Chemistry Journal of Moldova. General, Industrial and Ecological Chemistry

17-35

Authors: Boris Tsukerblat, Alex Tarantul, Achim Müller

In this paper we give a short overview of our efforts in the understanding of the magnetic properties of the fascinating nanoscopic cluster K6[VIV 15As6O42(H2O)]·8H2O (hereafter V15) exhibiting layers of magnetization. We analyze EPR and adiabatic magnetization of the V15 cluster with a triangular VIV 3 array causing spin frustration. A model for V15 includes isotropic and antisymmetric (AS) exchange interactions in the general form compatible with the trigonal symmetry. Orientation of the AS vector (but not only its absolute value) is shown to play an important physical role in spin-frustrated systems. We were able to reach perfect fi t to the experimental data on the stepwise dependence of magnetization vs. fi eld at ultra-low temperatures. Furthermore, it was possible for the fi rst time to estimate precisely two components of the AS vector coupling constant, namely, in-plane component and the perpendicular part. We show that only intramultiplet transitions in EPR are allowed when the vector of AS exchange is normal to the plane of vanadium triangle, meanwhile the in-plane part of AS exchange gives rise to a series of weak intermultiplet transitions. Experimental data on high-frequency EPR of V15 at low temperatures are discussed. The spin-vibronic effects in trimeric spin frustrated clusters are also studied and an important role of the interplay between the AS exchange and Jahn-Teller interaction is revealed. The results clarify the concept of spin-frustration in view of its magnetic and spectroscopic manifestations in metal clusters.

51-57

Authors: Lavinia Tofan, Doina Bilba, Carmen Paduraru and Ovidiu Toma

The obtained results concerning the Ga (III) ion retention on fl exible open cell polyurethane foam of polyether type pretreated with tri-n-butyl phosphate are presented. The infl uence of solution acidity, phases contact time, Ga (III) concentration and solution temperature have been investigated. The parameters of Ga (III) batch sorption have been optimized. On the basis of Langmuir isotherms, the sorption constants and the thermodynamic parameters, ΔG, ΔΗ and ΔS have been calculated.

63-66

Authors: Vasile Rusu, Aliona Vrînceanu and Igor Polevoi

Studies of the mineralogical composition of diatomite from the Ghidirim location of RM, as well as of the extracted clay phase are presented. The mineral phase of the diatomite contains a number of clay minerals, like montmorillonite (in a mixture with insignifi cant quantities of slightly chloritized montmorillonite), illite and kaolinite. Diatomite contains also non-clay components as fi ne-dispersed quartz and amorphous material, the more probable sources of which are opal, amorphous alumosilicates, aluminum and iron hydroxides. The applied procedure for separation of clay fractions by sizing settling in liquid media proves to be very useful, enabling possibilities for more accurate identifi cation of the clay constituents of diatomic material. Procedure allows to separate very clean clay fraction especially rich in montmorillonite, which can be utilized itself as mineral adsorbent for practical purposes.

78-82

Authors: Porubin Diana

The inhibition of nornicotine nitrosation was studied. The concentration of nornicotine was 100 μM and nitrite 1000 μM. As inhibitors were used following compounds: ascorbic acid (as reference) (800, 1000, and 5000 μM), dihydroxyfumaric acid (1000 μM), (+)catechin (1000 μM), resveratrol (1000 μM), tartaric acid (1000 μM), quercetin (1000 μM), and grape seed extract (50, 100, 150 μg/ml). The best inhibitory effect was obtained for AAs at 5000 μM (90.7%), (+)Ct (95.5 %) and GSE at 150 μg/ml (96.1%). The small inhibitory effect was observed for TA – 22,5%.

88-92

Authors: Krisztina Kovács, Alexander A. Kamnev, Alexei G. Shchelochkov, Ernő Kuzmann, János Mink, Tünde Megyes, Attila Vértes

Interactions of a series of indole-3-alkanoic acids (with n-alkanoic acid side-chains from C1 to C4) with iron(III) in acidic aqueous solutions have been shown to comprise two parallel processes including complexation and redox transformations giving iron(II) hexaaquo complexes. The structure and composition of the reaction products are discussed, as analysed using a combination of instrumental techniques including 57Fe Mössbauer, vibrational and 1H NMR spectroscopies.

98-101

Authors: Adina N. Lazar, Oksana Danylyuk, Kinga Suwinska and Anthony W. Coleman

The solid-state structure of the tri-potassium calix[4]arene dihydroxyphosphonate salt is presented. In this structure, two potassium cations bridge between layers of dimeric calixarene diphosphonate units and two other potassium cations bridge along the face of the layers. The ubiquitous dimeric association of the calixarenes shows the highest interdigitation value so far observed. As expected, the cations are solvated and are complexed exo with respect to calixarene crown. The octahedral coordination sphere of the potassium cations is formed by two phosphonate groups of the calixarenes and four water molecules. Electrostatic forces represent the major element of interaction in the solid-state system.

108-113

Authors: Irina Lunga, Pavel Chintea, Stepan Shvets, Anna Favel and Cosimo Pizza

Phytochemical analysis of the seeds of Hyocyamus niger L. (Solonaceae) resulted in the isolation of six steroidal glycosides, two furostanol (1, 2) and four spirostanol saponins (3, 4, 5, 6), which were found in this plant for the fi rst time. The structures of these compounds were determined by detailed analysis of their spectral data, including two-dimensional NMR spectroscopy and MS spectroscopy. The antifungal activity of a crude steroidal glycoside extract, fractions of spirostanoles and individual glicosides was investigated in vitro against a panel of human pathogenic fungi, yeasts as well as dermatophytes and fi lamentous species.

119-122

Authors: Macaev Fliur, Munteanu Viorica, Stingaci Eugenia, Barba Alic, Pogrebnoi Serghei

New functionalized imidazolium salts that can be classifi ed as ionic liquids were synthesized.