Chemistry Journal of Moldova

DOI: dx.doi.org/10.19261/cjm.2008.03(1).14

Graphical Abstract: The work presented in the paper discusses the contribution of the Novodnestrovsc water system to the formation of redox conditions in the lower Dniester. The conclusions were drawn on the basis of a long-term protocol of analyses that included the analysis of the oxygen regime, evaluation of the content of hydrogen peroxide, rH2, biological oxygen demand as well as other additional parameters.


Downloads: 24

DOI: dx.doi.org/10.19261/cjm.2008.03(1).17

Graphical Abstract: Differential scanning calorimetry has been used to study the α-relaxation (glass transition) in virgin polystyrene (PS), PS-clay nanocomposite, amorphous indomethacin (IM), maltitol (Mt) and glucose (Gl). Variation of the effective activation energy (E) throughout the glass transition has been determined by applying an advanced isoconversional method to DSC data on the glass transition. The relaxations have been characterized by determining the effective activation energies (E) and evaluating the sizes of cooperatively rearranging regions at the glass transition (Vg). The values of Vg have been determined from the heat capacity data. The α-relaxation demonstrates markedly larger values of E (~340 vs ~270 kJ mol-1) for the PS-clay system than for virgin PS. For IM in the glass transition region, the effective activation energy of relaxation decreases with increasing temperature from 320 to 160 kJ mol-1. In the Tg region E decreases (from~250 to ~150 kJ mol-1 in maltitol and from~220 to ~170 kJ mol-1 in glucose) with increasing T as typically found for the α-relaxation. It has been found that in the sub-Tg region E decreases with decreasing T reaching the values ~60 (glucose) and ~70 (maltitol) kJ -1 that are comparable to the literature values of the activation energies for the β-relaxation. Heat capacity measurements have allowed for the evaluation of the cooperatively rearranging region in terms of the linear size The PS-clay system has also been found to have a significantly larger value of Vg, 36.7 nm3 as compared to 20.9 nm3 for PS. Heat capacity measurements of IM have allowed for the evaluation of the cooperatively rearranging region (CRR) in term of linear size (3.4 nm) and the number of molecules (90). The size of CRR have been determined as 3.1 (maltitol) and 3.3 (glucose) nm.


Downloads: 17

Abstract (JPEG)

DOI: dx.doi.org/10.19261/cjm.2007.02(1).04

Graphical Abstract: A mixture of 7α- and 17-bromonorambreinolides was obtained on treatment of the mixture of isomeric methyl bicyclohomofarnesenoates, the norambreinolide transesterification product, with NBS and H2O2. The structure of 7α- and 17-bromonorambreinolides was elucidated on the basis of spectral data. The structure of 17-bromonorambreinolide was confirmed by its reduction with LiAlH4 into sclaradiol, and that of 7α-bromonorambreinolide by X-ray analysis.


Downloads: 13

DOI: dx.doi.org/10.19261/cjm.2007.02(1).05

Graphical Abstract: 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 first 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 filamentous species.

Downloads: 51

DOI: dx.doi.org/10.19261/cjm.2007.02(1).06

Graphical Abstract: Thiolato-bridged complex [Cu^I₄Cu^II₄(peampt)₄Cl₈]·2H₂O (Hpeampt = 1-(2-pyridylethyl)amino) methylpropane-2-thiol) has been synthesized and characterized by the elemental analysis, IR and UV-vis spectroscopies and magnetic susceptibility measurement. The X-ray crystal structure analysis of this complex shows a localized mixed-valence octanuclear cage structure made up of four trigonal-bipyramidal Cu^IIN₂SCl₂, two trigonal CuIS2Cl, and two tetrahedral Cu^IS₂Cl₂ coordination sites. Temperature dependence of magnetic susceptibility (4.5— 300 K) shows that a fairly strong antiferromagnetic interaction is operating between the four Cu^II ions.


Downloads: 23

DOI: dx.doi.org/10.19261/cjm.2007.02(1).07

Graphical Abstract: 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.


Downloads: 15

DOI: dx.doi.org/10.19261/cjm.2007.02(1).08

Graphical Abstract: The interaction of cis-Re₂(RCOO)₂Cl₄, trans-Re₂(RCOO)₂Cl₄, Re₂(RCOO)₃Cl₃ and Re₂(RCOO)₄Cl₂ (where R - alkyl group) with 1,3,5-triphenylverdazyle radical in 1,2-dichlorethane was investigated. It is discovered, that gradual substitution of halogenide ligands by carboxylates in dirhenium(III) clusters led to slowing down of reaction with a radical due to different influence of these ligands on parameters of rhenium - rhenium bond. Presented data showed perspectivity of Re₂⁶⁺-substances applications as therapeutic agents due to their low toxicity and antiradical properties that occured by δ-component of quadruple Re-Re bond electron transition.


Downloads: 16

DOI: dx.doi.org/10.19261/cjm.2007.02(1).09

Graphical Abstract: 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 HNMR spectroscopies.


Downloads: 13

DOI: dx.doi.org/10.19261/cjm.2007.02(1).10

Graphical Abstract: Four new heteronuclear lanthanide complexes with general formula [Ge(OH)(μ-HDTPA)LnGe(OH) (μ-DTPA)] (Ln = Sm – Dy) were synthesized and subsequently characterized by different physico- chemical methods. The structures of new compounds have been proposed. In considered complexes the 4f-luminescence of three-charged ions of samarium, europium, terbium and dysprosium is realized at UV-excitation. It is noteworthy that it is the first observation of 4f-luminescence in water solutions of heteronuclear f-p-complexes. The comparison of luminescent characteristics of hetero- and homonuclear landthanide complexes is described and discussed as well.

Downloads: 18