3-Methyl-1-propargylquinoxalin-2(1H)-one

The ten-membered fused ring of the title compound, C12H10N2O, is essentially planar in the two independent mol­ecules of the asymmetric unit (r.m.s. deviations = 0.012 and 0.015 Å)

Relaxation Dynamics and Magnetic Anisotropy in a Low-Symmetry DyIII Complex

The magnetic behaviour of a Dy(LH)3 complex (LH(-) is the anion of 2-hydroxy-N'-[(E)-(2-hydroxy-3-methoxyphenyl)methylidene]benzhydrazide) was analysed in depth from both theoretical and experimental points of view. Cantilever torque magnetometry indicated that the complex has Ising-type anisotropy, and provided two possible directions for the easy axis of anisotropy due to the presence of two magnetically non-equivalent molecules in the crystal. Ab initio calculations confirmed the strong Ising-type anisotropy and disentangled the two possible orientations. The computed results obtained by using ab initio calculations were then used to rationalise the composite dynamic behaviour observed for both pure Dy(III) phase and Y(III) diluted phase, which showed two different relaxation channels in zero and non-zero static magnetic fields. In particular, we showed that the relaxation behaviour at the higher temperature range can be correctly reproduced by using a master matrix approach, which suggests that Orbach relaxation is occurring through a second excited doublet

An iridium–SPO complex as bifunctional catalyst for the highly selective hydrogenation of aldehydes

A secondary phosphine oxide (SPO) ligand (tert-butyl(phenyl)phosphine oxide) was employed to generate an Ir–SPO complex which shows a particular ability to activate dihydrogen under mild conditions without the help of an external base or additive. Such an iridium (I) complex serves as a precursor for homogeneous catalysis since under H2 it is converted to a mixture of several iridium (III) hydride species that are the active catalysts. This system was found to be a highly active catalyst for the hydrogenation of substituted aldehydes, giving very high conversions and chemoselectivities for a wide range of substrates. The SPO ligand presumably plays a key role in the catalytic process through heterolytic cleavage of H2 by metal–ligand cooperation. In addition, an exhaustive characterization of the different iridium hydride species was performed by 1D and 2D NMR spectroscopy. The oxidative addition of H2 to the Ir(I)–SPO complex is highly stereoselective, as all generated Ir(III) hydrides are homochiral. Finally, the crystal structure, as determined by X-Ray Diffraction, of a dinuclear iridium (III) hydride complex is described

Temperature- and pressure-dependent metallic states in (BEDT-TTF)8[Hg4Br12(C6H5Br)2]

Temperature-driven metal-insulator and pressure-driven insulator-metal transitions observed in(BEDT-TTF)8[Hg4X12(C6H5Y)2]] with X = Y = Br are studied through band structure calculations based on X-ray crystal structure determination and Shubnikov-de Haas (SdH) oscillations spectra, respectively. In connection with chemical pressure effect, the transition, which is not observed for X = Cl, is due to gap opening linked to structural changes as the temperature decreases. Even though many body interactions can be inferred from the pressure dependence of the SdH oscillations spectra, all the data can be described within a Fermi liquid picture

1-Ethyl-3-methyl­quinoxalin-2(1H)-one

The asymmetric unit of the title compound, C11H12N2O, contains two independent mol­ecules. In the crystal structure, inter­molecular C—H⋯O hydrogen bonds link the mol­ecules. There are π–π contacts between the quinoxaline rings [centroid–centroid distances = 3.446 (2), 3.665 (2), 3.645 (3) and 3.815 (3) Å]. There also exist C—H⋯π contacts between the methyl groups and the quinoxaline rings

Mapping Out the Role of σ-Silane Complexes in the Ruthenium-Catalyzed Hydrosilylation of Nitriles

A combined synthetic, mechanistic, and computational study is reported, which provides unique insight into the role of σ-silane complexes in the catalytic hydrosilylation of nitriles. A novel, highly efficient, highly active, and regioselective catalytic monohydrosilylation of aromatic nitriles with secondary silanes using a ruthenium dihydrogen catalyst is reported along with a novel mechanism for hydrosilylation of nitriles. Investigations into the mechanism of this transformation have revealed the influence of σ-Si-H complexes in fine-tuning the selectivity of this hydrosilylation reaction. Displacement of the dihydrogen ligand on the ruthenium precatalyst, ruthenium bis-(dihydrogen) complex [RuH2(η2-H2)2(PCy3)2], 1, by diphenylsilane leads to the formation of new ruthenium σ-Si-H complexes, [RuH2(η2-H2)(η2-HSiHPh2)(PCy3)2], 2, and [RuH2(η3-H2SiPh2)(PCy3)2], 3. Complex 3 reacts readily with benzonitrile leading to hydrosilylation of the nitrile and coordination of the silylimine formed to the ruthenium as a σ-H-Si-N-silylimine complex, [RuH2(η2-HSiPh2NCHPh)(PCy3)2] (4). This systematic investigation of this reactivity led to the discovery of the first direct evidence of an N-silylimine-coordinated ruthenium complex and its involvement in a catalytic hydrosilylation reaction. This led to the discovery of a catalytic protocol for the efficient and selective coupling of secondary silanes with a range of nitriles using 1 as the catalyst. It is proposed that complexes 3 and 4 are key intermediates on the catalytic reaction coordinate, which leads to hydrosilylation of the nitrile. This is supported by DFT calculations along with the observation that 3 and 4 are catalytically active. The Si-N bond formation was found to proceed via direct attack of the nitrile at the silicon atom in 3. Through carefully chosen structural studies and tests of the new ruthenium complexes, along with DFT calculations, the mechanism of the catalytic hydrosilylation of nitriles has been successfully explained

Novel 8-nitroquinolin-2(1H)-ones as NTR-bioactivated antikinetoplastid molecules:Synthesis, electrochemical and SAR study

International audienceTo study the antiparasitic 8-nitroquinolin-2(1H)-one pharmacophore, a series of 31 derivatives was synthesized in 1-5 steps and evaluated in vitro against both Leishmania infantum and Trypanosoma brucei brucei. In parallel, the reduction potential of all molecules was measured by cyclic voltammetry. Structure-activity relationships first indicated that antileishmanial activity depends on an intramolecular hydrogen bond (described by X-ray diffraction) between the lactam function and the nitro group, which is responsible for an important shift of the redox potential (+0.3 V in comparison with 8-nitroquinoline). With the assistance of computational chemistry, a set of derivatives presenting a large range of redox potentials (from -1.1 to -0.45 V) was designed and provided a list of suitable molecules to be synthesized and tested. This approach highlighted that, in this series, only substrates with a redox potential above -0.6 V display activity toward L. infantum. Nevertheless, such relation between redox potentials and in vitro antiparasitic activities was not observed in T. b. brucei. Compound 22 is a new hit compound in the series, displaying both antileishmanial and antitrypanosomal activity along with a low cytotoxicity on the human HepG2 cell line. Compound 22 is selectively bioactivated by the type 1 nitroreductases (NTR1) of L. donovani and T. brucei brucei. Moreover, despite being mutagenic in the Ames test, as most of nitroaromatic derivatives, compound 22 was not genotoxic in the comet assay. Preliminary in vitro pharmacokinetic parameters were finally determined and pointed out a good in vitro microsomal stability (half-life > 40 min) and a 92% binding to human albumin