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showing 10 items of 2982 documents
Cyclam-strapped porphyrins and their iron(III)-copper(II) complexes as models for the resting state of cytochrome c oxidase
1999
International audience; The ESR study of two cyclam-strapped porphyrins in which, on one side, the cyclam is attached with a variable length linker to the porphyrin and, on the other side, a non-coordinating strap protects the iron from any intermolecular interaction, is reported. Variation of the linker length is made possible by the use of either a Michael reaction or a nucleophilic substitution, leading respectively to three or two carbon atom links. It is shown that in the case of the shortest link, the oxidized ironÈcopper complex exhibits a spin interaction. The distance between thetwo metal centers is evaluated to be around 4.5 Å, a value consistent with the one found in the natural …
Halogen bond preferences of thiocyanate ligand coordinated to Ru(II) via sulphur atom
2017
Halogen bonding between [Ru(bpy)(CO)2(S-SCN)2] (bpy = 2,2’-bipyridine), I2 was studied by co-crystallising the metal compound and diiodine from dichloromethane. The only observed crystalline product was found to be [Ru(bpy)(CO)2(S-SCN)2]⋅I2 with only one NCS⋅⋅⋅I2 halogen bond between I2 and the metal coordinated S atom of one of the thiocyanate ligand. The dangling nitrogen atoms were not involved in halogen bonding. However, computational analysis suggests that there are no major energetic differences between the NCS⋅⋅⋅I2 and SCN⋅⋅⋅I2 bonding modes. The reason for the observed NCS⋅⋅⋅I2 mode lies most probably in the more favourable packing effects rather than energetic preferences between …
Temperature-Induced Structural Transitions in the Gallium-Based MIL-53 Metal–Organic Framework
2013
We report a structural and thermodynamic investigation of the phase behavior of Ga(OH,F)-MIL-53, a gallium-based metal–organic framework (MOF) having the MIL-53 topology containing 0.7 wt % fluorine bonded to the metal. Despite some small structural differences, especially for the hydrated form, the overall physical chemistry behavior of Ga(OH,F)-MIL-53 is very similar to standard fluorine free Ga-MIL-53 material. A combination of in situ X-ray diffraction, in situ Fourier transform infrared spectroscopy, differential scanning calorimetry, and heat capacity measurements allowed us to establish that Ga(OH,F)-MIL-53 under vacuum (i.e., the empty material) exhibits two stable phases: a nonporo…
l-Arabinose Conformers Adsorption on Ruthenium Surfaces: A DFT Study
2012
Adsorption of 5 L-arabinose tautomers – one acyclic and four cyclic (α and β, pyranose and furanose) species – on a ruthenium surface was studied as a precursor-process of the, nowadays more and more, industrially important sugar catalytic hydrogenation on metal surfaces in water medium. The study was mostly referred to a 37-atom metal catalyst fragment, even though border-effects on the adsorption processes were also checked employing a 61-atom metal fragment. In order to figure out conformational effects on the title process the tautomer flexibility was, at first, investigated by the genetic-algorithm based code Balloon, considering the conformational spaces of the different aquo tautomer…
Selective Cobalt over Nickel separation using neat and confined ionic liquids
2020
International audience; Task Specific Ionic Liquids (TSILs) generated by association between tetraalkylammonium cations and coordinating anions such as dicyanamide (Dca-) and thiocyanate (SCN-) were used for the selective separation of Ni(II) over Co(II). SCN-based TSIL presents higher extraction efficiency than the Dca-based one towards Co(II) (E = 85.4 % vs 54.6 %) and Ni (II) (E = 22 % vs 0.5%) but lower separation factors (βCo/Ni = 21 vs 239). Interestingly, extraction of Co(II) and Ni(II) in Dca-based TSIL can be enhanced using salts with chaotropic anions such as NaNO3 (E > 90 % for Co(II) and E = 85% for Ni(II)). The use of NaCl allows, moreover, the efficient separation of both ions…
Comparative analysis of the remineralization potential of CPP–ACP with Fluoride, Tri-Calcium Phosphate and Nano Hydroxyapatite using SEM/EDX – An in …
2019
Background In recent years, the non-invasive management of non cavitated caries lesions using remineralization systems to repair the enamel have received more attention from the scientific community. Aim: To quantitatively evaluate the remineralization potential of Casein phosphopeptide-amorphous calcium phosphate-fluoride(CPP-ACPF), Tri-calcium phosphate(TCP) & Nano-hydroxyapatite(nHAP) using Scanning Electron Microscopy(SEM) and Energy dispersive X-ray Analysis(EDX). Material and Methods 40 enamel specimens were prepared, and immersed in demineralising solution at a pH of 4.4 for 96 hours at 37°C, to induce artificial carious lesions. Remineralization was carried out for a period of 30 da…
Selective Gold Recovery and Catalysis in a Highly Flexible Methionine-Decorated Metal–Organic Framework
2016
A novel chiral 3D bioMOF exhibiting functional channels with thio-alkyl chains derived from the natural amino acid l-methionine (1) has been rationally prepared. The well-known strong affinity of gold for sulfur derivatives, together with the extremely high flexibility of the thioether "arms" decorating the channels, account for a selective capture of gold(III) and gold(I) salts in the presence of other metal cations typically found in electronic wastes. The X-ray single-crystal structures of the different gold adsorbates Au(III)@1 and Au(I)@1 suggest that the selective metal capture occurs in a metal ion recognition process somehow mimicking what happens in biological systems and protein r…
ChemInform Abstract: New Binary Antimonide Hf5Sb3 - Differences and Similarities to the Zr Antimonides.
2010
Abstract Hf5Sb3 can be prepared by arc-melting of hafnium and previously synthesized HfSb2. It crystallizes like the high-temperature modification of Zr5Sb3 in the Y5Bi3 structure type, space group Pnma, Z=4, a=740.75(9) pm, b=871.8(1) pm, c=1073.6(1) pm, V=693.3(1) 106pm3. An antimonide analogous to the low-temperature form of Zr5Sb3 was not obtained during our investigations. In the structure of Hf5Sb3, the Hf atoms form a three-dimensional network with numerous short Hf–Hf contacts, including the Sb atoms in severely distorted two- and three-capped trigonal prismatic voids. Calculations of the electronic structure, performed with the extended Huckel approximation as well as the TB-LMTO-A…
Crystal structure, spectroscopic characterisation and magnetic properties of [Cu(BIP)(N3)]·H2O (BIP=3,3-bis(2-imidazolyl)propionate), a copper(II) po…
2001
Abstract The structure and the spectroscopic and magnetic properties of [3,3-bis(2-imidazolyl)propionato]azidocopper(II) monohydrate are described. The compound is built of [Cu(BIP)N3] entities which are connected through carboxylate groups from the BIP molecules —which act as a tridentate ligand—and asymmetrical μ-1,3-azido bridges, leading to a polymeric sheet-like structure. The copper atom is involved in a CuN3ON′ chromophore and lies in a distorted square-pyramidal environment. Both electronic and EPR spectra are indicative of an essentially dx2−y2 ground state for the copper(II) ions. Magnetic susceptibility measurements in the range 1.8–200 K show very weak antiferromagnetic exchange…
Synthesis, structure, spectral characterization and DNA binding affinity of new water soluble trinuclear copper(II) complexes with partial cubane Cu3…
2015
Two new water soluble trinuclear copper(II) complexes, [Na 6 (H 3 O) 4 ][Cu 3 (cbal) 3 (μ 3 -OH)(H 2 O) 3 ] 4 (ClO 4 ) 6 ·3H 2 O ( 1 ) and [K(H 2 O) 2 ][Cu 3 (cbal) 3 (μ 3 -OH)(H 2 O)]·3.75H 2 O ( 2 ) have been synthesized in good yield via the reaction of an unsymmetrical amino dicarboxylic ligand, N-(2-carboxybenzomethyl)-β-alanine (H 2 cbal), Cu(ClO 4 ) 2 ·6H 2 O and NaOH/K 2 CO 3 in methanol at room temperature. Complexes 1 and 2 have been characterized by elemental analysis, room temperature magnetic susceptibility measurements, FTIR, UV–Vis, mass spectrometry and single crystal X-ray crystallography. Both complexes contain a partial cubane [Cu 3 O 4 ] core consisting of the trinuclear…