Search results for "Catalyst"
showing 10 items of 516 documents
Thiourea Organocatalysts as Emerging Chiral Pollutants: En Route to Porphyrin-Based (Chir)Optical Sensing
2021
Environmental pollution with chiral organic compounds is an emerging problem requiring innovative sensing methods. Amino-functionalized thioureas, such as 2-(dimethylamino)cyclohexyl-(3,5-bis(trifluoromethyl)phenyl)thiourea (Takemoto’s catalyst), are widely used organocatalysts with virtually unknown environmental safety data. Ecotoxicity studies based on the Vibrio fischeri luminescence inhibition test reveal significant toxicity of Takemoto’s catalyst (EC50 = 7.9 mg/L) and its NH2-substituted analog (EC50 = 7.2–7.4 mg/L). The observed toxic effect was pronounced by the influence of the trifluoromethyl moiety. En route to the porphyrin-based chemosensing of Takemoto-type thioureas, their s…
First-Principles Modelling of N-Doped Co3O4
2018
The project Nr. AP05131211 “First Principles Investigation on Catalytic Properties of N-doped Co3O4” is supported by the Ministry of Education and Science of the Republic of Kazakhstan within the framework of the grant funding for scientific and (or) scientific and technical research for 2018-2020. The authors thank T. Inerbaev and A. Popov for fruitful discussions and valuable suggestions. Yu.M. thanks M.Putnina for the technical assistance in preparation of the manuscript.
Nanostructured Ni Based Anode and Cathode for Alkaline Water Electrolyzers
2019
Owing to the progressive abandoning of the fossil fuels and the increase of atmospheric CO2 concentration, the use of renewable energies is strongly encouraged. The hydrogen economy provides a very interesting scenario. In fact, hydrogen is a valuable energy carrier and can act as a storage medium as well to balance the discontinuity of the renewable sources. In order to exploit the potential of hydrogen it must be made available in adequate quantities and at an affordable price. Both goals can be potentially achieved through the electrochemical water splitting, which is an environmentally friendly process as well as the electrons and water are the only reagents. However, these devices stil…
Multidentate Tetrahydrofurfuryloxide Ligand in a Ziegler−Natta Catalyst Studied by Molecular Modeling
2008
The transition from a generation III Ziegler-Natta catalyst with a monodentate Lewis base to a more modem generation 1V/V system, containing a tetrahydrofuran derivative, the tetrahydrofurturyloxide C 4 H 7 O-CH 2 O - bidentate ligand (THFFO), was studied by means of molecular modeling and DFT calculations. This particular ligand was carefully chosen so that it remained in the titanium coordination sphere in the model active site. With such a constraint, the dual role of tetrahydrofurfuryloxide was identified: it was demonstrated how the presence of this ligand limits the number of isomeric active sites as well as enhances the selectivity of the species that can still exist. The results ind…
ChemInform Abstract: Switchable Palladium-Catalyst Reaction of Bromomethyl Sulfoxides, CO, and N-Nucleophiles: Aminocarbonylation at Csp3versus Oxida…
2013
Pd2(dba)3/ Xantphos-catalyzed coupling of the sulfoxides (I) and (V) with amines and carbon monoxide allows a new and efficient access to amides of type (IV) and (VI).
POSS-Al-porphyrin-imidazolium cross-linked network as catalytic bifunctional platform for the conversion of CO2 with epoxides
2023
Two heterogeneous catalysts were prepared with the aim of following the promising path of CO2 fixation into epoxides. The synthetic procedure involves a radical copolymerization of an octavinylsilsesquioxane as inorganic core building block and tetrastyrylporphyrin aluminum chloride monomer (TSP-AlCl) in presence (POSS-TSP-AlCl-imiBr) or in absence (POSS-TSP-AlCl) of a bis-vinylimidazolium bromide salt (bis-imiBr), in order to investigate if the bifunctional heterogeneous material can display better catalytic performance than the separate species. All the solids were fully characterized and tested in the synthesis of cyclic carbonates starting from CO2 and several epoxides. The synergic coo…
Enantiocontrol in the intermolecular cyclopropanation reaction catalyzed by dirhodium(II) complexes with ortho-metalated aryl phosphine ligands
2001
(P) and (M) dirhodium(II) complexes with ortho-metalated aryl phosphines are assessed as chiral catalysts in the enantioselective cyclopropanation of styrenes by ethyl diazoacetate; enantioselectivities up to 91% and up to 87%, respectively, for cis- and trans-2-arylcyclopropanecarboxylates are observed. Barberis, Mario, Mario.Barberis@uv.es ; Lahuerta Peña, Pascual, Pascual.lahuerta@uv.es ; Perez Prieto, Julia, Julia.Perez@uv.es ; Sanau Torrecilla, Mercedes, Mercedes.Sanau@uv.es
Hirālu piridīna organokatalizatoru izstrāde un pielietojums
2015
Maģistra darba ietvaros tika izstrādāta hirālu DMAP organokatalizatoru sintēze. Iegūto organokatalizatoru aktivitāte tika pārbaudīta tetrazola hemiaminālu dinamiskajā kinētiskajā sadalīšanā.
DFT analysis of titanium complexes with oxygen-containing bidentate ligands
2003
Strength of the TiO co-ordinate bond in several titanium complexes with bidentate ligands has been investigated by means of DFT. Mutual interaction of particular donors and their influence on Lewis acidity of the central atom have also been studied. The energy of ligand binding ranges from −19 to −454 kJ/mol, depending on the kind of donors. Calculations confirm that a strong donor, alkoxide anion, co-ordinatively saturates the titanium and makes binding of new ligands less exoenergetic. On the contrary, two oxygen atoms of similar donor number do not have much influence on each other. Strength of the TiO bonds in titanium complexes with certain oxygen-containing bidentate ligands has bee…
Theoretical study of isomerism in phenoxyimine-based precursors of coordinative olefin polymerization catalysts
2010
Precursors of post-metallocene olefin polymerization catalysts, unlike their predecessors, are usually octahedral transition metal complexes with multidentate ligands. Such ligands may wrap around the central atom in many ways, thus yielding several isomeric species. For a wide range of phenoxyimine (FI) ligands with different substituents, all the theoretically predicted diastereomers of group 4 and 5 complexes are available synthetically. However, only one of the isomers is usually preferred, and this is determined by the nature of the substituents in the FI ligand. The origin and mechanism of such preference has not been completely elucidated. We attempted to describe it quantitatively o…