Search results for "Hydrogen"

Transformation of monuron photosensitized by soil extracted humic substances: energy or hydrogen transfer mechanism?

1997

The humic and fulvic acids extracted from a Ranker type soil sensitize the transformation of monuron. When monuron is irradiated at 365 nm in the presence of the fulvic acid, its degradation is faster in deoxygenated medium than in air-saturated solution. Chloride ions are released, and the para-hydroxylated derivative is formed as upon direct photolysis. It is deduced that the consumption of monuron observed in the absence of oxygen is due to an energy transfer from reactive triplet states of the fulvic acid to monuron. Energy transfer reactions also take place when hydroquinone or acetophenone are used as sensitizers, showing that the energy level of the triplet state of monuron is lower …

Electrocatalytic Properties of Carbosilane‐Based Hyperbranched Polymers Functionalized with Interacting Ferrocenyl Units

2012

Two types of hyperbranched ferrocene-containing polycarbosilanes were obtained by hydrosilylation of polydiallylmethylsilane (hb-PDAMS) and polymethyldiundecenylsilane (hb-PMDUS) with diferrocenylmethylsilane. The redox properties of both polymers have been investigated both in solution and confined onto platinum electrodes. The electrocatalytic activity of polymer-modified electrodes toward the reduction of oxygen as well as the electrochemical reduction and oxidation of hydrogen peroxide has been examined.

Coordination versatility of pyridine-functionalized N-heterocyclic carbenes: a detailed study of the different activation procedures. Characterizatio…

2005

Three different reaction procedures for the coordination of N-n-butyl-N'-(2-pyridylmethyl)imidazolium salt have produced new N-heterocyclic complexes of Rh and Ir. The direct reaction of the imidazolium salt with [IrCl(cod)](2) provides a NHC-Ir(III)-H complex, while transmetalation from a silver-NHC complex and deprotonation with NEt(3) give new NHC complexes of M(I) and M(III) when reacting with [MCl(cod)](2) or [MCl(coe)(2)](2) (M = Rh, Ir). The crystal structures of the biscarbene Rh(III) and Ir(III) complexes are described. The catalytic properties of the compounds obtained have been tested in the hydrosilylation of acetylenes, the cyclization of acetylenic carboxylic acids, and hydrog…

An Efficient and Simple Entry to N-Substituted beta-Enamino Acid Derivatives from 2-Alkyl-2-oxazolines and 2-Alkyl-2-thiazolines.

1996

Reaction of azaenolates of 2-alkyl-oxa(thia)zolines 6 with imidoyl chlorides 7 as electrophiles to furnish masked N-substituted beta-enamino acid derivatives 1-2 in 70-90% yield is described. Alternative routes are discussed. Compounds 1-2 generally appear in one tautomeric form, imino or enamino, depending on the nature of the imidoyl chloride. The configuration of the enamino moiety (Z) and the conformation (s-cis) of compounds 1-2 obtained were established by an NMR study and unequivocally set by nuclear Overhauser effect difference experiments. An X-ray structure of compound 1e is also reported, showing a strong intramolecular NH.N hydrogen bond. Ab initio calculations (HF/3-21G and HF/…

Anion coordination chemistry in aqueous solution of polyammonium receptors

2006

The behavior of polyamines as receptors of selected families of anions in water is explored. First metallocyanide interaction with saturated polyammonium hosts is analyzed both in solution and in the solid state. The utility of potentiometry, multinuclear NMR, microcalorimetry and cyclic voltammetry to describe solution features of this chemistry is described for selected systems. Sulfate, phosphate, polyphosphate and nucleotide interactions with large polyammonium receptors are then reviewed. Hydrogen bond formation is discussed from a thermodynamic point of view. The influence of the presence of aromatic fragments within the structure on the binding strength is discussed. Factors affectin…

Diastereomeric Differentiation in the Quenching of Excited States by Hydrogen Donors

2003

2-(4-Fluorophenyl)-1-(4-pyridyl)cyclopentan-1-ol

2007

The crystal structure of the title compound, C16H16FNO, was determined as part of a study of the biological activity of pyridine-substituted cyclo­pentene derivatives as p38 mitogen-activated protein kinase (MAPK) inhibitors. The 4-fluoro­phenyl and 4-pyridyl rings are trans positioned with respect to each other. The compound exists as a racemic mixture. The synthesis was achieved via direct inter­action between the reactive complex Grignard reagent PyMgCl·LiCl and the enolizable ketone 4-fluoro­phenyl­cyclo­penta­none with the assistance of the neodymium salt catalyst NdCl3·2LiCl. The crystal packing is characterized by zigzag chains of mol­ecules, which are connected by O—H⋯N hydrogen bon…

The water association band as a marker of hydrogen bonds in trehalose amorphous matrices

2017

The relevant role played by residual water in modulating the dynamics and structure of a protein, a matrix and their coupling has been thoroughly studied in bioprotective amorphous saccharide matrices via experiments and simulations. In order to better characterize this residual water and the hydrogen bond structures in which it is involved, in this work infrared spectroscopy experiments are conducted on trehalose-water systems. The properties of water are inferred from the study of a peculiar infrared band, the water association band, which we exploited as a marker of the hydrogen bonds in which water is involved. Our aim was the identification of populations of water molecules, which give…

Slow magnetic relaxation in a hydrogen-bonded 2D array of mononuclear dysprosium(III) oxamates.

2013

The reaction of N-(2,6-dimethylphenyl)oxamic acid with dysprosium(III) ions in a controlled basic media afforded the first example of a mononuclear lanthanide oxamate complex exhibiting a field-induced slow magnetic relaxation behavior typical of single-ion magnets (SIMs). The hydrogen-bond-mediated self-assembly of this new bifunctional dysprosium(III) SIM in the solid state provides a unique example of 2D hydrogen-bonded polymer with a herringbone net topology.

Single-Component Polymerization Catalysts for Ethylene and Styrene:  Synthesis, Characterization, and Reactivity of Alkyl and Hydrido Yttrium Complex…

1999

Yttrium alkyl complexes Y(η5:η1-C5Me4SiMe2NCMe2R)(CH2SiMe3)(THF) (R = Me, Et) and Y(η5:η1-C9H6SiMe2NCMe3)(CH2SiMe3)(THF) can be prepared in high yields by a σ-bond metathesis reaction between Y(CH2SiMe3)3(THF)2 and amino-functionalized cyclopentadienes or indene. The structure of Y(η5:η1-C5Me4SiMe2NCMe2Et)(CH2SiMe3)(THF) was shown by single-crystal X-ray diffraction to be that of a three-legged piano stool. Reaction of Y(CH2SiMe3)3(THF)2 with the tridentate linked amido−cyclopentadienyl ligands (C5Me4H)SiMe2NHR (R = CH2CH2OMe, CH2CH2NMe2, CH2CH2CH2OMe, CMe2CH2OMe), which contain an additional donor site, results in the cleavage of the silicon−cyclopentadienyl bond and the formation of the t…