N,N′-(1,4-Phenyl­ene)bis­(4-chloro­butanamide)

The title mol­ecule, C14H18Cl2N2O2, lies on a crystallographic inversion center and the each 4-chloro­butanamide group adopts an anti-staggered conformation. In the crystal, adjacent mol­ecules are linked through N—H⋯O contacts, forming infinite ribbons extending parallel to the a axis

Hexanuclear and undecanuclear iron(III) carboxylates as catalyst precursors for cyclohexane oxidation

Two multinuclear complexes [Fe-6(mu(3)-O)(2)(mu(4)-O-2)L-10(OAc)(2)(H2O)(2)]center dot 2.625Et(2)O center dot 2.375H(2)O (1) and [(Fe11Cl)-Cl-III-(mu(4)-O)(3)(mu(3)-O)(5)L-16(dmf)(2.5)(H2O)(0.5)]center dot Et2O center dot 1.25dmf center dot 3.8H(2)O (2), where HL = 3,4,5-trimethoxybenzoic acid and dmf = dimethylformamide, have been prepared from trinuclear iron(III) carboxylates via their structural rearrangement in dimethylformamide or diethyl ether-dimethylformamide 9:1, respectively, and slow vapor diffusion of diethyl ether into the reaction mixture. Both compounds have been characterized by X-ray diffraction, optical, Mossbauer spectroscopy, and magnetic measurements. Complex 1 possesses a hexanuclear ferric peroxido-dioxido {Fe-6(O-2)(O)(2)}(12+) core unit, which adopts a recliner conformation, while complex 2 contains an unprecedented {Fe11O8Cl}(16+) core, in which 9 ferric ions are six-coordinate and the remaining two are five-coordinate. Another structural feature of note of the undecanuclear core is the presence of a deformed cubane entity {Fe-4(mu(3)-O)(mu(4)-O)(3)}(4+). Both complexes act as catalyst precursors for the oxidation of cyclohexane to cyclohexanol and cyclohexanone with aqueous H2O2, in the presence of pyrazinecarboxylic acid. Remarkable TONs and TOFs (the latter mainly for 1) with concomitant quite good yields have been achieved under mild conditions. Moreover, 1 exhibits remarkably high activity in an exceptionally short reaction time (45 min), being unprecedented for any metal catalyzed alkane oxidation by H2O2. The catalytic reactions proceed via Fenton type chemistry

PHYSICAL METHODS IN CHEMISTRY INVESTIGATIONS OF THE CHEMISTRY INSTITUTE OF ASM

The following classes of compounds are presented: terpenes, cyclic nitrogen compounds, dioximates, carboxylates etc., which have been studied with the participation of experts on physical methods of research - IR, UV-Vis, Atomic, Mössbauer spectroscopy, as well as Mass-spectrometry and Nuclear Magnetic Resonance in the IC ASM. Also, a number of significant scientific results obtained in collaboration of chemists and specialists in physical methods are described

METALLIC COMPOUNDS IN THE PHASE OF THE RETICULATED IONIC POLYMERS

Using the Mossbauer spectroscopy and other physical methods it was demonstrated the presence of different iron compounds like β-FeOOH, α-Fe2O3, and jarosite mineral type compounds: (R4N,H3O)[Fe3(OH)6(SO4)2] or coordination modes: {RCOO-Fe(L4)-OOCR}1+, {R-CO2=Fe(X2)=O2C-R}n, {R-COO-Fe(X4)-OOC-R}n, and {(-NCH2CH2N-)= Fe(X2) =(-NCH2CH2N-)}, where X= H2O, OH-, SO42-., n= from 3- to 1+ in the ion-exchange resins (KU-2, AN-31, AV-17, Varian – AD, EDE-10P) after the contact with sulphate of iron(III) solutions at different conditions: type of solvent, temperature, air atmosphere. In special conditions the ultrafine superparamagnetic particles of Fe2O3 have been obtaine

SYNTHESIS AND CHARACTERIZATION OF CdSe COLLOIDAL QUANTUM DOTS IN ORGANIC SOLVENT

In this paper we present experimental results on preparation and characterization of colloidal CdSe quantum dots in organic solvent. CdSe QDs were synthesized following a modified literature method. CdSe QDs were isolated by adding acetone to the cooled solution followed by centrifugation. CdSe QDs have been characterized by UV-Vis absorption and photoluminescent (PL) spectroscopy. The average CdSe particles size estimated from the UV-Vis absorption spectra was found to be in the range 2.28-2.92 nm which is in good agreement with PL measurements

2,6-Bis(bromomethyl)pyridine

In the title molecule, C7H7Br2N, the C—Br vectors of the bromomethyl groups extend to opposite sides of the pyridine ring and are oriented nearly perpendicular to its plane. In the crystal, the molecules related by a c-glide-plane operation are arranged into stacks along the c axis, with centroid–centroid distances between neighboring aromatic rings of 3.778 (2) Å. A short Br...Br contact of 3.6025 (11) Å is observed within a pair of inversion-related molecules

CRYSTAL STRUCTURE OF {[La2(CNCH2COO)6(H2O)4]H2O}n COMPLEX

The lanthanum(III) cyanoacetate complex of formula {[La2(CNCH2COO)6 (H2O)4]∙H2O}n (1), has been prepared and characterized by X-ray diffraction analysis. Compound crystallizes in the triclinic centrosymmetric space group P-1 (No.2), a=8.997(5) Å, b=9.251(5) Å, c=9.728(5) Å, α=67.849(5)°, β=84.224(5)°, γ=81.351(5)°. Single-crystal X-ray diffraction study reveals that crystals of 1 exhibits one-dimensional coordination polymer structure, which is composed of cyanoacetate bridged lanthanum(III) ions. The O9 coordination surrounding of La cation is completed by oxygen atoms of six carboxylate ligands that are coordinated in the bidentate bridging and tridentate-chelating bridging mode and two water molecules. The cations are bridged in a polymeric chain by four exo-bidentate cyanoacetate ligands or through µ2-O function of two other chelato-bridgind cyanoacetate ligands. The La∙∙∙La separation along the polymer is equal to 4.754(3) Å and 4.608(2) Å

MIXED-LIGANDS μ3-OXO TRINUCLEAR CARBOXYLATES [Fe3O(CH2BrCOO)1.5(CH2ClCOO)4.5(H2O)3]Br0.75Cl0.25 5H2O and [Fe3O(BrCH2COO)6(H2O)3] NO3⋅2.63H2O

Two novel μ3-oxo-centered carboxylate-bridged triiron complexes [Fe3O(BrCH2COO)6(H2O)3] NO3·2.63H2O (1) and [Fe3O(CH2BrCOO)1.5(CH2ClCOO)4.5(H2O)3]Br0.75Cl0.25 5H2O (2) were synthesized and their structures were characterized by X-ray crystallography. The opportunity of mixed-ligand complex formation in iron(III)-bromoacetic acid system was shown. The first co-ordination sphere of the iron atom in compound 2 includes two different carboxylate anions, CH2BrCOO- and CH2ClCOO- in the capacity of syn-syn- bidentate-bridged ligands, while Br- and Cl- anions being in the ratio 1:1, formulate the external sphere of the complex. The IR spectra, thermic analysis and magnetic properties of complexes were studied

Goethite nanorods as a cheap and effective filler for siloxane nanocomposite elastomers

Iron oxide (goethite) with a nanorod morphology was prepared by a chemical precipitation method and characterized by FTIR, EDX, TEM, WAXD. This was used as an active filler to prepare dielectric elastomer nanocomposites by its incorporation, besides silica, in a silicone matrix consisting in a high molecular weight polydimethylsiloxane-α,ω-diol (PDMS). The nanocomposites were processed as films, stabilized by peroxidic crosslinking at high temperature, and their properties of interest for potential use in the structure of electromechanical devices were studied. It is for the first time that such composites, based on PDMS and iron oxide in a well-defined type (goethite) and shape (nanorods) are approached from the perspective of dielectric elastomers. The introduction of iron oxide nanoparticles into the polymer matrix resulted in improvements in both mechanical and dielectric properties. Thus the breaking strain and the dielectric constant values increased in comparison with those of the pure polymer sample, while the dielectric loss preserved low values specific for dielectrics