Préparation de quelques 4-nitroisoxazoles à partir de pseudonitrosites de cétones éthyléniques du type chalcone

The Synthesis of some 4-Nitroisoxazoles from Pseudonitrosites of Chalcones The action of dinitrogen trioxide with α,β-unsaturated ketones of the chalcone type leads to pseudonitrosites (Table 1) which are cyclized to 4-nitro-3,5-diarylisoxazoles (Table 2).     

Theoretical Study of the Distortion from Regular Tetrahedral Structure of M(NH2)4 Complexes

Theoretical study on tetrakis-amido complexes (M(NR₂)₄, M = Ti, V, Cr, and Mo; R = H, Me) is presented. At first a rough investigation of the potential energy surface indicates that all stationary points are of S ₄ or D ₂ symmetry depending on the coupled rotations of the NR₂ groups. Qualitative correlation diagrams are calculated within S ₄ or D ₂ symmetry constraint between two limiting structures of D ₂ d symmetry. DFT (B3LYP) calculations on these two paths are presented for unsubstituted complexes (R = H) and the various minima are optimized and characterized. These results are discussed in the light of the correlation diagrams. Finally, optimization of the different minima has been performed on substituted species (R = Me) and the theoretical results are shown to be in good agreement with the experimental structural determination when available.     

The Photochemistry of 2-Cyclopentenyl Methyl Ketones

2-Cyclopentenyl and 3-phenyl-2-cyclopentenyl methyl ketones (15–18, 30, 31) undergo a 1,3-acetyl shift on direct irradiation, and the oxa-di-π-methane rearrangement to photochemically non-interconverting endo and exo bicyclo-[2.1.0]pentyl methyl ketones on triplet sensitization. Exceptions include the 2-methyl-3-phenyl-2-cyclopentenyl methyl ketone 32 and the 1-phenyl-2-cyclo-pentenyl methyl ketone 44 which are unreactive on direct irradiation and on triplet sensitization, respectively, and the 2-phenyl-2-cyclopentenyl methyl ketones 42 and 43 which do not react under either condition. The reactive triplet of the 3-phenyl-2-cyclopentenyl methyl ketone 30 has been identified as the localized styrene π,π*-state of E_T=59 kcal/mol by comparison of its phosphorescence at 77K in rigid glasses with that of 1-phenyl-cyclopentene, and by the independence of the quantum yield on sensitizer energy in the range of 61–74 kcal/mol.     

X-ray crystal structures of three nonbenzodiazepinic ligands for the benzodiazepine receptor sites: SR95926, CMW1842, and L16317:nab initio MO study of the electronic properties

The crystal structures ofp-methoxyphenyl-3-triazolo [4,3-a] isoquinoline (SR95926),p-methoxyphenyl-3-triazolophtalazine (CMW1842), andp-methoxyphenyl-3-N-dimethoxyethylamino-6-triazolophtalazine (L16317) have been solved by direct methods from single-crystal X-ray diffraction data, and refined by full-matrix least squares. SR95926: monoclinic,P2₁/n,a=20.950(3),b=6.769(1),c=9.465(2) Å,=100.90(1)°. CMW1842: triclinic,P¯1,a=8.784(1),b=9.160(4),c=8.555(1) Å,=99.10(2),=93.90(1), =106.77(1)°. L16317: monoclinic,P2₁/_n,a=20.124(3),b=9.586(1),c=10.788(1) Å,=91.91(1)°. FinalR factors are 0.034, 0.037, and 0.053, respectively. Experimental geometries were used to perform STO-3Gab initio molecular-orbital calculations. A relationship between the electronic pattern within the molecules and the affinity of the benzodiazepine receptor sites is pointed out.     

A grothendieck factorization theorem on 2-convex schatten spaces

We prove that for every bounded linear operatorT:C ^2p →H(1≤p<∞,H is a Hilbert space,C ^{2 p} p is the Schatten space) there exists a continuous linear formf onC ^p such thatf≥0, ‖f‖(C _C ^p)*=1 and $$\forall x \in C^{2p} , \left\| {T(x)} \right\| \leqslant 2\sqrt 2 \left\| T \right\|< f\frac{{x * x + xx*}}{2} > 1/2$$ . Forp=∞ this non-commutative analogue of Grothendieck’s theorem was first proved by G. Pisier. In the above statement the Schatten spaceC ^2p can be replaced byE _E ² whereE ⁽²⁾ is the 2-convexification of the symmetric sequence spaceE, andf is a continuous linear form onC _E. The statement can also be extended toL _E{(su2)}(M, τ) whereM is a Von Neumann algebra,τ a trace onM, E a symmetric function space.     

Sur les séries de Taylor et les transformations de Möbius

Given a non-empty closed subsetF of the unit circle |z|=1, and a Möbius transformationM(z) of the unit disc |z|1, such thatM(0)0, there exists a functionf(z) holomorphic in the unit disc,F being the singular set at the boundary, whose Taylor coefficients tend to zero while the Taylor coefficients off(M(z)), do not tend to zero.     

Magnetic properties on holmium iron garnet in high magnetic field. Optical absorption spectra in the infra-red region

On single crystals of holmium iron garnet (HoIG), magnetic properties have been studied in magnetic field up to 150kOe applied parallel to the main crystallographic directions in the 4.2–300K temperature range. Above 130 K, the magnetization is isotropic and linear magnetic field dependent as previously found in polycrystals and predicted by Néel's ferrimagnetic theory. Nevertheless the paramagnetic Curie temperature is much higher than the polycrystal value. Below 130K, due to the onset of the umbrella structure, the ferrite magnetization presents a non linear field variation with [111] as easy direction. The field evolutions of the anisotropy constants (K ₁ andK ₂) were calculated. Optical absorption measurements of both 5₈5I ₆ and 5I ₈5I ₇ transitions are reported and compared to the results of the literature in terms of inequivalent magnetic sites.     

Kb/Ka X-ray intensity ratios in calcium and potassium compounds

Summary Kb/Ka X-ray intensity ratios of some K and Ca compounds were studied. The samples were excited with 59.5 keV g-rays emitted from 75 mCi ²⁴¹Am radioisotope source and characteristic K X-ray from the samples were counted by means of an Si(Li) detector which has a resolution 155 eV at 5.9 keV. We found that Kb/Ka X-ray intensity ratios are changed by chemical effect for different K and Ca compounds. The experimental values were compared with the calculated theoretical values for elemental K and Ca.