Mesomorphic and ferroelectric properties of FLCP/FLC binary mixtures

We have prepared several ferroelectric polysiloxanes with two and three benzenic ring moieties. The siloxane backbone is favorable to ferroelectric S phase formation, and the chiral S phase is observed in all of the polymers. Some of the spontaneous polarizations are very high, more than 100 nC/cm² (10^?3 C/m²) and the response times are less than 1 ms near the I-S or S_a–SS transition. Several binary mixtures between FLC copoly-siloxanes and different low molar mass LC have been studied, and have shown the complete miscibility of these two components and richer mesomorphic sequences than for the polymers alone; for example, an N^*–S_a sequence.     

Electrochemical sensor for superoxide anion radical using polymeric iron porphyrin complexes containing axial 1‐methylimidazole ligand as cytochrome c mimics

A needle‐type electrochemical sensor for the facile detection of superoxide anion radical (O) was devised using an electrodeposited film of a polymeric porphyrin complex attached to a carbon microelectrode which was placed in a stainless steel 18G needle tube as an auxiliary electrode. The sensing element was prepared by means of electropolymerization of bromoiron(III) meso‐ tetra(3‐thienyl)porphyrin in the presence of 1‐methylimidazole in CH₂Cl₂ containing 100 mM tetrabutylammonium perchlorate (TBAP) as a supporting electrolyte, which gave a smooth film of the corresponding polymer. The film was electrochemically active to give a redox response near −0.05 V versus Ag/AgCl due to the iron(II/III) couple. The microsensor was applied to detect O produced by xanthine oxidation catalyzed by xanthine oxidase. The amperometric response for O was monitored at an electrode potential of 0.5 V versus the auxiliary electrode in a 10 mM phosphate buffer. The microsensor displayed a high catalytic activity for the oxidation of O and showed a linear relationship between the current and the O concentration. Axial coordination of an imidazole ligand to the iron porphyrin center enhanced selectivity for O by impeding the undesired coordination of H₂O₂ that resulted from the dismutation of O. Copyright © 2005 John Wiley & Sons, Ltd.     

Second-order nonlinear optical properties of side-chain liquid crystalline polymers studied by second harmonic generation from thin films

The two independent elements of the second-order nonlinear optical susceptibility tensor of a range of contact poled, donor–acceptor substitued side-chain polymers are reported. The susceptibilities were measured by second harmonic generation from thin films, typically less than 0.5 μm thick, at a fundamental wavelength of 1064 nm. The largest value was χ = 2.64 pm/V which is three times greater than the χ value of KDP and was measured in a nitrobenzylidene side chain, polyhydroxystyrene polymer with an eleven unit alkyl chain spacer attaching the side group to the backbone. Typical susceptibility values obtained were χ～0.3 pm/V and X⁽²⁾₃₃～1 pm/V. The coherence lengths of the materials, which lay in the range 4–12 μm, were measured at 1064 nm by the maker fringe technique using thick, wedge-shaped samples.     

Synthesis,characterization, and hoping transport properties of HCl doped conducting biopolymer‐co‐polyaniline zwitterion hybrids

A series of electrically conductive zwitterion hybrid materials were facilely synthesized with anionic acacia gum (AG) and cationic HCl doped polyaniline (PANI) through radical copolymerization method. A representative acacia gum‐polyaniline hybrid (AG‐PANI) was characterized using UV‐vis, FTIR, ¹H NMR, and SEM. HCl doped AG‐PANI possesses zwitterion character due to the presence of NH on PANI and ? COO^? of AG. The cyclic voltammogram of AG‐PANI showed three anodic peaks at 0.20 V, 0.58 V, and 0.64 V along with two cathodic peaks at 0.50 V and 0.40 V with large capacitive background currents. AG‐PANI exhibited electrical conductivity that was found dependent on the ratio of aniline to AG, temperature, and pH. Its electrical conductivity versus temperature plot indicated Mott's nearest‐neighbor hopping mechanism at the temperature range 83–323 K. The hybridization of AG and PANI yielded eco‐friendly advanced functional materials for technological applications. Copyright © 2008 John Wiley & Sons, Ltd.     

63Cu-NMR.-Untersuchungen von Kupfer (I)-Tetrapyridin-und Kupfer (I)-Tetraacetonitrilsolvaten

⁶³Cu-NMR.-Spectra of Cu(CH₃CN)₄X (X = ClO, BF, PF) and Cu(C₅H₅N)₄X (X = ClO, BF) in solution are reported at different temperatures and concentrations. The influence of temperature on the linewidth and chemical shift indicates an equilibrium of Cu(CH₃CN) and Cu(C₅H₅N) with another complex of lower symmetry. The preferential solvation of Cu (I) by pyridin in a mixture acetonitrile/pyridine is clearly shown.     

A fragmentation study of dihydroquercetin using triple quadrupole mass spectrometry and its application for identification of dihydroflavonols in Citrus juices

A mass spectrometric method using electrospray ionization with triple quadrupole and quadrupole time‐of‐flight hybrid (Q‐Tof) mass spectrometry has been applied to the structural characterization of dihydroflavonols. This family of compounds has been studied by liquid chromatography/tandem mass spectrometry (LC/MS/MS) for the first time in this work. A comprehensive study of the product ion MS spectra of the [M+H]⁺ ion of a commercially available standard has been performed. The most useful fragmentations in terms of structural identification are those that involve cleavage of the C‐ring, resulting in diagnostic ions of dihydroflavonol family: ^1,3A, ^1,2B, ^1,2B‐CO, ^0,2A, ^0,2A‐H₂O, ^0,2A‐CO, and ^0,2A‐H₂O‐CO, that allow the characterization of the substituents in the A‐ and B‐rings. In addition to those ions, other product ions due to losses of H₂O and CO molecules from the Y ion were observed. Their fragmentation mechanisms and ion structures have been proposed. The established fragmentation patterns have been used to successfully identity three dihydroflavonols found in tangerine juices for the first time. Copyright © 2009 John Wiley & Sons, Ltd.     

Reaction mechanism of platinum dimer cation with ammonia based on the relativistic density functional study

The gas‐phase reactions between Pt and NH₃ have been investigated using the relativistic density functional approach (ZORA‐PW91/TZ2P). The quartet and doublet potential energy surfaces of Pt + NH₃ have been explored. The minimum energy reaction path proceeds through the following steps: Pt(⁴Σ_u) + NH₃ → q‐1 → d‐2 → d‐3 → d‐4 → d‐Pt₂NH⁺ + H₂. In the whole reaction pathway, the step of d‐2 → d‐3 is the rate‐determining step with a energy barrier of 36.1 kcal/mol, and exoergicity of the whole reaction is 12.0 kcal/mol. When Pt₂NH⁺ reacts with NH₃ again, there are two rival reaction paths in the doublet state. One is degradation of NH and another is loss of H₂. In the case of degradation of NH, the activation energy is only 3.4 kcal/mol, and the overall reaction is exothermic by 8.9 kcal/mol. Thus, this reaction is favored both thermodynamically and kinetically. However, in the case of loss of H₂, the rate‐determining step's energy barrier is 64.3 kcal/mol and the overall reaction is endothermic by 8.5 kcal/mol, so it is difficult to take place. Predicted relative energies and barriers along the suggested reaction paths are in reasonable agreement with experimental observations. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Zusammensetzung und Stabilität von Komplexen des Kupfer(II)-Ions mit DL-Threonin in Lösung

The equilibria in Cu(II) ion and DL-threonine (ThrH₂) solutions have been studied. It was found that in the pH interval from 2 to 13.5 the following compounds can exist: CuThrH⁺, Cu(ThrH), Cu(Thr)(ThrH)^? and Cu(Thr). The stoichiometric instability constants of the first two compounds were determined by the spectrophotometric method and by a combination of spectrophotometric and potentiometric methods. In addition, it was established in the same way that the Cu(ThrH) complex behaves like a weak dibasic acid, whose ionisation constants were determined too. Finally, the absorptionspectra of the above complex compounds are given.     

Evidence for the production of NO and N2O in two contrasting subsoils following the addition of synthetic cattle urine

Nitrogenous materials can be transferred out of the topsoil, either vertically to a greater depth, or in lateral pathways to surface waters, and they may also become transformed, with the potential of generating environmentally active agents. We measured the production of NO and N₂O in two contrasting subsoils (70 to 90 cm): one poorly drained and the other freely drained and compared this with the topsoil (0 to 20 cm) of the corresponding soils. The soils were incubated aerobically in jars with subtreatments of either synthetic cattle urine or deionised water and sampled at intervals up to 34 days. ¹⁵N‐NO was used to determine the processes responsible for NO and N₂O production. The headspace was analysed for the concentrations of N₂O, NO and CO₂ and ¹⁵N enrichment of N₂O. The soil samples were extracted and analysed for NO, NO and NH, and the ¹⁵N enrichment of the extracts was measured after conversion into N₂O and N₂. The study demonstrated the potential for NO, N₂O and NO to be generated from subsoils in laboratory incubations. Differences in these N dynamics occurred due to subsoil drainage class. In the freely drained subsoil the rates of NO and NO production were higher than those observed for the corresponding topsoil, with mean maximum production rates of 3.5 µg NO‐N g⁻¹ dry soil on day 16 and 0.12 µg NO‐N g⁻¹ dry soil on day 31. The calculated total losses of N₂O‐N as percentages of the applied synthetic urine N were 0.37% (freely drained subsoil), 0.24% (poorly drained subsoil), 0.43% (freely drained topsoil) and 2.09% (poorly drained topsoil). The calculated total losses of NO‐N as percentages of the applied synthetic urine N were 1.53% (freely drained subsoil), 0.02% (poorly drained subsoil), 0.25% (freely drained topsoil) and 0.08% (poorly drained topsoil). Copyright © 2010 John Wiley & Sons, Ltd.     

Kinetic study of the interaction of adenosine 5′‐monophosphate with diaqua (2‐hydrazinopyridine) palladium(II) in aqueous medium

The interaction of the palladium(II) complex [Pd(hzpy)(H₂O)₂]²⁺, where hzpy is 2‐hydrazinopyridine, with purine nucleoside adenosine 5′‐monophosphate (5′‐AMP) was studied kinetically under pseudo‐first‐order conditions, using stopped‐flow techniques. The reaction was found to take place in two consecutive reaction steps, which are both dependent on the actual 5′‐AMP concentration. The activation parameters for the two reaction steps, i.e. ΔH = 32 ±2 kJ mol^?1, ΔS = ?168 ±7 J K^?1 mol^?1, and ΔH = 28 ± 1 kJ mol^?1, ΔS = ?126 ± 5 J K^?1 mol^?1, respectively, were evaluated and suggested an associative mode of activation for both substitution processes. The stability constants and the associated speciation diagram of the complexes were also determined potentiometrically. The isolated solid complex was characterized by C, H, and N elemental analyses, IR, magnetic, and molar conductance measurements. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 42: 132–142, 2010     

Arrhenius parameters for the gas‐phase reactions of O3 with two butenes and two methyl‐substituted butenes over the temperature range of 295–351 K

Gas‐phase reactions of ozone with two butenes (1‐butene and isobutene) and two methyl‐substituted butenes (2‐methyl‐1‐butene and 3‐methyl‐1‐butene) have been studied in an indoor chamber at 295–351 K. The O₃ concentrations were monitored by Model 49C‐Ozone analyzer. The butene concentrations were measured by gas chromatography–flame ionization detector. The Arrhenius expressions of k=3.50×10^?15e^{(?1756±84)/T} cm³ molecule^?1 s^?1, k=3.39×10^?15e^{(?1697±52)/T} cm³ molecule^?1 s^?1, k=6.18×10^?15e^{?(1822±80)/T} cm³ molecule^?1 s^?1, and k=7.24×10^?14e^{?(2741±139)/T} cm³ molecule^?1 s^?1 were obtained for the ozonolysis reactions of 1‐butene, isobutene, 2‐methyl‐1‐butene, and 3‐methyl‐1‐butene, respectively. Both the reaction rate constant and activation energy obtained in this work are in good agreement with those reported by using different techniques in the literature. © 2011 Wiley Peiodicals, Inc. Int J Chem Kinet 43: 238–246, 2011     

One‐ to Three‐Dimensional CuI and CuCN Based Coordination Polymers containing the Alkali Cation Ligating Thiacrown Ether 1, 10‐Dithia‐18‐Crown‐6

Treatment of an acetonitrile solution of CuI with 1, 10‐dithia‐18‐crown‐6 (1, 10DT18C6) in the presence of Rb₂CO₃ leads to formation of the lamellar coordination polymer [Rb{Cu₄I₅(1, 10DT18C6)₂}] ( 1 ).The anionic network of 1 is composed of parallel [(Cu₄I₅)^—] chains linked by bridging thiacrown ether ligands, pairs of which coordinate the Rb⁺ counter cations. [Cs{Cu₅I₆(1, 10DT18C6)₂}] ( 2 ) can be prepared under similar conditions but contains separated helical anionic chains. In this case 1, 10DT18C6 ligands bridge copper atoms of individual chains in an intrastrand manner. In contrast the coordination networks in [(CuCN)₂(1, 10DT18C6)] ( 3 ) and [K₂{Cu₁₂(CN)₁₄(1, 10DT18C6)₃} · CH₃CN] ( 4 ) are both three‐dimensional and based on CuCN‐containing sheets bridged by 1, 10DT18C6 ligands. In the latter compound pairs of K⁺ cations are coordinated by groups of three thiacrown ether molecules. The neutral network of 3 can imbibe up to 31 % KNO₃ per 1, 10DT18C6 pair without loss of lattice integrity.     

Complexes of Silver(l) with arsenic and phosphorus donor ligands. Co-ordination number 4

Some tetracoordinated complexes having the formulae, [AgL₄]X (L = Triphenyl-arsine; X = NO, ClO and BrO) and [AgL₃X] (L = Triphenyl-arsine/phosphine; X = SCN^? and NCO^?) have been prepared and characterised by analyses, conductance, magnetic susceptibility and infra-red spectroscopy.     

Darstellung,Kristallstruktur und Schwingungsspektren von (n-Bu4N)2[(Mo6I)(NCS)]

Synthesis, Crystal Structure, and Vibrational Spectra of (n-Bu₄N)₂[(Mo₆I)(NCS)] By treatment of [(Mo₆I)I]^2– with (SCN)₂ in dichloromethane at –20 °C the hexaisothiocyanato cluster anion [(Mo₆I)(NCS)]^2– is formed. The X-ray structure determination of (n-Bu₄N)₂[(Mo₆I)(NCS)] · 2 Me₂CO (monoclinic, space group P2₁/c, a = 13.168(5), b = 11.964(5), c = 24.636(5) Å, β = 104.960(5)°, Z = 2) shows, that the thiocyanate groups are coordinated exclusively via N atoms with Mo–N bond lengths of 2.141–2.150 Å, Mo–N–C angles of 166–178° and N–C–S-angles of 174–180°. The vibrational spectra exhibit characteristic innerligand vibrations at 2073–2054 (ν_CN), 846–844 (ν_CS) and 480–462 cm^–1 (δ_NCS).     

Do‐it‐yourself functionalized silicones part 2: synthesis by ring opening polymerization of commercial cyclosiloxanes

The second paper of the series devoted to the preparation and characterization of vinyl and hydrido‐functionalized silicones proposes readily available techniques to polymerize commercially available cyclosiloxanes. This study is divided into two main sections: one relies on the synthesis of various functional silicone oils by heterogeneous cationic ring opening polymerization (ROP) of cyclotetrasiloxanes (D₄, D) and appropriate 1,3‐difunctional disiloxanes; the second part describes the anionic ROP of hexamethylcyclotrisiloxane (D₃) initiated by potassium silanolates to prepare both homo‐ and hetero‐vinyl functionalized silicones. The conditzions in which polymers with desired molecular weights can be obtained have been established and some kinetic considerations are also reported. The width of the final molar mass distribution ranged between 1.5 and 1.8, respectively, in any case narrower than the mixtures proposed by different providers (around 2). Polymers were characterized by different techniques of size exclusion chromatography (SEC), proton and silicon nuclear magnetic resonance (¹H and ²⁹Si NMR), and mass spectrometry. Copyright © 2009 John Wiley & Sons, Ltd.     

Complex dynamical behavior in a new chemical oscillator: The chlorite–thiourea reaction in a CSTR

The reaction between chlorite ion and thiourea has been studied both in a closed (batch) system and in a flow reactor (CSTR). The principal stoichiometry is given by In batch, the reaction displays an induction period, whose length is proportional to [CS(NH₂)₂]/[ClO] [H⁺], followed by the rapid buildup and disappearance of a ClO₂ intermediate. At [ClO]/[CS(NH₂)₂] ratios between 2.5 and 3.5, a second peak in the ClO₂ absorbance is observed. In the CSTR, this iodine-free system displays simple and complex periodic oscillation, bistability, aperiodic oscillation, and birhythmicity.     

Nonlinear dynamics in the oxidations of substituted thioureas I: The reaction of 4‐methyl‐3‐thiosemicarbazide with acidic iodate [1]

The substituted thiourea, 4‐methyl‐3‐thiosemicarbazide, was oxidized by iodate in acidic medium. In high acid concentrations and in stoichiometric excess of iodate, the reaction displays an induction period followed by the formation of aqueous iodine. In stoichiometric excess of methylthiosemicarbazide and high acid concentration, the reaction shows a transient formation of aqueous iodine. The stoichiometry of the reaction is: 4IO + 3CH₃NHC(S)NHNH₂ + 3H₂O → 4I⁻ + 3SO + 3CH₃NHC(O)NHNH₂ + 6H⁺ (A). Iodine formation is due to the Dushman reaction that produces iodine from iodide formed from the reduction of iodate: IO + 5I⁻ + 6H⁺ → 3I₂(aq) + 3H₂O (B). Transient iodine formation is due to the efficient acid catalysis of the Dushman reaction. The iodine produced in process B is consumed by the methylthiosemicarbazide substrate. The direct reaction of iodine and methylthiosemicarbazide was also studied. It has a stoichiometry of 4I₂(aq) + CH₃NHC(S)NHNH₂ + 5H₂O → 8I⁻ + SO + CH₃NHC(O)NHNH₂ + 10H⁺ (C). The reaction exhibits autoinhibition by iodide and acid. Inhibition by I⁻ is due to the formation of the triiodide species, I, and inhibition by acid is due to the protonation of the sulfur center that deactivates it to further electrophilic attack. In excess iodate conditions, the stoichiometry of the reaction is 8IO + 5CH₃NHC(S)NHNH₂ + H₂O → 4I₂ + 5SO + 5CH₃NHC(O)NHNH₂ + 2H⁺ (D) that is a linear combination of processes A and B. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 193–203, 2000     

Theoretical study of one‐electron bonds in a series of high‐spin lithium–beryllium–hydrogen clusters: “Valence shell single‐electron repulsion” rule and electron localization function analysis

A series of high‐spin clusters containing Li, H, and Be in which the valence shell molecular orbitals (MOs) are occupied by a single electron has been characterized using ab initio and density functional theory (DFT) calculations. A first type (⁵Li₂, ⁿ⁺¹LiH_n+ (n = 2–5), ⁸Li₂H) possesses only one electron pair in the lowest MO, with bond energies of ～3 kcal/mol. In a second type, all the MOs are singly occupied, which results in highly excited species that nevertheless constitute a marked minimum on their potential energy surface (PES). Thus, it is possible to design a larger panel of structures (⁸LiBe, ⁷Li₂, ⁸Li, ⁴LiH⁺, ⁶BeH, ⁿ⁺³LiH (n = 3, 4), ⁿ⁺²LiH (n = 4–6), ⁸Li₂H, ⁹Li₂H, ²²Li₃Be₃ and ²²Li₆H), single‐electron equivalent to doublet “classical” molecules ranging from CO to C₆H₆. The geometrical structure is studied in relation to the valence shell single‐electron repulsion (VSEPR) theory and the electron localization function (ELF) is analyzed, revealing a striking similarity with the corresponding structure having paired electrons. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Subgroup 4 (Ti,Zr, Hf) derivatives of Cobalt Carbonyls

Bimetallic and trimetallic compounds containing unsupported bonds of subgroup 4 metals (M = Ti, Zr, Hf) and Co were prepared by hydride elimination (A) from RM derivatives (R¹ = PhCH₂; RN; R² = Me, Et)) and by salt elimination (B) from RMX (X = Cl, Br; R.¹ = PhCH₂, RN and R³O; R³= i-Pr, n-Bu)) by reaction with HCo(CO)₄ and Na[Co(CO)₄], respectively. Compounds RMCo(CO)₄ with R¹ = PhCH₂, RM[Co(CO)₄]₂ R.¹ = PhCH₂, were prepared both by methods A and B, while (R³O)₄-n Ti[Co(Co)₄]n (n = 1, 2) compounds were obtained by reaction B. Several tertiary phosphine and phosphite derivatives of the former two types were obtained by substitution of a carbonyl group by PR ligand or by A type reaction of HCo(CO)³(PR with RM compounds.     

Darstellung,Schwingungsspektrum und Kristallstruktur von (n‐Bu4N)2[(W6Cl)F] · 2 CH2Cl2 und 19F‐NMR‐spektroskopischer Nachweis der gemischten Clusteranionen [(W6Cl)FCl]2–, n = 1–6

Synthesis, Vibrational Spectra, and Crystal Structure of ( n ‐Bu₄N)₂[(W₆Cl )F ] · 2 CH₂Cl₂ and ¹⁹F NMR Spectroscopic Evidence of the Mixed Cluster Anions [(W₆Cl )F Cl ]^2–, n = 1–6 The reaction of (n‐Bu₄N)₂[(W₆Cl)Cl] with CF₃COOH in dichloromethane gives intermediately a mixture of the cluster anions [(W₆Cl)(CF₃COO)Cl]^2–, n = 1–6. By treatment with NH₄F the outer sphere coordinated trifluoracetato ligands are easily substituted and the components of the series [(W₆Cl)FCl], n = 1–6 are formed and characterized by their distinct ¹⁹F NMR chemical shifts. An X‐ray structure determination has been performed on a single crystal of (n‐Bu₄N)₂[(W₆Cl)F] · 2 CH₂Cl₂ (orthorhombic, space group Pbca, a = 15.628(4), b = 17.656(3), c = 20.687(4) Å, Z = 4). The low temperatur IR (60 K) and Raman (20 K) spectra are assigned by normal coordinate analysis based on the molecular parameters of the X‐ray determination. The valence force constants are f_d(WW) = 1.89, f_d(WF) = 2.43 and f_d(WCl) = 0.93 mdyn/Å.