Synthesis and Structure of Complexes Formed in the CuCl2–Cu–N-allylquinolinium Chloride System

The crystals of [C₉H₇N(C₃H₅)]₂Cu^IICl₄(IV) were obtained through ac electrochemical synthesis using CuCl₂· 2H₂O, N-allylquinolinium chloride, and copper electrodes in an ethanol-benzene medium. These crystals transformed with time into crystals of the [C₉H₇N(C₃H₅)][Cu^IICl₃(C₉H₇N)] complex (V). When tin(II) chloride was added to the initial reagents, the [C₉H₇N(C₃H₅)]Cu^I ₂Cl₃complex (VI) was obtained. The X-ray diffraction analysis (DARCh-1 autodiffractometer, MoK radiation, Zr filter) indicated that complexes IVand Vcrystallize in the triclinic system: space group P ; for IV, a= 12.817(4), b= 10.435(3), c= 9.606(3) Å, = 97.94(2)°, = 107.28(2)°, = 95.99(2)°, V= 1200.6(6) ų, Z= 2; for V, a= 16.992(5), b= 8.243(2), c= 7.345(3) Å, = 91.89(3)°, = 91.19(3)°, = 88.18(3)°, V= 1027.5(6) ų, Z= 2. Crystals VIare monoclinic, space group P2₁/n, a= 13.578(5), b= 15.079(4), c= 6.953(4) Å, = 105.08(4)°, V= 1370.6(10) ų, Z= 4. Structures IV–VIconsist of N-allylquinolinium cations and different anions: isolated [CuCl₄]^2–tetrahedrons (IV), [C₉H₇NCuCl₃]^–tetrahedrons (V) containing a quinoline molecule, and a polymer chain |[Cu^I ₄Cl₆]^2–} _n (VI) in which two independent metal atoms have trigonal-pyramidal and planar-trigonal environments. The C=C bond of the allyl group is not involved in cooordination with the Cu(I) atom.     

ESR of Gd<Superscript>3+</Superscript> ions in potassium yttrium tungstate

The software in MATHLAB medium has been developed to model ESR spectra of paramagnetic centers in single crystals. By means of this program, the angular dependences of ESR spectra found in KY(WO₄)₂, potassium yttrium tungstate, doped with gadolinium were analyzed. The spectra analysis indicates that they are determined by the presence of Gd³⁺ ions with the electron spin S = 7/2 occupying the structural position of Y³⁺ ions in the crystal structure. Parameters of spin Hamiltonian were defined for the analyzed ESR spectrum of Gd³⁺. Unusual features of the analyzed ESR spectra have been discovered in the region of 9.5 GHz which remind by appearance SHF line. The researches made show the position of this line to correspond to the region of quasi-intersection of energetic levels, and along with the line shape it is most likely to reflect the peculiarities of the region in whose interval wave functions of the energetic levels undergo substantial modifications.     

Effect of Continuous and Discontinuous Microwave-Assisted Heating on Starch-Derived Dietary Fiber Production

Dietary fiber can be obtained by dextrinization, which occurs while heating starch in the presence of acids. During dextrinization, depolymerization, transglycosylation, and repolymerization occur, leading to structural changes responsible for increasing resistance to starch enzymatic digestion. The conventional dextrinization time can be decreased by using microwave-assisted heating. The main objective of this study was to obtain dietary fiber from acidified potato starch using continuous and discontinuous microwave-assisted heating and to investigate the structure and physicochemical properties of the resulting dextrins. Dextrins were characterized by water solubility, dextrose equivalent, and color parameters (L* a* b*). Total dietary fiber content was measured according to the AOAC 2009.01 method. Structural and morphological changes were determined by means of SEM, XRD, DSC, and GC-MS analyses. Microwave-assisted dextrinization of potato starch led to light yellow to brownish products with increased solubility in water and diminished crystallinity and gelatinization enthalpy. Dextrinization products contained glycosidic linkages and branched residues not present in native starch, indicative of its conversion into dietary fiber. Thus, microwave-assisted heating can induce structural changes in potato starch, originating products with a high level of dietary fiber content.     

Indirect determination of formaldehyde by alternating-current voltammetry at a hanging mercury drop in the presence of oxygen

An alternating-current voltammetric procedure has been developed for the indirect determination of formaldehyde as its hydrazone at a stationary hanging mercury drop over the formaldehyde concentration range from 0.2 to 15 mg/L in a buffer solution of pH 5.6 ± 0.4 without removing dissolved oxygen. An EKOTEST-VA miniature voltammetric analyzer connected to a computer was used. The detection limit for formaldehyde in the proposed procedure was 0.2 mg/L.     

Structure of the homodimer of uridine phosphorylase from <Emphasis Type="Italic">Salmonella typhimurium</Emphasis> in the native state at 1.9 Å resolution

Uridine phosphorylase (UPh) belongs to pyrimidine nucleoside phosphorylases. This enzyme catalyzes cleavage of the C-N glycoside bond in uridine to form uracil and ribose-1’-phosphate. Uridine phosphorylase supplies cells with nucleotide precursors by catalyzing the phosphorolysis of purine and pyrimidine nucleosides. This is an alternative to de novo nucleotide synthesis. The three-dimensional structure of native uridine phosphorylase from Salmonella typhimurium (StUPh) in a new crystal form was solved and refined at 1.90 Å resolution (R _st = 20.37%; R _free = 24.69%; the rmsd of bond lengths and bond angles are 0.009 Å and 1.223°, respectively). A homodimer containing two asynchronously functioning active sites was demonstrated to be the minimum structural unit necessary for function of the hexameric StUPh molecule (L ₃3L ₂). Each active site is formed by amino acid residues of both subunits.     

Selective Formation of Products of Interrupted Feist-Benary Reaction under the Conditions of Hantzsch Pyrrole Synthesis

Russian Journal of Organic Chemistry - Reaction of 3-aryl-2-chloropropanal with 1-arylsulfonylpropan-2-ones in aqueous ammonia and alcohol under the conditions of Hantzsch pyrrole synthesis led to...     

Near Infrared LED Based on PbS Nanocrystals

Optics and Spectroscopy - The principle of operation of near-infrared LEDs based on PbS nanocrystals and aspects of their development are considered. The aging of nanocrystals with different ligand...