Single crystal ESR study of bis(N-benzylpyridoxaldiminato) copper(II)

Single crystals of bis(N-benzylpyridozaldiminato) Cu(II) were studied by ESR in three perpendicula planes at 300 K and 9.4 GHz. Only one exchange—narrowed line was observed for the two magnetically inequivalent copper ions in the monoclinic symmetry lattice with space group P2₁/a and elementary cell parameters a = 9.561(9), B = 16.605(8), C = 17.561(2) Å and β = 104(1°). Each ligand is bidentate via the phenolic oxygen and the imino nitrogen atoms, leading to tetrahedrally distorted square planar environment around the copper atom. The ESR linewidth remained Lorentzian for all orientations considered. The components of the g_xx = 2.043(4), g_yy = 2.064(4), g_zz = 2.259(4). The linewidth anisotropy was analyzed in terms of dipole-dipole interactions, magnetic inequivalence of molecules and hyperfine interactions.     

An unprecedented process involving normal and redox transmetallation reactions between Hg and Pt affording the unexpected K[Pt2[CH2C(O)Me]6(mu-Cl)3] complex: the key role of X-ray powder diffraction in unravelling its nature and structure

[Hg{CH2C(O)Me}2] reacts with K[PtCl3(CH2=CH2)](2 : 1 molar ratio) to give K[Pt2{CH2C(O)Me}6(mu-Cl)3] (1); the intermediate [Pt{CH2C(O)Me}Cl2(CH2=CH2)]- has been detected in solution and isolated as a Me4N+ salt; the process occurs through successive normal and redox transmetallation reactions and an ab initio X-ray powder diffraction study of has proven to be essential to establish its nature.     

Thermo-oxidative degradation of some elastomers with a high content of 3,4 isoprene units

New elastomers with high content of 3,4 isoprene units have been developed during the last decades in an attempt to ensure superior performances of the final products and the present study is devoted to the investigation of some peculiarities of their ageing behaviour. On thermo-oxidative degradation, 3,4 isoprene units are less affected in comparison to cis-1, 4 and trans-1, 4 isoprene units. The degradation process consists mainly in splitting of the main chains at temperatures of 80–100 °C while at higher temperatures (120–130 °C) branching becomes a significant modification and this reaction is enhanced for the polymers containing preponderantly 3,4 units. Such behaviour leads to the fact that the processability of polymers containing high amounts of 1,2 and 1,3 isoprene units is less affected by thermo-oxidative degradation in comparison with cis-1, 4-polyisoprene, which could be explained by the fact that large amounts of double bonds are not present in the backbone of macromolecules but in the pendent groups.     

GRAFTED STYRENE-DIVINYLBENZENE COPOLYMERS CONTAINING BENZALDEHYDES AND THEIR WITTIG REACTIONS WITH VARIOUS PHOSPHONIUM SALTS

A chloromethylated styrene-divinylbenzene copolymer support system functionalized with 4-benzaldehyde and 2-benzaldehyde was prepared.The degree of functionalization with aldehyde groups is well suited for the subsequent use of the products as Wittig reagents.The polymer bound aldehyde was reacted with Wittig reagents to give olefin groups grafted on styrene-divinylbenzene copolymers.The reactions were carried out in phase transfer catalysis conditions.A simple procedure for the calculation of the degree of functionalization and the statistical modeling of the structural repetitive unit of the copolymer are reported.     

Sur Les Phénomènes D'oxydo-réduction En chimie Analytique

The theoretical bases of oxidation-reduction phenomena, from the point of view of analytical use, have been surveyed.The phenomena mainly considered have been: apparent potentials, dismutation, measured electrode-potentials, and allied to these the very important practical case of so-called irreversible systems.     

Novel fluorescence nanostructured materials obtained by entrapment of an ornamental bush extract in hybrid silica glass

Synthesis of some novel fluorescence nanomaterials loaded with photoactive polyphenols originated from plants with a high spectrum of biological activity, by replacing synthetic chemicals, may open new opportunities for optical and bio-medical applications. This paper presents the synthesis, characterization and fluorescence properties of a new class of materials based on host hybrid matrices obtained through templated sol–gel route, by hydrolysis and co-condensation of tetraorthoethylsilicate with octaisobutyltetracyclo [7.3.3.1^5,11] octasiloxane-endo-3,7-diol. The aim of paper is focused on the evaluation of the behavior of the fluorescence properties of ornamental bush extract at immobilization in a templated silica matrix and in a silica-silsesquioxane network, using as templates a neutral, non-toxic and biodegradable surfactant from poly(ethyleneglycol) class and a high biocompatible non-surfactant from glucidic class. The proofs of ornamental bush extract entrapment by physical interactions in silica based networks were provided by FT-IR and UV–VIS spectroscopy. The changes of polymer network due to the hydrogen bond interactions between residual Si–OH groups and functional groups of organic molecules from extract were evidenced by shifts of specific vibrations. In UV–VIS-NIR domain, the chromophore groups from ornamental bush extract were also evidenced by similar small shifts. As a result of ornamental bush extract entrapment, in all the immobilized samples the fluorescence intensity was more than 10 times amplified in samples templated with poly(ethylenglycol) surfactant) and of about 5 times in samples with glucidic template due to the physical adsorption of polyphenolic molecules from extract, excellent synergistic optical properties of SiO₂ and silsesquioxane compound and also due to a favorable conformational arrangement. The size of synthesized polymeric materials, estimated by dynamic light scattering technique showed main diameters less then 1.4 μm, namely 1,060 and 211 nm—for samples with d-glucose template and 1,330 and 531 nm—for samples with poly(ethyleneglycol) template, respectively, with a narrow size distribution and a polidispersity varying between 0.022 and 0.426. These results are in good accordance with TEM images that evidenced the presence of some polymeric aggregates which contain the vegetal extract immobilized inside hybrid SiO₂-Sq polymeric network of about hundred nanometers size. This study bring new contributions to the development of the sol–gel procedure by entrapment of a complex vegetable mixture in polymeric matrices as integral component of silica and hybrid silica-silsesquioxane networks which leads to a significant enhancement of the functional properties of the final material, thus diversifying the potential applications of organic doped sol–gel glasses.     

Rapid determination of hydroflumethiazide in dosage forms by time-resolved chemiluminescence

Hydroflumethiazide was determined from the chemiluminescence produced in its reaction with Ce(IV) in acidic medium containing rhodamine 6G as a sensitizer using flow injection techniques (stopped flow mode). A straightforward automatic method based on measuring the peak height and peak area, which are directly proportional to the hydroflumethiazide concentration, was thus developed. The calibration graphs were linear over the concentration range of 1.0–30 μg mL⁻¹. The limit of detection as determined according to Clayton was 0.97 and 0.91 μg mL⁻¹ for peak height and peak area measurements, respectively. The relative standard deviation for ten samples was less than 3.0% with both types of measurements. The procedure was applied to the determination of hydroflumethiazide in pharmaceutical formulations, yielding excellent recoveries, since the determination is free of interference from common excipients and other drugs which are present in the formulation.     

Dimeric self-assembling capsules derived from the highly flexible tribenzylamine skeleton

Tris(m-ureidobenzyl)amines dimerize both in solid state and in solution to give molecular capsules which are able to encapsulate small molecules. The self-assembly was confirmed by crystal X-ray analysis and NMR spectroscopy. The X-ray structure showed the encapsulation of one molecule of CH(2)Cl(2). This new type of capsules presents a propeller-like topology and a belt of six hydrogen-bonded ureas. Encapsulation studies in solution and heterodimerization processes are also disclosed.