NH3PbI3, passivating the trap states of CH3NH3PbI3 and thus improving the device performance and suppressing hysteresis greatly. Moreover, PyCEE ETLs were applied in flexible PSCs, achieving a PCE of 15.25%. Our results demonstrated the applicability of PyCEE ETLs in flexible devices and provided new opportunity for the commercialization of PSCs.

3.
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.

4.
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.

5.
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.

6.
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.

7.
Nanoscale ; 9(45): 17893-17901, 2017 Nov 23.
Artigo em Inglês | MEDLINE | ID: mdl-29119988

RESUMO

Organic-inorganic perovskite solar cells have emerged as a promising photovoltaic technology because of their advantages such as low cost, high efficiency, and solution processability. The performance of perovskite solar cells is highly dependent on the crystallinity and morphology of the perovskite films. Herein, we report a simple, one-step anti-solvent deposition process using di-isopropyl ether as a dripping solvent to obtain extremely uniform and highly crystalline CH3NH3PbI3 perovskite films. Compared to toluene, chlorobenzene, chloroform, or diethyl ether, di-isopropyl ether has proven to be a more suitable solvent for an anti-solvent deposition process. The perovskite solar cells fabricated by the anti-solvent deposition process using di-isopropyl ether treatment exhibit an average power conversion efficiency (PCE) of 17.67 ± 0.54% and the highest PCE of 19.07%. Moreover, the higher boiling point of di-isopropyl ether makes the anti-solvent deposition process more tolerant to elevated ambient temperature, which can be carried out at ambient temperatures up to 40 °C. Our results demonstrate that di-isopropyl ether is an excellent dripping solvent in the anti-solvent deposition process for efficient and reproducible perovskite solar cells.

8.
Colloids Surf B Biointerfaces ; 159: 613-619, 2017 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-28858664

RESUMO

Fullerenes with novel structures find numerous potential applications, particularly in the fields of biology and pharmaceutics. Among various fullerene derivatives, those exhibiting amphiphilic character and capable of self-assembly into vesicles are particularly interesting, being suitable for delayed drug release. Herein, we report the synthesis and self-assembly of biocompatible hollow nanovesicles with bilayer shells from amphiphilic functionalized fullerenes C60R5Cl (R=methyl ester of 4-aminobutyric/glutamic acid or phenylalanine). The thus prepared vesicles exhibit sizes of 80-135nm (depending on R) and can be used as delayed-release carriers of anti-cancer drugs such as 5-fluorouracil, cyclophosphamide, and cisplatin, with the time of 5-fluorouracil release from drug-containing vesicles exceeding that of non-encapsulated forms by a factor of three. We further reveal the effect of R on the loading amount and release rate/amount of vesicle-encapsulated drugs, demonstrating a potential pharmaceutical application of the prepared nanovesicles depending on the nature of R.


Assuntos
Aminoácidos/química , Antineoplásicos/química , Cloretos/química , Liberação Controlada de Fármacos , Fulerenos/química , Cisplatino/química , Ciclofosfamida/química , Sistemas de Liberação de Medicamentos/métodos , Fluoruracila/química
9.
Chemistry ; 22(52): 18709-18713, 2016 Dec 23.
Artigo em Inglês | MEDLINE | ID: mdl-27735092

RESUMO

Despite being widely used as electron acceptor in polymer solar cells, commercially available PC71 BM (phenyl-C71 -butyric acid methyl ester) usually has a "random" composition of mixed regioisomers or stereoisomers. Here PC71 BM has been isolated into three typical isomers, α-, ß1 - and ß2 -PC71 BM, to establish the isomer-dependent photovoltaic performance on changing the ternary composition of α-, ß1 - and ß2 -PC71 BM. Mixing the isomers in a ratio of α/ß1 /ß2 =8:1:1 resulted in the best power conversion efficiency (PCE) of 7.67 % for the polymer solar cells with PTB7:PC71 BM as photoactive layer (PTB7=poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]thiophenediyl]]). The three typical PC71 BM isomers, even though sharing similar LUMO energy levels and light absorption, render starkly different photovoltaic performances with average-performing PCE of 1.28-7.44 % due to diverse self-aggregation of individual or mixed PC71 BM isomers in the otherwise same polymer solar cells.

10.
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.

11.
Inorg Chem ; 55(14): 6861-5, 2016 Jul 18.
Artigo em Inglês | MEDLINE | ID: mdl-27341488

RESUMO

As a bridge to connect medium-sized fullerenes, fused-pentagon C74 is still missing heretofore. Of 14 246 possible isomers, the first fused-pentagon C74 with the Fowler-Manolopoulos code of 14 049 was stabilized as C74Cl10 in the chlorine-involving carbon arc. The structure of C74Cl10 was identified by X-ray crystallography. The stabilization of pristine fused-pentagon C74 by stepwise chlorination was clarified in both theoretical simulation with density functional theory calculations and experimental fragmentation with multistage mass spectrometry.

12.
Inorg Chem ; 55(2): 543-5, 2016 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-26726707

RESUMO

Two monoxides of typical smaller chlorofullerenes, (#271)C50Cl10O and (#913)C56Cl10O, featured with double-fused-pentagons, were synthesized to demonstrate further regioselective functionalization of non-IPR (IPR = isolated pentagon rule) chlorofullerenes. Both non-IPR chlorofullerene oxides exhibit an epoxy structure at the ortho-site of fused pentagons. In terms of the geometrical analysis and theoretical calculations, the principles for regioselective epoxy oxidation of non-IPR chlorofullerenes are revealed to follow both "fused-pentagon ortho-site" and "olefinic bond" rules, which are valuable for prediction of oxidation of non-IPR chlorofullerenes.

13.
Acta Crystallogr E Crystallogr Commun ; 71(Pt 1): m1-2, 2015 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-25705469

RESUMO

The title compound, poly[(N,N-di-methyl-acetamide-κO)(µ4-5-methyl-isophthalato-κ(5) O,O':O',O'':O'')manganese(II)], [Mn(C9H6O4)(C3H7NO)] n , was obtained from a mixture containing MnCl2·4H2O and 5-methyl-isophthalic acid in N,N-di-methyl-acetamide solution. The Mn(2+) ion is coordinated by five O atoms from four bridging 5-methyl-isophthalate ligands and one O atom from one N,N-di-methyl-acetamide ligand, defining a considerably distorted coordination polyhedron with one very long Mn-O bond of 2.623 (2) Å. The Mn(2+) ions are joined by carboxyl-ate groups, forming rod-shaped secondary building units along the a axis. The rods are further connected by 5-methyl-isophthalate ligands to form the pcu (primitive cubic net) structure.

14.
Chem Commun (Camb) ; 50(94): 14728-31, 2014 Dec 07.
Artigo em Inglês | MEDLINE | ID: mdl-25317970

RESUMO

Three polynuclear lanthanide clusters: (NH4)2[Dy6Mo4O12(rac-L(3-))4(OOCCH3)8]·4CH3OH·6H2O (I), (Et3NH)2[Dy6Mo4O12(rac-L(3-))4(OOCCH3)8]·18H2O (II), and (Me4N)2[Dy6Mo4O12(rac-L(3-))4(OOCCH3)8]·CH3OH·14H2O (III) (H3L = (E)-2-((2,3-dihydroxypropylimino)methyl)-phenol) were synthesized. Single-crystal analysis reveals that cluster I crystallized in the centrosymmetric space group (P42/n), while clusters II and II crystallized in the chiral space group (P3121 or P3221), and cluster I can be transformed into clusters II and III, when Et3NH(+) and Me4N(+), respectively, are used to replace NH4(+). Investigation on the solid-state vibrational circular dichroism (VCD) spectra shows that the clusters II and III are homochiral crystallization. Powder X-ray diffraction study demonstrates that the transformation between chiral and achiral clusters is reversible.


Assuntos
Elementos da Série dos Lantanídeos/química , Compostos Organometálicos/química , Modelos Moleculares , Conformação Molecular , Estereoisomerismo
15.
Chem Commun (Camb) ; 50(65): 9161-4, 2014 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-24989647

RESUMO

The reaction of nickel(II) nitrate with isonicotinic acid and 2,6-dimethyl-pyridine-3,5-dicarboxylic acid affords a novel, tetranuclear nickel(II)-based metal-organic framework that exhibits spin-canted antiferromagnetism with a canted angle of 1.65° and high adsorptive selectivity for light hydrocarbons.

16.
Dalton Trans ; 43(30): 11579-86, 2014 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-24941105

RESUMO

A tripodal amide based ligand, tris-{(2-carbamoyl-5-carbomethoxy-pyridine)-2-ethyl}amine (H3L, 1), was synthesized and structurally characterized by single crystal X-ray diffraction. Investigation of the cation recognition behavior showed that the ligand has selective colorimetric sensing properties for cobalt(II) ions by an obvious color change from colorless to yellow. To investigate the sensing mechanism of H3L for Co(2+) ions, UV-vis absorption spectroscopy and single-crystal structural analysis were performed. The mixture of the ligand and cobalt(II) ions displayed selective colorimetric sensing properties for weak acid anions, such as CO3(2-), Ac(-), HCO3(-), SO3(2-), and PO4(3-). Detailed (1)H NMR experiments revealed that the basicity of the anions played an important role in the intensity of the interaction between the ligand and anions. The structures of compounds CoL (2), Co-Ac-HL (3), H4L-NO3 (4), and H4L-ClO4 (5) were also determined by single crystal diffraction studies.


Assuntos
Amidas/química , Cobalto/química , Colorimetria/instrumentação , Colorimetria/métodos , Ácidos , Cristalografia por Raios X , Ligantes , Espectroscopia de Ressonância Magnética , Sensibilidade e Especificidade , Espectrofotometria Ultravioleta
17.
Inorg Chem ; 53(10): 5246-52, 2014 May 19.
Artigo em Inglês | MEDLINE | ID: mdl-24779402

RESUMO

In our previous work ( Chen , X.-Y. ; Chem. Commun. 2013 , 49 , 10977 - 10979 ), we have reported the crystal structure and spin-crossover properties of a compound [Fe(NCS)2(tppm)]·S [1·S, tppm = 4,4',4″,4‴-tetrakis(4-pyridylethen-2-yl)tetraphenylmethane, S = 5CH3OH·2CH2Cl2]. Here, its analogues [Fe(X)2(tppm)]·S [X = NCSe(-), NCBH3(-), and N(CN)2(-) for compounds 2·S, 3·S, and 4·S, respectively] have been synthesized and characterized by variable-temperature X-ray diffraction and magnetic measurements. The crystal structure analyses of 2·S and 3·S reveal that both compounds possess the same topologic framework (PtS-type) building from the tetrahedral ligand tppm and planar unit FeX2; the framework is two-fold self-interpenetrated to achieve one-dimensional open channels occupied by solvent molecules. Powder X-ray diffraction study indicates the same crystal structure for 4. The average values of Fe-N distances observed, respectively, at 100, 155, and 220 K for the Fe1/Fe2 centers are 1.969/2.011, 1.970/2.052, and 2.098/2.136 Å for 2·S, whereas those at 110, 175, and 220 K are 1.972/2.013, 1.974/2.056, and 2.100/2.150 Å for 3·S, indicating the presence of a two-step spin crossover in both compounds. Temperature-dependent magnetic susceptibilities (χMT) confirm the two-step spin-crossover behavior at 124 and 200 K in 2·S, 151 and 225 K in 3·S, and 51 and 126 K in 4·S, respectively. The frameworks of 2-4 are reproducible upon solvent exchange and thereafter undergo solvent-dependent spin-crossover behaviors.

18.
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.

19.
Inorg Chem ; 53(2): 897-902, 2014 Jan 21.
Artigo em Inglês | MEDLINE | ID: mdl-24392969

RESUMO

Four 3D POM-based silver coordination polymers, namely, [Ag17(ptz)11(PW12O40)2]n (1), [Ag17(ptz)11(PMo12O40)2]n (2), [Ag12(ptz)6(CN)2(SiW12O40)]n (3), and [Ag19(ptz)8(H2ptz)(H3ptz)(AgP5W30O110)·7H2O]n (4), have been obtained by solvothermal reaction of AgNO3 and 5-phenyl-1H-tetrazole (Hptz) ligand in the presence of four types of polyoxometalates. Structural analysis shows that four types of Ag(I)···π interactions, m-η(1), m/p-η(2), o/m-η(2), and o/m/p-η(3), were observed in compounds 1-4, depending on the polyoxometalates used. The in situ generated CN(-) ion in compound 3 shows unprecedented mixed σ and π bonding modes, similar to the C2(2-) ion in well-studied silver acetylides. For 4, the Na(+) ion in the Preyssler heteropolyoxoanion, [NaP5W30O110](14-), was exchanged by Ag(I) under solvothermal conditions, generating a novel [AgP5W30O110](14-) anion. In addition, the photoluminescence behavior of 1-4 was also investigated.

20.
J Am Chem Soc ; 136(2): 558-61, 2014 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-24369720

RESUMO

We carried out photopolymerization by [2 + 2] dimerization of a photoreactive guest molecule in the channels of a photoreactive porous coordination polymer. The photoreactions of the guest and two host ligands were monitored by single-crystal X-ray crystallography, providing snapshots of the interplay between the reactive centers. By correlating the structures of these three photocenters, a strong synergism was discovered among three reaction (quasi)equilibria and three types of photochemical reactions (isomerization, dimerization, and polymerization). This result indicates a strong coupling and feedback mechanism among the photocenters moderated by the coordination backbone.

SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA