Search results for "ACETYLENE"
showing 10 items of 143 documents
On-surface synthesis on a bulk insulator surface
2018
On-surface synthesis has rapidly emerged as a most promising approach to prepare functional molecular structures directly on a support surface. Compared to solution synthesis, performing chemical reactions on a surface offers several exciting new options: due to the absence of a solvent, reactions can be envisioned that are otherwise not feasible due to the insolubility of the reaction product. Perhaps even more important, the confinement to a two-dimensional surface might enable reaction pathways that are not accessible otherwise. Consequently, on-surface synthesis has attracted great attention in the last decade, with an impressive number of classical reactions transferred to a surface as…
Rapid one-pot propargylamine synthesis by plasmon mediated catalysis with gold nanoparticles on ZnO under ambient conditions
2013
Surface plasmon excitation of gold nanoparticles on ZnO in the presence of an aldehyde, an amine and phenylacetylene led to rapid and selective formation of propargylamines with good yields (50-95%) at room temperature. Plasmon mediated catalysis is the best available route for this ternary coupling.
Surface characterization of functional poly(diacetylene) and poly(butadiene) mono- and multilayers
1982
The surface properties of Langmuir-Blodgett mono- and multilayers of a variety of amphiphilic poly(diacetylene)s and poly(butadiene)s were investigated by contact angle, streaming potentialζ, ellipsometry, and X-ray photoelectron spectroscopic (XPS) measurements. Captive air and octane angles varied between approximately 60° and 105° for hydrophobicx-layers and 31° to 46° for hydrophilic surfaces depending on the particular head group, whereas advancing angles determined via the vertical plate method are considerably higher. Negative streaming potentials were obtained for all surfaces. Positively charged monolayers yielded less negativeζ- potential values (−28 mV) than negatively charged (−…
Spin Crossover Metal-Organic Frameworks with Inserted Photoactive Guests: On the Quest to Control the Spin State by Photoisomerization
2021
International audience; Three Hofmann-like metal-organic frameworks {Fe(bpac)[Pt(CN)4]}•G (bpac=1,2-bis(4-pyridyl)acetylene) were synthesized with photoisomerizable guest molecules (G = trans-azobenzene, trans-stilbene or cis-stilbene) and were characterized by elemental analysis, thermogravimetry and powder X-ray diffraction. The insertion of guest molecules and their conformation were inferred from Raman and FTIR spectra and from single-crystal X-ray diffraction and confronted with computational simulation. The magnetic and photomagnetic behaviors of the framework are significantly altered by the different guest molecules and different conformations. On the other hand, photoisomerization …
Diacetylene Linked Anthracene Oligomers Synthesized by One-Shot Homocoupling of Trimethylsilyl on Cu(111)
2018
On-surface chemical reaction has become a very powerful technique to conjugate small precursor molecules and several reactions have been proposed with the aim to fabricate functional nanostructures on surfaces. Here we present an unforeseen adsorption mode of 9,10-bis-((trimethylsilyl)ethynyl)anthracene on a Cu(111)surface and the resulting one-shot desilylative homocoupling of of the adsorbate by annealing at 400 K. With a combination of high-resolution atomic force microscopy and density functional theory calculations, we found that the triple bonds and silicon atoms of the monomer chemically interact with the copper surface. After the oligomerization, we discovered that the anthracene un…
The extraction of negative carbon ions from a volume cusp ion source
2017
Acetylene and carbon dioxide gases are used in a filament-powered volume-cusp ion source to produce negative carbon ions for the purpose of carbon implantation for gettering applications. The beam was extracted to an energy of 25 keV and the composition was analyzed with a spectrometer system consisting of a 90° dipole magnet and a pair of slits. It is found that acetylene produces mostly C−2 ions (up to 92 µA), while carbon dioxide produces mostly O− with only trace amounts of C−. Maximum C−2 current was achieved with 400 W of arc power and, the beam current and composition were found to be highly dependent on the pressure in the source. The beam properties as a function of source settings…
A New Heterogeneous Catalyst Obtained via Supramolecular Decoration of Graphene with a Pd2+ Azamacrocyclic Complex
2019
A new G-(H2L)-Pd heterogeneous catalyst has been prepared via a self-assembly process consisting in the spontaneous adsorption, in water at room temperature, of a macrocyclic H2L ligand on graphene (G) (G + H2L = G-(H2L)), followed by decoration of the macrocycle with Pd2+ ions (G-(H2L) + Pd2+ = G-(H2L)-Pd) under the same mild conditions. This supramolecular approach is a sustainable (green) procedure that preserves the special characteristics of graphene and furnishes an efficient catalyst for the Cu-free Sonogashira cross coupling reaction between iodobenzene and phenylacetylene. Indeed, G-(H2L)-Pd shows an excellent conversion (90%) of reactants into diphenylacetylene under mild conditio…
Aminobisphenolate supported tungsten disulphido and dithiolene complexes
2015
Dioxotungsten(vi) complexes with tetradentate amino bisphenolates were converted into the corresponding Cs-symmetric amino bisphenolate disulphido complexes by a reaction with either Lawesson's reagent or P2S5. Further reaction with diethyl acetylenedicarboxylate leads to the formation of diamagnetic tungsten(iv) dithiolene compounds. The syntheses, crystal structures, spectroscopic and electrochemical characterization of such disulphido and dithiolene complexes are presented.
Organometallic Oligomers Based on Bis(arylacetylide)bis(P-chirogenic phosphine)platinum(II) Complexes: Synthesis and Photonic Properties
2013
A series of P-chirogenic oligomers of the type (-C≡C-aryl-C≡C-PtL2-)n [L = (R)- and (S)-P(Ph)(iPr)(C17H35); aryl = 1,4-benzene, 2,1,3-benzothiadiazole] along the corresponding achiral analogues (L = PBu3) and model complexes PhC≡CPtL2C≡CPh were prepared from the ephedrine strategy and were fully characterized [(1)H, (31)P NMR; IR; small-angle X-ray scattering (SAXS); gel permeation chromatography (GPC); thermal gravimetric analysis (TGA); circular dichroism, UV-vis, and luminescence spectroscopy; photophysics, and degree of anisotropy measurements]. From the CD measurements, the chiral environment of the phosphine ligands is modestly felt by the aryl moieties. Concurrently, the TGA shows th…
A DFT study of the ionic [2+2] cycloaddition reactions of keteniminium cations with terminal acetylenes
2015
Abstract The molecular mechanism of the ionic [2+2] cycloaddition (I-22CA) reactions of a keteniminium cation (KC) with acetylene and propyne has been investigated using DFT methods at the MPWB1K/6-311G(d,p) level. These I-22CA reactions take place via a two-step mechanism. The first step is the nucleophilic attack of these alkynes on the central carbon of KC, yielding cyclopropene intermediates, while the second step corresponds to the conversion of these intermediates into more stable cyclobuteniminium cations (CCs). The first step is the rate-determining step, while the second step is responsible for the formation of the two regioisomeric CCs experimentally observed in the reaction with …