Experimental Study of the Effect of Temperature,Pressure, and Concentration on the Viscosity of Aqueous KBr Solutions

The viscosity of five (0.1240, 0.2378, 0.4645, 0.9440, and 2.2310 mol⋅kg⁻¹) binary aqueous KBr solutions have been measured with a capillary flow technique. Measurements were made at pressures up to 30 MPa for the temperature range 298 to 577 K. The total uncertainties of the viscosity, pressure, temperature, and composition measurements were estimated to be less than 1.6%, 0.05%, 15 mK, and 0.02%, respectively. The temperature and pressure coefficients of the viscosity of KBr(aq) were studied as a function of molality and temperature. The measured viscosities were compared with data, predictions and correlations previously reported in the literature. The viscosity data were used to accurately calculate the physical-meaningful parameters (viscosity A- and B-coefficients) of the extended Jones-Dole equation for the relative viscosity (η/η ₀). Various theoretical models {absolute rate theory, Tammann-Tait-Gibson (TTG) model, and extended Einstein model} were used to accurately represent the measured viscosities. Values of hydrodynamic molar volume V _k (effective rigid molar volume of the salt) were calculated using the present experimental data. The high-pressure viscosity measurements were used to test the predictive capability of the TTG model.     

Reactivity of triruthenium thiophyne and furyne clusters: competitive S-C and P-C bond cleavage reactions and the generation of highly unsymmetrical alkyne ligands

The synthesis and reactivity of the thiophyne and furyne clusters [Ru3(CO)7(mu-dppm)(mu3-eta2-C4H2E)(mu-P(C4H3E)2)(mu-H)] (E = S, O) is reported. Addition of P(C4H3E)3 to [Ru3(CO)10(mu-dppm)] (1) at room temperature in the presence of Me3NO gives simple substitution products [Ru3(CO)9(mu-dppm)(P(C4H3E)3)] (E = S, 2; E = O, 3). Mild thermolysis in the presence of further Me3NO affords the thiophyne and furyne complexes [Ru3(CO)7(mu-dppm)(mu3-eta2-C4H2E)(mu-P(C4H3E)2)(mu-H)] (E = S, 4; E = O, 6) resulting from both carbon-hydrogen and carbon-phosphorus bond activation. In each the C4H2E (E = S, O) ligand donates 4-electrons to the cluster and the rings are tilted with respect to the mu-dppm and the phosphido-bridged open triruthenium unit. Heating 4 at 80 degrees C leads to the formation of the ring-opened cluster [Ru3(CO)5(mu-CO)(mu-dppm)(mu3-eta3-SC4H3)(mu-P(C4H3S)2)] (5) resulting from carbon-sulfur bond scission and carbon-hydrogen bond formation and containing a ring-opened mu3-eta3-1-thia-1,3-butadiene ligand. In contrast, a similar thermolysis of 3 affords the phosphinidene cluster [Ru3(CO)7(mu-dppm)(mu3-eta2-C4H2O)(mu3-P(C4H3O))] (7) resulting from a second phosphorus-carbon bond cleavage and (presumably) elimination of furan. Treatment of 4 and 6 with PPh3 affords the simple phosphine-substituted products [Ru3(CO)6(PPh3)(mu-dppm)(mu3-eta2-C4H2E)(mu-P(C4H3E)2)(mu-H)] (E = S, 8; E = O, 9). Both thiophyne and furyne clusters 4 and 6 readily react with hydrogen bromide to give [Ru3(CO)6Br(mu-Br)(mu-dppm)(mu3-eta2-eta1-C4H2E)(mu-P(C4H3E)2)(mu-H)] (E = S, 10; E = O, 11) containing both terminal and bridging bromides. Here the alkynes bind in a highly unsymmetrical manner with one carbon acting as a bridging alkylidene and the second as a terminally bonded Fisher carbene. As far as we are aware, this binding mode has only previously been noted in ynamine complexes or those with metals in different oxidation states. The crystal structures of seven of these new triruthenium clusters have been carried out, allowing a detailed analysis of the relative orientations of coordinated ligands.     

9,10‐Diphenylanthracene as a matrix for MALDI‐MS electron transfer secondary reactions

The most common secondary‐ionization mechanism in positive ion matrix‐assisted laser desorption/ionization (MALDI) involves a proton transfer reaction to ionize the analyte. Peptides and proteins are molecules that have basic (and acidic) sites that make them susceptible to proton transfer. However, non‐polar, aprotic compounds that lack basic sites are more difficult to protonate, and creating charged forms of this type of analyte can pose a problem when conventional MALDI matrices are employed. In this case, forming a radical molecular ion through electron transfer is a viable alternative, and certain matrices may facilitate the process. In this work, we investigate the performance of a newly developed electron‐transfer secondary reaction matrix: 9,10‐diphenylanthracene (9,10‐DPA). The use of 9,10‐DPA as matrix for MALDI analysis has been tested using several model compounds. It appears to promote ionization through electron transfer in a highly efficient manner as compared to other potential matrices. Thermodynamic aspects of the observed electron transfers in secondary‐ionization reactions were also considered, as was the possibility for kinetically controlled/endothermic, electron‐transfer reactions in the MALDI plume. Copyright © 2012 John Wiley & Sons, Ltd.     

Quantum-chemical calculations of the tautomeric forms of azo derivatives of acetylacetone and determination of the stability constants of their complexes with rare-earth metals

The effective atomic charges in the tautomeric forms (enol-azo, keto-azo, and hydrazo) of 3-(2-hydroxy-5-nitro-3-sulfophenylazo)pentane-2,4-dione (L¹), 3-(2-hydroxy-3,5-disulfophenylazo)pentane-2,4-dione (L²), 3-(5-chloro-2-hydroxy-3-sulfophenylazo)pentane-2,4-dione (L³), 3-(2-hydroxy-4-nitrophenylazo)pentane-2,4-dione (L⁴), and 3-(2-hydroxyphenylazo)pentane-2,4-dione (L⁵) were calculated by the Hückel method (MO LCAO). It was found that the hydrazo form is most reactive for meta- and meta’-substituted derivatives (L^1–3) and the keto-azo form is most reactive for para-substituted (L⁴) and unsubstituted ones (L⁵). The stability constants of complexes of rare-earth metals (La, Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) with L^1–5 determined by potentiometric titration decrease in the order: Lu > Yb > Tm > Er > Ho > Dy > Tb > Gd > Eu > Sm > Nd > Ce > La. Functionalization of the aromatic part of ligands L affected neither the rare-earth metal: L ratio (1: 2) nor the above order of the stability constants.     

9,10-Diphenylanthracene as a matrix for MALDI-MS electron transfer secondary reactions

The most common secondary-ionization mechanism in positive ion matrix-assisted laser desorption/ionization (MALDI) involves a proton transfer reaction to ionize the analyte. Peptides and proteins are molecules that have basic (and acidic) sites that make them susceptible to proton transfer. However, non-polar, aprotic compounds that lack basic sites are more difficult to protonate, and creating charged forms of this type of analyte can pose a problem when conventional MALDI matrices are employed. In this case, forming a radical molecular ion through electron transfer is a viable alternative, and certain matrices may facilitate the process. In this work, we investigate the performance of a newly developed electron-transfer secondary reaction matrix: 9,10-diphenylanthracene (9,10-DPA). The use of 9,10-DPA as matrix for MALDI analysis has been tested using several model compounds. It appears to promote ionization through electron transfer in a highly efficient manner as compared to other potential matrices. Thermodynamic aspects of the observed electron transfers in secondary-ionization reactions were also considered, as was the possibility for kinetically controlled/endothermic, electron-transfer reactions in the MALDI plume. Copyright ? 2012 John Wiley & Sons, Ltd.     

Controllability of Some Nonlinear Systems in Hilbert Spaces

In this paper, several abstract results concerning the controllability of semilinear evolution systems are obtained. First, approximate controllability conditions for semilinear systems are obtained by means of a fixed-point theorem of the Rothe type; in this case, the compactness of the linear operator is assumed. Next, the exact controllability of semilinear systems with nonlinearities having small Lipschitz constants is derived by means of the Banach fixed-point theorem; in this case, the compactness of the operators is not assumed. In both cases, it is proven that the controllability of the linear system implies the controllability of the associated semilinear system. Finally, these abstract results are applied to the controllability of the semilinear wave and heat equations.     

Novel rGO@Fe3O4 nanostructures: An active electrocatalyst for hydrogen evolution reaction in alkaline media

Because of energy crisis, the hydrogen evolution reaction (HER) limits the feasible utilization of water splitting. Herein, we report reduced graphene-oxide (rGO) with Iron-oxide (Fe₃O₄) nanostructures as highly active electrocatalyst for HER. As-prepared [email protected]₃O₄ shows superior electrochemical responses to those of corresponding its monometallic rGO and Fe₃O₄. The overpotential of [email protected]₃O₄ has been achieved as 300 mV at 10 mA/cm² current density with a Tafel slope of 80 mV/dec. The [email protected]₃O₄ nanostructure has its stability for 24 h to reveal long term electrochemical performance.