Synthesis and characterization of two binuclear iron(III) complexes of aminoethanol derivatives of aminophenol as models for non-heme iron enzymes active sites

Two aminoethanol derivatives of aminophenol ligands were synthesized and characterized by IR and ¹H NMR spectroscopies. The binuclear iron(III) complexes of these ligands have been prepared and characterized by IR, ¹H NMR and UV-Vis spectroscopic techniques, cyclic voltammetry, single crystal X-ray diffraction and magnetic susceptibility studies. X-ray analysis revealed binuclear complexes, Fe₂(L₂), in which Fe(III) centers are surrounded by two phenolate and hydroxyl oxygen atoms, and amine nitrogens of the ligands. The metal active sites of both complexes are held together by the two above mentioned hydroxyl bridges. Variable temperature magnetic susceptibility indicates antiferromagnetic coupling between the iron centers of both complexes. This exchange coupling is stronger for Fe₂(L^ae)₂, such that it shows a room temperature strong coupling between the two iron centers. The investigated complexes undergo irreversible electrochemical oxidation and reduction.     

Ni(II) and V(IV) Schiff base complexes derived from 2,2′-dimethylpropandiamine: the crystal structure,electrochemical properties and catalytic activities in oxidation of sulfides

Tetradentate Schiff base (H₂L) derived from 2,2′-dimethylpropandiamine and its nickel(II) and oxo-vanadium(IV) complexes (NiL, VOL) have been prepared and characterized. The crystal structure of NiL has been determined. The reported structure contains two molecules of the complex revealing slightly different conformation and the coordination sphere around nickel is distorted square planar. The electrochemical properties of the Ni and oxo-vanadium Schiff base complexes were investigated in CH₃CN by cyclic voltammetry. The catalytic activities of the complexes were studied in the oxidation of sulfides in ethanol. Under the optimized reaction conditions, in the presence of NiL, 89% and VOL, 100% conversion of methyl phenyl sulfide with 100% selectivity for sulfoxide were obtained.     

New chiral selenium electrophiles derived from functionalized terpenes

A convenient method for the synthesis of optically active dialkyl diselenides derived from bicyclic terpenes functionalized with hydroxy, etheral, sulfide, and selenide groups is described. The diselenides were used for a synthesis of chiral electrophilic selenium reagents, then in the asymmetric selenenylation of styrene and selenocyclization with o-allylphenol. The influence of nonbonding selenium-heteroatom interactions in the generated organoselenium electrophiles on the stereoselectivity of an addition reaction has been investigated. Calculations by a DFT method on a B3LYP (6-311G (d)) level, confirmed the existence of nonbonded selenium-heteroatom interactions in the investigated systems.     

Some theorems and tables for spin waves in thin films

In this paper some theorems are given concerning spin waves in thin films represented by an infinite plate cut out from an infinite perfect crystal in some crystallographic direction. Furthermore, some numerical results are presented containing tables of the eigenvalues of the energy and spin wave amplitudes for films of the type Fe(111).On leave from theDepartment of Theoretical Physics, University of ód, Poland.Our thanks are due to Professor Dr. V. Pleskot, head of the Laboratory of Mathematics of the Czech Technical University in Prague, and to his co-workers, who enabled us to carry out the numerical calculations in the Laboratory of Mathematics.     

Chiral terpene auxiliaries. Part 1: Highly enantioselective reduction of ketones with borane catalyzed by an oxazaborolidine derived from (−)-β-pinene

(1R,2S,3R,5R)-3-Amino-6,6-dimethyl-2-hydroxybicyclo[3.1.1]heptane was synthesized in three steps from (−)-β-pinene. It was used for the in situ generation of a B-methoxy-oxazaborolidine catalyst for the asymmetric reduction of alkyl-aryl ketones with borane-dimethyl sulfide complex. In the presence of 3 mol % of the catalyst, the product alcohols were obtained in high yields and with enantiomeric excesses in the range of 93-98%.     

Surface melting description

The surface melting is regarded in terms of the order parameter profiles which characterise phases extended inside a whole sample. The characterisation of the phase is, however, due to the order parameter behavior at the surface. The phase really observed is predicted by means of the thermodynamic conditions; thus, the surface melting phase is in competition to the softening modes at the surface. The presented idea is based on the discussion concerning the possible results of the leading theories, a modified van der Waals approach and an Ising type model for pseudospins. The experimental evidence is reviewed and interpreted.     

Study of the thermal behaviour of copolymers of styrene with magnesium,calcium, strontium and barium acrylates

The processes of thermal destruction of copolymers of styrene with magnesium, calcium, strontium and barium acrylates have been investigated by TG and the temperature characteristics have been determined. Though the thermal stability of the metal acrylates exceeds markedly that of polystyrene, the introduction of low concentrations of the salts caused an observable deterioration of the thermal resistance of the copolymers. This was in agreement with the calculated values of the kinetic parameters of decomposition for the samples studied.

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Zusammenfassung Mittels TG wurde der thermische Abbauvorgang von Kopolymeren aus Styrol und Magnesium-, Calcium-, Strontium- und Bariumacrylaten untersucht und eine Temperaturcharakteristik erstellt. Obwohl die thermische Stabilität der Metallacrylate die von Polystyrol eindeutig übertrifft, führt die Einführung dieser Salze in geringer Konzentration zu einer merklichen Verschlechterung der Hitzebeständigkeit der Kopolymere. Diese Feststellung stimmt mit den für die Zersetzung der untersuchten Proben berechneten kinetischen Parametern überein.