Synthesis and DFT Defined trans (O5O6) Molecular Structure of Cs[Fe(1,3- pddadp )] · 2H2O. Strain Analysis and Spectral Assignment of the Complex

An iron(III) complex with the hexadentate ligand 1,3-propanediamine-N,N′-diacetate-N,N′-di-3-propionate (1,3-pddadp) was prepared, chromatographically isolated as its isomer trans(O₅O₆)-Cs[Fe(1,3-pddadp)] · 2H₂O, and characterized. The trans(O₅O₆) configuration of the iron(III) compound was found to dominate and this geometry was established by means of IR spectroscopy and Density Functional Theory (DFT). Structural data correlating the octahedral geometry of the [Fe(1,3-pddadp)]⁻ unit and an extensive strain analysis are discussed in relation to the information obtained for similar complexes. Antibacterial activities of the free ligand and its corresponding iron(III) complex towards common Gram-negative and Gram-positive bacteria are reported as well.     

Osmotic and Activity Coefficients of {yKCl+(1−y)MgCl2}(aq) at T=298.15 K

Isopiestic vapor-pressure measurements were made at the temperature 298.15 K for aqueous KCl + MgCl₂ solutions using KCl(aq) as the reference standard. The measurements for these ternary solutions were made at KCl ionic strength fractions of y=0.0, 0.1989, 0.3996, 0.5993, 0.7925 and 1.0 (with two additional sets at y=0.0, 0.2021, 0.3998, 0.6125, 0.8209 and 1.0) for the ionic strength range from 0.4014 to 6.2790 mol?kg^?1. Our results, and those from two previous isopiestic studies, were combined and used with previously determined parameters for KCl(aq) and those determined here for MgCl₂(aq) to evaluate mixing parameters for the Clegg-Pitzer-Brimblecombe model. These combined data were also used to determine the mixing parameters of the Scatchard model. Both sets of model parameters are valid for ionic strengths of I≤12.8 mol?kg^?1, where higher-order electrostatic effects have been included in the Clegg-Pitzer-Brimblecombe mixture model. The activity coefficients for KCl and MgCl₂ were calculated from these models and the results for KCl were compared to experimental data from Emf measurements. The Scatchard model interaction parameters were used for calculation of the excess Gibbs energy as a function of the ionic strength and ionic strength fraction of KCl. The Zdanovskii-Robinson-Stokes rule of linearity for mixing of isopiestic solutions was tested.     

On the extremal geometric–arithmetic graphs with fixed number of vertices having minimum degree

Annals of Operations Research - The geometric–arithmetic index GA of a graph is defined as sum of weights of all edges of graph. The weight of one edge is quotient of the geometric and...     

Coexistence of composite bosons and composite fermions in nu = 1/2 + 1/2 quantum Hall bilayers

In bilayer quantum Hall systems at filling fractions near nu=1/2+1/2, as the spacing d between the layers is continuously decreased, intralayer correlations must be replaced by interlayer correlations, and the composite fermion (CF) Fermi seas at large d must eventually be replaced by a composite boson (CB) condensate or "111 state" at small d. We propose a scenario where CBs and CFs coexist in two interpenetrating fluids in the transition. Trial wave functions describing these mixed CB-CF states compare very favorably with exact diagonalization results. A Chern-Simons transport theory is constructed that is compatible with experiment.     

Complex configuration mixing method

A method analogous to the configuration interaction scheme, based on the complex molecular orbital (CMO) wavefunction as a zero-order approximation, is developed. The CMO pairing representation is employed to solve problems related to non-orthogonalities characteristic of the CMO method. This complex configuration mixing method may compete with present theories of electronic correlation in molecules.     

Isopiestic determination of the osmotic and activity coefficients of the {yKCl + (1 − y)K2HPO4}(aq) system at T = 298.15 K

The osmotic coefficients of aqueous mixtures of KCl and K₂HPO₄ have been measured at T = (298.15 ± 0.01) K by the isopiestic vapor pressure method over the range of ionic strengths from (2.3700 to 11.250) mol · kg⁻¹ using CaCl₂(aq) as the reference solution. Our new experimental results were modeled with an extended form of Pitzer’s ion-interaction model equations, both with the usual mixing terms and with Scatchard’s neutral–electrolyte mixing terms, and with the Clegg–Pitzer–Brimblecombe equations based on the mole-fraction-composition scale. There is a dearth of previously published isopiestic data for mixtures containing salts of and, consequently, no previous measurements are available for comparison with the present results. The present study yields mixing parameters for these three models that are needed for modeling the thermodynamic activities of solute components of natural waters and other complex aqueous electrolyte mixtures.