The fluorobasicities of ReF7 and IF7 as measured by the enthalpy change ΔH°(EF7(g) → EF6+(g) + F−(g))

Iridium hexafluoride oxidizes ReF₆ (via an ReF₆⁺ salt) and at room temperatures IrF₆, ReF₆, ReF₇ and (IrF₅)₄ are each present in the equilibrium mixture. From these and related findings: ΔH°(ReF₆ → ReF₆⁺ + e^?) 1092 ± 27 kj mole^?1(261 ± 6 kcal mole^?1), and thermodynamic data are selected to yield ΔH°(ReF_7(g) → ReF₆⁺_(g) + F^?_(g))=893 ± 33 kj mole^?1(213 ± 8 kcal mole^?1). From observations on the stability of IF₆⁺BF₄^? and the lattice enthalpy evaluation for the salt, ΔH°(IF_7(g) → IF₆⁺_(g) + F^?_(g))= 870 ± 24 kj mole^?1(208 ± 6 kcal mole^?1).     

Correlation between structure and thermal properties in 2-hydroxy-benzophenone Co(II) complexes

In this study, simultaneous TG/DTG–DTA technique was used for the simple cobalt(II) complex [Co(dpamH)₃]Br₂ (1) (dpamH = 2,2′-dipyridylamine) and the novel mixed-ligand complexes [Co(dpamH)₂(bpo)]Br (2) and [Co(dpamH)₂(opo)]Br (3), (bpo = the anion of 2-hydroxybenzophenone and opo = the anion of 2-hydroxy-4-methoxybenzophenone), in order to determine their thermal degradation in static air and dynamic nitrogen atmospheres. The cationic complexes were characterized by physicochemical methods, spectroscopy (FT-IR, UV–Vis), and single-crystal X-ray analysis, revealing octahedral coordination around cobalt(II) with chromophore CoN₄O₂, being chelated by one anionic 2-hydroxy-benzophenone ligand and two neutral dpamH molecules. The compounds crystallize as ethanol or ethanol/water solvates, with solvent molecules involved, to a different extent, in hydrogen bonding giving quite different packing modes and thus influencing their stability. The differences in crystal structures are reflected in thermal stabilities of the compounds. Thus, in the crystals of 3 ethanol is more weakly bound than in 2 and anticipate that the former one exhibit lower thermal stability, which is in agreement with the results found by TG–DTA. The thermal decomposition of the title complexes was found to be a multi-step decomposition related to the release of the solvent and ligand molecules, leading at 1,000 °C to pure metallic cobalt in nitrogen atmosphere, while in air atmosphere to the expected cobalt oxides.     

Electrooxidation of Methanol on Platinum–Ruthenium Catalysts Applied to a Cation-Exchange Membrane

Possibilities for production of active Pt–Ru electrodes for the direct methanol fuel cell with a decreased content of platinum-group metals in them are studied. Platinum and ruthenium are electrodeposited on a thin layer of carbon black applied to a Nafion 117 membrane. The deposition potential effect on the specific surface area of the catalyst and its electrochemical activity in the methanol oxidation is studied. The oxidation currents are related to unit true surface area or unit catalyst mass. The dependence of activity on the Pt : Ru ratio in the plating solution and in the deposit is studied. The effect of the catalyst amount deposited and the particle size on the activity is studied. It is shown that the catalytic activity decreases at the average diameter of Pt–Ru particles less than 4 nm. The results are compared with the size effects observed earlier.     

Optical spectroscopy and photochemical hole burning studies of the supramolecule C60-H2TPP in poly vinylbutiral at low temperatures

We present some preliminary results on the photophysical properties of a new supramolecular assembly C₆₀-H₂TPP, studied at low temperatures by optical spectroscopy. While the absorption spectrum in the long wavelength range reflects the dominant contribution of the porphyrin moiety, the fluorescence spectrum is dominated by the emission coming from the pyrrolidino[60]fullerene moiety. No fluorescence line narrowing effect was observed when exciting within the lowest absorption band assigned to the porphyrin moiety. However, the demonstration that narrow spectral holes can be burnt in this band reveals that the excited state of the porphyrin moiety is not strongly affected by electron-phonon coupling with the host despite its covalent link with a bulky fullerene.     

Thermoanalytical,magnetic and structural investigation of Co(II) complexes with dipyridylamine and 2-hydroxyphenones

The simultaneous TG/DTG–DTA technique was used for three new cobalt(II) complexes with dipyridylamine (dpamH) and the anion of a 2-hydroxyphenone ligand (phenone), with the general formula [Co(dpamH)₂(phenone)]Br, in order to determine their thermal degradation in static air and dynamic nitrogen atmospheres, which was found to be a multi-step decomposition related to the release of the ligand molecules. The complexes were characterized by elemental analyses, FT-IR and UV–Vis spectroscopy, magnetic and conductivity measurements. All structures were determined by X-ray crystallography revealing octahedral coordination of cobalt(II) and monomeric nature of the compounds, [Co(dpamH)₂(2-OH-acetophenone)]Br (1), [Co(dpamH)₂(2-OH-propiophenone)]Br (2) and [Co(dpamH)₂(2-OH, 5-CH₃-acetophenone)]Br·EtOH (3). The variable temperature (76–303 K) magnetic susceptibility measurements showed a paramagnetic nature of the complexes, in accordance with their molecular structure.     

Effect of a bioactive curcumin derivative on DPPC membrane: A DSC and Raman spectroscopy study

Interactions of dimethoxycurcumin (1) a lipophilic bioactive curcumin derivative with dipalmitoyl phosphatidylcholine (DPPC) were investigated. The thermodynamic changes caused by (1) and its location into DPPC lipid bilayers were monitored by differential scanning calorimetry and Raman spectroscopy. The results reveal that (1) influences the thermotropic properties of DPPC lipid membrane causing abolition of the pretransition and broadening of the phase-transition profile and slightly decreases the T_m at increasing concentrations. The Raman height intensity ratios of the peaks I_2935/2880, I_2844/2880 and I_1090/1130 are representative of the interaction of (1) with the alkyl chains and furnish information about the ratio between disorder and order that exists in the conformation of the alkyl chain. The intensity changes of the peak at 715 cm⁻¹ indicates interaction between the choline head group and (1). The Raman spectroscopy results are in agreement with the thermal analysis results. Biologically active lipophilic molecules such as (1) should be studied in terms of their interaction with lipid bilayers prior to the development of advanced lipid carrier systems such as liposomes. The results of these studies provide information on the membrane integrity and physicochemical properties that are essential for the rational design lipidic drug delivery systems.     

Platinum-Ruthenium Catalysts,Manufactured by Means of Ion Exchange in Nafion Layers

Catalytic layers of platinum-ruthenium of preliminarily specified compositions are manufactured with the aid of ion exchange and subsequent chemical and electrochemical reduction in polymeric Nafion films applied onto carbonaceous materials and inside a standard Nafion 117 membrane. The procedure used for conducting the ion-exchange procedure ensures a high process rate and a short time required to conduct it, which makes it possible to obtain large roughness factors at relatively small contents of platinum metals (0.1–0.2 mg cm^?2). The electrochemical activity of catalyzed membrane samples for methanol oxidation in aqueous and sulfuric acid solutions is close to the activity of standard E-TEK platinum-ruthenium catalysts.     

Preparation and properties of substituted iron tungstates

Polycrystalline samples of members of the systems Fe_2?xCr_xWO₆ and Fe_1?xMn_xWO₄ were prepared and single crystals of Fe_1?xMn_xWO₄ were grown by chemical vapor transport. Their crystallographic parameters and electrical properties were characterized. Fe₂WO₆ crystallizes with the tri-α-PbO₂ structure and is an n-type semiconductor. For 0.3 ≤ x ≤ 2, the system Fe_2?xCr_xWO₆ crystallizes with the inverse trirutile structure and is nonconducting due to blocking of iron(II)-iron(III) conduction paths by chromium(III). For 0 ≤ x ≤ 1, the system Fe_1?xMn_xWO₄ crystallizes with the wolframite structure and shows p-type semiconducting behavior. The nature of the variation of resistivity with x of Fe_1?xMn_xWO₄ suggests that interchain electron transfer may occur in this structure.