Showing papers in "Inorganic Chemistry in 1987"

Electrochemical polymerization of amino-, pyrrole-, and hydroxy-substituted tetraphenylporphyrins

Abstract: are described. Oxidations of these monomers lead to thin polymeric coatings on electrodes by coupling reactions analogous to those operative in polyaniline, polypyrrole, and polyphenol electropolymerization. The films contain from two to several hundred layers of porphyrin sites and display reductive electrochemical and electronic spectroscopic properties similar to those of monomer solutions in acetonitrile or methylene chloride. The pyrtolyl- and amino-based polymers are polycationic and thus anion exchangers, whereas the hydroxy-based polymers (at pH >8) are polyanionic. Films prepared from electropolymerization of cobalt tetrakis(o-aminopheny1)porphyrin display a split Co(III/II) wave in aqueous acid and base and are good oxygen reduction catalysts, whereas films prepared from all other cobalt porphyrin monomers display only one Co(III/II) wave and are poor catalysts.

Solubility of amorphous chromium(III)-iron(III) hydroxide solid solutions

Abstract: Neutralization of acidic solutions containing Cr(III) and Fe(III) at room temperatures results in coprecipitation of these elements as an amorphous solid solution (Cr/sub x/Fe/sub 1-x/(OH)/sub 3/). The solubilities of the Cr/sub x/Fe/sub 1-x/(OC)/sub 3/ precipitates prepared with different mole fractions (x) of Cr(OH)/sub 3/ (0.99, 0.89, 0.69, 0.49, 0.36, 0.15, 0.09, 0.01, 0.00) were determined in 0.01 M prechlorate solutions between pH 2 and 6 in an N/sub 2/ atmosphere. The Cr concentrations in 0.0018-..mu..m filtrates at various times between 5 and 210 days, from initially undersaturated and oversaturated solutions, show that equilibrium was attained within about 7 days when x < 0.5 and more slowly when higher mole fractions of Cr(OH)/sub 3/ were used. In general, aqueous Cr concentrations decrease with decreasing Cr contents in the solids, suggesting that Cr/sub x/Fe/sub 1-x/(OH)/sub 3/ behaves thermodynamically like a solid solution. Activity coefficients for Cr(OH)/sub 3/ in the solid solutions were calculated from the solubility data and are given by the equation log lambda/sub Cr(OH)3/ = -1.60 + 0.28(1 - x)/sup 2/ - 1.79(1 - x)/sup 3/ for 0.01 less than or equal to x less than or equal to 0.69. Aqueous Fe activities were generally too low for reliable measurement;more » therefore, the corresponding activity coefficients for Fe(OH)/sub 3/ (log lambda/sub Fe(OH)3/ = -2.26x/sup 2/ + 1.39x/sup 3/) were calculated by a Gibbs-Duhem equation. A general relationship (log (CrOH/sup 2 +/) = -2pH + 4.18 + 0.28(1 - x)/sup 2/ - 1.79(1 - x)/sup 3/ + log x) developed from these data can be used to calculate Cr concentrations in solutions between pH 2 and 6 that are in equilibrium with Cr-bearing ferric hydroxides with known Cr content. 12 references, 6 figures, 1 table.« less

Novel polypyrazolylborate ligands: coordination control through 3-substituents of the pyrazole ring

Abstract: Co(HB[t-butyl-3 pyrazolyl-1] 3 )(NCS) et Co(HB[phenyl-3 pyrazolyl-1] 3 )(NCS)(THF) cristallisent dans le systeme monoclinique avec le groupe d'espace P2 1 /n. Affinement des structures jusqu'a 0,042 et 0,043 respectivement. La coordination autour de Co(II) dans le premier complexe est tetraedrique. Dans le second complexe, elle est bipyramidale rhomboedrique

A2Ln2Ti3O10 (A = potassium or rubidium; Ln = lanthanum or rare earth): a new series of layered perovskites exhibiting ion exchange

Abstract: Several layered perovskites $A_2Ln_2Ti_3O_{10}$ (A = K or Rb; Ln = rare earth) and their monohydrates, crystg. in tetragonal structures related to ${Sr_4Ti_3O_10}$, were prepd. The alkali ions in $K_2Ln_2Ti_3O_{10}$ are topochem. exchanged by protons in aq. acid or by other alkali ions in molten salts. $H_2Ln_2Ti_3O_{10}$ also adopt a tetragonal structure similar to the parent oxides. Dehydrated $H_2La_2Ti_3O_{10}$ crystallizes at 1000 giving a new defect perovskite, $La_2/3TiO_3$, possessing a tetragonal structure.

Perhalogenated tetraphenylhemins: stable catalysts of high turnover catalytic hydroxylations

Abstract: Preparation d'un catalyseur Fer III-porphyrine a partir de Zn-porphyrine par action d'une solution de FeBr 2 /DMF

Structure and redox and photophysical properties of a series of ruthenium heterocycles based on the ligand 2,3-bis(2-pyridyl)quinoxaline

Abstract: The synthesis, structure, and redox and photophysical properties of (Ru(bpy)/sub n/(BL)/sub 3-n/)/sup 2 +/, where n = 0-2, bpy is 2,2'-bipyridine, and BL is 2,3-bis(2-pyridyl)quinoxaline, are described. The (Ru(bpy)/sub 2/(BL))(PF/sub 6/)/sub 2/ complex crystallized in the monoclinic space group P2/sub 1//a and the cell parameters are repeated. All non-H atoms were refined anisotropically to an R value of 0.0672 for 5766 reflections with I > sigma(I). The ruthenium to nitrogen bond distances were Ru-N(pyridine) = 2.06 A (average) and Ru-N(pyrazine) = 2.096 (4) A. Absorption spectra contained bands (250-300 nm) in the ultraviolet region that were assignable to ligand ..pi.. ..-->.. ..pi..* transitions and visible bands (517-300 nm) that were assignable to d..pi.. ..-->.. ..pi..* MLCT transitions. Reduction potentials for the Ru/sup 3+/2+/ couples varied from about 1.40 to 1.70 V vs SSCE. Three reductions were observed and assigned to the one-electron reduction of each bidentate ligand. Weak luminescence was observed, and corrected emission energy maxima were located at 766 +/- 4 nm. Excited-state reduction potentials were estimated from the difference between emission energy maxima and ground-state reduction potentials. Excited-state lifetimes at room temperature in 4:1 EtOH-MeOH ranged from 167 to < 70 ns. Temperature-dependent-lifetime (90-298 K) data gave evidencemore » for ..delta..E' values of 1100 +/- 300 cm/sup -1/. The temperature dependence was attributed to either the third MLCT state according to the localized-orbital model or the presence of a fourth CT state for (Ru(BL)/sub 2/(bpy))/sup 2 +/, since little photochemistry was found for it, and to the third and/or the fourth CT state and the dd state for both (Ru(BL)/sub 2/(bpy))/sup 2 +/ and (Ru(BL)/sub 3/)/sup 2 +/. 54 references, 7 figures, 6 tables.« less

Oxygen content of superconducting perovskites, lanthanum strontium copper oxide La2-xSrxCuOy and yttrium barium copper oxide YBa2Cu3Oy

Abstract: Studies of the composition of YBa/sub 2/Cu/sub 3/O/sub y/ in which the oxidation states of Y and Ba are +3 and +2, respectively, have shown a direct relationship between the Cu(II)/Cu(III) ratio and the oxygen stoichiometry. Idometry or hydrogen reduction has generally been used for the Cu(III) determination. A modification of the idometric method that is simple to apply and is particularly suited to analyses of La/sub 2-x/Sr/sub x/CuO/sub y/ and YBa/sub 2/Cu/sub 3/O/sub y/ is described. The results of application to determination of the oxygen content of YBa/sub 2/Cu/sub 3/O/sub y/ are presented, and the oxygen content is related to the crystallographic and superconducting properties of the material. Results indicated that at room-temperature large variations of the oxygen content of the orthorhombic phase of YBa/sub 2/Cu/sub 3/O/sub y/ could occur without change in the lattice parameters or appreciable impairment of the resistive superconducting transition or diamagnetic properties. 13 references, 1 figure, 1 table.

Magnetism of manganese(II)copper(II) and nickel(II)copper(II) ordered bimetallic chains. Crystal structure of MnCu(pba)(H2O)3.2H2O (pba = 1,3-propylenebis(oxamato))

Abstract: Le compose du titre cristallise dans le systeme orthorhombique, groupe Pnma. La structure est constituee de chaines bimetalliques ordonnees avec les ions Mn(II) en coordination octaedrique et les ions Cu(II) en coordination pyramidale a base carree, relies par des groupes oxamato. Importantes interactions antiferromagnetiques intrachaine et tres faibles interactions antiferro-interchaine

Occurrence of superoxide radical ion in crystalline calcium aluminate 12CaO.7Al2O3 prepared via solid-state reactions

Abstract: Superoxide radical ion O/sub 2//sup -/ is an active species of oxygen and is known to play important roles in many chemical reactions involving O/sub 2/. The formation of O/sub 2//sup -/ on or in solid oxides is usually achieved with the aid of energetic photons such as uv, X-ray, or ..gamma..-ray radiation. It has been found that O/sub 2//sup -/ occurs in the 12CaO 7Al/sub 2/O/sub 3/ crystal prepared by the solid-state reaction between CaCO/sub 3/ and Al/sub 2/O/sub 3/ or Al(OH)/sub 3/ powder without any accompanying irradiation; the concentration of O/sub 2//sup -/ goes up to ca. 4 x 10/sup 18/ units/g.From the change in the line shape with temperature, the O/sub 2//sup -/ is concluded to be included in the structural cavity inherent in the crystal lattice. A drastic reduction in the concentration of O/sub 2//sup -/ on anion substitution and on heating under an oxygen-free atmosphere strongly suggests that the occurrence of O/sub 2//sup -/ is closely related with free oxygen, which is a unique characteristic of the 12CaO 7Al/sub 2/O/sub 3/ crystal. Such characteristics found for 12CaO 7Al/sub 2/O/sub 3/ are analogous to those for ultramarine, Na/sub 8/(Si/sub 6/Al/sub 6/O/sup 24/)S/sub 2/. 25 references, 4more » figures, 2 tables.« less

Syntheses, structures, and spectroscopic properties of six-coordinate mononuclear oxo-molybdenum(V) complexes stabilized by the hydrotris(3,5-dimethyl-1-pyrazolyl)borate ligand

Abstract: Le compose LMoO(SPh) 2 avec L=hydrotris(3,5-dimethyl-1-pyrazolyl) borate cristallise dans le systeme monoclinique groupe d'espace P2 1 /c et sa structure est affinee jusqu'a R=0,071

Nickel catalysis of olefin epoxidation

Abstract: Etude de l'epoxydation catalytique des olefines par une large variete de complexes du nickel II, derivant de differents macrocycles tetraaza, bases de Schiff, porphyrines et phosphines bidentes

Ruthenium and osmium complexes of N,O chelators: syntheses, oxidation levels, and distortion parameters

Abstract: Les coordinats N, O concernes sont: R-quinoleinol-8, et N-arylsalicylaldimine. On synthetise les complexes MQ 3 (M=Ru, Os), RuL 3 et [Et 4 N][OsX 2 Q 2 ] et [RuL 3 ]PF 6 , [OsQ 3 ]ClO 4 et OsX 2 Q 2 . Donnees IR, RPE et comportement electrochimique

Phthalocyanine. pi. -cation-radical species: photochemical and electrochemical preparation of (ZnPc(-1))/sup. +/ in solution

Abstract: The ..pi..-cation-radical species of ZnPc, (ZnPc(-1))/sup .+/ (Pc = phthalocyanine), has been formed quantitatively as a stable product in solution following photochemical reactions with visible-region light in the presence of electron acceptors. The photolyses were carried out by excitation into the phthalocyanine's Q band (lambda > 580 nm), with carbon tetrabromide as an irreversible electron acceptor. The neutral parent species could be regenerated following photooxidation by the addition of sodium dithionite. Cyclic voltammetry of neutral ZnPcL species identified the ring oxidation potentials; for ZnPc(py) and ZnPc(im) (py = pyridine; im = imidazole). In dimethylacetamide, there is one oxidation couple at 0.70 and 0.71 V vs. SCE, respectively, and there are two reduction couples, at -0.96 and -1.28 V vs SCE, for the pyridine complex, and at -0.98 and -1.53 V vs SCE, for the imidazole complex. Each of these reactions was reversible on the cyclic voltammetry time scale. The electrochemical and photochemical oxidation products were characterized by absorption, magnetic circular dichroism (MCD), and electron paramagnetic resonance (EPR) spectroscopies. Four clearly resolvable, optical transitions, centered at 440, 500, 720, and 825 nm, are observed in the absorption spectrum of the cation radical species. EPR spectra obtained from frozen solutions of themore » ..pi.. cation radicals gave isotropic g values that are characteristic of the oxidation at the phthalocyanine ligand (the g values were between 2.0055 and 2.0068). 52 references, 4 figures, 2 tables.« less

Nitrogen-hydrogen activation. 1. Oxidative addition of ammonia to iridium(I). Isolation, structural characterization and reactivity of amidoiridium hydrides

Abstract: Etude sur le complexe Ir(PEt 3 ) 2 (C 2 H 4 ) 2 Cl qui reagissant avec NH 3 donne [Ir(PEt 3 ) 2 (μ-NH 2 )(NH 3 )(H)] x Cl x que l'on traite par NaBPh 4 . La reactivite des complexes est dominee par la stabilite du pont Ir−NH 2 −Ir

Synthesis, molecular structure, and tumor-inhibiting properties of imidazolium trans-bis(imidazole)tetrachlororuthenate(III) and its methyl-substituted derivatives

Abstract: [ImH] + [RuCl 4 Im 2 ] − cristallise dans le systeme monoclinique avec le groupe d'espace C2/c. [(Me-4ImH)] + [Ru(Me-4Im) 2 Cl 4 ] − cristallise dans le systeme monoclinique avec le groupe d'espace P2 1 /a. Affinement de la structure jusqu'a 0,029 et 0,039 respectivement

Spectroscopic and Theoretical Studies of the Unusual EPR Parameters of Distorted Tetrahedral Cupric Sites:' Correlations to X-ray Spectral Features of Core Levels

Abstract: X-ray spectral data and self-consistent field-Xa-scattered wave (SCF-Xa-SW) calculations are presented for D4h and D u CuC12in order to evaluate specific contributions to the small hyperfine in distorted tetrahedral copper sites and to compare the mechanism of hyperfine reduction in these complexes with that for the blue copper site in plastocyanin. Comparison of the 2p3,2 XPS data for the two geometries indicates that the extent of delocalization of the d,z+ ground state in the D u salt is slightly less than in the D4h complex. Multiplet splitting of satellite structure from Cu 3s photoemission shows no change going from D4h to D u CuCIz-, indicating that the indirect Fermi contact contribution to the hyperfine from the core Cu 3s level does not change between the two complexes. Analysis of X-ray edge data for Cs2CuC14 ( D u ) indicates that there is at most 5.8% 4p, mixed into the ground-state wave function, an amount that is insufficient to explain the reduced hyperfine in this distorted Td complex. SCF-Xa-SW calculations performed with sphere radii adjusted so that the ground-state wave function fits the experimental g values indicate that -70% of the reduction in All between D4h and D2d comes from increased orbital angular momentum in the ground state of the Du salt arising from decreased ligand field transition energies. In contrast, increased delocalization relative to D4h CUCI,~accounts for most of the reduction in the blue copper proteins. The remaining 30% of the reduction in All is associated with a -50 X lo4 cm-I reduction in Fermi contact between the two salts. Xa calculations of a number of Cu complexes with < D u symmetry indicate that this reduction is not associated with direct 4s mixing into the half-occupied ground state but is most likely due to increased polarization of the filled totally symmetric valence levels in DZd CuCI,” resulting from increased 4s mixing as compared with D,,, CuCIt-. These studies are then extended to include copper sites exhibiting rhombically split g and A values. Single-crystal optical and EPR studies on copper-doped bis( 1,2-dimethylimidazole)zinc(II) dichloride (Zn[Cu] (dmi),C12) combined with ligand field and SCF-Xa-SW calculations indicate that the rhombic features in these complexes can be explained through admixture of -3% d,z character in the ground-state wave function. Finally, the structurally uncharacterized blue copper protein stellacyanin, which also shows a rhombic EPR spectrum similar to that in Zn[C~](dmi)~Cl~, is considered. In contrast to the C, effective symmetry found in the structurally defined site in plastocyanin, stellacyanin is predicted to have C, effective symmetry. A ligand field calculation using the plastocyanin site as a starting point indicates that stellacyanin requires a stronger field ligand along the Cu-methionine coordinate to produce the observed dzz mixing.

Synthesis, structure, and electrochemistry of a novel macrocyclic dicopper(II) complex. Four one-electron-transfer steps producing binuclear copper(III) and copper(I) species and mixed-valence-state species

Abstract: Donnees relatives au complexe dinucleaire de cuivre (II) soit [Cu 2 L1(ClO 4 ) 2 ] avec H 2 L1=(dihydroxydimethyl) tetraaza [7,7] metacyclophane

Electrochemistry and spectroelectrochemistry of mononuclear and binuclear cobalt phthalocyanines

Abstract: : The electrochemistry of 9, 16, 23-TETRA(NEOPENTOXY)PHTHALOCYANATO cobalt, and some binuclear analogs, has been studied in dichlorobenzene and in dimethylformamide. The redox mechanisms and species on the electrode are discussed. Using an optically thin electrode, the electronic spectra of seven different oxidation states of the mononuclear derivative are reported. Data for a selection of oxidation states of several binuclear species are also presented.

Anion-Exchanged Hydrotalcite-like-Clay-Modified Electrodes

Abstract: Etudes des proprietes electrochimiques des electrodes modifiees par de l'hydrotalcite (Mg 6 Al 2 (OH) 16 CO 3 •4H 2 O) et contenant des especes anioniques redox, dans le film modificateur

Mechanism of dissolution of magnetite by oxalic acid-ferrous ion solutions

Abstract: L'etape determinant la vitesse serait le transfert d'electron dans la sphere externe de Fe II (C 2 O 4 ) 2 2− au complexe superficiel oxalate-fer (III)