ADVANCED FUNCTIONAL MATERIALS, Issue 13 2008
Ari Laiho
Abstract Ionic self-assembled (ISA) surfactant complexes present a facile concept for self-assembly of various functional materials. However, no general scheme has been shown to allow their overall alignment beyond local polydomain-like order. Here we demonstrate that ionic complexes forming a columnar liquid-crystalline phase in bulk can be aligned within polymer blends upon shearing, taken that the matrix polymers have sufficiently high molecular weight. We use an ISA complex of N,N,-bis(ethylenetrimethylammonium)perylenediimide/bis(2-ethylhexyl) phosphate (Pery-BEHP) blended with different molecular weight polystyrenes (PS). Based on X-ray scattering studies and transmission electron microscopy the pure Pery-BEHP complex was found to form a two-dimensional oblique columnar phase where the perylene units stack within the columns. Blending the complex with PS lead to high aspect ratio Pery-BEHP aggregates with lateral dimension in the mesoscale, having internal columnar liquid-crystalline order similar to the pure Pery-BEHP complex. When the Pery-BEHP/PS blend was subjected to a shear flow field, the alignment of perylenes can be achieved but requires sufficiently high molecular weight of the polystyrene matrix. The concept also suggests a simple route for macroscopically aligned nanocomposites with conjugated columnar liquid-crystalline functional additives. [source]

Ionic and radical fragmentations of alkoxyhalocarbenes , a perspective

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 4 2009
Robert A. Moss
Abstract Fragmentations of secondary or tertiary alkoxyhalocarbenes in polar solvents generate carbocations as components of ion pairs. A variety of carbocations can be produced including acyclic, alicyclic, benzyl, bridgehead, cyclopropyl, cyclopropylcarbinyl, and norbornyl examples. Laser flash photolysis (LFP) studies provide kinetics and activation parameters for the carbene fragmentations, which are orders of magnitude faster, and require considerably reduced activation energies, compared to analogous solvolytic carbocation-generative processes. In some cases, the time required for solvent and anion equilibration of the ion pairs can be estimated. In nonpolar solvents, the gas phase, or cryogenic matrices, homolytic carbene fragmentation may, in certain cases, supplant heterolytic fragmentation. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Ionic and excited species in irradiated poly(dimethylsiloxane) doped with pyrene

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 23 2004
M. Szadkowska-Nicze
Abstract The influence of temperature (77,230 K) on the fate of pyrene (Py) radical ions and Py excited states in irradiated poly(dimethylsiloxane) (PDMS) doped with Py is described. At 77 K, the Py radical ions seem to be stable, whereas the Py excited states [fluorescence (, = 395 nm) and phosphorescence (, = 575,650 nm)] are generated via tunneling charge transfer. In the range of the glass-transition temperature (Tg = 152,153 K), the Py radical ions start to decay, taking part in a recombination process and leading to the Py monomer and Py excimer fluorescence (, = 475 nm). The wavelength-selected radiothermoluminescence (WS RTL) observed at approximately 395, 475, and 600 nm has helped us to identify the Tg range (152,153 K). The absorption maximum at approximately 404 nm, found in the temperature range under consideration, is thought to represent PyH,, cyclohexadienyl-type radicals produced as a result of the reaction of Py,, with protonated PDMS macromolecules. With the initial-rise method of evaluating the activation energy (Ea) with the WS RTL peaks observed in the Tg range, Ea values of 123,151 kJ mol,1 have been found. Such high Ea values can be explained by the contribution of energy connected to the molecular relaxation of the matrix in the Tg range. The well-known Williams,Landel,Ferry equation, with universal constants C1 = 17.4 and C2 = 12.7, has been successfully applied to the interpretation of old pulse-radiolysis/viscosity data found for crosslinked PDMS doped with Py. The mechanisms involved in these phenomena are discussed. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 6125,6133, 2004 [source]

Ionic and electronic defects in a-BaTiO3 thin films studied by transient and steady state conductivity measurements

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 3 2007
F. El Kamel
Abstract Conduction mechanisms in BaTiO3 films deposited at low temperatures on Cu-electrodes have been investigated in transient and steady regimes as a function of temperatures and electric field. This work aims to identify possible defects which govern the leakage current. Electrical measurements reveal that Space Charge Limited Current (SCLC) constitutes the main leakage mechanism in both the transient and the steady regimes. Based on the theory of SCLC, two types of defects can be detected. At higher temperatures, oxygen vacancies constitute the main defects which migrate across the film to generate an ionic leakage current. Diffusion of these defects is thermally activated with an activation energy around 1 eV. Moreover, at lower temperatures the J - E measurements reveals the presence of a discrete set of shallow traps at 0.45 eV below the conduction band with an effective density of 4 × 1022 m,3. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Ionic and electronic processes in non-linear optical crystals

PHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 1 2005
Igor N. Ogorodnikov
Abstract The paper presents the results of a study of the formation and decay of lattice defects in nonlinear optical crystals of NH4H2PO4 (ADP), KH2PO4 (KDP), Li2B4O7 (LTB) and LiB3O5 (LBO) with a sublattice of mobile hydrogen (ADP, KDP) and lithium (LTB, LBO) cations. By means of the luminescent and absorption optical spectroscopy with (the) a nanosecond time resolution under excitation with an electron beam, it was revealed that the optical absorption of these crystals in the visible and UV spectral ranges is produced by optical hole-transitions from the local defect level to the valence band states. The valence band density of the states determines the optical absorption spectral profile, and the relaxation kinetics is rated by the interdefect radiationless tunnel recombination between the trapped hole center and the H0 and Li0 electron trapped centers. At 290 K, the H0 and Li0 centers are subject to thermally stimulated migration. All manifestations of a radiative recombination observed in these crystals are accounted for by the involvement of additional electronic and hole centers of a different nature in the recombination process. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

A three-dimensional hydrogen-bonded network in bis(4-hydroxyanilinium) selenate(VI) dihydrate

ACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2009
Jan Janczak
The title compound, 2C6H8NO+·SeO42,·2H2O, contains 4-hydroxyanilinium cations, selenate(VI) anions and water molecules. One of the two independent cations is nearly planar (excluding the ammonium H atoms), while the other is markedly nonplanar, with the hydroxy and ammonium groups displaced from the plane of the benzene ring. This results from the antiparallel orientation of the cations, which interact through oppositely polarized ammonium and hydroxy groups. Ionic and hydrogen-bonding interactions join the oppositely charged units into a three-dimensional network. This work demonstrates the usefulness of 4-aminophenol in the crystal engineering of organic,inorganic hybrid compounds. [source]

ChemInform Abstract: Baylis,Hillman Reaction Promoted by a Recyclable Protic,Ionic,Liquid Solvent,Catalyst System: DABCO,AcOH,H2O.

CHEMINFORM, Issue 8 2010
Ying Song
Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source]

Guest,Framework Interaction in Type I Inorganic Clathrates with Promising Thermoelectric Properties: On the Ionic versus Neutral Nature of the Alkaline-Earth Metal Guest A in A8Ga16Ge30 (A: Sr, Ba)

CHEMINFORM, Issue 50 2003
Carlo Gatti
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Solid-State Ionics: Roots, Status, and Future Prospects

JOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 7 2002
Philippe Knauth
This review represents the authors' view of the evolution of solid-state ionics over approximately the past 100 years. A brief history, introducing milestones of the development of this discipline, is followed by a short summary of the theory of ionic conduction in the bulk and the more recently developed theory of ionic conduction at interfaces. The central part of the article gives examples of ionic-conducting materials systems with structures ranging from one- to three-dimensional disorder. Important experimental techniques for analyzing ionic conduction, including alternating-current impedance spectroscopy, direct-current coulometry, and direct-current current-voltage measurements with blocking electrodes, are also summarized. The main technological applications, that is, batteries, solid-oxide fuel cells, electrochemical sensors, electrochromic windows, and oxygen-separation membranes, are reviewed. Finally, new concepts in solid-state ionics are presented, including the investigation of new materials (such as nanostructured phases), the study of boundaries (for example, using microelectrodes), the development of computational techniques, and the connections with other classes of materials (notably magnetic and semiconducting materials). [source]

Glucose-induced inhibition: how many ionic mechanisms?

ACTA PHYSIOLOGICA, Issue 3 2010
D. Burdakov
Abstract Sensing of sugar by specialized ,glucose-inhibited' cells helps organisms to counteract swings in their internal energy levels. Evidence from several cell types in both vertebrates and invertebrates suggests that this process involves sugar-induced stimulation of plasma membrane K+ currents. However, the molecular composition and the mechanism of activation of the underlying channel(s) remain controversial. In mouse hypothalamic neurones and neurosecretory cells of the crab Cancer borealis, glucose stimulates K+ currents displaying leak-like properties. Yet knockout of some of the candidate ,leak' channel subunits encoded by the KCNK gene family so far failed to abolish glucose inhibition of hypothalamic cells. Moreover, in other tissues, such as the carotid body, glucose-stimulated K+ channels appear to be not leak-like but voltage-gated, suggesting that glucose-induced inhibition may engage multiple types of K+ channels. Other mechanisms of glucose-induced inhibition, such as hyperpolarization mediated by opening of Cl, channels and depolarization block caused by closure of KATP channels have also been proposed. Here we review known ionic and pharmacological features of glucose-induced inhibition in different cell types, which may help to identify its molecular correlates. [source]

Ion-Conducting Probes for Low Temperature Plasmas

CONTRIBUTIONS TO PLASMA PHYSICS, Issue 5-7 2008
S. A. Meiss
Abstract Probes interacting with a low temperature plasma are typically built of electron conducting materials, mostly metals. We apply yttria-stabilized zirconia (YSZ) which is oxygen ion conducting at elevated temperatures and which is a typical solid electrolyte with high ionic and negligible electronic conductivity. The processes at the plasma|YSZ interface are discussed and first results of measurements with ion-conducting single- and double-probes in oxygen containing radio frequency plasmas are presented. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Death and survival of heterozygous Lurcher Purkinje cells In vitro

DEVELOPMENTAL NEUROBIOLOGY, Issue 8 2009
Hadi S. Zanjani
Abstract The differentiation and survival of heterozygous Lurcher (+/Lc) Purkinje cells in vitro was examined as a model system for studying how chronic ionic stress affects neuronal differentiation and survival. The Lurcher mutation in the ,2 glutamate receptor (GluR,2) converts an orphan receptor into a membrane channel that constitutively passes an inward cation current. In the GluR,2+/Lc mutant, Purkinje cell dendritic differentiation is disrupted and the cells degenerate following the first week of postnatal development. To determine if the GluR,2+/Lc Purkinje cell phenotype is recapitulated in vitro, +/+, and +/Lc Purkinje cells from postnatal Day 0 pups were grown in either isolated cell or cerebellar slice cultures. GluR,2+/+ and GluR,2+/Lc Purkinje cells appeared to develop normally through the first 7 days in vitro (DIV), but by 11 DIV GluR,2+/Lc Purkinje cells exhibited a significantly higher cation leak current. By 14 DIV, GluR,2+/Lc Purkinje cell dendrites were stunted and the number of surviving GluR,2+/Lc Purkinje cells was reduced by 75% compared to controls. However, treatment of +/Lc cerebellar cultures with 1-naphthyl acetyl spermine increased +/Lc Purkinje cell survival to wild type levels. These results support the conclusion that the Lurcher mutation in GluR,2 induces cell autonomous defects in differentiation and survival. The establishment of a tissue culture system for studying cell injury and death mechanisms in a relatively simple system like GluR,2+/Lc Purkinje cells will provide a valuable model for studying how the induction of a chronic inward cation current in a single cell type affects neuronal differentiation and survival. © 2009 Wiley Periodicals, Inc. Develop Neurobiol, 2009 [source]

Capillary electrochromatography with zwitterionic stationary phase on the lysine-bonded poly(glycidyl methacrylate- co -ethylene dimethacrylate) monolithic capillary column

ELECTROPHORESIS, Issue 12 2006
Xiaoli Dong
Abstract A polymer-based neutral monolithic capillary column was prepared by radical polymerization of glycidyl methacrylate and ethylene dimethacrylate in a 100,,m id fused-silica capillary, and the prepared monolithic column was subsequently modified based on a ring opening reaction of epoxide groups with 1,M,lysine in solution (pH,8.0) at 75°C for 10,h to produce a lysine chemically bonded stationary phases in capillary column. The ring opening reaction conditions were optimized so that the column could generate substantial EOF. Due to the zwitterionic functional groups of the lysine covalently bonded on the polymer monolithic rod, the prepared column can generate cathodic and anodic EOF by varying the pH values of running buffer during CEC separation. EOF reached the maximum of ,2.0×10,8,m2v,1s,1 and 2.6×10,8,m2v,1s,1 with pH of the running buffer of 2.25 and 10, respectively. As a consequence, neutral compounds, ionic solutes such as phenols, aromatic acids, anilines, and basic pharmaceuticals were all successfully separated on the column by CEC. Hydrophobic interaction is responsible for separation of neutral analytes. In addition, the electrostatic and hydrophobic interaction and the electrophoretic migration play a significant role in separation of the ionic or ionizable analytes. [source]

Chiral ion-exchange capillary electrochromatography of arylglycine amides with dextran sulfate as a pseudostationary phase

ELECTROPHORESIS, Issue 4-5 2005
Yi Chen
Abstract A low-cost tunable chiral ion-exchange capillary electrochromatographic method has been developed for the separation of arylglycine amide racemic mixtures with dextran sulfate (DS) as an anionic and chiral pseudostationary phase and Tris-tartrate as a buffer system. The concentrations of DS and Tris had opposite influences on retention and resolution and could serve as ideal factors to finely tune the running speed and chiral resolution. Tartrate and pH largely impact the separation but pH should be confined within 3.0,5.5, only suitable for coarse tuning, while tartrate was preserved as the key buffering reagent, normally maintained at 40 mmol/L. With a working system composed of 0.1,1.0% DS, 20,60 mmol/L Tris, and 40 mmol/L tartrate at pH 3.50,4.50, the enantioresolution of arylglycine amides was shown to be dependent on their chemical structure: The chiral resolution increased when the hydrogen at the ,-amino group or at the p -position of phenyl ring was replaced by other larger group(s) but the resolution decreased when the group at the o- or m- site on the phenyl ring was enlarged. Further, the electronegative substitute of -Cl had larger resolution increment than methyl or methoxy at the position p- of phenyl ring but much lower increment at position m- . It is possible to well explain the resolution variation phenomenon by considering the group resistance and the variation of hydrogen-bonds formed inside the amino amides and between the solutes and DS. The amido group was shown irreplaceable to have chiral resolution with DS alone as an ionic and chiral pseudostationary phase. [source]

Ion transport and osmotic adjustment in Escherichia coli in response to ionic and non-ionic osmotica

ENVIRONMENTAL MICROBIOLOGY, Issue 1 2009
Lana Shabala
Summary Bacteria respond to osmotic stress by a substantial increase in the intracellular osmolality, adjusting their cell turgor for altered growth conditions. Using Escherichia coli as a model organism we demonstrate here that bacterial responses to hyperosmotic stress specifically depend on the nature of osmoticum used. We show that increasing acute hyperosmotic NaCl stress above ,1.0 Os kg,1 causes a dose-dependent K+ leak from the cell, resulting in a substantial decrease in cytosolic K+ content and a concurrent accumulation of Na+ in the cell. At the same time, isotonic sucrose or mannitol treatment (non-ionic osmotica) results in a gradual increase of the net K+ uptake. Ion flux data are consistent with growth experiments showing that bacterial growth is impaired by NaCl at the concentration resulting in a switch from net K+ uptake to efflux. Microarray experiments reveal that about 40% of upregulated genes shared no similarity in their responses to NaCl and sucrose treatment, further suggesting specificity of osmotic adjustment in E. coli to ionic and non-ionic osmotica. The observed differences are explained by the specificity of the stress-induced changes in the membrane potential of bacterial cells highlighting the importance of voltage-gated K+ transporters for bacterial adaptation to hyperosmotic stress. [source]

Limits of life in MgCl2 -containing environments: chaotropicity defines the window

ENVIRONMENTAL MICROBIOLOGY, Issue 3 2007
John E. Hallsworth
Summary The biosphere of planet Earth is delineated by physico-chemical conditions that are too harsh for, or inconsistent with, life processes and maintenance of the structure and function of biomolecules. To define the window of life on Earth (and perhaps gain insights into the limits that life could tolerate elsewhere), and hence understand some of the most unusual biological activities that operate at such extremes, it is necessary to understand the causes and cellular basis of systems failure beyond these windows. Because water plays such a central role in biomolecules and bioprocesses, its availability, properties and behaviour are among the key life-limiting parameters. Saline waters dominate the Earth, with the oceans holding 96.5% of the planet's water. Saline groundwater, inland seas or saltwater lakes hold another 1%, a quantity that exceeds the world's available freshwater. About one quarter of Earth's land mass is underlain by salt, often more than 100 m thick. Evaporite deposits contain hypersaline waters within and between their salt crystals, and even contain large subterranean salt lakes, and therefore represent significant microbial habitats. Salts have a major impact on the nature and extent of the biosphere, because solutes radically influence water's availability (water activity) and exert other activities that also affect biological systems (e.g. ionic, kosmotropic, chaotropic and those that affect cell turgor), and as a consequence can be major stressors of cellular systems. Despite the stressor effects of salts, hypersaline environments can be heavily populated with salt-tolerant or -dependent microbes, the halophiles. The most common salt in hypersaline environments is NaCl, but many evaporite deposits and brines are also rich in other salts, including MgCl2 (several hundred million tonnes of bischofite, MgCl2·6H2O, occur in one formation alone). Magnesium (Mg) is the third most abundant element dissolved in seawater and is ubiquitous in the Earth's crust, and throughout the Solar System, where it exists in association with a variety of anions. Magnesium chloride is exceptionally soluble in water, so can achieve high concentrations (> 5 M) in brines. However, while NaCl-dominated hypersaline environments are habitats for a rich variety of salt-adapted microbes, there are contradictory indications of life in MgCl2 -rich environments. In this work, we have sought to obtain new insights into how MgCl2 affects cellular systems, to assess whether MgCl2 can determine the window of life, and, if so, to derive a value for this window. We have dissected two relevant cellular stress-related activities of MgCl2 solutions, namely water activity reduction and chaotropicity, and analysed signatures of life at different concentrations of MgCl2 in a natural environment, namely the 0.05,5.05 M MgCl2 gradient of the seawater : hypersaline brine interface of Discovery Basin , a large, stable brine lake almost saturated with MgCl2, located on the Mediterranean Sea floor. We document here the exceptional chaotropicity of MgCl2, and show that this property, rather than water activity reduction, inhibits life by denaturing biological macromolecules. In vitro, a test enzyme was totally inhibited by MgCl2 at concentrations below 1 M; and culture medium with MgCl2 concentrations above 1.26 M inhibited the growth of microbes in samples taken from all parts of the Discovery interface. Although DNA and rRNA from key microbial groups (sulfate reducers and methanogens) were detected along the entire MgCl2 gradient of the seawater : Discovery brine interface, mRNA, a highly labile indicator of active microbes, was recovered only from the upper part of the chemocline at MgCl2 concentrations of less than 2.3 M. We also show that the extreme chaotropicity of MgCl2 at high concentrations not only denatures macromolecules, but also preserves the more stable ones: such indicator molecules, hitherto regarded as evidence of life, may thus be misleading signatures in chaotropic environments. Thus, the chaotropicity of MgCl2 would appear to be a window-of-life-determining parameter, and the results obtained here suggest that the upper MgCl2 concentration for life, in the absence of compensating (e.g. kosmotropic) solutes, is about 2.3 M. [source]

Determination of physicochemical properties of tetrabromobisphenol A

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2008
Hidetoshi Kuramochi
Abstract Aqueous solubility (Sw), 1-octanol/water partition coefficient (KOW), and vapor pressure of the nonionic form of 2,2,,6,6,-tetrabromo-4,4,-isopropylidenediphenol (tetrabromobisphenol A or TBBP-A) were measured. From this, enthalpies of solution and vaporization were estimated. Furthermore, enthalpy of fusion and melting point were measured to estimate subcooled liquid vapor pressure, the infinite dilution activity coefficient, and Henry's law constant. Since TBBP-A is expected to exit in both ionic and nonionic forms at near neutral pH, pH effects on physicochemical properties were also examined. Because of the ionization of TBBP-A, Sw increased by five orders of magnitude, while KOW decreased by eight orders of magnitude. Furthermore, an analytical model based on mass balance and dissociation of TBBP-A was applied to represent the pH dependence. [source]

Thermally Stable Nanocrystalline Mesoporous Gallium Oxide Phases

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2009
Chinmay A. Deshmane
Abstract Semicrystalline and fully crystalline mesoporous galliumoxide phases were synthesized in the presence of ionic and non-ionic structure directing agents via Evaporation-Induced Self-Assembly (EISA) and Self-Assembly Hydrothermal-Assisted (SAHA) methods respectively. EISA led to partially crystalline mesoporous gallium oxide phases displaying unimodal pore size distribution in the range of ca. 2,5 nm and surface areas as high as 300 m2/g. SAHA led to nanocrystalline mesoporous uniform micron-sized gallium oxide spheres (ca. 0.3,6.5 ,m) with narrow size distribution displaying cubic spinel type structure. These mesophases displayed surface areas as high as ca. 221 m2/g and unimodal pore size distribution in the 5,15 nm range. Textural properties such as surface areas and pore sizes were effectively fine-tuned by the nature and relative concentration of the structure directing agents. Due to their high surface areas, tunability of pore sizes and the nature of the wall structure, these gallium oxide mesophases could find potential applications as heterogeneous catalysts.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Theoretical Study on a Class of Organometallic Complexes Based on All-Metal Aromatic Ga3, Through Sandwiching Stabilization

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2008
Li-ming Yang
Abstract We report the theoretical study on a class of organometallic complexes containing the all-metal aromatic unit Ga3, on the basis of density functional theory calculations on a series of model sandwich-like compounds [DM(Ga3)]q, as well as those of the saturated compounds [DMn(Ga3)] [D = Ga3,, Cp,(C5H5,); M = Li, Na, K, Be, Mg, Ca] and extended compounds (Cp,)m(Li+)n(Ga3,)o (m, n, and o are integers). For the six metals, the all-metal aromatic Ga3, can only be assembled and stabilized in the "heterodecked sandwich" scheme (e.g. [CpM(Ga3)]q,) so as to avoid cluster fusion. Moreover, we designed a novel class of all-metal aromatic "metalloid" compounds. The ground state heterodecked sandwich species (Cp),(M)q+(Ga3), (M = Li, Na, K, q = 1; M = Be, Mg, Ca, q = 2) and the extended sandwich species (Cp,)m(Li+)n(Ga3,)o are mainly ionic bonded, cluster-assembled "polyatomic molecule", grown from the combination of Cp,, M atoms, and Ga3,. As a prototype for ionic bonding involving intact Ga3, subunits, [CpM(Ga3)]q, may be a stepping stone toward forming ionic, cluster-assembled all-metal aromatic Ga3 -based bulk solids or materials. Additionally, our results for the first time showed that the electronic, structural, and aromatic properties of the all-metal aromatic Ga3, could be well retained during cluster assembly, which is indicative of "building block" character. Bearing the significant difference in bonding patterns between our designed metalloid compounds and the known metalloid species, synthesis of these novel species might present an attractive challenge to experimental chemists. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Synthesis and Structure of [nPr3N(CH2)6NnPr3][CuFe3Br3(SePh)6], [Cu5Fe(SePh)7(PPh3)4] and [Cu4Fe3(SePh)10(PPh3)4],

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2007
Andreas Eichhöfer
Abstract CuBr and Fe(OOCCH3)2 react with PhSeSiMe3 in acetonitrile in the presence of the diammonium salt [nPr3N(CH2)6NnPr3]Br2 to yield ionic [nPr3N(CH2)6NnPr3][CuFe3Br3(SePh)6]. The neutral complexes [Cu5Fe(SePh)7(PPh3)4] and [Cu4Fe3(SePh)10(PPh3)4] were obtained by similar reactions of different stoichiometric mixtures of CuOOCCH3 and FeCl2 with PPh3 and PhSeSiMe3. The crystal structures of the compounds were determined by single-crystal X-ray analysis to give new structural types of molecular cluster compounds formed by copper, iron and selenium. Thermal treatment of [Cu5Fe(SePh)7(PPh3)4] and [Cu4Fe3(SePh)10(PPh3)4] resultsin the formation of mixtures of binary Cu2Se and ternaryCuFeSe2.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

Extended X-ray Absorption Fine Structure Study of Copper(I) and Copper(II) Complexes in Atom Transfer Radical Polymerization

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2003
Tomislav Pintauer
Abstract Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy has been used to investigate structural features of CuIBr and CuIIBr2 complexes with dNbpy, PMDETA, Me6TREN, tNtpy, and Me4CYCLAM in various solvents {dNbpy = 4,4,-bis(5-nonyl)-2,2,-bipyridine, PMDETA = N,N,N,,N,,,N,, -pentamethyldiethylenetriamine, Me6TREN = tris[2-(dimethylamino)ethyl]amine, tNtpy = 4,4,,4,,-tris(5-nonyl)-2,2,:6,,2,,-terpyridine, Me4CYCLAM = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane}. The structures of the CuI and CuII complexes were found to depend on the solvent polarity and the number of nitrogen atoms in the ligand. Generally, in non-polar media and with monomers typically used in ATRP, CuI complexes preferred a tetracoordinate geometry, and were either ionic as observed in [CuI(dNbpy)2]+[CuIBr2], (CuI,NAV = 2.00 Å, CuI,BrAV = 2.25 Å) and [CuI(Me4CYCLAM)]+[CuIBr2], (CuI,NAV = 2.06 Å, CuI,BrAV = 2.23 Å), or neutral as in [CuI(PMDETA)Br] (CuI,NAV = 2.12 Å, CuI,BrAV = 2.33 Å), and [CuI(tNtpy)Br] (CuI,NAV = 2.03 Å, CuI,BrAV = 2.29 Å). The EXAFS analysis of CuIIBr2 complexes indicated a preference for a coordination number of five, such as in [CuII(dNbpy)2Br]+[Br], (CuII,NAV = 2.03 Å, CuII,BrAV = 2.43 Å), [CuII(PMDETA)Br2] (CuII,NAV = 2.03 Å, CuII,Br1,AV = 2.44 Å, CuII,Br2,AV = 2.64 Å) and [CuII(Me6TREN)Br]+[Br], (CuII,NAV = 2.09 Å, CuII -BrAV = 2.39 Å), with the exception of the neutral tetracoordinate [CuII(dNbpy)Br2] (CuII,NAV = 2.02 Å, CuII,BrAV = 2.36 Å), which has been observed in non-polar media. Additionally, polar media were found to favor bromide dissociation in [CuII(Me6TREN)Br]+[Br], and [CuII(PMDETA)Br2], as indicated by a decrease in the Br and Cu coordination numbers at the Cu- and Br- K -edges, respectively. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Synthesis, Characterization and Drug Release Behavior of pH-Responsive O-carboxymethyl Chitosan-graft-poly(N-vinylpyrrolidone) Hydrogel Beads,

ADVANCED ENGINEERING MATERIALS, Issue 12 2009
Liwei Ma
In this work, the carboxymethyl chitosan (CMCTS) grafted poly(N-vinylpyrrolidone) (PVP) copolymers were synthesized. The hydrogel beads containing VB2 were prepared from the copolymers by an ionic crosslinked. The experimental results shown that VB2 drug release rate from those beads decreased with the increasing grafting percentage, crosslinker concentration and pH value of the medium. Besides, the beads have the better control ability for releasing of model drug than CMCTS does. [source]

Ionic Liquids: Electropolymerization of a Bifunctional Ionic Liquid Monomer Yields an Electroactive Liquid-Crystalline Polymer (Adv. Funct.

ADVANCED FUNCTIONAL MATERIALS, Issue 13 2010
Mater.
M. A. Firestone et al. present a polymer that incorporates an electronic component with an ionic liquid and produces a mixed ionic and electronic conductor on page 2063. Electropolymerization of a bifunctional imidazolium-based ionic liquid monomer incorporating both vinyl and thiophene groups yields a liquid-crystalline polymer that adopts an interconnected network structure formed by two orthogonally oriented lamellar sheets. The structural ordering leads to enhanced electrical conductivity. [source]

Synthetic Strategies for Controlling the Morphology of Proton Conducting Polymer Membranes,,

FUEL CELLS, Issue 2 2005
Y. Yang
Abstract The nanostructure and morphology of proton conducting polymers is of considerable interest in the search for next generation materials and optimization of existing ones. Synthetic methodologies for tailoring molecular structures that promote nanoscopic phase separation of ionic and non-ionic domains, and the effect of phase separation on parameters such as proton conductivity, are considered. Rather than distinguish proton conducting polymers according to chemical class, they are categorized under sub-headings of random, block, and graft copolymers. The synthetic methodology available to access archetypal polymer structures is dependent on the nature of the monomers and restrictive compared to conventional non-ionic polymer systems. Irrespective of the methodology, ionic aggregation and phase separation are consistently found to play an important role in the proton conductivity of low ion exchange capacity,(IEC) membranes, but less of a role in high IEC membranes. Significant research is required to further develop relationships between polymer architecture, morphology, and electrolytic properties. [source]

Immunosensors: (Ionic-Liquid-Doped Polyaniline Inverse Opals: Preparation, Characterization, and Application for the Electrochemical Impedance Immunoassay of Hepatitis B Surface Antigen) Adv.

ADVANCED FUNCTIONAL MATERIALS, Issue 19 2009
Funct.
Xing-Hua Li et al. describe the preparation of ionic liquid-doped polyaniline (IL-PANI) inverse opaline film with surface assemblies of gold nanoparticles. The resulting AuNP/IL-PANI film is conjugated with Hepatitis B surface antibody molecules to fabricate a immunosensor with a low detection limit for Hepatitis B surface antigen. [source]

Ionic Iridium(III) Complexes with Bulky Side Groups for Use in Light Emitting Cells: Reduction of Concentration Quenching

ADVANCED FUNCTIONAL MATERIALS, Issue 13 2009
Carsten Rothe
Abstract Here, the photophysics and performance of single-layer light emitting cells (LECs) based on a series of ionic cyclometalated Ir(III) complexes of formulae and where ppy, bpy, and phen are 2-phenylpyridine, substituted bipyridine and substituted phenanthroline ligands, respectively, are reported. Substitution at the N,N ligand has little effect on the emitting metal-ligand to ligand charge-transfer (MLLCT) states and functionalization at this site of the complex leads to only modest changes in emission color. For the more bulky complexes the increase in intermolecular separation leads to reduced exciton migration, which in turn, by suppressing concentration quenching, significantly increases the lifetime of the excited state. On the other hand, the larger intermolecular separation induced by bulky ligands reduces the charge carrier mobility of the materials, which means that higher bias fields are needed to drive the diodes. A brightness of ca. 1000,cd,m,2 at 3,V is obtained for complex 5, which demonstrates a beneficial effect of bulky substituents. [source]

Fabrication and Electrochemical Properties of Epitaxial Samarium-Doped Ceria Films on SrTiO3 -Buffered MgO Substrates

ADVANCED FUNCTIONAL MATERIALS, Issue 11 2009
Simone Sanna
Abstract Thin films of samarium-oxide-doped (20,mol%) ceria (SDC) are grown by pulsed-laser deposition (PLD) on (001) MgO single-crystal substrates. SrTiO3 (STO) prepared by PLD is used as a buffer layer on the MgO substrates to enable epitaxial growth of the fluorite-structured SDC film; the STO layer provides a proper crystalline match between SDC and MgO, resulting in highly crystalline, epitaxial SDC films grown in the (001) orientation. Film conductivity is evaluated by electrochemical impedance spectroscopy measurements, which are performed at various temperatures (400,775,°C) in a wide range of oxygen partial pressure (pO2) values (10,25,1,atm) in order to separate ionic and electronic conductivity contributions. At 700,°C, SDC/STO films on (100) MgO exhibit a dominant ionic conductivity of about 7,×,10,2,S cm,1, down to pO2 values of about 10,15,atm. The absence of grain boundaries make the SDC/STO/MgO heterostructures stable to oxidation-reduction cycles at high temperatures, in contrast to that observed for the more disordered SDC/STO films, which degraded after hydrogen exposure. [source]

Binding Studies of Asymmetric Pentacoordinate Copper(II) Complexes Containing Phenanthroline and Ethane-1,2-diamine Ligands with Calf-Thymus DNA

HELVETICA CHIMICA ACTA, Issue 9 2005
Farukh Arjmand
New chiral complexes of the composition [MLL,], where HL=1,2-bis(1H -benzimidazol-2-yl)ethane-1,2-diol=H2bimedol, M=CoII, NiII, CuII, and L,=1,10-phenanthroline (phen) or ethane-1,2-diamine (en), were synthesized and characterized. The ligand L exhibited a coordination mode involving the O-atom of only one OH group, the other one being directed away from the metal center. The complexes [Cu(Hbimedol)(en)]Cl (1), [Cu(Hbimedol)(phen)]Cl (2), [Co(Hbimedol)(phen)]Cl (3), [Ni(Hbimedol)(en)]Cl (4), and [Ni(Hbimedol)(phen)]Cl (5) were ionic in nature and stable at room temperature. The donor sets involved in coordination with the metal ions were the O-atom of one OH group and two N-atoms of the two benzimidazole moieties, besides the two N-atoms of phen or en (Fig.,1.). The proposed five-coordinate geometry of 1,5 was established by analysis of spectroscopic data; the ball-and-stick models supported the proposed structures of 1,5 since they showed apparently no strain on any bond and angle. The interaction of complexes 1 and 2 with calf-thymus DNA were carried out by UV/VIS titration, circular dichroism, electrochemical methods, and viscometry. The intrinsic binding constant Kb of 1 and 2 was determined as 1.57,104 and 1.51,104,M,1, respectively, suggesting that both complexes bind strongly to calf-thymus DNA. [source]

Structure and bonding in some S -methylsulfonium halides

HETEROATOM CHEMISTRY, Issue 4 2005
D. B. Chesnut
Density functional theory (DFT) calculations have been carried out at the B3LYP 6-311+G(d,p) level to characterize the geometric and electronic characteristics of a series of S-methylsulfonium halides that possess unusual molecular structures. Atoms-in-molecules (AIM), electron localization function (ELF), and NMR data support the idea that the binding in these gas phase species is predominately ionic with some small degree of covalent bonding. © 2005 Wiley Periodicals, Inc. 16:263,270, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20087 [source]

Poly(9,9-dioctylfluorene)-Based Conjugated Polyelectrolyte: Extended ,-Electron Conjugation Induced by Complexation with a Surfactant Zwitterion

ADVANCED MATERIALS, Issue 18 2010
Giuseppina Pace
We report on a conjugated polyelectrolyte (CPE) based on fluorene repeat units, which forms a supramolecular complex with a zwitterion surfactant. The complex self-assembles into multilamellar structures on solid substrates. The luminescence efficiency, low in the uncomplexed polymer, is strongly increased after complexation. This originates from the phase segregation between the aromatic backbone and ionic sides, reducing conformational defects and ionic dipole-induced quenching. [source]