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1.
J Am Chem Soc ; 146(19): 12889-12894, 2024 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-38690854

RESUMO

We have successfully achieved selective and efficient functionalization of sheet edges in microcrystalline multilayer γ-graphyne through two methods: cross-coupling with residual bromide edge groups and copper-catalyzed azide-alkyne cycloaddition (CuAAC) with edge terminal alkyne groups. This modification significantly enhances the ease of mechanical exfoliation and dispersibility of the sheets of γ-graphyne. Specifically, C18-grafted γ-graphyne forms stable dispersions in compatible organic solvents, allowing for the imaging of atomically thin layers of γ-graphyne for the first time. Additionally, we have discovered that phenylacetylide edge groups alter the preferred stacking mode of γ-graphyne sheets. Few-layer flakes of Ph-edge γ-graphyne exhibit a preference for the R3m space group, contrasting with the aperiodic stacking of Br-edge γ-graphyne. These results open the door for scalable exfoliation of few-layer flakes of γ-graphyne with a high aspect ratio, enabling potential applications in carbon electronics.

2.
J Am Chem Soc ; 144(39): 17999-18008, 2022 Oct 05.
Artigo em Inglês | MEDLINE | ID: mdl-36130080

RESUMO

γ-Graphyne is the most symmetric sp2/sp1 allotrope of carbon, which can be viewed as graphene uniformly expanded through the insertion of two-carbon acetylenic units between all the aromatic rings. To date, synthesis of bulk γ-graphyne has remained a challenge. We here report the synthesis of multilayer γ-graphyne through crystallization-assisted irreversible cross-coupling polymerization. A comprehensive characterization of this new carbon phase is described, including synchrotron powder X-ray diffraction, electron diffraction, lateral force microscopy, Raman spectroscopy, infrared spectroscopy, and cyclic voltammetry. Experiments indicate that γ-graphyne is a 0.48 eV band gap semiconductor, with a hexagonal a-axis spacing of 6.88 Å and an interlayer spacing of 3.48 Å, which is consistent with theoretical predictions. The observed crystal structure has an aperiodic sheet stacking. The material is thermally stable up to 240 °C but undergoes transformation at higher temperatures. While conventional 2D polymerization and reticular chemistry rely on error correction through reversibility, we demonstrate that a periodic covalent lattice can be synthesized under purely kinetic control. The reported methodology is scalable and inspires extension to other allotropes of the graphyne family.

3.
Langmuir ; 31(10): 2931-5, 2015 Mar 17.
Artigo em Inglês | MEDLINE | ID: mdl-25740116

RESUMO

We describe a system in which the self-replication of micellar aggregates results in a spontaneous amplification of chirality in the reaction products. In this system, amphiphiles are synthesized from two "clickable" fragments: a water-soluble "head" and a hydrophobic "tail". Under biphasic conditions, the reaction is autocatalytic, as aggregates facilitate the transfer of hydrophobic molecules to the aqueous phase. When chiral, partially enantioenriched surfactant heads are used, a strong nonlinear induction of chirality in the reaction products is observed. Preseeding the reaction mixture with an amphiphile of one chirality results in the amplification of this product and therefore information transfer between generations of self-replicating aggregates. Because our amphiphiles are capable of catalysis, information transfer, and self-assembly into bounded structures, they present a plausible model for prenucleic acid "lipid world" entities.

4.
Chem Commun (Camb) ; 53(85): 11638-11641, 2017 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-28956878

RESUMO

A strategy for arraying small gold nanoparticles on a mesoporous support modified with single-component or mixed self-assembled monolayers is described. The use of mixed surface modifiers allows easy access to a range of surface chemistries and modalities of interaction between nanoparticles and supports. A combination of thiol groups and linear semifluorinated chains effectively stabilized the nanoparticles against aggregation, while preserving their catalytic activity. The thiol-fluorous-supported catalyst was found active in Ullmann-type homocoupling of aryl halides and showed exceptional selectivity in this reaction.

5.
Chem Commun (Camb) ; 52(48): 7576-9, 2016 Jun 18.
Artigo em Inglês | MEDLINE | ID: mdl-27216276

RESUMO

A unique organocatalytic system for Mukaiyama-type aldol reactions based on the cooperative action of nitro compounds and thioureas has been identified. This system is compatible with a wide range of substrates and does not require low temperatures, inert atmospheres, or an aqueous workup. A catalytic mechanism based on nitro group-mediated silyl cation transfer has been proposed.

6.
Org Lett ; 17(19): 4826-9, 2015 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-26397957

RESUMO

An approach for supporting a Pd-NHC complex on a soluble star polymer with nanoscale dimensions is described. The resulting star polymer catalyst exhibits excellent activity in cross-coupling reactions, is stable in air and moisture, and is easily recoverable and recyclable. These properties are distinct and unattainable with the small-molecule version of the same catalyst.

7.
ACS Comb Sci ; 17(2): 76-80, 2015 Feb 09.
Artigo em Inglês | MEDLINE | ID: mdl-25544983

RESUMO

A rapid approach to identifying complementary catalytic groups using combinations of functional polymers is presented. Amphiphilic polymers with "clickable" hydrophobic blocks were used to create a library of functional polymers, each bearing a single functionality. The polymers were combined in water, yielding mixed micelles. As the functional groups were colocalized in the hydrophobic microphase, they could act cooperatively, giving rise to new modes of catalysis. The multipolymer "clumps" were screened for catalytic activity, both in the presence and absence of metal ions. A number of catalyst candidates were identified across a wide range of model reaction types. One of the catalytic systems discovered was used to perform a number of preparative-scale syntheses. Our approach provides easy access to a range of enzyme-inspired cooperative catalysts.


Assuntos
Técnicas de Química Combinatória , Micelas , Polímeros/química , Catálise , Estrutura Molecular , Tamanho da Partícula , Polímeros/síntese química , Propriedades de Superfície
8.
ACS Comb Sci ; 16(10): 513-7, 2014 Oct 13.
Artigo em Inglês | MEDLINE | ID: mdl-25229602

RESUMO

Using the copper-catalyzed azide-alkyne cycloaddition "click" reaction, a library of triazole amphiphiles with a variety of functional polar "heads" and hydrophobic or superhydrophobic "tails" was synthesized. The amphiphiles were evaluated for their ability to stabilize small Au nanoparticles, and, at the same time, serve as templates for nanocasting porous SiO2. One of the Au@SiO2 materials thus prepared was found to be a highly active catalyst for the Au nanoparticle-catalyzed regioselective hydroamination of alkynes.


Assuntos
Química Click/métodos , Compostos de Ouro/química , Dióxido de Silício/química , Alcinos/síntese química , Azidas/química , Catálise , Reação de Cicloadição , Nanopartículas Metálicas/química , Bibliotecas de Moléculas Pequenas , Tensoativos/química , Triazóis/síntese química , Triazóis/química
10.
Org Lett ; 12(19): 4217-9, 2010 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-20825167

RESUMO

1,5-Diarylsubstituted 1,2,3-triazoles are formed in high yield from aryl azides and terminal alkynes in DMSO in the presence of catalytic tetraalkylammonium hydroxide. The reaction is experimentally simple, does not require a transition-metal catalyst, and is not sensitive to atmospheric oxygen and moisture.


Assuntos
Triazóis/síntese química , Catálise , Hidróxidos/química , Estrutura Molecular , Elementos de Transição/química
11.
J Am Chem Soc ; 129(42): 12696-704, 2007 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-17914816

RESUMO

Tris(2-benzimidazolylmethyl)amines have been found to be superior accelerating ligands for the copper(I)-catalyzed azide-alkyne cycloaddition reaction. Candidates bearing different benzimidazole N-substituents as well as benzothiazole and pyridyl ligand arms were evaluated by absolute rate measurements under relatively dilute conditions by aliquot quenching kinetics and by relative rate measurements under concentrated conditions by reaction calorimetry. Benzimidazole-based ligands with pendant alkylcarboxylate arms proved to be advantageous in the latter case. The catalyst system was shown to involve more than one active species, providing a complex response to changes in pH and buffer salts and the persistence of high catalytic rate in the presence of high concentrations of coordinating ligands. The water-soluble ligand (BimC4A)3 was found to be especially convenient for the rapid and high-yielding synthesis of several functionalized triazoles with 0.01-0.5 mol % Cu.


Assuntos
Benzimidazóis/química , Química Orgânica/métodos , Cobre/química , Alcinos/química , Azidas/química , Soluções Tampão , Calorimetria/métodos , Catálise , Concentração de Íons de Hidrogênio , Cinética , Ligantes , Modelos Químicos , Estrutura Molecular , Fatores de Tempo , Triazóis/química
12.
J Am Chem Soc ; 129(42): 12705-12, 2007 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-17914817

RESUMO

The experimental rate law for the Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction was found to vary in complex ways with concentration, the presence of chloride ion, and the presence of accelerating ligands. Several examples of discontinuous ("threshold behavior") kinetics were observed, along with a decidedly nonlinear correlation of electronic substituent parameter with the rate of CuAAC reaction with p-substituted arylazides. The previously observed tendency of the CuAAC reaction to provide ditriazoles from a conformationally constrained 1,3-diazide was found to be affected by a class of polybenzimidazole ligands introduced in the accompanying article. Various lines of evidence suggest that the standard tris(triazolylmethyl)amine ligand binds less strongly to Cu(I) than its benzimidazole analogues. On the basis of these observations, it is proposed that (a) a central nitrogen donor provides electron density at Cu(I) that assists the cycloaddition reaction, (b) the three-armed motif bearing relatively weakly coordinating heterocyclic ligands serves to bind the metal with sufficient strength while providing access to necessary coordination site(s), (c) at least two active catalysts or mechanisms are operative under the conditions studied, and (d) pendant acid or ester arms in the proper position can assist the reaction by speeding the protiolysis step that cleaves the Cu-C bond of a Cu.triazolyl intermediate.


Assuntos
Azidas/química , Cobre/química , Alcinos/química , Motivos de Aminoácidos , Catálise , Química Orgânica/métodos , Ésteres , Íons , Cinética , Ligantes , Modelos Químicos , Modelos Teóricos , Triazóis/química
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