Search results for "Deriva"
showing 10 items of 1423 documents
Maximal ℓ p ‐regularity of multiterm fractional equations with delay
2020
[EN] We provide a characterization for the existence and uniqueness of solutions in the space of vector-valued sequences l(p) (Z, X)for the multiterm fractional delayed model in the form Delta(alpha)u(n) + lambda Delta(beta)u(n) = Lambda u(n) + u(n-tau) + f(n), n is an element of Z, alpha, beta is an element of R+, tau is an element of Z, lambda is an element of R, where X is a Banach space, A is a closed linear operator with domain D(A) defined on X, f is an element of l(p)(Z,X) and Delta(Gamma) denotes the Grunwald-Letkinov fractional derivative of order Gamma > 0. We also give some conditions to ensure the existence of solutions when adding nonlinearities. Finally, we illustrate our resu…
Synthesis of quadruped-shaped polyfunctionalized o-carborane synthons
2011
[EN] o-Carborane derivatives with precisely defined patterns of substitution have been prepared from 8,9,10,12-I-4-1,2-closo-C2B10H8 by replacing the iodine atoms, bonded to four adjacent boron vertices in the cluster, with allyl, and subsequently 3-hydroxypropyl groups. The resulting structures, comprising four pendant arms and two reactive vertices located on opposite sides of a central o-carborane core, can be envisaged as versatile precursors for dendritic growth
Fast evaluation of a linear number of local exchange matrices
2002
A fast method is described for evaluating multiple exchange matrices in a Gaussian atomic orbital basis. For insulators, it is asymptotically linear scaling, and is a generalization of the linear scaling exchange (LinK) method, which was formulated for a single exchange matrix [J. Chem. Phys. 109 (1998) 1663]. It is employed to evaluate exchange-type contractions of all derivative density matrices with two-electron integrals for a series of linear alkanes, linear polyacenes, and water clusters using STO-3G, 3-21G, and 6-31G* basis sets. Significant computational savings are obtained for molecules with as few as 10 non-hydrogen atoms.
Preparation and structural characterization of Ph3Sn(IV)+ complexes with pyridinecarboxylic acids or hydroxypyridene, -pyrimidine and –quinoline.
2006
A number of [Ph3Sn(IV)](+) complexes formed with ligands containing -OH (-C=O), or -COOH group(s) and aromatic IN) donor atom have been prepared. The binding sites of the ligands were identified by FT-IR spectroscopic measurements. In the complexes containing hydroxy and carboxylate functions, the carboxylato group is coordinated to the organotin(IV) centres in monodentate or bridging bidentate manner. It was also found that in the hydroxypyridine and -pyrimidine complexes the [Ph3Sn(IV)]+ moiety in most cases reacts with the phenolic form of the ligands. The rationalisation of the experimental Sn-119 Mossbauer nuclear quadrupole splittings, vertical bar Delta(exp)vertical bar - according t…
Preparation and structural studies on the tBu2Sn(IV) complexes with aromatic mono- and dicarboxylic acids containing hetero {N} donor atom
2004
Nine complexes of 'Bu2Sn(IV)(2+) were obtained in the solid state with ligands containing -COOH group(s) and aromatic (N) donor atom. The binding sites of the ligands were identified by FT-IR spectroscopic measurements. It was found that in most cases the -COO- groups are co-ordinated in monodentate manner. Nevertheless, in some of our complexes, the -COO- group forms bridges between two central {Sn} atoms resulting in the formation of an oligomeric structure, a motif that is characteristic only to the nicotinate compound. These pieces of information and the rationalisation of the experimental Sn-119 Mossbauer nuclear quadrupole splittings, Delta, - according to the point charge model forma…
Multiple Roles of Isocyanides in Palladium-Catalyzed Imidoylative Couplings: A Mechanistic Study
2016
International audience; Kinetic, spectroscopic and computational studies examining a palladium-catalyzed imidoylative coupling highlight the dual role of isocyanides as both substrates and ligands for this class of transformations. The synthesis of secondary amides from aryl halides and water is presented as a case study. The kinetics of the oxidative addition of ArI with RNC-ligated Pd-0 species have been studied and the resulting imidoyl complex [(ArC=NR)Pd(CNR)(2)I] (Ar=4-F-C6H4, R = tBu) has been isolated and characterized by X-ray diffraction. The unprecedented ability of this RNC-ligated imidoyl-Pd complex to undergo reductive elimination at room temperature to give the amide in the p…
Acid-induced rearrangement of epoxygermacra-8,12-olides: synthesis and absolute configuration of guaiane and eudesmane derivatives from artemisiifolin
2010
A study on the acid-induced rearrangement of 4,5-epoxy- and 1,10-epoxygermacra-8,12-olides was carried out. From a 4,5-epoxy derivative, guaianes were obtained, whereas 1,10-epoxy derivatives furnished, depending on the stereochemistry of the C-1/C-10 epoxy ring, trans-5β,10α- or trans-5α,10β-eudesmanolides.
New optical paper sensor for in situ measurement of hydrogen sulphide in waters and atmospheres
2016
A novel and low-cost colorimetric sensor for the determination of hydrogen sulphide in environmental samples has been developed. This sensor is based on the immobilization of the reagent N,N-Dimethyl-p-phenylenediamine and FeCl3 in paper support, in which the H2S is adsorbed in order to give rise to the formation of methylene blue as reaction product. The sensor has been applied to determine H2S in water and air samples. Two different sampling systems for H2S caption from the air have been assayed: active and passive sampling. The analytical properties of the different systems have been obtained and compared. The analytical signals, corresponding to the methylene blue, have been obtained me…
Influence of the differentiation system on the analytical parameters for the spectrophotometric determination of clonazepam in urine
1991
Abstract Electronic and mathematical differentiation of the ultraviolet visible spectra were compared from the study of the analytical parameters of the direct determination of clonazepam in urine samples. Third-order derivative spectra were used. The mathematical differentiation provides higher sensitivity, a lower limit of detection, and better accuracy and precision than the electronic one. The use of a diode array instrument provides lower sensitivity than that found using a conventional spectrometer; however, the limit of detection obtained in both cases is of the same order.
On-line analysis of carbonyl compounds with derivatization in aqueous extracts of atmospheric particulate PM10 by in-tube solid-phase microextraction…
2011
Abstract A new device for carbonyl compounds based on coupling on-line and miniaturizing both, sample pretreatment and chromatographic separation, is reported. Two capillary columns, a GC capillary column (95% methyl–5% phenyl substituted backbone, 70 cm × 0.32 mm i.d., 3 μm film thickness) in the injection valve for in-tube solid-phase microextraction (IT-SPME) and a Zorbax SB C18 (150 mm × 0.5 mm i.d., 5 μm particle diameter) LC capillary column were employed. Different combinations of IT-SPME and derivatization using 2,4-dinitrophenylhydrazine (DNPH) were examined for mixtures containing 15 carbonyl compounds (aliphatic, aromatic and unsaturated aldehydes and ketones). A screening analys…