11-Aryl-3,3-dimethyl-7- and 7,8-Substituted 1,2,3,4,10,11-Hexahydro-5H-dibenzo[b,e]-1,4-diazepin-1-ones

In reactions of 3-(5- and 5,6-substituted 2-aminophenylamino)-5,5-dimethylcyclohex-2-en-ones with carbaldehydes of pyridine, thiophene, and furan and substituted benzaldehydes, we have obtained 21 novel 7H-7-methoxycarbonyl-, 7-benzoyl-, 7-trifluoromethyl-, 7-nitro- and 7,8-dichloro-11-aryl-3,3-dimethyl-1,2,3,4,10,11-hexahydro-5H-dibenzo[b,e]-1,4-diazepin-1-one.     

Synthesis and characterization of Mn-, La-Mn- and La-Ca-Mn-citrates as precursors for LaMnO<Subscript>3</Subscript> and La<Subscript>1−x</Subscript>Ca<Subscript>x</Subscript>MnO<Subscript>3</Subscript>

Mn-, LaMn- and LaCaMn-citrates were synthesized at 60–120°C in ethylene glycol medium using chlorides or nitrates as metal sources. Their composition, IR spectra and thermal decomposition were studied. Equimolar La/Mn ratio has been established in the complex, prepared from chloride solution with the same initial composition of the metals. In the isolated three-metallic complex the molar ratio of the metals deviates from the composition in the initial solution. The final products of the heating of Mn- and mixed-metal LaMn-citrates at 1000°C are phase-homogeneous Mn₃O₄ (hausmannite) and LaMnO₃ respectively. Parasitic phase(s) are observed in La_xCa_1−xMn_yO₃, produced from LaCaMn-citrate.     

Intramolecular Dynamics and Molecular Structure of Europium(III) Chelate Complexes with Crown Ethers as Studied by NMR Spectroscopy

Earlier the intramolecular inversion of the 18-crown-6 molecules was found in the complex ion pairs [Ln(ptfa)₂ (18-crown-6)]⁺ [Ln(ptfa)₄]⁻ (H₂O)₄ where Ln = La(1), Ce (2), Pr (3), Nd (4), and ptfa is 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione. In this work the peculiarities of the molecular structure and dynamics were studied for [Eu(ptfa)₂ (18-crown-6)]⁺ [Eu(ptfa)₄]⁻ (H₂O)₄ (5) by NMR spectroscopy techniques. Through VT-NMR spectra analysis the temperature dependence was obtained for the rate constant. The free energy ΔG^‡(320) of 18-crown-6 ring inversion activation was found to be 65 ± 5 kJ mol⁻¹ for 5 in CDCl₃. This result is comparable with the earlier data [S.P. Babailov and D.A. Mainichev: J. Inclusion Phenom. Macrocyclic Chem. 43, 187–193 (2002)] for complexes 2, 3, 4 in deuterated toluene (ΔG^‡(320)=65 ± 9, 64 ± 9, 64 ± 9 kJ mol⁻¹ respectively). It was found by relaxation NMR spectroscopy that the effective distance between Ln and protons of the crown molecule is 4.5 ± 0.2 Å. The analysis of structural parameters testifies that the crown ether and chelated anions are in the first coordination sphere of a Ln cation. Obtained geometrical parameters show that the complex cations of Eu, Ce and Pr have similar spatial structures.This revised version was published online in July 2005 with a corrected issue number.     

Chitosan-dextran branched copolymers: Synthesis and properties

Chitosan-dextran branched copolymers have been synthesized, and the rheological properties of their aqueous acetic acid solutions have been studied. On the basis of the data of FTIR spectroscopy, the formation of chemical bonds between chitosan and dextran at the nitrogen atom has been confirmed. With the use of dynamic mechanical analysis and differential scanning calorimetry, the temperatures of relaxation transitions in the resulting branched copolymers have been determined. It is shown that, along with the formation of a branched copolymer, the chemical crosslinking of chitosan macrochains can occur. Mechanical properties of films formed from solutions of the obtained polymers have been studied.     

Molecular structure and barriers to internal rotation of α-naphthalenesulfonyl chloride: a study by gas-phase electron diffraction and quantum chemical calculations

α-Naphthalenesulfonyl chloride, α-NaphSC, was studied by gas-phase electron diffraction (GED) and quantum chemical calculations (HF/6-311 + G**, HF/aug-cc-pVDZ, B3LYP/cc-pVDZ, B3LYP/cc-pVTZ, B3LYP/aug-cc-pVDZ, B3LYP/aug-cc-pVTZ, MP2/cc-pVDZ, and MP2/cc-pVTZ). The calculations predict the existence of two conformers with C ₁ (I) and C _s (II) symmetries. The most stable conformer I has an enantiomer. The experimental data of α-NaphSC obtained at 370(5) K could be best fitted by a C ₁ symmetry model indicating that only this form exists in the gas-phase. In this model the C_α–S–Cl plane deviates from the perpendicular orientation relative to the plane of the naphthalene skeleton. Under the applied experimental conditions, the mole fraction of a second less stable conformer II of α-NaphSC predicted by calculations is no more than 1 %. The following geometrical parameters of conformer I were obtained from the experiment (Å and °; uncertainties are in parentheses): r _h1(C–H) = 1.082(6), r _h1(C–C)_cp = 1.407(3), r _h1(C–S) = 1.764(5), r _h1(S–O)_av = 1.425(3), r _h1(S–Cl) = 2.051(5), ∠C–C_α–C = 122.5(1), ∠C_α–S–Cl = 101.5(10); C9–C1–S–Cl = 71.4(21). The calculated barriers to internal rotation of the sulfonyl chloride group exceed considerably the thermal energy values corresponding to the temperatures of the GED experiments. Natural bond orbitals analysis of the electron density distribution was carried out to explain the peculiarities of the molecular structure of the studied compound and the deviation from the structures of β-NaphSHal molecules and their benzene analogs.     

Reactions of 4-oxobenz[1,3-e]oxazinium perchlorates with α-aminoazoles

Reactions of 4-oxo benz[1,3-e]oxazinium perchlorates with 1-R¹-3-R²-5-aminopyrazoles lead to the formation of derivatives of pyrazolo[3,4-d]pyrimidine and pyrazolo[1,5-a]1,3,5]triazine series, and with 3-amino-1,2,4-triazole, to [1,2,4]triazolo[1,5-a][1,3,5]triazines.     

Analysis of Cadmium and Cadmium Oxide by Inductively Coupled Plasma Atomic Emission Spectrometry

A procedure of the multielement analysis of cadmium and cadmium oxide by inductively coupled plasma atomic emission spectrometry is proposed. The effect of the concentration of the matrix component on the analytical signals of impurity elements is studied and the analytical lines of the analytes are chosen. For the chosen concentration of the matrix component, the optimum conditions of analysis are selected, i.e., power delivered to the plasma and the flow rate of sputtering argon gas. The accuracy of the developed procedure, ensuring the determination of up to 41 impurity elements with limits of detection in the range from n × 10^–7 to n × 10^–4 wt %, is estimated.     

Enhanced Physical and Mechanical Properties of Nitrile-Butadiene Rubber Composites with N-Cetylpyridinium Bromide-Carbon Black

The physical and mechanical properties of nitrile–butadiene rubber (NBR) composites with N-cetylpyridinium bromide-carbon black (CPB-CB) were investigated. Addition of 5 parts per hundred rubber (phr) of CPB-CB into NBR improved the tensile strength by 124%, vulcanization rate by 41%, shore hardness by 15%, and decreased the volumetric wear by 7% compared to those of the base rubber-CB composite.     

4,5-Dihydropyrazolo[3,4-f]quinazolines

By reaction of 6-dimethylamino-5-oxo-2-phenyl-5,6,7,8-tetrahydroquinazoline with hydrazine, phenylhydrazine, 4-bromo-, 4-chlorophenylhydrazines, and also reaction of 6-dimethylaminomethylene-5-oxo-2-(4-pyridyl)-5,6,7,8-tetrahydroquinazoline with hydrazine, 4-methoxy- and 2-carboxyphenylhydrazines, we have obtained the corresponding 7-phenyl(4-pyridyl)-substituted 1H(2H)- or 1-aryl-4,5-dihydropyrazolo[3,4-f]quinazolines. Methylation of 7-phenyl-4,5-dihydro-1(2H)-pyrazolo[3,4-f]quinazoline by methyl iodide led to its 2-methyl derivative.     

Dehydration of Organic Solvents by Evaporation through Membranes Based on Polyelectrolytic Complexes

Evaporation of binary aqueous-organic mixtures through composite membranes with coatings based on polyelectrolytic complexes including different combinations of polyelectrolytic polycations and polyanions was studied. The possibility of efficient dehydration of organic solvents by their pervaporation was demonstrated.