Volume 222, Issue 12

FTIR spectra (50–4000 cm –1 ) were obtained in the temperature region 16–295 K for (E)2-hydroxyimino-2-cyanoacetic acid ethyl ester. A broadening of some peaks was observed while increasing the temperature. Broadening of the peak at 1187 cm –1 and its analysis vs. temperature enabled us to determine the barrier for CH 2 twisting-rocking of 1.89±0.08 kJ/mole. The strong intensity dependence of the C=N stretching peak on temperature within the IR spectra is a sign of some nonlinear properties of the investigated substance. The splitting of several peaks connected with the C=N (azomethine), C=O and N-O vibrations provides evidence of two rotamers theoretically identified previously. The two rotamers existing distinctly (from the experimental point of view) at low temperatures differ one from the other only by 1 J/mol.

From the adsorptive precipitation of Cl – , eosin Y (EY) and Ag + , we developed in-situ inclusion of EY into growing silver chloride particles to form ternary electronegative micro-conductors. The composition of the particles was determined by inductively coupled plasma atomic emission spectrometry (ICP-OES), ion chromatography (IC) and spectrophotometry and the size and pattern of the particles characterized by the particle size analysis, X-ray diffractometer (XRD), scanning electron microscopy (SEM), and thermogravimetry. The results showed that the in-situ inclusion of EY into AgCl crystal particles in layer-by-layer and the supermolecular complex {[(AgCl) 50 EY] n } 2n– was formed in cubic and globe-like shape. The ternary inclusion particles adsorbed cationic dyes selectively, rapidly and with high efficiency. A representative cationic dye, victoria blue B (VBB), was used to investigate the performance of the ternary particles as adsorbents and the mechanism involved. The equilibrium adsorption capacity of the ternary particles is 353 mg/g VBB, over 10 times higher than absorption to the silver chloride–only particles and over 3 times to activated carbon. Moreover, the adsorption approached the equilibrium in 10 min, which is much less than that with activated carbon in about 2 h. This work advanced a sample method for preparation of the supramolecular inclusion materials as dye adsorbent and it provided a simple, efficient and practical approach for the recovery or removal of organic substances from aqueous.

The Fe(III)-dithiocarbamate-nitroxyl (Fe-dtc-nitroxyl) complex, where nitroxyl represents nitroxyl free radical (R-N(O)-R’), has been shown to trap nitric oxide (NO) in aqueous solution, replacing the nitroxyl ligand. As a result, non-complexed nitroxyl radical was released to the solution. Fe(III)-dithiocarbamate (Fe-dtc) complexes without the nitroxyl ligand also traps NO, producing NO-Fe-dtc complex. These two reactions have been used for the purpose of NO detection. We investigated how the ligand structure and external pressure influence NO trapping rates in these complexes. The ratios of NO trapping rates ( k 1 / k 2 ) between various Fe-dtc-nitroxyl complexes and the Fe-dtc complex were determined by using a competitive NO trapping method. The ratio k 1 / k 2 was 29.8±2.8 for Fe-dtc-nitroxyl and Fe-dtc, where dtc = N -(dithiocarboxy) sarcosine (DTCS) and nitroxyl = 2,2,6,6-tetramethyl- piperidine-1-oxyl (TEMPO). For another combination, dtc = N -methyl-D-glucamine dithiocarbamate (MGD)/nitroxyl = TEMPO, k 1 / k 2 was 7.19±0.25. Overall, NO trapping rate of the Fe-dtc-nitroxyl complex was faster than that of the Fe-dtc complex, and k 1 / k 2 for Fe-MGD complex was dependent on the electron-withdrawing or -repelling nature of the functional group in the ligand. Based on pressure dependence experiments for the competitive reaction, we obtained large negative activation volumes for NO trapping of the Fe-dtc-nitroxyl complex as well as the difference in activation volumes (–45 to –26 cm 3 mol –1 ) between the NO trapping reactions by the two Fe complexes. These data sets with different nature allowed us to speculate the reaction mechanism for NO trapping of the Fe-dtc-nitroxyl complex.

Cobalt hexacyanoferrates have a relatively low energy barrier for the charge transfer between cobalt and iron atoms. That energy barrier can be overcome by irradiation with light in the ultraviolet-blue region or through the sample heating. Such feature for that charge transfer process is determined by structural and compositional factors. In this contribution the role of a second metal partially substituting to Co in the material composition on the heat induced charge transfer is studied. Samples of the solid solution Co 3–x T x [Fe(CN) 6 ] 2 yH 2 O with T = Mn, Ni, Cu, Zn and Cd, were prepared by a simple synthetic route and their behavior on moderate heating, from 80 to 160 °C, was evaluated. The behavior of the solid solution on heating was followed by infrared, X-ray diffraction and Mössbauer data. The heat induced charge transfer appears to be favored once the crystal water is removed, when the metal-metal interaction, through the CN bridges, reaches its maximum strength. From this fact, when a metal like Cu, Zn and Cd, with a relatively weak interaction with the coordinated water molecules and, as a consequence, with a low dehydration temperature, is present in the material structure, a lower activation energy is required to be able the heat induced charge transfer. Even in the presence of a second divalent transition metal occupying a fraction of the structural sites for Co, the charge transfer was observed, which is particularly pronounced in the 120–140 °C temperature range. The heat-induced charge transfer was also evaluated from the photo-induced inverse process in the heated samples using photo-acoustic spectroscopy.

Sterols regulate biological processes and sustain the domain structure of cellular membranes. While cholesterol is the major sterol of vertebrates, ergosterol plays a key role in fungal membranes. In this study, small-angle neutron scattering in combination with the H/D contrast variation technique was employed to probe the lateral compositional organization in dipalmitoyl-phosphatidylcholine/ergosterol (DPPC/erg) model membranes over the temperature range from 26 to 78 °C. In addition, small-angle X-ray scattering and calorimetric measurements were carried out to characterize the phase behavior of this system in the temperature interval covered. The SANS measurements clearly demonstrate the absence of critical-point-like composition fluctuations at the temperature where the liquid-ordered/liquid-disordered (l o /l d ) two-phase region closes and gives way to the all-fluid phase. Furthermore, no scattering due to large-scale composition fluctuations has been found in the whole l o +l d two-phase region of the system. It is concluded that this binary phospholipid-sterol mixture in the l o +l d coexistence region exhibits a homogeneous membrane with fluctuating nano-scale domains rather than a macroscopically separated two-phase coexistence region as observed for ternary phospholipid-sterol mixtures. Such small domains are expected to have particular properties like an increased line energy, a spontaneous curvature and limited lifetimes, which will probably also prevail for the small raft-like domains in cellular membranes.

Laser ion-molecule reaction interaction through long range dipole moments leads to potential energy surface crossings. We will show here by using gauge representation (electric field gauge) for wave length λ = 20.6 μm, Intensity I = 5×10 12 W/cm 2 , I = 1×10 13 W/cm 2 , I = 3×10 13 W/cm 2 , that we can create laser induced potential energy surface crossing in the virtual transition state region (4.a.u.) where the dipole moment changes sign. We illustrate such effects for the Li H + CH 3 + ↔ Li + + CH 4 reaction which takes the form of inverted Morse (without a barrier) using ab-initio methods for calculating the reaction path and the permanent dipole moment of this ion-molecule reaction.

Cyclic voltammetry studies in the presence of EDTA in aqueous solution were found to offer some noteworthy improvements in the electrodeposition synthesis of ZnS compound. EDTA has shown its capacity for improving the longevity of the deposition bath as well as adhesion of the deposited material on the substrate. The deposition condition of ZnS compound in the presence of EDTA was found to be favorable in low acidic medium. The process could be carried out at room temperature without the need to increase solution temperature.