Coordination Environment Of Ag Research Articles

Probing the Bioinorganic Chemistry of Cu(I) with 111Ag Perturbed Angular Correlation (PAC) Spectroscopy

The two most common oxidation states of copper in biochemistry are Cu(II) and Cu(I), and while Cu(II) lends itself to spectroscopic interrogation, Cu(I) is silent in most techniques. Ag(I) and Cu(I) are both closed-shell d10 monovalent ions, and to some extent share ligand and coordination geometry preferences. Therefore, Ag(I) may be applied to explore Cu(I) binding sites in biomolecules. Here, we review applications of 111Ag perturbed angular correlation (PAC) of γ-ray spectroscopy aimed to elucidate the chemistry of Cu(I) in biological systems. Examples span from small blue copper proteins such as plastocyanin and azurin (electron transport) over hemocyanin (oxygen transport) to CueR and BxmR (metal-ion-sensing proteins). Finally, possible future applications are discussed. 111Ag is a radionuclide which undergoes β-decay to 111Cd, and it is a γ-γ cascade of the 111Cd daughter nucleus, which is used in PAC measurements. 111Ag PAC spectroscopy may provide information on the coordination environment of Ag(I) and on the structural relaxation occurring upon the essentially instantaneous change from Ag(I) to Cd(II).

Self-assembly of three Ag-polyoxovanadates frameworks for their efficient construction of C[sbnd]N bond and detoxification of simulant sulfur mustard

Three imidazole-modified Ag-polyoxovanadates frameworks (APFs) with a controllable molar ratio of Ag+ to polyoxovanadates (POVs) [Ag(IM)2]2V4O12·2Ag(IM)2 (APF-1), [Ag2(1-eIM)4]2[Ag(1-eIM)2]3·2Ag(1-eIM)2·3(1-HeIM)[V10O28]2 (APF-2) and [Ag(1-pIM)2]3[HV10O28]·2Ag(1-pIM)2·2H2O (APF-3) (IM = imidazole; 1-eIM = 1-ethylimidazole and 1-pIM = 1-propylimidazole) have been successfully achieved by self-assembly of POVs, Ag+ cations, and three different imidazole derivatives. Interestingly, the molar ratios of Ag+ to POVs vary from 4:1, 4.5:1 to 5:1 by changing the vanadium resources and imidazole derivatives. Notably, the coordination environment of Ag+ cations and the structure of POVs in the APFs are also different. Specifically, for APF-1, the four Ag atoms adopt three-coordinated and four-coordinated geometries, respectively, and Ag-imidazole complexes and [V4O12]4− cluster form the one-dimensional polymeric chains. While Ag atoms in APF-2 and APF-3 exhibit two-, four- and five-coordinated geometries for APF-2, four-, five- and six-coordinated geometries for APF-3, respectively. These Ag+ cations and decavanadate clusters are assembled into the 2D supramolecular structure through the Ag-O bonds and Ag…Ag argentophilic interaction. Remarkably, thus-obtained APF-2 can serve as powerful efficient heterogeneous catalyst for construction of CN bond and detoxification of simulant sulfur mustard (yields up to 99%), which enable successful recycling for three cycles with remained catalytic activities and structure stability.

The coordination environment of Ag and Cu in ternary chalcogenide glasses

An analysis is made of the information provided by the method of isotopic substitution in neutron diffraction on the metal atom coordination environment in M-A-X glasses, where M denotes Ag or Cu, A a Group IVB or VB element, and X a chalcogen. It is found that the M-X coordination number is low (~ 3–4) but there is no clear correlation between its precise value and whether the material is a semiconductor or fast-ion conductor. When the concentration of M is high it is possible to measure the M-M partial pair distribution function g M-M(r) . In those systems for which results are available it is found that, irrespective of the electrical conductivity mechanism, short M-M nearest-neighbour distances are present. However, the first peak in g M-M(r) is more clearly defined in the case of semiconducting glasses.

Structure of fast-ion conducting chalcogenide glasses: the AgAsSe system

The coordination environment of Ag in bulk-quenched Ag 4As 37.6Se 58.3 and Ag 2As 3Se 4 glasses is investigated by using the method of isotopic substitution in neutron diffraction. It is found that there is little change in the short-range order about Ag between the two compositions: Ag is covalently bonded to an average of ≈ 3 Se atoms at a distance of ≈ 2.68 A ̊ in both samples. The absence of a pronounced change in the structure about the metal atom in the AgAsSe system, between glass compositions where the electrical conductivity is electronic (4 at.% Ag)_and where it is predominantly ionic (22.2 at.% Ag), is by direct contrast with the case observed for glasses in the AgAsS system.