Complex formation of N-donor ligands with group 11 monovalent ions

Thermodynamic data on complex formation between nitrogen donor ligands (amines, pyridines) and group 11 monovalent ions in water and non-aqueous media are reviewed here. Particular emphasis is paid to Ag(I) complex formation in water and dimethylsulfoxide (DMSO), due to the amount and quality of data available. The influence of different basicities and steric properties of ligands, together with the solvation of the species involved, on the stability and nature of the resulting complexes is discussed. It emerges generally that the coordination properties of amines towards 1+ ions are all modulated through the number and basicity of nitrogen atoms present in the ligand, chelate ring sizes, degree of N-functionalisation, and the nature of the solvent. When possible, the thermodynamic properties of the complexes are related to the structural features of the ligands.     

Discontinuous Galerkin finite element discretization of a strongly anisotropic diffusion operator

The discretization of a diffusion equation with a strong anisotropy by a discontinuous Galerkin finite element method is investigated. This diffusion term is implemented in the tracer equation of an ocean model, thanks to a symmetric tensor that is composed of diapycnal and isopycnal diffusions. The strong anisotropy comes from the difference of magnitude order between both diffusions. As the ocean model uses interior penalty terms to ensure numerical stability, a new penalty factor is required in order to correctly deal with the anisotropy of this diffusion. Two penalty factors from the literature are improved and established from the coercivity property. One of them takes into account the diffusion in the direction normal to the interface between the elements. After comparison, the latter is better because the spurious numerical diffusion is weaker than with the penalty factor proposed in the literature. It is computed with a transformed coordinate system in which the diffusivity tensor is diagonal, using its eigenvalue decomposition. Furthermore, this numerical scheme is validated with the method of manufactured solutions. It is finally applied to simulate the evolution of temperature and salinity due to turbulent processes in an idealized Arctic Ocean. Copyright © 2014 John Wiley & Sons, Ltd.     

Application of a new AMIQAS computer program for integrated quality control, method evaluation and proficiency testing

Summary The computer program AMI - Quality Assessment Scheme (AMIQAS) was designed to give easy statistical management of analytical data in relation to method evaluation, internal quality control and proficiency testing. The program is designed in accordance with the recommendation of the ISO 5725 guideline and other official recommendations. The program consists of a database, test for outliers, statistics and graphs for evaluation of an analytical method for chemical, biological and environmental analysis, different control charts to be used in day-to-day internal quality control (Shewhart charts and z-charts). Finally the program has facilities to perform proficiency testing (also called external quality control) and produce the relevant evaluation reports for the documentation of method performance and quality control of results of measurements. The present paper demonstrates the applicability of the AMIQAS program for integrated method evaluation, internal quality control and proficiency testing using the determination of the concentration of lead in human whole blood as the numerical example.     

Passively Q-switched 0.1-mJ fiber laser system at 1.53 mum

We demonstrate a passively Q-switched fiber laser system generating pulses with as much as 0.1 mJ of pulse energy at 1.53 mum and a >1-kHz repetition rate. These results were achieved with a simple master oscillator-power amplifier scheme with a single pump source, realized with large-mode-area fiber and multiple reflections upon a semiconductor saturable-absorber mirror.     

Solvent Role on Cobalt(II) Dioxygen Carriers Based on Simple Polyamine Ligands

The kinetics and thermodynamics of O₂ addition to Co^II complexes containing the simple triamine ligand (L) diethylenetriamine (=N‐(2‐aminoethyl)ethane‐1,2‐diamine; dien) or N,N″‐dimethyldiethylenetriamine (=N‐methyl‐N′‐[2‐(methylamino)ethyl]ethane‐1,2‐diamine; dmdien) in the aprotic solvent dimethyl sulfoxide (DMSO) were studied by UV/VIS spectrophotometry, potentiometry, and O₂ absorption measurements. A parallel investigation on the anaerobic formation of Co^II complexes with dmdien, as well as on their reactivity towards O₂, was carried out in aqueous 0.1M NaClO₄ solution. [CoL]²⁺ and [CoL₂]²⁺ were the common species formed under anaerobic conditions in both aqueous and DMSO solutions. Under aerobic conditions, O₂ adducts of different stoichiometry were formed: a superoxo complex [CoL₂O₂]²⁺ in DMSO and dimeric species in H₂O. The role of the reaction medium as well as effects of N‐alkylation of the triamine ligand in the formation and reactivity of the [Co^II(triamine)] complexes are discussed.     

Mixed nitrogen/oxygen ligand affinities for bipositive metal ions and dioxygen binding to cobalt(II) complexes

The complex formation of Co(II) and Cd(II) with mixed N/O ligands in dimethylsulfoxide (dmso) at 298 K is investigated by means of potentiometric, UV-Vis, calorimetric, FT-IR, NMR and electrochemical techniques. The linear and cyclic ligands investigated are: 2,2'-oxydiethylamine (NON), N-(2-hydroxyethyl)-ethylenediamine (NNO), 1,4,10-trioxa-7,13-diaza-cyclopentadecane (2,1) and 1,4,7,10-tetraoxa-13-azacyclopentadecane (2,2). The results are discussed by taking into account the donor strength of donor atoms, strain effects in the formation of chelate rings, steric and inductive effects and the size of the cavity when macrocyclic ligands are concerned. DFT studies are also performed to gain an insight into the stabilization of the lower oxidation state of the CoL2(2+/3+) couple in order to understand the different reactivity of the Co(II) complexes towards dioxygen. The kinetics of dioxygen uptake has been studied by UV-Vis measurements and the results reveal an interesting strong solvent effect, which is active in lowering the rate constant for formation of the initial superoxo complex.     

Solvation effects on the stability of silver(I) complexes with pyridine-containing ligands studied by thermodynamic and DFT methods

The formation of Ag(I) complexes with 2,2'-bipyridine (bipy), 2,2'6',2' '-terpyridine (terpy), 2-(aminomethyl)pyridine (amp), and bis((2-pyridyl)methyl)amine (dpa) is studied in dimethyl sulfoxide (dmso) by means of potentiometric and calorimetric measurements. Enthalpy-stabilized mononuclear MLj complexes are formed, whereas entropy changes counteract complex formation. Additionally, a comparison with analog Ag-polyamine species is made to evidence the significant different coordination behavior of these classes of ligands. The results are discussed in terms of different basicity and steric requirements of the ligands and solvation effects. The dpa ligand, with an unprecedented coordination pattern, forms also a bimetallic complex [Ag2(dpa)2]2+ that has been structurally characterized in the solid state by X-ray diffraction. The influence of solvent, water and dmso, on the binding energy of the monodentate pyridine to Ag(I) has also been assessed by means of density functional theory (DFT) calculations. This study has been extended also in vacuum to the reaction of Ag(I) with the simple monoamine methylamine (mea). These results are correlated with the experimental evidence and used to interpret the different affinities of pyridine for the Ag(I) ion in the two media.