Search results for "stoichiometry"
showing 10 items of 270 documents
Exploring new water soluble bridged dicopper(II) assemblies: Synthesis, structure, spectroscopic characterization, properties, and their interactions…
2021
Abstract Three new water soluble dimetallic copper(II) complexes, [Cu(H2O)5][Cu2(cpdp)(µ-O2As(CH3)2)]2Br2·13.83H2O·0.67CH3OH (1), [Cu2(Hcpdp)(µ-SO4)]·5H2O (2) and [Cu2(cpdp)(µ-pz)]·16H2O (3) (H3cpdp = N,N′-Bis[2-carboxybenzomethyl]-N,N′-Bis[2-pyridylmethyl]-1,3-diaminopropan-2-ol; (CH3)2AsO2− = cacodylate; SO42− = sulfate; pz− = pyrazolate) have been successfully synthesized and characterized for the investigation of coordination/binding aspects with biologically significant monosaccharide, d -glucosamine. Preparation of 1, 2 and 3 has been achieved by carrying out reaction of H3cpdp with stoichiometric quantities of CuCl2·2H2O/NaO2As(CH3)2·3H2O, CuSO4·5H2O and CuCl2·2H2O/1H-pyrazole, respe…
Compounds of tungsten(VI) with citric acid: A spectrophotometric, polarimetric and hydrogen-1, carbon-13 N.M.R. study of the formation and interconve…
1986
Tungsten(VI)-citrate complexes, which occur in aqueous solution, were studied by polarimetric and absorbance measurements. The pH of the medium is the principal variable controlling complex formation and interconversion equilibria. At high pH (>6), the stable complexes are monomers with 1∶2 and 1∶1 stoichiometry, depending on the tungsten(VI)-citrate ratio, while at lower pH two different dinuclear complexes are formed. The intervals of existence of these species with the pH, the number of equivalents of acid necessary for their formation, as well as the conditional stability constant, have also been calculated. The structure of these compounds have been investigated by1H and13C-n.m.r. spec…
Complexes of molybdenum(VI) with organic diacid ligands: The molybdenum(VI)-malonic acid system
1983
Malonic acid (C3O4H4) and MoVI form in aqueous solution two dinuclear dioxo-complexes of which the stability is a function of the pH of the medium. Both complexes have a 1∶1 metal-ligand stoichiometric ratio, and the interconversion may involve a structural rearrangement. Conditional dissociation constants have been determined spectrophotometrically. Saline cryoscopy supports the spectrophotometric results. Salts of [Co(en)3]3+ have been isolated. The ligand behaviour of malonic acid differs partially from that observed for α-polyhydroxy ligands.
Chemical heterogeneities in nanometric titanomagnetites prepared by soft chemistry and studied ex situ : evidence for fe-segregation and oxidation ki…
2001
Nanocrystalline Fe-based spinels with composition Fe3-xTixO4 are synthesized using soft chemistry. Two steps are involved: precipitation in an aqueous solution followed by thermal annealing under a reducing mixture of N2/H2/H2O gases. Fe-segregation is found inside stoichiometric particles when the powders are studied ex situ; they exhibit a strong surface iron enrichment. This heterogeneity is related to kinetic effects linked to the difference of mobility between Fe2+ and Ti4+ cations during the partial oxidation of cations occurring ex situ. Stresses in the grains induced by oxidation govern the oxidation kinetics and lead to an abrupt compositional variation inside each particle. These…
The dynamics of 57Fe nuclei in Fe(II)-DNA and [Fe(II)(1-methyl-2-mercaptoimidazole)2]-DNA condensates.
2002
Abstract Alcoholic solutions of FeCl 2 and Fe II (Hmmi) 2 Cl 2 (Hmmi=1-methyl-2-mercaptoimidazole) induce calf thymus DNA condensation from aqueous solutions buffered at pH 7.4. A 1:1 Fe II –(DNA monomer) stoichiometry is assumed. The 57 Fe Mossbauer hyperfine parameters suggest an octahedral coordination environment, severely distorted, in both Fe II –(DNA monomer) and [Fe II (Hmmi) 2 ]–(DNA monomer) condensates. The dynamic properties of iron nuclei in freeze-dried samples were investigated by means of variable temperature 57 Fe Mossbauer spectroscopy. Mean square displacements, 〈 x 2 〉( T ), were calculated, such as the effective vibrating mass and the Mossbauer lattice temperature of th…
Conformational investigations of bis(α-aminoalkyl)phosphinic acids and studies of the stability of their complexes with Cu(II)
2008
Abstract Conformational investigations of a group of bis(α-aminoalkyl)phosphinic acids were performed by use of NMR spectroscopy and theoretical calculations. In the case of one of the studied compounds, substituted with aminobenzyl and amino(p-chlorobenzyl) moieties, a pH-dependent equilibrium between conformers, stabilized by intermolecular hydrogen bonds was observed. Potentiometric studies proved that these molecules formed stable complexes with copper(II) ions, where stoichiometry was 1:1 and 1:2 depending on pH of their aqueous solution.
Iron deposition on TiO2(110): effect of the surface stoichiometry and roughness
1999
Abstract Characterizations of ultra-thin iron films deposited on TiO 2 (110) surfaces with different stoichiometries, roughnesses and crystallinities have been carried out by X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). For a high initial roughness of the substrate, a 2D growth mode is observed up to three monolayers. But, if the initial roughness is low, clusters grow on the TiO 2 surface. Whatever the initial surface stoichiometry, electronic exchanges occur between titanium and iron leading to a reduction of titanium and an oxidation of iron. This interaction between iron and titanium dioxide surface takes place only at the interface between the metal and…
Inhibitoren der Korrosion 19 (1). Autoxidationsstudien an Fe2+-Trimethylen-1,3-bis-phosphonat als Modell einer die Korrosion inhibierenden Deckschicht
1976
Die Autoxidationsgeschwindigkeit der Fe2+. Salze ist stark abhangig vom pH und ist bei pH 2 praktisch gleich Null, bei pH 5–7 sehr hoch. Durch Zusatz von Trimethylen-1,3-bis-phosphonsaure wird die Autoxidation etwas verlangsamt und der Sauerstoffverbrauch starker erhoht als es der Stochiometrie der Fe2+-Oxidation entspricht. Dieser Umstand erklart sich durch den oxidativen Abbau der Trimethylen-1,3-bis-phosphonsaure zu Phosphorsaure, wobei Salze des dreiwertigen Eisens als Niederschlag ausfallen. Diese Fe3+-bis-phosphonate sind dreidimensional vernetzt; das Fe:P-Verhaltnis liegt zwischen 0.5 und 0.9 und wird mit abnehmendem pH-Wert geringer. Inhibitors of corrosion 19 (1). Autoxidation stud…
Synthesis and structural studies by infrared and Mössbauer spectroscopy of adducts of tin(IV) and organotin(IV) derivatives with 2,2′-azopyridine
1985
Abstract A number of complexes have been prepared by the reaction between 2,2′-azopyridine(AZP) and tin(IV) halides and organotin(IV) halides, and characterized by elemental analysis and infrared and variable temperature 119Sn Mossbauer spectroscopies. All of the new compounds have 1:1 stoichiometry, with the AZP ligand occupying two coordination sites by bonding through one of the ring and one of the azo group nitrogen atoms, to give rise to distorted octahedral structures. In the diorganotin complexes the two organic groups occupy trans positions. The infrared and Mossbauer spectroscopic data suggest that these compounds are monomeric in the solid state.
On thermal behaviour of DMC catalysts for ring opening polymerization of epoxides
2016
Abstract The thermoanalytical studies of two types of the double metal cyanide catalysts were carried out. The identity of the catalysts was characterized by an elemental analysis and FTIR. The thermoanalytical examinations performed with the use of TG-DSC, EGA-FTIR, EGA-MS shed new light on views of the bonding of the ligands in the DMC. The chemical justification of the processes responsible for the TG/DSC steps was proposed. Several organic ligand complexing states were found in both types of catalysts. The ligand-DMC bondings were decomposing stepwise in relatively low temperature ranges, which could suggest their negligible role at catalytic reaction being performed usually at higher t…