Coordination complex | EPFL Graph Search

A coordination complex is a chemical compound consisting of a central atom or ion, which is usually metallic and is called the coordination centre, and a surrounding array of bound molecules or ions, that are in turn known as ligands or complexing agents. Many metal-containing compounds, especially those that include transition metals (elements like titanium that belong to the periodic table's d-block), are coordination complexes. Nomenclature and terminology Coordination complexes are so pervasive that their structures and reactions are described in many ways, sometimes confusingly. The atom within a ligand that is bonded to the central metal atom or ion is called the donor atom. In a typical complex, a metal ion is bonded to several donor atoms, which can be the same or different. A polydentate (multiple bonded) ligand is a molecule or ion that bonds to the central atom through several of the ligand's atoms; ligands with 2, 3, 4 or even 6 bonds to the central atom are

Syntheses, structures and properties of silver(I) complexes constructed from nitrogenous aromatic heterocyclic carboxylic acids and N-donor ligands

Chi Wai Cheung, Hong-Ling Gao

Four new coordination complexes with silver(I) ions and nitrogenous aromatic heterocyclic carboxylic ligands, namely [AB(4)(Pac)(Phen)(4)]center dot 8H(2)O (1), {[AB(4)(Pztc)(bPe)(3)] center dot 5H(2)O}(n) (2), [Ag-4(Hmptc)(2)(4,4'-bPY)(3)] center dot 4.5H(2)O (3), and [Ag-2(H(2)mPtc)(2)(2,2'-bPY)(2)] (4) (H(4)Pztc = pyrazine-2,3,5,6-tetracarboxylic acid, H(3)mptc = 6-methyl2,3,5-pyridine-tricarboxylic acid, phen = 1,10-phenanthroline, bpe = trans-1,2-bis(4-pyridyl)ethylene, 4,4'bpy = 4,4'-bipyridine, 2,2'-bpy = 2,2'-bipyridine), have been synthesized by the self-assembly reactions and characterized by X-ray diffraction single crystal structure analysis, elemental analysis, IR, PXRD, fluorescence and thermal analysis. In I, four crystallographically independent silver(l) atoms are found to coordinate with only one pztc(4-) ligand. Complex 2 is a 2D grid structure. Complexes 3 and 4 are extended from OD to 2D or 1D by the Ag center dot center dot center dot O interactions. (C) 2014 Elsevier B.V. All rights reserved.

Elsevier2014

The effect of Cr composition on the local atomic and magnetic structure of pristine and ion-irradiated FeCr alloys

Andi Idhil Ismail

High Cr (9-14% Cr) ferritic/martensitic steels are considered as one of the most promising candidates for structural materials for advanced nuclear power plants. Therefore, the understanding of the evolution of properties under operation conditions is of primary importance. This work focuses on the effect of Cr composition on the local atomic and magnetic structure of pristine and ion-irradiated FeCr alloys. The materials considered for this study are commercial purity FeCr binary alloys with varying Cr content up to 16% at.Cr, which were also implanted with heavy ions (Fe+) under different conditions. Using a combination of spatially resolved and element specific techniques the following results were obtained: - The dependence of the total (bulk) magnetic moments is linearly decreasing as the Cr-content is increasing - The Fe magnetic moments at the surface reduced by the presence of impurities and defects. The dependence on Cr-content is non-linear, with a tendency of increasing the spin moments above 10% Cr. - The Cr spin moments exhibit a reorientation transition around 9% Cr from ferromagnetically to anti-ferromagnetically aligned with respect to the Fe spin moments. - The effects of ion irradiation are fairly complex, with an overall higher spin magnetic moment after exposure to the heavy ions. The ion dose has a reduced effect on the spin moments while the target temperature shows a more significant, but scattered influence on the Fe spin moments. - All specimens show a decrease of the Cr nearest neighbor distance for Cr contents between 6 – 10% Cr. Also, the atomic disorder around the Cr atoms is enhanced compared to the Fe atoms. - For the Fe9% Cr irradiated alloy the effect of elevated temperatures and dose is clearly seen as a reduction of atomic coordination numbers around the Cr atoms, which can be associated with formation of vacancies. - For the Fe5% Cr and Fe12% Cr alloys, the number of nearest neighbors around the Cr atoms is not sensitive to irradiation.

EPFL2013

The effect of Cr composition on the local atomic and magnetic structure of pristine and ion-irradiated FeCr alloys

Andi Idhil Ismail

EPFL2013