Anion recognition through hydrogen bonding by adamantane-dipyrromethane receptors

Adamantane-dipyrromethane (AdD) receptors [di(pyrrole-2-yl)methyladamantane (1), 2,2-di(pyrrole-2-yl)adamantane (2), 1,3-bis[di(pyrrole-2-yl)methyl]adamantane (3), 2,2,6,6-tetra(pyrrole-2-yl)adamantane (4)] form complexes with F⁻, Cl⁻, Br⁻, AcO⁻, NO₃⁻, HSO₄⁻, and H₂PO₄⁻. The association constants of the complexes were determined by ¹H NMR titrations, whereas the geometries of complexes 1·F⁻ (2:1), 2·F⁻ (2:1), 2·Cl⁻ (2:1), 2·AcO⁻ (2:1), and 4·F⁻ (1:1) were determined by X-ray structural analysis. The most stable complexes are of 2:1 stoichiometry with F⁻ and AcO⁻. The stability constants are in accordance with the anion basicity and the ability of AdD receptors to place the hydrogen bonding donor groups in a tetrahedral fashion around anions. The binding energies of the complexes between receptors 1-4 and F⁻ anion are calculated using quantum chemical methods. The calculated results show that the solvent polarity is important for the complexation of fluoride ion with AdD receptors 1-4.     

Crystallization Behavior of Alkoxy-Derived Cordierite Gels

Alkoxy-derived cordierite gels were synthesized from tetraethylorthosilicate (TEOS), aluminum isopropoxide (Al(OPr ⁱ )₃), and magnesium ethoxide (Mg(OEt)₂). TEOS was partially hydrolyzed at molar ratios H₂O/TEOS = 1.2, in the presence of hydrochloric acid as a catalyst, HCl/TEOS = 0.1. Aluminum and magnesium alkoxides were added successively or as a double alkoxide. Phase transformations occurring in the gel were studied by differential thermal analysis, x-ray diffractometry, and Fourier-transform infrared spectroscopy. In all cases, -cordierite crystallized at similar temperatures (950–1000°C) with small amounts of spinel, which confirms dominant influence of the optimal conditions for partial hydrolysis of TEOS on the gels homogeneity. The transformation of - into -cordierite began at about 1100°C. Broadening of diffraction peaks and appearance of new bands in the FT IR spectra confirmed the transformation of - into modulated -cordierite at temperatures above 1300°C. Differential thermal analysis under nonisothermal conditions also proved homogeneous nucleation with constant rate and three-dimensional crystallite growth during -cordierite crystallization. The overall activation energy of the crystallization of -cordierite is 580 ± 81 kJ/mol.     

Stark width and shift of singly-ionized tin spectral lines

Stark widths and shifts of six singly-ionized tin spectral lines have been measured in a pulsed linear arc plasma in SF₆, at 33000 K electron temperature and 0.96 × 10²³ m^?3 electron density, and compared with existing experimental results.     

Fluoridbestimrnung in Wasser und Luft mit ionenselektiven Elektroden

Zusammenfassung Systematische Bestimmungen des Fluoridgehaltes in verschiedenen Wasserproben aus Serbien und in Luftproben aus einigen In-dustriegebieten und aus der Stadt Belgrad wurden durchgeführt. Außerdem wurde der Fluoridgehalt in einigen meistkonsumierten Mineralwässern aus alien Territorien Jugoslawiens geprüft. Etwa 600 Proben wurden analysiert. Die Ergebnisse sollen für die kartographische Erfassung der Verteilung von Fluor im Trinkwasser dienen.

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Determination of fluoride in Yugoslavian air and water with an ion-sensitive electrode

Summary Fluoride has been measured in over 600 samples of air and water with an ion-sensitive electrode. The concentrations found in the air samples were 1.6–l08g/m³ for industrial areas, 1.9–25.6g/m³ for urban areas and 1.1–18.4g/m³ for rural areas. Most of the samples had fluoride levels below 20g/m³3. The concentrations found in water samples were 0.12–0.34g/litre for drinking water and 0.27–5.6g/litre, for mineral waters.

     

Conformational study of Co(II), Ni(II), and Cr(III) complexes of the edta-type: Crystal structure of 1D polymeric trans(O)-Ba[Co(1,3-pddadp)] · 8H2O complex stabilized by infinite water tapes

The trans(O⁶) isomer of the Ba[Co(1,3-pddadp)] · 8H₂O complex (where 1,3-pddadp represents hexadentate 1,3-propanediamine-N,N′-diacetate-N,N′-di-3-propionate ion) has been prepared and characterized by X-ray crystallography. In the crystal structure the complex cations and anions are bridged by carboxylate oxygen atoms from the in-plane coordinated glycinate rings (G-rings) of [Co(1,3-pddadp)]²⁻ and by the barium-coordinated water molecules, thus forming 1D polymeric chains, separated by infinite water tapes hydrogen bonded to the [Co(1,3-pddadp)]²⁻ carboxylate oxygens from the out-of-plane β-alaninate rings (R-rings). Conformational analysis of the three possible geometrical isomers: trans(O⁵), trans(O⁵O⁶), and trans(O⁶) of the [Co(1,3-pddadp)]²⁻ complex, with ligand acting as hexadentate, as well as of the corresponding complexes of Ni(II) and Cr(III) has been performed using the consistent force field (CFF) method, with the parameters developed previously for edta-type complexes of chromium(III) and supplemented with new parameters for cobalt(II) and nickel(II). The energy-minimized structure of the trans(O⁵O⁶) isomer represents the global minimum for the [M(1,3-pddadp)]ⁿ⁻ (M = Co(II), Ni(II), and Cr(III)) species. The occurrence of the least energetically favored trans(O⁶) isomer in a crystal and the exceptional conformation of the axially oriented β-alaninate rings can be accounted for by the stabilizing role of the infinite tapes of planar cyclic water pentamers and hexamers which act as a “glue” to reinforce the coordination polymeric chains.     

Effects of acute gamma-irradiation on extracellular adenine nucleotide hydrolysis in developing rat brain

Cell membrane is highly sensitive to irradiation which, acting directly or indirectly, may disturb functions of constitutive proteins including membrane enzymes. Plasma membrane surface-located enzyme chain of ecto-nucleotide triphospho diphosphohydrolases (NTPDases) and 5′-nucleotidase are involved in termination of cell purinergic signalization by hydrolyzing extracellular, excitatory adenosine triphosphate (ATP), as well as nucleotide di-, and mono-phosphate (ADP and AMP) to neuroprotective adenosine. Extracellular ATP, ADP, and AMP hydrolyzes were examined in purified synaptic plasma membranes after whole-body acute irradiation. All measurements were done 24 h after irradiation of developing (15-, 30-day-old) and adult (90-day-old) rats with low (50 cGy) and high (2 Gy) dose of gamma-rays. Both, high and low doses inhibited nucleotide hydrolyses in 15-day-old rats; in 30-day-old rats low dose of radiation inhibited ADP and AMP hydrolyses while high dose inhibited only ATP hydrolyse. In adult rats high dose induced no effects, while low dose stimulated nucleotides hydrolyses. According to obtained results it was concluded that ecto-nucleotidases of young rats are more sensitive to irradiation, since even low dose induces inhibition of ecto-nucleotidases activities. Ionizing radiation, by decreasing brain nucleotide hydrolyses in developing rats, induces accumulation of ATP and decreases production of adenosine in synaptic cleft which could be neurocytotoxic. On the contrary, in adult rats low dose of radiation stimulates NTPDase and 5′-nucleotidase activity and protective adenosine production which indicates protective and adaptive mechanisms developed in adult brain neuronal cells. The article is published in the original.     

Sub- and super-equivalence method of isotope dilution analysis. Determination of strontium

Sub- and super-equivalence method of isotope dilution analysis /variant CCV/ was applied for the determination of trace of strontium in radioactive solutions in the presence of about 1000-times larger amount of calcium. DC-18-C-6 crown ether was used as a selective reagent. Picrate anion was chosen as a complementary ion.     

Critical behaviour of Mn1.11Al0.89 alloys

The diffraction maxima (001) and (100) of the Mn_1.11Al_0.89 alloy have been measured by the neutron powder diffraction method in the temperature range from 23 to 427 C. The Curie temperature is found to be (404 ±2)°C. Temperature dependence of the magnetic structure factor gave the critical exponent β = 0.31±0.02.The disorder parameter has been found to decrease with the temperature. A convenient expression describing this behaviour has been proposed and discussed.