Non-Fermi-liquid behavior in UCu(4+x)Al(8-x) compounds

We report on experimental studies of the Kondo physics and the development of non-Fermi-liquid scaling in UCu(4+x)Al(8-x) family. We studied 7 different compounds with compositions between x = 0 and 2. We measured electrical transport (down to 65 mK) and thermoelectric power (down to 1.8 K) as a function of temperature, hydrostatic pressure, and/or magnetic field. Compounds with Cu content below x = 1.25 exhibit long-range antiferromagnetic order at low temperatures. Magnetic order is suppressed with increasing Cu content and our data indicate a possible quantum critical point at x(cr) approximate to 1.15. For compounds with higher Cu content, non-Fermi-liquid behavior is observed. Non-Fermi-liquid scaling is inferred from electrical resistivity results for the x = 1.25 and 1.5 compounds. For compounds with even higher Cu content, a sharp kink occurs in the resistivity data at low temperatures, and this may be indicative of another quantum critical point that occurs at higher Cu compositions. For the magnetically ordered compounds, hydrostatic pressure is found to increase the Neel temperature, which can be understood in terms of the Kondo physics. For the non-magnetic compounds, application of a magnetic field promotes a tendency toward Fermi-liquid behavior. Thermoelectric power was analyzed using a two-band Lorentzian model, and the results indicate one fairly narrow band (10 meV and below) and a second broad band (around hundred meV). The results imply that there are two relevant energy scales that need to be considered for the physics in this family of compounds. (C) 2011 Elsevier B.V. All rights reserved.

On the Nucleophilicity of Boryllithium Compounds. A Theoretical Study

Boron compounds are widely used in synthetic chemistry. The synthesis of the compounds is relatively easy, presenting thermodynamic stability and synthetic versatility. Almost all of them show electrophilic reactivity. Recently, some boryllithium species have been reported as a base or a nucleophile in reaction with organic electrophiles in S(N)2 reactions. In the present work, the proton affinity (PA) of boryllithium compounds was calculated. These values can be useful as theoretical reference values and to provide valuable complementary information for the interpretation and discussion of the basicity of these compounds. The proton affinity was calculated using a theoretical method based on density functional theory and high-level theoretical methods through MP2 and G2MP2 levels of theory. In addition, some global and local reactivity indexes based on density functional theory (DFT) on boryllithium compounds were studied. In order to compare and discuss the chemical reactivity of these compounds, some analogues and electrophilic boron compounds were also studied. Our results showed a local and global nucleophilic reactivity of the boryllithium molecules in agreement with the experimental. reactivity. The boryllithium compounds revealed to be strong bases in comparison to other analogue compounds studied in this work.

Control of Two-Photon Absorption in Organic Compounds by Pulse Shaping: Spectral Dependence

In this work, we investigate the control of the two-photon absorption process of a series of organic compounds via spectral phase modulation of the excitation pulse. We analyzed the effect of the pulse central wavelength on the control of the two-photon absorption process for each compound. Depending on the molecules` two-photon absorption position relative to the excitation pulse wavelength, different levels of coherent control were observed. By simulating the two-photon transition probability in molecular systems, taking into account the band structure and its positions, we could explain the experimental results trends. We observed that the intrapulse coherent interference plays an important role in the nonlinear process control besides just the pulse intensity modulation.

Formation of beta-nickel hydroxide plate-like structures under mild conditions and their optical properties

Nanostructural beta-nickel hydroxide (beta-Ni(OH)(2)) plates were prepared using the microwave hydrothermal (MH) method at a low temperature and short reaction times. An ammonia solution was employed as the coordinating agent, which reacts with [Ni(H(2)O)(6)](2+) to control the growth of beta-Ni(OH)(2) nuclei. A trigonal beta-Ni(OH)(2) single phase was observed by X-ray diffraction (XRD) analyses, and the crystal cell was constructed with structural parameters and atomic coordinates obtained from Rietveld refinement. Field emission scanning electron microscopy (FE-SEM) images revealed that the samples consisted of hexagonal-shaped nanoplates with a different particle size distribution. Broad absorption bands assigned as transitions of Ni(2+) in oxygen octahedral sites were revealed by UV-vis spectra. Photoluminescence (PL) properties observed with a maximum peak centered in the blue-green region were attributed to different defects, which were produced during the nucleation process. We present a growth process scheme of the beta-Ni(OH)(2) nanoplates. (C) 2011 Elsevier Inc. All rights reserved.

Detection of phenolic compounds using impedance spectroscopy measurements

Langmuir-Blodgett (LB) and layer-by-layer films (LbL) of a PPV (p-phenylenevinylene) derivative, an azo compound and tetrasulfonated phthalocyanines were successfully employed as transducers in an ""electronic tongue"" system for detecting trace levels of phenolic compounds in water. The choice of the materials was based on their distinct electrical natures, which enabled the array to establish a fingerprint of very similar liquids. Impedance spectroscopy measurements were taken in the frequency range from 10 Hz to 1 MHz, with the data analysed with principal component analysis (PCA). The sensing units were obtained from five-layer LB films of (poly[(2-methoxy-5-n-hexyloxy)-p-phenylenevinylene]), OC(1)OC(18)-PPV (poly(2-methoxy,5-(n-octadecyl)-p-phenylenevinylene)), DR (HEMA-co-DR13MA (poly-(hydroxyethylmethacrylate-co-[4`-[[2-(methacryloyloxy)-ethyl]ethylamino]-2-chloro-4-nitroazobenzene]))) and five-bilayer LbL films of tetrasulfonated metallic phthalocyanines deposited onto gold interdigitated electrodes. The sensors were immersed into phenol, 2-chloro-4-methoxyphenol, 2-chlorophenol and 3-chlorophenol (isomers) solutions at 1 x 10(-9) mol L(-1), with control experiments carried out in ultra pure water. Samples could be distinguished if the principal component analysis (PCA) plots were made with capacitance values taken at 10(3) Hz, which is promising for detection of trace amounts of phenolic pollutants in natural water.

Phase-transition studies of Ba(0.90)Ca(0.10)(Ti(1-x)Zr(x))O(3) ferroelectric ceramic compounds

Perovskite-structured Ba(0.90)Ca(0.10)(Ti(1-x)Zr(x))O(3) ceramics were prepared in this work and subsequently studied in terms of composition-dependent dielectric and high-resolution long-range order structural properties from 30 to 450 K. The dielectric response of these materials was measured at several frequencies in the range from 1 kHz to 1 MHz. Combining both techniques, including Rietveld refinement of the X-ray diffraction data, allowed observing that, when increasing Zr(4+) content, the materials change from conventional to diffuse and relaxor ferroelectric compounds, the transition occurring spontaneously at the x = 0.18 composition. Interestingly, this spontaneous transition turned out to be prevented for a further increase of Zr(4+). On the basis of all the dielectric and structural results processed, a phase diagram of this system is presented. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Two-photon absorption properties of a novel class of triarylamine compounds

Two-photon absorption spectra of a triarylamine compounds dissolved in toluene were measured using the well-known Z-scan technique, employing 120-fs laser pulse-width. According to the results, an extra band located at around 900 nm was observed only for triarylamine with azoaromatic units. On the other hand, a shift in the two-photon absorption band for triarylamine, with and without azoaromatic units, is observed when different electron donor/acceptors groups are changed. The fitting of the spectra, using sum-over-states model, allowed us to obtain the spectroscopic parameters of each molecule, which appears to be in reasonable agreement with molecules presenting similar structural moieties. (C) 2010 Elsevier B.V. All rights reserved.

Adsorption kinetics and charge inversion in layer-by-layer films from nickel tetrasulfonated phthalocyanine and poly(allylamine hydrochloride)

Layer-by-layer (LBL) films of nickel tetrasulfonated phthalocyanine (NiTsPc) alternated with poly(allylamine hydrochloride) (PAH) have been prepared, whose surface charge has been evaluated using surface potential measurements. From adsorption kinetics results, we obtained the immersion time of similar to 40 s, which was used to assemble layers of NiTsPc. The effect of gold (Au) and aluminum (Al) electrodes on the charge behavior was examined. We found that the surface potential (i.e. surface charge) was inverted each time a layer of PAH was alternated with another of NiTsPc molecules for the two types of electrodes, which was attributed to charge overcompensation between positive charges of PAH molecules, and negative charges from NiTsPc molecules. (C) 2009 Elsevier B.V. All rights reserved.

Immobilization of Poly(propylene imine) Dendrimer/Nickel Phtalocyanine as Nanostructured Multilayer Films To Be Used as Gate Membranes for SEGFET pH Sensors

We describe the assembly of layer-by-layer films based on the poly(propylene imine) dendrimer (PPID) generation 3 and nickel tetrasulfonated phthalocyanine (NiTsPc) for application as chemically sensitive membranes in sepal alive extended-gate field effect transistor (SEGFET) pH sensors PPID/NiTsPc films wet e adsorbed on quartz, glass. indium tin oxide. or gold (Au)-covered glass substrates Multilayer formation was monitored via UV-vis absorption upon following the increment in the Q-band intensity (615 nm) of NiTsPc The nanostructured membranes were very stable in a pH range of 4-10 and displayed a good sensitivity toward H(+), ca 30 mV/pH for PPID/N(1)TsPc films deposited on Au-covered substrates For films deposited on ITO, the sensitivity was ca 52 4 mV/pH. close to the expected theoretical value for ton-sensitive membranes. The use of chemically stable PPID/NiTsPc films as gate membranes in SEGFETs, as introduced here, may represent an alternative for the fabrication of nanostructured, porous platforms for enzyme immobilization to be used in enzymatic biosensors.

Heterobimetallic compounds [Ru(eta(5)-Cp)(dppf)X] (X = Cl, Br, I and N(3)): synthesis, electrochemical analysis, and the crystal structure of [Ru(eta(5)-Cp)(dppf)I] [dppf=1,1`-bis(diphenylphosphino)ferrocene]

A series of new ruthenium-iron based derivatives [Ru(eta(5)-Cp)(dppf)Cl] (1), [Ru(eta(5)-Cp)(dppf)Br] (2), [Ru(eta(5)-Cp)(dppf)I] (3) and [Ru(eta(5)-Cp)(dppf)N(3)] (4) were obtained by reactions of [Ru(eta(5)-Cp)(PPh(3))(2)Cl] with 1,1`-bis(diphenylphosphino) ferrocene (dppf) and characterized by IR, NMR ((1)H, (13)C and (31)P), (57)Fe Mossbauer spectroscopy and cyclic voltammetry. Additionally, the compound (3) was structurally characterized by X-ray crystallography, and the results were as follows: orthorhombic, Pbca, a = 18.2458(10), b = 20.9192(11), c = 34.4138(19) a""<<, alpha = beta = gamma = 90A degrees, V = 13135.3(12) a""<<(3) and Z = 16.

Binuclear zinc(II) complexes with the anti-inflammatory compounds salicylaldehyde semicarbazone and salicylaldehyde-4-chlorobenzoyl hydrazone (H(2)LASSBio-1064)

Complexes [Zn(2)(HL(1))(2)(CH(3)COO)(2)] (1) and [Zn(2)(L(2))(2)] (2) were synthesized with salicylaldehyde semicarbazone (H(2)L(1)) and salicylaldehyde-4-chlorobenzoyl hydrazone (H(2)LASSBio-1064, H(2)L(2)), respectively. The crystal structure of (1) was determined. Upon recrystallization of previously prepared [Zn(2)(HL(2))(2)(Cl)(2)] (3) in 1:9 DMSO:acetone crystals of [Zn(2)(L(2))(2)(H(2)O)(2)]center dot[Zn(2)(L(2))(2)(DMSO)(4)] (3a) were obtained. The crystal structure of 3a was also determined. All crystal structures revealed the presence of phenoxo-bridged binuclear zinc(II) complexes. (C) 2011 Elsevier Ltd. All rights reserved.

Analyzing Ru(III)-dmso and Ru(III)-dms motifs in compounds used in the synthesis of the antimetastatic agents

The chemistry of Ru(III) complexes containing dmso as a ligand has become an interesting area in the cancer treatment field. Because of this, structural knowledge and chemistry of the moiety Ru(III)-dmso have become important to cancer research. The crystal structures of the compounds mer-[RuCl(3)(dms)(3)] (1) and mer-[RuCl(3)(dms)(2)(dmso)]:mer-[RuCl(3)(dms)(3)] (2) were determined by X-ray crystallography and a speciation of the presence of intramolecular hydrogen bond in these structures has been studied. Compound (1) crystallizes in the orthorhombic space group, Pna2(1); a = 16.591(8) angstrom, b = 8.724(2) angstrom. c = 10.547(3) angstrom; Z = 12 and (2) crystallizes in the space group, P2(1)/C: a = 11.9930(2) angstrom, b = 7.9390(2) angstrom, c = 15.8700(3) angstrom, beta = 93.266(1)degrees, Z = 2. From the X-ray structures solved in this work, were possible to suggest an interpretation for the broad lines observed in the EPR spectra of the Ru(III) compounds explored here. Also, the exchange interactions detected by EPR spectroscopy in solid state and in solution, confirm the presence of van der Waals interactions such as C-H center dot center dot center dot Cl in the compounds (1), (2) and (3). The use of techniques such as IR, UV-vis, (1)H NMR and EPR Spectroscopy and Cyclic Voltammetry were applied in this work to analyze the behavior of these metallocompounds. (c) 2008 Elsevier B.V. All rights reserved.

Syntheses, crystal structure and theoretical investigation of novel heteroleptic complexes of nickel(II) with N-R-sulfonyldithiocarbimate and phosphine ligands

Five new complexes of general formula: [Ni(RSO(2)N=CS(2))(dppe)], where R = C(6)H(5) (1), 4-ClC(6)H(4) (2), 4-BrC(6)H(4) (3), 4-IC(6)H(4) (4) and dppe = 1,2-bis(diphenylphosphino) ethane and [Ni(4-IC(6)H(4)SO(2)N=CS(2))(PPh(3))(2)] (5), where PPh3 = triphenylphosphine, were obtained in crystalline form by the reaction of the appropriate potassium N-R-sulfonyldithiocarbimate K(2)(RSO(2)N=CS(2)) and dppe or PPh(3) with nickel(II) chloride in ethanol/water. The elemental analyses and the IR, (1)H NMR, (13)C NMR and (31)P NMR spectra are consistent with the formation of the square planar nickel(II) complexes with mixed ligands. All complexes were also characterized by X-ray diffraction techniques and present a distorted cis-NiS(2)P(2) square-planar configuration around the Ni atom. Quantum chemical calculations reproduced the crystallographic structures and are in accord with the spectroscopic data. Rare C-H center dot center dot center dot Ni intramolecular short contact interactions were observed in the complexes 1-5. (C) 2011 Elsevier B. V. All rights reserved.

New insights on the Lewis acidity of diorganolead(IV) compounds: Diphenyllead(IV) complexes with N,O,S-chelating ligands

The reactions of PbPh2(OAC)(2) with alkylglyoxylate thiosemicarbazones (HRGTSC, R = Et, Bu) afforded complexes of the type [PbPh2(GTSC)] center dot H2O, [PbPh2(RGTSC)(2)] and [PbPh2Cl(BUGTSC)]. The structures of HRGTSC (R = Me, Et, Bu), [PbPh2(OAc)(RGTSC)](R = Me, Et, Bu), [PbPh2Cl(BuGTSC)] and [PbPh2(GTSC)] center dot H2O have been studied by X-ray diffraction. [PbPh2(OAc)(RGTSC)] and [PbPh2(GTSC)] center dot H2O have [PbC2NO3S] kernels and the coordination sphere of the metal is pentagonal bipyramidal. [PbPh2Cl(BuGTSC)] has a [PbC2NOSCI] kernel and the coordination geometry around lead is pentagonal bipyramidal with one vacant site. Analysis of the bond distances in [PbPh2(GTSC)] center dot H2O suggests a significant affinity between diphenyllead(IV) and carboxylate donor groups, supporting a borderline acidic character for this organometallic cation. H-1 and C-13 NMR spectra in DMSO-d(6) suggest the partial dissociation of the acetate in [PbPh2(OAc)(RGTSC)] solutions and indicate some differences in the coordination mode of the two RGTSC(-) ligands in [PbPh2(RGTSC)(2)] complexes. (C) 2007 Elsevier Ltd. All rights reserved.

The mer-[RuCl(3)(dppb)(H(2)O)] complex: A versatile tool for synthesis of Ru(II) compounds

The complex mer-[RuCl(3)(dppb)(H(2)O)] [dppb = 1,4-bis(diphenylphosphino)butane] was used as a precursor in the synthesis of the complexes tc-[RuCl(2)(CO)(2)(dppb)], ct-[RuCl(2)(CO)(2)(dppb)]. cis-[RuCl(2)(dppb)(Cl-bipy)], [RuCl(2Ac4mT)(dppb)] (2Ac4mT = N(4)-meta-tolyl-2-acetylpyridine thiosemicarbazone ion) and trans-[RuCl(2)(dppb)(mang)] (mang = mangiferin or 1,3,6,7-tetrahydroxyxanthone-C2-beta-D-glucoside) complexes. For the synthesis of Run complexes, the Ru(III) atom in mer-[RuCl(3)(dppb)(H(2)O)] may be reduced by H(2)(g), forming the intermediate [Ru(2)Cl(4)(dppb)(2)], or by a ligand (such as H2Ac4mT or mangiferin). The X-ray structures of the cis-[RuCl(2)(dppb)(Cl-bipy)], tc-[RuCl(2)(CO)(2)(dppb)] and [RuCl(2Ac4mT)(dPpb)] complexes were determined. (C) 2010 Elsevier Ltd. All rights reserved.