Determination of gallium in biological fluids using inductively coupled plasma mass spectrometry

A procedure for the determination of gallium in biological fluids by inductively coupled plasma mass spectrometry was developed. The detection limits of gallium calculated from the 3s value were 60 ng/L for urine, 32 ng/L for a model solution of intestinal juice, and 50 ng/L for serum. The accuracy of the procedure was tested using a standard addition method. The nature of a background signal on the masses of gallium isotopes was studied with the use of a high-resolution mass spectrometer, and the background concentration of gallium in biological fluids was evaluated (5–7 ng/L). It was found that a background level in measurements performed on a quadrupole mass spectrometer depends on the interfering influence of polyatomic ions with close m/z ratios rather than on the background concentration of gallium. The procedure makes it possible to study the stability of pharmaceutical preparations based on gallium in biological media, their metabolism, and the excretion of preparations from the body.     

Synthesis, structure, and properties of nitronyl nitroxyl tetraradical with calix[4]arene framework

A reaction of calix[4]arene tetraaldehyde with 2,3-bis(hydroxyamino)-2,3-dimethylbutane in DMF resulted in the corresponding 1,3-dihydroxyimidazolidine tetraadduct, whose oxidation gave a calix[4]arene (1,3-alternate) bearing four nitronyl nitroxyl-containing substituents at the upper rim.     

Influence of a doubly charged cation nature on the formation and properties of mixed oxides MAlO x (M = Mg2+, Zn2+, Ni2+) obtained from the layered hydroxide precursors

Influence of the nature of a doubly charged cation in the layered double hydroxides (LDH) on the conditions of formation and properties of mixed oxide phase MAlO _x (M = Mg²⁺, Zn²⁺ and Ni²⁺), its ability to reconstruct the structure of the original precursor under contact with water has been studied. Hydrotalcite-like compounds and corresponding oxides with different M²⁺: M³⁺ ratio were investigated by XRD, TEM, TG-DTG-DTA, ²⁷Al NMR, N₂ adsorption, and differentiating dissolution. It has been found that the nature of the cation M²⁺ influences the conditions of LDH thermal decomposition, structural and textural characteristics of the formed mixed oxides. The obtained data can be used to synthesize the oxide supports with desired acid-base and adsorption properties.     

1,1,2,2-Tetramethyl-3-trimethylsilyl-1,2-disilacyclobutane: synthesis and spontaneous polymerization

Gas-phase dehalogenation of 1,2-bis[chloro(dimethyl)silyl]-2-trimethylsilylethane with alkali metals gave 1,1,2,2-tetramethyl-3-trimethylsilyl-1,2-disilacyclobutane (3). Its spontaneous ring-opening polymerization at room temperature afforded an amorphous linear polymer with T _g = ?8.9°C, M _w = 3.47·10⁵–3.85·10⁵, and M _w /M _n = 2.43—2.86. According to spectroscopic data (IR and ¹H, ¹³C, and ²⁹Si NMR), the backbone of the polymer consists of alternating monomer units joined in the “head-to-tail” ([Me₂SiCH(SiMe₃)CH₂SiMe₂SiMe₂CH-(SiMe₃)CH₂SiMe₂]) and “head-to-head” ways ([Me₂SiCH₂CH(SiMe₃)SiMe₂SiMe₂CH-(SiMe₃)CH₂SiMe₂]).     

Cyclic peroxides and related initiating systems for radical polymerization of methyl methacrylate

Cyclic peroxides as initiators for the radical polymerization of methyl methacrylate were proposed. The initial rates, initiation rates, and effective activation energies of polymerization initiated by cyclic peroxides and cyclic peroxide-1-pyridyl-2-ferrocene systems were determined. The radical yields to the volume upon the thermal decomposition of cyclic peroxides and their catalytic decomposition in the presence of 1-pyridyl-2-ferrocene were determined. In combination with 1-pyridyl-2-ferrocene cyclic peroxides form efficient initiating systems favoring an increase in the polymerization rate, a decrease in the molecular weights, and an increase in syndiotacticity of the synthesized poly(methyl methacrylate).     

Structures of branched oligophenylenes studied by NMR spectroscopy

A series of model cyclotrimers was studied by NMR spectroscopy using 2D COSY, HSQC, and HMBC correlations to establish the structures of branched oligophenylenes, whose branching center is the 1,3,5-triphenyl-substituted benzene ring.     

Fluorinated 2-amino-5-phenyl-1,3,4-thiadiazines: synthesis and structures

Fluorinated 2-amino-5-phenyl-1,3,4-thiadiazines were obtained for the first time. A study of their tautomeric structures revealed that trifluoromethyl-containing 1,3,4-thiadiazines exist as the 4H-tautomer in both solutions and the solid state, while their monofluoroaryl analogs exist as the 6H-tautomer.     

Crystal structures of pyridinemonocarboxylic acid peroxosolvates

The crystal structures of new peroxosolvates of the following pyridinemonocarboxylic acids were studied: picolinic 2-C₅H₄NCOOH·H₂O₂ (1), nicotinic 3-C₅H₄NCOOH·H₂O₂ (2), and isonicotinic 4-C₅H₄NCOOH·2H₂O₂ (3). In these compounds, the acids exist exclusively as zwitterions, as opposed to non-solvated crystals. In compounds 1–3, the hydrogen peroxide molecules form two donor hydrogen bonds and, in some cases, one additional acceptor hydrogen bond. Peroxosolvate 2 can be considered as a novel drug formulation of vitamin B₃.     

Synthesis and structure of 2,2′-diaminodiphenylditelluride bis-imines

Bis-imines of 2,2′-diaminodiphenylditelluride and 2-tosylamino (9a) and 2-hydroxybenzaldehyde (9b) were prepared and studied by X-ray diffraction, heteronuclear (¹H, ¹³C, ¹⁵N, and ¹²⁵Te) magnetic resonance, and quantum chemical calculations (Pbe1pbe/DGDZVP). According to the X-ray diffraction data, compound 9b in the crystal phase has nonsymmetrical structure: one of the tellurium atoms forms hypervalent bonding with the adjacent oxygen atom, while the second one is not involved in such interaction. The NMR study showed the symmetric molecular structure of imines 9a,b in DMSO-d₆ with the tellurium atoms interacting hypervalently with the C=N nitrogen atoms.