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排序方式: 共有170条查询结果,搜索用时 15 毫秒
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Candelaria Goycoolea Mauricio Barrera Fernando Zuloaga 《International journal of quantum chemistry》1989,36(4):455-472
Electronegativity χ and hardness η for 54 atoms and their positive and negative ions are calculated by means of self-interaction-corrected DFT including correlation terms. The exchange potential energy is treated by local spin density approximation corrected to account for self-interaction effects as suggested by Rae. The highest occupied orbital eigenvalues for ions are identified to the chemical potential μ± for positive and negative charged atoms depending upon the developing charge process. Values of χ±δ and η± for the different ionic species are given for several values of δ. Average values for 〈χ〉 and 〈η〉 in the sense of Mulliken finite formula for neutral atoms are also tabulated and compared with Mulliken values from experimental data. The agreement among them is almost quantitative. 相似文献
3.
F. Hernández-Luis M. Barrera H. R. Galleguillos L. Fernández-Mérida M. Pérez 《Journal of solution chemistry》1996,25(2):219-229
The activity coefficients of sodium bromide in the ternary system NaBr+NaClO4+H2O were determined at 25°C and constant ionic strength of 0.1, 0.5, 1, 2, and 3 mol-kg?1 from emf of the cell without, liquid junction $$ISE - Na|NaBr(m_A ), NaClO_4 (m_B ), AgCl_{(s)} 1 Ag$$ The experimental activity coefficients were comparatively analyzed by using the Harned, Scatchard, Pitzer and Lim-HOLL treatments. All these methods are adequate for the analysis of the experimental data. The results have been compared with those of Lanier for the system: NaCl+NaClO4+H2O. The Gibbs excess energy of mixing was obtained and qualitatively interpreted in terms of ionic interactions. 相似文献
4.
The substitution chemistry of TcCl(3)(PPh(3))(2)(CH(3)CN) is rather facile relative to the analogous rhenium complex, since both the chloride and phosphine ligands are easily substituted for various pyridine ligands. Consequently a series of Tc(III) complexes with amine, pyridine, and polypyridyl ligands were prepared and characterized by (1)H NMR and cyclic voltammetry. In addition, the zinc reduction of TcCl(4)(py)(2) in the presence of pyridine results in TcCl(2)(py)(4). Structural and spectroscopic data indicate that this Tc(II) complex exhibits strong metal-pyridine interactions characteristic of low-valent amine complexes of Re(II) and Os(II). For example, a decrease of 0.04 and 0.06 ? is observed for the trans-Tc-N bond length in TcCl(2)(py)(4 )relative to mer-TcCl(3)(pic)(3) and [TcCl(2)(py)(3)(PPh(3))](+), respectively. This ability of pyridine to function both as a strong sigma-donor and moderate pi-acid ligand has resulted in the isolation of technetium complexes in various oxidation states with similar ligand environments. As a result, a structural comparison of [TcCl(2)(py)(3)(PPh(3))](+), TcCl(2)(py)(4), TcCl(tpy)(py)(2), and other known Tc(III) and Tc(II) pyridine complexes is presented. Crystals of [TcCl(2)(py)(3)(PPh(3))]PF(6) are triclinic, with space group P&onemacr;, Z = 2, and lattice parameters a = 12.677(4) ?, b = 13.064(4) ?, c = 13.103(5) ?, alpha = 110.14(3) degrees, beta = 101.12(3) degrees, gamma = 96.61 degrees, V = 1959 ?(3), and R = 0.0615 (R(w) = 0.1148). Crystals of TcCl(2)(py)(4) are tetragonal, with space group I4(1)/acd, Z = 8, and lattice parameters a = 15.641(4) ?, c = 16.845(6) ?, V = 4121 ?(3), and R = 0.0373 (R(w) = 0.0290). Crystals of TcCl(tpy)(py)(2) are orthorhombic, with space group C222(1), Z = 4, and lattice parameters a = 9.359(3) ?, b = 16.088(6) ?, c = 18.367(4) ?, V = 2765 ?(3), and R = 0.0499 (R(w) = 0.0599). 相似文献
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Ana Barrera Corinne Binet Frdric Dubois Pierre-Alexandre Hbert Philippe Supiot Corinne Foissac Ulrich Maschke 《Molecules (Basel, Switzerland)》2021,26(10)
In the present work, the dielectric properties of recycled liquid crystals (LCs) (non-purified, purified, and doped with diamond nanoparticles at 0.05, 0.1, and 0.2 wt%) were investigated. The studied LC mixtures were obtained from industrial recycling of end-of-life LC displays presenting mainly nematic phases. Dielectric measurements were carried out at room temperature on a frequency range from 0.1 to 106 Hz using an impedance analyzer. The amplitude of the oscillating voltage was fixed at 1 V using cells with homogeneous and homeotropic alignments. Results show that the dielectric anisotropy of all purified samples presents positive values and decreases after the addition of diamond nanoparticles to the LC mixtures. DC conductivity values were obtained by applying the universal law of dielectric response proposed by Jonscher. In addition, conductivity of the doped LC mixtures is lower than that of the undoped and non-purified LC. 相似文献
7.
Dr. Manuela Leticia Kim Dr. Deicy Barrera Dr. Mutsumi Kimura Prof. Dr. Juan P. Hinestroza Prof. Dr. Karim Sapag Dr. Eugenio Hernán Otal 《化学:亚洲杂志》2021,16(9):1086-1091
We report on a detailed textural analysis of mechanochemically synthesized MOF-199 including N2 adsorption-desorption and CO2 adsorption isotherms data at 77 K and 273 K (up to atmospheric pressure), respectively, and CH4 adsorption data at 298 K (up to 35 bar). We used the isotherm adsorption data to determine the micropore volume of the MOF-199 structures, to establish their methane uptake capacity and to understand how these properties depended on the Ethanol/BTC ratio used during the synthesis. The maximum methane uptake capacity for our specimens was recorded at 130 v/v at 35 bars. These results open an avenue for a better understanding of alternative manufacturing processes of MOF structures for gas storage applications. 相似文献
8.
Dr. Julian Heinrich Dr. Karolina Bossak-Ahmad Mie Riisom Dr. Haleh H. Haeri Tasha R. Steel Vinja Hergl Alexander Langhans Corinna Schattschneider Jannis Barrera Dr. Stephen M. F. Jamieson Prof. Matthias Stein Prof. Dariush Hinderberger Prof. Christian G. Hartinger Prof. Wojciech Bal Prof. Nora Kulak 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(72):18093-18102
Redox-active Cu(II) complexes are able to form reactive oxygen species (ROS) in the presence of oxygen and reducing agents. Recently, Faller et al. reported that ROS generation by Cu(II) ATCUN complexes is not as high as assumed for decades. High complex stability results in silencing of the Cu(II)/Cu(I) redox cycle and therefore leads to low ROS generation. In this work, we demonstrate that an exchange of the α-amino acid Gly with the β-amino acid β-Ala at position 2 (Gly2→β-Ala2) of the ATCUN motif reinstates ROS production (•OH and H2O2). Potentiometry, cyclic voltammetry, EPR spectroscopy and DFT simulations were utilized to explain the increased ROS generation of these β-Ala2-containing ATCUN complexes. We also observed enhanced oxidative cleavage activity towards plasmid DNA for β-Ala2 compared to the Gly2 complexes. Modifications with positively charged Lys residues increased the DNA affinity through electrostatic interactions as determined by UV/VIS, fluorescence, and CD spectroscopy, and consequently led to a further increase in nuclease activity. A similar trend was observed regarding the cytotoxic activity of the complexes against several human cancer cell lines where β-Ala2 peptide complexes had lower IC50 values compared to Gly2. The higher cytotoxicity could be attributed to an increased cellular uptake as determined by ICP-MS measurements. 相似文献
9.
A. M. A. P. Fernandes G. D. Fernandes D. Barrera‐Arellano G. F. de Sá R. D. Lins M. N. Eberlin R. M. Alberici 《Journal of mass spectrometry : JMS》2014,49(5):ii-ii
Knowledge of the major effects governing desorption/ionization efficiency is required for the development and application of ambient mass spectrometry. Although all triacylglycerols (TAG) have the same favorable protonation and cationization sites, their desorption/ionization efficiencies can vary dramatically during easy ambient sonic‐spray ionization because of structural differences in the carbon chain. To quantify this somewhat surprising and drastic effect, we have performed a systematic investigation of desorption/ionization efficiencies as a function of unsaturation and length for TAG as well as for diacylglycerols, monoacylglycerols and several phospholipids (PL). Affinities for Na+ as a function of unsaturation level have also been assayed via comprehensive metadynamics calculations to understand the influence of this phenomenon on the ionization efficiency. The results suggest that dipole–dipole interactions within a carbon chain tuned by unsaturation sites govern ionization efficiency of TAG and PL. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
10.
G. López L. A. Barrera Y. Garibo H. Hernández J. C. Salazar C. A. Vargas 《International Journal of Theoretical Physics》2004,43(10):2009-2021
The constants of motion of the following systems are deduced: a relativistic particle with linear dissipation; a no-relativistic particle with a time explicitly depending force; a no-relativistic particle with a constant force and time depending mass; and a relativistic particle under a conservative force with position depending mass. The Hamiltonian for these systems, which is determined by getting the velocity as a function of position and generalized linear momentum, can be found explicitly at first approximation for the first system. The Hamiltonians for the other systems are kept implicitly in their expressions for their constants of motion. 相似文献