Search results for "ACETYLENE"
showing 10 items of 143 documents
Calculation of excited-state properties using general coupled-cluster and configuration-interaction models.
2004
Using string-based algorithms excitation energies and analytic first derivatives for excited states have been implemented for general coupled-cluster (CC) models within CC linear-response (LR) theory which is equivalent to the equation-of-motion (EOM) CC approach for these quantities. Transition moments between the ground and excited states are also considered in the framework of linear-response theory. The presented procedures are applicable to both single-reference-type and multireference-type CC wave functions independently of the excitation manifold constituting the cluster operator and the space in which the effective Hamiltonian is diagonalized. The performance of different LR-CC/EOM-…
A computational and conceptual DFT study on the mechanism of hydrogen activation by novel frustrated Lewis pairs.
2015
A computational and conceptual density functional theory (DFT) study on the mechanism of molecular hydrogen activation by a set of three frustrated Lewis pairs (FLPs) was performed at the ωB97X-D/6-311G(d,p) level of theory. A reduced model and other two prototypes derived from experimental data, based on the donor nitrogen and acceptor boron atoms, were used. Analysis based on the energy results, geometries and the global electron density transfer at the TSs made it possible to obtain some interesting conclusions: (i) despite the well-known very low reactivity of molecular hydrogen, the catalytic effectiveness of the three FLPs produces reactions with almost unappreciable activation energi…
The reactivity of 2-vinylindoles with dimethyl acetylenedicarboxylate
1984
Abstract The overall rates of reaction of 1-substltuted-1- (1-methyl-2-indolyl)ethenes with dimethyl acetylenedicarboxylate are considerably lower than those of the corresponding 2-vinyl- pyrroles. Steric interaction between the N-methyl group on the indole ring and the 1-substituent on the ethenyl group prevents the diene system adopting a coplanar cisoid configuration and, thereby, inhibits the π4 + π2 cycloaddition reaction of the system with dimethyl acetylenedicarboxylate. Under such conditions, the indolylethene preferentially undergoes a Michael addition reaction at the 3-position. The π4 + π2 cycloaddition reaction is promoted at elevated temperatures. No evidence was found for a Co…
1981
C,N-chelated diaminocarbene platinum(II) complexes derived from 3,4-diaryl-1H-pyrrol-2,5-diimines and cis-dichlorobis(isonitrile)platinum(II): Synthe…
2020
The reaction of 3,4-diaryl-1H-pyrrol-2,5-diimines with cis-dichlorobis(isonitrile)platinum(II) affords the C,N-chelated diaminocarbene platinum(II) complexes, which have been fully characterized including molecular spectroscopy, single crystal X-ray diffraction and DFT calculations. The obtained platinum(II) complexes are effective catalysts for the hydrosilylation of alkynes and alkenes. Thus, the reaction of phenylacetylene with triethoxysilane leads to the formation of α- and β-(E)-vinylsilanes, generating TON's in the range of 103 to 104 and TOF's in the range of 102 to 103 h−1. Also, the cross-linked silicones, possessing the luminescence properties, were obtained by the hydrosilylatio…
Gold(I)-doped films: new routes for efficient room temperature phosphorescent materials
2021
The synthesis of four novel gold(I)-phosphane complexes coordinated to 9-phenanthrene chromophore has been carried out through the reaction of 9-phenanthreneboronic acid and the corresponding AuClPR3 (PR3 = PPh3 for triphenylphosphane (1a); 1,4-bis(diphenylphosphanyl)butane or dppb (2b); bis(diphenylphosphanyl)acetylene or dppa (2c); (AuCl)2(diphos) (diphos = bis(diphenylphosphanyl)methane or dppm (3)) sources. The X-ray crystal structures of compounds 1a and 2b show the existence of MOF-like intermolecular assemblies that contain empty inner cavities in the absence of aurophilic contacts. In contrast, the formation of a tetranuclear complex with intramolecular aurophilic interactions was e…
Real Time Nuclear Magnetic Resonance Detection of Fumarase Activity using Parahydrogen-Hyperpolarized [1-13C]fumarate
2019
Hyperpolarized fumarate can be used as a probe of real-time metabolism in vivo, using carbon-13 magnetic resonance imaging. Dissolution dynamic nuclear polarization is commonly used to produce hyperpolarized fumarate, but a cheaper and faster alternative is to produce hyperpolarized fumarate via PHIP (parahydrogen induced polarization). In this work we trans-hydrogenate [1-13C]acetylene dicarboxylate with para-enriched hydrogen using a commercially available Ru catalyst in water to produce hyperpolarized [1-13C]fumarate. We show that fumarate is produced in 89% yield, with succinate as a side product in 11% yield. The proton polarization is converted into 13C magnetization using a constant …
Diacetylene polymerization on a bulk insulator surface
2017
| openaire: EC/FP7/610446/EU//PAMS Molecular electronics has great potential to surpass known limitations in conventional silicon-based technologies. The development of molecular electronics devices requires reliable strategies for connecting functional molecules by wire-like structures. To this end, diacetylene polymerization has been discussed as a very promising approach for contacting single molecules with a conductive polymer chain. A major challenge for future device fabrication is transferring this method to bulk insulator surfaces, which are mandatory to decouple the electronic structure of the functional molecules from the support surface. Here, we provide experimental evidence for…
Compound Membranes of Linearly Polymerized and Cross-Linked Macrolipids with Phospholipids: Preparation, Microstructure and Applications
1985
Methods for the assembly and for studying the structural and dynamic properties of partially polymerized membranes are described. Mixtures of two classes of polymerizable amphiphiles with diacyl phosphatidylcholines are studied: (1) phosphatidylcholines carrying a diacetylene group per chain (abbreviated as (m,n)-DIINPC (where m + n + 6 equals number of C-Atoms per chain) and (2) a phospholipid-like molecule with a polymerizable methacryl ligand connected to the phosphate head group via (CH2CH2O)m spacers which is abbreviated as (m.n)-POMECY (n = number of C-atoms per chain). — Phase diagrams of the lipid mixtures are established by static light scattering in combination with freeze fractur…
Material transport and organizing phenomena of Langmuir—Blodgett membranes from polymerizable built up diacetylene amphiphiles on hydrophobic supports
1986
Abstract Langmuir—Blodgett multilayers of polymerized diin amphiphiles on different porous, hydrophobic ultrafilters have been studied as composite membranes under the conditions of reverse osmosis. Influences of differently structured surfaces of the supports on structure and phase change occurring during polymerization have been investigated by scanning electron microscopy and X-ray diffraction and are discussed with reverse osmosis data. When conditioned, fine porous hydrophobic supports become permeable to aqueous solutions at low pressures. Under these conditions permeate flux and retention were found to depend on the number of layers deposited.