The modified `phosphine imide' reaction: a safe and soft alternative ureas synthesis

In this work we present a new way for the direct and general synthesis of urea compounds from primary amines by the modified `phosphine imide' reaction. A large panel of amine structures are compatible with the smooth reaction conditions. Particularly in the case of sensitive l-aminoesters, it is interesting to note that the stereochemistry at the asymmetric centre was unmodified in the reaction conditions.     

Oxidation state of vanadium introduced in dealuminated beta zeolite by impregnation with VIVOSO4 solution: influence of preparation parameters

Vanadium was introduced in dealuminated beta zeolite by impregnation with a VIVOSO4 aqueous solution at 353 K in air or argon (to prevent oxidation of VIV), leading to VSibeta and VSibeta-Ar zeolites, respectively. The samples were characterized by spectroscopy, XRD, and N2-physisorption. The oxidation state and environment of V in Sibeta zeolite depend on the preparation parameters (i.e., on the way the solid is recovered after impregnation and on the drying temperature). In solids recovered by centrifugation, washed with distilled water, and then dried overnight at 298 K in argon, vanadium is found as extra-lattice octahedral VIV ions as evidenced by EPR. In contrast, in solids not washed but directly dried overnight at 353 K in air or argon, vanadium is found in both cases as lattice tetrahedral VV ions. These ions are incorporated into vacant T sites associated with SiOH, SiO-, oxygen vacancies (OVs) or nonbridging oxygen (NBOs) defects as shown by diffuse reflectance UV-visible, 51V MAS NMR, FT-IR, and photoluminescence. The oxidation to VV ions is suggested to be due to an electron transfer from VO2+ to trigonal identical with Si+ defect sites followed by reaction of the resulting VO2+ ions with particular defects of vacant T sites. These processes occur already upon drying of V-impregnated Sibeta at 353 K. 51V MAS NMR allows detection of one kind of lattice tetrahedral V ions in VSibeta and two kinds in VSibeta-Ar. The formation of different kinds of tetrahedral V species is related to the presence in vacant T sites of Sibeta zeolite of different types of defect sites such as trigonal identical with Si+ defect or SiOH and SiO- groups.     

Photochemical reaction of gadolinium(III) tetraphenylporphyrin in toluene solution containing an electron acceptor or donor

In this paper we have studied by absorption spectroscopy the course of the steady state photolysis of gadolinium(III) complex with 5,10,15,20-tetraphenylporphyrin. The result has been compared with the photolysis of free base tetraphenylporphyrin. Irradiation of GdTPP(acac) and H₂TPP (H₂TPP ≡ tetraphenylporphyrin; Hacac ≡ acetylacetone) with visible light in the presence of triethylamine as an electron donor, leads to their photoreduction. Formation of the gadolinium tetraphenylchlorin complex and tetraphenylchlorin is observed. The process of irradiation in the presence of CCI₄ as an electron acceptor has different pathways for GdTPP(acac) and H₂TPP. The gadolinium complex is mono oxidized, giving rise to the π⁺ radical cation while, for unmetallated porphyrin, dication H₄(TPP)²⁺ formation is observed.     

Reactions of commercial ruthenium chlorides with O-donor ligands. Reactions with water: u.v.-vis. investigation of soluble products; analysis,thermogravimetry and an i.r. study of precipitated solids

Summary The u.v.-vis. absorption spectra of the products of reaction of commercial ruthenium chlorides with water have been measured. Deconvolution analysis revealed that hexaaquo-, pentaaquohydroxy- and pentaaquo-chlororuthenium(III) ions are formed, in addition to four unknown compounds.Analysis of the concentration data suggests the formation of soluble oligomers of the primary products over several hours following dissolution. Storage of the solution for ca. 170 h furnishes insoluble materials, characterized by analysis, thermogravimetry and i.r. The bulk of these solids can be described as [Ru_{2n + 2}O_{3n + 3}] ·mH₂O or [Ru_{2n + 2}O_{(3n + 3) - a} (OH)_2a ·mH₂O. We suggest the existence of ruthenium hydrides in these precipitated solids.     

Synthesis of Chiral 2,4-Chiral 2,4-Dichloro-6-menthoxy-1,3,5-triazines and 2-Chloro-4, 6-Dimenthoxy-1,3,5-triazines as Enantiodifferentiating Coupling Reagents. An X-ray Study on 2,4,6-Trimenthoxy-1,3,5-triazine

Chiral mono-di-and trimenthoxy-1,3,5-triazines ware obtained from natural menthol and cyanuric chloride and applied as enantioselective coupling reagents in the synthesis of dipeptides.     

Structure and dynamics of ferroelectric liquid crystals under random geometrical restrictions

The dynamics of ferroelectric liquid crystals confined in porous nitro-cellulose membrane (Synpor) are investigated by broadband dielectric spectroscopy, and a characterization of the mesomorphism is achieved by DSC and X-ray scattering. The complex inner membrane structure of random interconnected voids can be treated as a frozen random defect disorder in the mesophases. Its influence on the molecular dynamics of the confined mesogens is negligible. However, Goldstone and soft modes of DOBAMBC (2-methylbutyl 4-(4-decyloxybenzylideneamino)cinnamate) are suppressed by the confinement and not detected dielectrically. In the short pitch and high spontaneous polarization material C7, 4-(3-methyl-2-chloropentanoyloxy)-4'-heptyloxybiphenyl, confinement has a minor influence on the soft mode, and the Goldstone mode is clearly present, although with reduced strength, broadened with respect to the bulk, and shifted to higher frequencies by more than one decade. The results are interpreted as effects of random confinement on the length scale of the helical pitch.     

Inverse problems for multi-valued quasi variational inequalities and noncoercive variational inequalities with noisy data

ABSTRACT

We study the inverse problem of identifying a variable parameter in variational and quasi-variational inequalities. We consider a quasi-variational inequality involving a multi-valued monotone map and give a new existence result. We then formulate the inverse problem as an optimization problem and prove its solvability. We also conduct a thorough study of the inverse problem of parameter identification in noncoercive variational inequalities which appear commonly in applied models. We study the inverse problem by posing optimization problems using the output least-squares and the modified output least-squares. Using regularization, penalization, and smoothing, we obtain a single-valued parameter-to-selection map and study its differentiability. We consider optimization problems using the output least-squares and the modified output least-squares for the regularized, penalized and smoothened variational inequality. We give existence results, convergence analysis, and optimality conditions. We provide applications and numerical examples to justify the proposed framework.     

Studies of intrawall porosity in the hexagonally ordered mesostructures of SBA-15 by small angle X-ray scattering and nitrogen adsorption

Ordered mesoporous silicas (OMSs) such as SBA-15 (p6mm symmetry group) synthesized in the presence of block copolymers containing poly(ethylene oxide) blocks possess irregular complementary pores in the walls of ordered mesopores. The X-ray scattering caused by this complementary porosity contributes to the background of the SAXS patterns. This work shows the possibility of using the SAXS data for the study of intrawall channels interconnecting ordered cylinders in SBA-15. The proposed SAXS analysis was tested by using a series of SBA-15 samples obtained at different temperatures of hydrothermal treatment (from 60 to 180 °C). The structural modelling of the SAXS patterns recorded for a series of SBA-15 samples was performed by using the continuous density function (CDF) technique in combination with the derivative difference minimization (DDM) method of full-profile refinement. This method is well suited for extraction of the background curves from the SAXS patterns. The resulting smooth background curves were analyzed by the well-known method in the SAXS theory used for evaluation of heterogeneity distributions, which in this case characterize the intrawall complementary porosity. A relatively good agreement has been observed between the data obtained by SAXS and nitrogen adsorption analysis. The SAXS analysis is sufficiently sensitive for examination of heterogeneous microporosity in SBA-15 materials. The average diameter of intrawall pores for the SBA-15 sample obtained at 60 °C was only about 1.4 nm. However, this diameter increased with the increasing temperature of hydrothermal treatment; namely, it was 1.5, 1.8, 2.6, 2.6, 3.5 and 5.2 nm for the SBA-15 samples hydrothermally treated at 80, 100, 120, 140, 160 and 180 °C, respectively.     

S-adenosylhomocysteine analogues with the carbon-5' and sulfur atoms replaced by a vinyl unit

Cross-metathesis of suitably protected 5'-deoxy-5'-methyleneadenosines with racemic and chiral N-Boc-protected six-carbon amino acids bearing a terminal double bond in the presence of the Hoveyda-Grubbs catalyst gave adenosylhomocysteine analogues with the C5'-C6' double bond. Bromination with pyridinium tribromide and dehydrobromination with DBU followed by standard deprotections yielded the 5'-(bromo)vinyl analogue. [structure: see text]     

Variational analysis of fully coupled electro‐elastic frictional contact problems

We consider a mathematical model which describes the static frictional contact between a piezoelectric body and a foundation. The material behavior is described with a nonlinear electro‐elastic constitutive law. The novelty of the model consists in the fact that the foundation is assumed to be electrically conductive and both the frictional contact and the conductivity on the contact surface are described with subdifferential boundary conditions which involve a fully coupling between the mechanical and electrical variables. We derive a variational formulation of the problem which is in the form of a system coupling two hemivariational inequalities for the displacement and the electric potential fields, respectively. Then we prove the existence of a weak solution to the model and, under additional assumptions, its uniqueness. The proofs are based on recent results for inclusions of subdifferential type in Sobolev spaces (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)