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91.
92.
Volobuyev M Saint-Martin H Adamowicz L 《The journal of physical chemistry. B》2007,111(37):11083-11089
A computational model, which includes both tunneling and thermal hopping mechanisms, has been applied to study the charge transfer in DNA (GC)n and (AT)n strands. The calculations revealed the crucial role played by the A or G NH2-group vibrations in the hole transfer in both types of strands. Charge-transfer rates in the two strands have been determined based on the molecular dynamics calculations. They are in good agreement with the available experimental data. The modeling approach used here may be employed in the theoretical study of the charge transfer in natural and artificial DNA strands containing AT and GC pairs. 相似文献
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95.
Inside Cover: New Chiral Reagent for Installation of Pharmacophoric (S)‐ or (R)‐2‐(Alkoxyphosphono)‐1‐amino‐2,2‐difluoroethyl Groups (Chem. Eur. J. 21/2016) 下载免费PDF全文
96.
We present explicit water molecular dynamics simulations of solutions of aliphatic 3,3- and 6,6-ionene oligocations neutralized with (i) fluoride, chloride, bromide, or iodide counterions, respectively, or (ii) with a 1:1 mixture of chloride and bromide anions in presence of a low molecular weight salt at 298 K. The SPC/E model was used to describe water molecules. Results of the simulation are presented in form of the pair distribution functions between various atoms on the ionene oligoion and counterions in solution. In addition, we were interested in the dynamics of counterions around model ionenes. We showed that counterions residing in the vicinity of the oligoion exchange rapidly with those in the bulk solution, with the frequency depending on the nature of the counterion and on the charge density of the oligoion. We calculated the average residence times of the various counterion species to the oligoions and proposed the model which divides the counterions into "free" and "bound" and calculated the fraction of "free" counterions. In the second part of the study, we investigated interaction of the sodium chloride and sodium bromide, being simultaneously present in the solution, with differently charged ionenes in water. The selectivity effect was clearly observed: bromide ions tend to replace chloride ions in the immediate vicinity of the ionene oligoions. Simulation results are discussed in light of our recent measurements of thermodynamic and transport properties of aqueous ionene solutions. 相似文献
97.
Slobodyanik NS Terebilenko KV Ogorodnyk IV Zatovsky IV Seredyuk M Baumer VN Gütlich P 《Inorganic chemistry》2012,51(3):1380-1385
The possibility of PO(4)(3-) for MoO(4)(2-) partial substitution in the langbeinite framework has been studied by exploration of the K-Fe(Sc)-Mo(W)-P-O systems using the high-temperature solution method. It was shown that 1/3PO(4)(3-) for MoO(4)(2-) substitution leads to formation of three novel compounds K(2)Fe(MoO(4))(PO(4))(2), K(2)Sc(MoO(4))(PO(4))(2), and K(2)Sc(WO(4))(PO(4))(2) with slightly increased lattice parameters and significant distortion of the anion tetrahedra without structure changes. In contrast, the antiferromagnetic structure is modified by substitution in the low-temperature region. The structural peculiarities are discussed in light of bond-valence sums calculations. 相似文献
98.
Lukšič M Bončina M Vlachy V Druchok M 《Physical chemistry chemical physics : PCCP》2012,14(6):2024-2031
Aliphatic x,y-ionenes are polyelectrolytes in which x and y denote the numbers of methylene groups separating quaternary ammonium ions. They represent useful model substances for studying hydrophobic and charge effects in aqueous solutions. We used isothermal titration calorimetry to measure the enthalpies of mixing, ΔH(mix), of 3,3- and 6,6-ionene fluorides and bromides with low molecular weight salts (NaF, NaCl, NaBr, and NaI) at 298 K in water. The signs and magnitudes of the measured enthalpies depend on the hydrophobicity of the ionene and on the nature of the added salt. For example, addition of sodium fluoride to solutions of 3,3- and 6,6-ionene fluorides produced endothermic effects, while addition of sodium bromide to 3,3-ionene bromide resulted in a strong exothermic effect. Interestingly, mixing of 6,6-ionene bromide and NaBr solutions in water gave a small exothermic heat effect. Polyelectrolyte theories, based on continuum-solvent models, predict enthalpies of mixing to be positive (endothermic) for all the solutions examined in this work. The ion-specific effect is more strongly expressed in ionene solutions with higher charge density (3,3-ionene). The most important result of this work is the finding that the enthalpy of mixing of 3,3- (and of 6,6-ionene) fluorides with sodium halides can be expressed as a linear function of the enthalpy of hydration of the halide counterions. The experimental results were complemented with an explicit water molecular dynamics simulation of solutions of oligoions modelling 3,3- and 6,6-ionenes. The computer simulation results for various nitrogen-counterion pair distribution functions were in most cases consistent with the enthalpy measurements. 相似文献
99.
Kateryna V. Terebilenko Alexander A. Kirichok Maksym Sereduk P. Gütlich 《Journal of solid state chemistry》2010,183(6):1473-1476
AgFeP2O7 has been synthesized by flux crystallization and characterized by single crystal and powder X-ray diffraction (sp. gr. P21/c, a=7.3298(2), b=7.9702(2), c=9.5653(2) Å, β=111.842(1)°, V=518.68(2) Å3) and FTIR-spectroscopy. The structure is composed of isolated iron octahedra and phosphate tetrahedra interconnected into 3D network with hexagonal channels, where silver counter-ions are located. The magnetic behavior of the compound approaches the Curie-Weiss equation with a Weiss constant θ=−165.9 K indicating strong antiferromagnetic interaction between iron(III) ions. 相似文献
100.
Yarema M Kovalenko MV Hesser G Talapin DV Heiss W 《Journal of the American Chemical Society》2010,132(43):15158-15159
A simple and reproducible synthesis of highly monodisperse and ligand-protected bismuth nanoparticles (Bi NPs) is reported. The size of the single-crystalline and spherically shaped NPs is controlled between 11 and 22 nm mainly by the reaction temperature. The high uniformity of the NPs allows their self-assembly into long-range-ordered two- and three-dimensional superstructures. 相似文献