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171.
Goher Mohamed A. S. Abdou Azza E. H. Abu-Youssef Morsy A. M. Mautner Franz A. 《Transition Metal Chemistry》2001,26(1-2):39-43
Two new copper(II) azido complexes, namely bis-(tetraethylammonium)[tetraazidocuprate(II)] (1) and catena-di--1,1-azido-[di--1,1-azido-bis-(2,4-dimethylpyridine)dicopper(II)] (2), have been prepared and characterized by spectroscopic and crystallographic methods. Complex (1) consists of isolated NEt+
4 cations and [Cu(N3)4]2– anions. The site symmetry around the copper atom in the anion is 4/m. Complex (2) features a 1 D chain structure, five coordinated square pyramidal copper(II) atoms with both azides functioning as -1,1-bridges. The i.r. spectra reveal that both complexes contain asymmetric azido ligands. The solid and solution electronic spectra of (1) and (2) show very strong absorption bands in the visible region associated with N–
3 CuII charge-transfer transitions. The e.p.r. spectra of powder samples and solutions at room temperature were recorded and discussed. 相似文献
172.
Solvatochromism and Solvatofluorchromism of Brooker's merocyanine 1-methyl-4- (4′-hydroxystyryl) pyridinium betaine, M, were studied in twelve polar protic and aprotic solvents. Moderate hypsochromic fluorescence energy shifts are 4.57 kcal mole−1 while strong hypsochromic absorption energy shifts are 16.63 kcal mole−1. Decreasing of the dipole moment of M upon excitation is the factor, which is responsible for the difference between the two energy shifts. The change of both energies rectilinearly with solvent acidity scale shows the importance of oxygen atom of M as a strong basic center. The application of the atom superposition and electron delocalization molecular orbital (ASED-MO) theory reproduces geometrical and electronic structures for M, which agree well with the experimental observations. The calculations suggest strongly that the dye has a benzenoid valence structure in the ground state and shifts towards a quinonoid one upon excitation with an observed decreasing of the dipole moment. The changing of the dipole moment is explained clearly depending upon the calculated charge distribution over the whole skeleton of the molecule. The formation of a H-bond between the water molecule and the highly negative oxycyclic oxygen atom of M has slightly effect on its dipole moment in the ground state. This leads to suggest that this kind of interaction could be represented as attacking of water with acidic character on the basic site of M. Also, the calculations predict that the formation of monohydrated complex is an exothermic, down hill reaction, which is confirmed from the stabilization of the frontier molecular orbitals, oxygen lone-pair and the HOMO levels. 相似文献
173.
The thermodynamic properties of the mixed aqueous electrolyte of ammonium and alkaline earth metal nitrates have been studied using the hygrometric method at 25?°C. The water activities of these {yNH4NO3+(1?y)Y(NO3)2}(aq) systems with Y ≡ Ba2+, Mg2+ and Ca2+ were measured at total molalities ranging from 0.10 mol?kg?1 to saturation for different NH4NO3 ionic-strength fractions of y=0.20, 0.50 and 0.80. These data allow the calculation of osmotic coefficients. From these measurements, the ionic mixing parameters are determined and used to calculate the solute activity coefficients in the mixtures at different ionic-strength fractions. The results of these ternary solution measurements are compared with those for binary solutions of the alkaline earth nitrates of magnesium, calcium and barium with ammonium nitrates. The behavior of the aqueous electrolyte solutions containing mixtures of barium or calcium or magnesium with ammonium nitrates are correlated and show that ionic interactions are more important for the system containing Mg2+ than for Ca2+ or Ba2+. The trends are mainly due to the effects of the ionic size, polarizability and the hydration of the ions in these solutions. 相似文献
174.
Mohamed Ali Saada Annie Hémon-Ribaud Vincent Maisonneuve 《Journal of fluorine chemistry》2005,126(7):1072-1077
Tren amine cations [(C2H4NH3)3N]3+ and zirconate or tantalate anions adopt a ternary symmetry in two hydrates, [H3tren]2·(ZrF7)2·9H2O and [H3tren]6·(ZrF7)2·(TaOF6)4·3H2O, which crystallise in R32 space group with aH = 8.871 (2) Å, cH = 38.16 (1) Å and aH = 8.758 (2) Å, cH = 30.112 (9) Å, respectively. Similar [H3tren]2·(MX7)2·H2O (M = Zr, Ta; X = F, O) sheets are found in both structures; they are separated by a water layer (Ow(2)-Ow(3)) in [H3tren]2·(ZrF7)2·9H2O. Dehydration of [H3tren]2·(ZrF7)2·9H2O starts at room temperature and ends at 90 °C to give [H3tren]2·(ZrF7)2·H2O. [H3tren]2·(ZrF7)2·H2O layers remain probably unchanged during this dehydration and the existence of one intermediate [H3tren]2·(ZrF7)2·3H2O hydrate is assumed. Ow(1) molecules are tightly hydrogen bonded with -NH3+ groups and decomposition of [H3tren]2·(ZrF7)2·H2O occurs from 210 °C to 500 °C to give successively [H3tren]2·(ZrF6)·(Zr2F12) (285 °C), an intermediate unknown phase (320 °C) and ZrF4. 相似文献
175.
The dynamics of phase separation of three-dimensional fluids containing nanospheres, which interact preferentially with one of the two fluids, is studied by means of large-scale dissipative particle dynamics simulations. We systematically investigated the effect of volume fraction, radius, and mass of the nanoparticles on both kinetics and morphology of the binary mixture. We found that nanospheres lead to a reduction of domain growth which is intensified as their volume fraction is increased for a given radius of nanoparticles, or as the nanoparticles radius is decreased for a given volume fraction. Up to moderate volume fractions of nanoparticles, the growth law, however, is found to be identical to that pure binary fluids, i.e., R(t) approximately t(n), with n=1. For relatively high volume fractions of nanoparticles, a diffusive growth regime was detected. The crossover to the slower growth regime as the nanoparticles volume fraction is increased or their radius is decreased is associated with the crystallization of the nanospheres within the preferred component. These results are qualitatively in good agreement with previous two-dimensional simulations using molecular dynamics [M. Laradji and G. MacNevin, J. Chem. Phys. 119, 2275 (2003)] and a time-dependent Ginzburg-Landau model [M. Laradji, J. Chem. Phys. 120, 9330 (2004)], as well as recent experiments. 相似文献
176.
Mohamed Ahmed Khaireh Marie Angot Clara Cilindre Grard Liger-Belair David A. Bonhommeau 《Molecules (Basel, Switzerland)》2021,26(6)
The diffusion of carbon dioxide (CO) and ethanol (EtOH) is a fundamental transport process behind the formation and growth of CO bubbles in sparkling beverages and the release of organoleptic compounds at the liquid free surface. In the present study, CO and EtOH diffusion coefficients are computed from molecular dynamics (MD) simulations and compared with experimental values derived from the Stokes-Einstein (SE) relation on the basis of viscometry experiments and hydrodynamic radii deduced from former nuclear magnetic resonance (NMR) measurements. These diffusion coefficients steadily increase with temperature and decrease as the concentration of ethanol rises. The agreement between theory and experiment is suitable for CO. Theoretical EtOH diffusion coefficients tend to overestimate slightly experimental values, although the agreement can be improved by changing the hydrodynamic radius used to evaluate experimental diffusion coefficients. This apparent disagreement should not rely on limitations of the MD simulations nor on the approximations made to evaluate theoretical diffusion coefficients. Improvement of the molecular models, as well as additional NMR measurements on sparkling beverages at several temperatures and ethanol concentrations, would help solve this issue. 相似文献
177.
Ashour A. Ahmed Oliver Kühn Rifaat H. Hilal Mohamed F. Shibl 《International journal of quantum chemistry》2013,113(9):1394-1400
Geometry and energetics of low energy conformers of sodium dihydrogen triacetate (SDHTA) and its anion are studied using density functional theory (DFT) at the Becke, Lee‐Yang‐Parr hybrid functional (BLYP) and Becke, three‐parameter, Lee‐Yang‐Parr hybrid functional (B3LYP) levels. For both cases, two structures of comparable energy are found, which have different symmetry with respect to the two hydrogen bonds (HBs). DFT‐based Born–Oppenheimer molecular dynamics simulations are performed for SDHTA, which show that both structures are visited at room temperature conditions. The trajectory analysis further reveals that the two HBs behave anticooperative, that is, on average elongation of one HB is accompanied by a compression of the other one. This is in accord with nuclear magnetic resonance (NMR) experimental studies for a similar counter ion–dihydrogen triacetate complex. © 2012 Wiley Periodicals, Inc. 相似文献
178.
A new Schiff base ligand (HL) was prepared via a condensation reaction of quinoline‐2‐carboxaldhyde with 2‐aminophenol in a molar ratio of 1:1. Its transition metal mixed ligand complexes with 1,10‐phenanthroline (1,10‐phen) as co‐ligand were also synthesized in a 1:1:1 ratio. HL and its mixed ligand complexes were characterized using elemental analysis, infrared, 1H NMR, mass and UV–visible spectroscopies, molar conductance, magnetic measurements, solid reflectance, thermal analysis, electron spin resonance and X‐ray diffraction. Molar conductance measurements showed that all complexes have an electrolytic nature, except Cd(II) complex. From elemental and spectral data, the formulae [M(L)(1,10‐phen)(H2O)]Clx?nH2O (where M = Cr(III) (x = n = 2), Mn(II) and Ni(II) (x = 1, n = 2), Fe(III) (x = n = 2), Co(II), Cu(II) and Zn(II) (x = 1, n = 2)) and [Cd(L)(1,10‐phen)Cl]?3H2O for the metal complexes have been proposed. The geometric structures of complexes were found to be octahedral. Powder X‐ray diffraction reflected the crystalline nature of the complexes; however, the Schiff base is amorphous. HL and its mixed ligand complexes were screened against Gram‐positive bacteria (Streptococcus pneumoniae and Bacillus subtilis) and Gram‐negative bacteria (Pseudomonas aeruginosa and Escherichia coli). Antifungal activity was determined against Aspergillus fumigatus and Candida albicans, the data showing that most complexes had activity less than that of the Schiff base while Mn(II), Fe(III) and Ni(II) complexes showed no significant antifungal activity. The anticancer activity of HL and its metal complexes was also studied against breast and colon cell lines. The metal complexes showed IC50 higher than that of HL, especially the Cu(II) complex which showed the highest IC50 against breast cell line. 相似文献
179.
180.