Synthesis of the first rare earth metal bis(alkyl)s bearing an indenyl functionalized N-heterocyclic carbene

Treatment of indenyl-modified imidazolium bromide [C9H7CH2CH2(NCHCHN(C6H2Me3-2,4,6)CH)Br] ((IndH-NHC-H)Br) with rare earth metal tetra(alkyl) lithium (Ln(CH2SiMe3)(4)Li(THF)(4)) or with (trimethylsilylmethyl)lithium (LiCH2SiMe3) and rare earth metal tris(alkyl)s (Ln(CH2SiMe3)(3)(THF)(2)) sequentially afforded the first NHC-stabilized monomeric rare earth metal bis(alkyl) complexes (Ind-NHC)Ln(CH2SiMe3)(2) (1, Ln = Y; 2, Ln = Lu; 3, Ln = Sc) via double-deprotonation reactions. Complexes 1-3 are THF-free isostructural monomers. The monoanionic Ind-NHC species bond to the central metal ion in a eta(5):kappa(1) constrained geometry configuration (CGC) mode, which combine with the two cis-located alkyl moieties to form a tetrahedron ligand core, leading to the chirality of the complexes. Under the presence of activators AlEt3 and [Ph3C][B(C6F5)(4)], complex 2 showed catalytic activity toward the polymerization of isoprene to afford 3,4-regulated polyisoprene (91%).

The enhancement effect of Eu3+ on electro-oxidation of ethanol at Pt electrode

It is reported for the first time that the slow electrochemical kinetics process for the electro-oxidation of ethanol can be promoted by changing the electrochemical environment. The electro-oxidation of ethanol at a Pt electrode in the presence of Eu3+ cations was studied and an enhancement effect was exhibited. Cyclic voltammetry experiment results showed that the peak current density for the electro-oxidation of ethanol was increased in the presence of EU3+ in the ethanol solution. A preliminary discussion of the mechanism of the enhancement effect is given. This is based on a CO stripping experiment, which shows that either the onset potential or the peak potential of CO oxidation is shifted negatively after adding Eu3+ to the solution.

PH-Dependent syntheses and structures of two Copper(II)/Phenanthroline/p-Sulfonatocalix[4]arene supramolecular compounds with 1D water-filled channels

Two copper-organic framework supramolecular assemblies of p-sulfonatocalix[4]arene and 1,10-phenanthroline Cu-2[C12H8N2][C28H20S4O16][H2O](23.5) (1) and Cu-3[C12H8N2](3)[C28H19S4O16]Cl[H2O](17.6) (2) were obtained by pH-dependent synthesis at room temperature. Both structures show ID water-filled channels (rectangular shape in I and triangular in 2) with the solvent-accessible volume occupying 30.8% (1) and 24.2% (2) of the unit-cell volume, respectively. The calixarene molecules in both structures assume analogous cone shapes of C-2 nu symmetry instead of the conventional C-4 nu symmetry. Their connecting to different amounts of copper/phenanthroline cations leads to the formation of different structures.

Hydrothermal synthesis, structure characterization of a new mixed Mo/V metal-oxygen cluster compound: [Co(phen)(3)](2)[HPMo4V (Mo4V6IV)-V-VI M2O44]center dot 4H(2)O, (M=0.78Mo(V)+0.22V(IV))

A new polyoxometalate [Co(phen)(3)](2)[HPMo4V Mo-4(VI) V-6(IV) M2O44]center dot 4H(2)O (M = 0.78Mo(V)+ 0.22V(IV)) 1 was hydrothermally synthesized and characterized by IR, elemental analyses, X-ray photoelectron spectrum, ESR and single crystal X-ray diffraction. The title compound is in the triclinic space group P (1) over bar with a = 12.0953(7) angstrom, b = 14.0182(6) angstrom, c = 14.6468(7) angstrom, V=2402.55(18) angstrom(3), alpha = 105.134(2), beta = 91.841(3), gamma = 91.401(2), Z = 1, and R-1 (wR(2)) = 0.0617 (0.1701). The compound was prepared from tetra-capped pseudo-Kepin with phosphorus-centered polyoxoanions [PMo8V6M2O44](5-) , [Co(phen)(3)](2+) cations and linked through hydrogen bonds and pi-pi stacking interaction into three-dimensional supramolecular framework. Astudy of the magnetic properties of 1 demonstrates that it exhibits antiferromagnetic coupling interactions.

Grain boundary conductivity of high purity neodymium-doped ceria nanosystem with and without the doping of molybdenum oxide

Solid solutions of Ce1-xNdxO2-x/2 (0.05 <= x <= 0.2) and (Ce1-xNdx)(0.95)MO0.05O2-delta (0.05 <= x <= 0.2) have been synthesized by a modified sol-gel method. Both materials have very low content of SiO2 (similar to 27 ppm). Their structures and ionic conductivities were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and electrochemical impedance spectroscopy (M). The XRD patterns indicate that these materials are single phases with a cubic fluorite structure. The powders calcined at 300 degrees C with a crystal size of 5.7 nm have good sinterability, and the relative density could reach above 96% after being sintered at 1450 degrees C. With the addition Of MoO3, the sintering temperature could be decreased to 1250 degrees C. Impedance spectroscopy measurement in the temperature range of 250-800 degrees C indicates that a sharp increase of conductivity is observed when a small amount of Nd2O3 is added into ceria, of which Ce0.85Nd0.15O1.925 (15NDC) shows the highest conductivity. With the addition of a small amount Of MoO3, the grain boundary conductivity of 15NDC at 600 degrees C increases from 2.56 S m(-1) to 5.62 S m(-1).

Tetraaqua(1,10-phenanthroline-kappa N-2,N ')cobalt(II) dinitrate: a hydrogen-bonded supramolecular network

The structure of the title compound, [Co(C12H8N2)(H2O)(4)]-(NO3)(2), consists of tetraaqua(1,10- phenanthroline)cobalt(II) cations and nitrate anions. The Co atom is located on a twofold rotation axis and is coordinated by the two N atoms of a 1,10-phenanthroline ligand and four O atoms of water molecules. The cations and anions are linked by hydrogen-bond interactions into a three-dimensional supramolecular network.

Structural and magnetic properties of Sr2Fe1−xGaxMoO6 (0≤x≤0.25)

We have investigated the structure, magnetization and magnetoresistance (MR) of the double perovskite compounds Sr2Fe1−xGaxMoO6 (0≤x≤0.25). Rietveld refinement results show that the anti-site defects (ASDs) concentration increases with x, giving rise to highly disordered samples at the B/B positions, for the highest doping levels. The evolution of bond lengths and ions oxidation states could be understood by the distribution of trivalent Ga ions at the B/B positions, which leads to the formation of more disorder structure. The saturation magnetization and Curie temperature decreased with the Ga content increases in the samples, and their origin was found that the cations disorder for the Ga-doped compounds is annihilating double exchange mechanism due to the presence of significant amounts of Fe and Ga cations on the B site. The low-field magnetoresistance of Sr2FeMoO6 (SFMO) can be greatly enhanced by replacing the Fe by the nonmagnetic Ga ion up to a temperature of 300 K,since Ga ions may act as a barrier for electron transport along the chain in the ferromagnetic segregation and weaken the ferromagnetic exchange.

High-dimensional assembly depending on polyoxoanion templates, metal ion coordination geometries, and a flexible bis(imidazole) ligand

By introducing the flexible 1,1'-(1,4-butanediyl)bis(imidazole) (bbi) ligand into the polyoxovanadate system, five novel polyoxoanion-templated architectures based on [As8V14O42](4-) and [V16O38Cl](6-) building blocks were obtained: [M(bbi)(2)](2)[As8V14O42(H2O)] [M = Co (1), Ni (2), and Zn (3)], [Cu(bbi)](4)[As8V14O42(H2O)] (4), and [Cu(bbi)](6)[V16O38Cl] (5). Compounds 1-3 are isostructural, and they exhibit a binodal (4,6)-connected 2D structure with Schlafli symbol (3(4)center dot 4(2))(3(4)center dot 4(4)center dot 5(4)center dot 6(3))(2), in which the polyoxoanion induces a closed four-membered circuit of M-4(bbi)(4). Compound 4 exhibits an interesting 3D framework constructed from tetradentate [As8V14O42](4-) cluster anions and cationic ladderlike double chains. There exists a bigger M-8(bbi)(6)O-2 circuit in 4. The 3D extended structure of 5 is composed of heptadentate [V16O38Cl](6-) anions and flexural cationic chains; the latter consists of six Cu(bbi) segments arranged alternately. It presents the largest 24-membered circuit of M-24(bbi)(24) so far observed made of bbi molecules and transition-metal cations. Investigation of their structural relations shows the important template role of the polyoxoanions and the synergetic interactions among the polyoxoanions, transition-metal ions, and flexible ligand in the assembly process.

Magnetic behavior of polyaniline doped with oxidized ferrocenesulfonic acid

Ferrocenesulfonic acid (FSA) was oxidized by iodine (I-2) and then used as dopant for polyaniline emeraldine base. The resulted polyaniline showed an electrical conductivity of 4.50 x 10(-2) S/cm and a ferromagnetic interaction with a positive Weiss constant of 15 K, the magnetic behavior is attributed to the ferromagnetic coupling between ferrocenium cations in the counter-ions along the polyaniline chain.

Electronic structures of MCO (M = Nb, Ta, Rh, Ir, Pd, Pt) molecules by density functional theory

Equilibrium geometries, vibrational frequencies, and dissociation energies of the transition metal carbonyls MCO (M = Nb, Ta, Rh, Ir, Pd, Pt) were studied by use of diverse density functional methods B3LYP, BLYP, B3P86, B3PW91, BHLYP, BP86, and PBE1PBE. It was found that the ground electronic state is (6)Sigma(+) for NbCO and TaCO, (2)Sigma(+) for RhCO,(2)Delta for IrCO, and (1)Sigma(+) for PdCO and PtCO, in agreement with previous theoretical studies. The calculated properties are highly dependent on the functionals employed, in particular for the dissociation energy. For most of the molecules, the predicted bond distance is in agreement with experiments and previous theoretical results. BHLYP is the worst method in reproducing the experimental results compared with the other density functional methods for the title molecules.

UV-vis spectrophotometric titrations and vibrational spectroscopic characterization of meso-(p-hydroxyphenyl)porphyrins

Sequentially spectrophotometric titrations by sodium hydroxide of meso-tetraphenylporphyrin derivatives bearing one, two, three, or four p-hydroxyl groups result in new types of spectra. The strong new bands appear in the visible region with splitting or broadening of the Soret band and its significant loss of oscillator strength. To understand the molecular origin of these phenomena, the Resonance Raman (RR) and Fourier Transform Infrared (FTIR) experiments are carried out. The results demonstrate that the charges of the deprotonated para-hydroxy substituted meso-tetraphenylporphyrins are localized on the substituents, not delocalized into the pi system of the porphyrin macrocycles and that the ground states of the macrocycles remain essentially unperturbed. Both the related behavior of diprotonated tetrakis(p-(dimethylamino)phenyl) porphyrin and protonated Schiff base porphyrins show that the new bands considered as hyperporphyrin spectra are due to pi(phenoxide anion) --> pi*(porphyrin) transitions, where pi is an orbital on the phenoxide anion substitutent and pi* is a LUMO on the porphyrin.

Surface charge influence on the surface plasmon absorbance of electroactive thiol-protected gold nanoparticles

Gold nanoparticles (3.1-5.0 nm in size) surface-derivatized with both electroactive and nonelectroactive self-assembled monolayers were synthesized. The surface-derivatized electroactive particles can be easily oxidized/reduced at an electrode surface based on the diffusion-controlled current-voltage curve observed in cyclic voltammetry measurements. Spectroelectrochemical investigation demonstrated that the maximum absorbance of the nanoparticles in their oxidized state red-shifted compared with their reduced state to a different extent according to their size distribution. In the case of the particles surface-derivatized with nonelectroactive monolayers, much less shift was observed. This study showed that surface plasmon absorbance of gold nanoparticles was not only related to core charge states but was also influenced by surface charge states as well.

mer-(4-aminobenzenesulfonato-kappa N)triapua(1,10-phenanthroline-kappa N-2,N ')cobalt(II) chloride

Both coordination and hydrogen bonds contribute to networking in the supramolecular title compound, [Co(C6H6NO3S)(C12H8N2)(H2O)(3)]Cl, which contains a discrete [Co(C6H6NO3S)(C12H8N2)(H2O)(3)](+) complex cation, formed by one 4-aminobenzenesulfonate ligand, one 1,10-phenanthroline ligand and three coordinated water molecules, together with one uncoordinated chloride anion. These discrete cations and chloride anions are connected by hydrogen-bonding interactions into a two-dimensional supramolecular motif. Further hydrogen-bonding interactions consolidate the structural architecture and extend the two-dimensional supramolecular structure into a three-dimensional network.

Bis[tris(2,2 '-bipyridyl-kappa N-2,N ')iron(II)] cyclo-tetravanadate decahydrate

The hydrothermal reactions of metavanadate and divalent iron salts in the presence of nitrogen-donor chelating ligands yield the complex [Fe(C10H8N2)(3)](2)[V4O12].10H(2)O, which consists of one centrosymmetric eight-membered ring [V4O12](4-) anion cluster, formed by four VO4 tetrahedra sharing vertices, two discrete octahedral [Fe(C10H8N2)(3)](2+) cations, formed by three 2,2'-bipyridyl ligands coordinated to Fe-II, and ten water molecules of solvation. The anion and coordination cations are isolated and form anion and cation layers, respectively. In the anion layers, these anions and water molecules of solvation are linked to each other, in a two-dimensional motif, through hydrogen-bonding interactions.

Solvent extraction of scandium(III), yttrium(III), lanthanum(III) and gadolinium(III) using Cyanex 302 in heptane from hydrochloric acid solutions

The extractions of the selected rare earths (Sc, Y, La and Gd) from hydrochloric acid solutions have been investigated using bis(2,4,4-trimethylpentyl)-mono thiophosphinic acid (Cyanex 302, HL) in heptane as an extractant. The results demonstrate that the extractions of rare earths occur via the following reaction: Sc(OH)(2+) + 2[(HL)(2)]((O)) double left right arrow [Sc(OH)L-2 (.) 2(HL)]((O)) + 2H(+) Y3+ + 3[(HL)(2)]((O)) double left right arrow [Y(HL2)(3)]((O)) + 3H(+) La(OH)(2)(+) + 3[(HL)(2)](O) double left right arrow [La(OH)(2)L (.) 5(HL)]((O)) + H+ Gd(OH)(2+) + 3[(HL)(2)]((O)) double left right arrow [Gd(OH)L-2 (.) 4(HL)]((O)) + 2H(+) The pH(1/2) values and equilibrium constants of the extracted complexes have been deduced by taking into account the aqueous phase complexation of the metal ion with hydroxyl ligands and plausible complexes extracted into the organic phase. According to the pH(1/2) values, it is possible to realize mutual separation among Sc(III), Y(III), La(III) and Gd(III) with Cyanex 302 by controlling aqueous acidity.