Heteroatom derivatives of aziridine

Reaction of ethyleneimine with boron trichloride and tribromide below −20° C, with reactants in ratios 1∶1 and 2∶1, gives labile N-β-halo-genoethyl-substituted halogenoborazenes of the types XCH₂CH₂NHBX₂ and (XCH₂CH₂NH)₂BX (X = Cl, Br). These compounds decomposed spontaneously on coming to room temperature, with the evolution of HX and formation of substances whose compositions are, respectively C₂H₄NBX₂ and C₄H₉N₂BX₂. With a 3∶1 ratio of reactants the product is the relatively stable tris(β-halogenoethylamino)borane (XCH₂CH₂NH)₃ B (X = Cl, Br), which loses only one molecule of HX when heated under vacuum. For Part V see [1].     

1-(Bromoacetyl)pyrene,a novel photoinitiator for the copolymerization of styrene and acrylonitrile

A comparative study on photoinitiated solution copolymerization of Styrene (Sty), with acrylonitrile (AN) using pyrene, 1-acetylpyrene, and 1-(bromoacetyl)pyrene (BrPy) as initiators, showed that the introduction of a chromophoric moiety, bromoacetyl (–COCH₂Br), significantly increased the photoinitiating ability of pyrene. The kinetics and mechanism of copolymerization of Sty with AN (Sty–co–AN) using BrPy as photoinitiator has been studied in detail. The kinetic data, inhibiting effect of benzoquinone, and electron spin resonance (ESR) studies suggest that the polymerization proceeds via a free radical mechanism. The system followed non-ideal kinetics (R _p α[BrPy]^0.7[Sty]^1.09[AN]^1.01) and degradative solvent transfer reasonably explained these kinetic non-idealities. The co-monomer reactivity ratios calculated by using the Finemann–Ross and Kelen–Tudos models were r ₁ (Sty) = 0.39 and r ₂ (AN) = 0.05. The reactivity ratios strongly indicate that the two monomers enter in almost alternating arrangement along the copolymer chain.     

Thermodynamic studies of the binding interactions of surfactin analogues to lipid vesicles Application of isothermal titration calorimetry

Isothermal titration calorimetry was applied for studying the binding interactions of cyclic and linear surfactins with different ionic charge (z= −2 and −3) and lipid chain length (n=14 and 18) to 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidyl-choline (POPC) vesicles in 10mMTris buffer at pH8.5with 150mMNaCl at 25°C. Surfactin analogues interacted spontaneously (ΔG _D ^w→b < 0) with POPC vesicles. The binding reactions were endothermic (ΔH _D ^w→b > 0) and entropy-driven process (ΔS _D ^w→b > 0). Moreover, significant differences in the binding constant values (K) ranging from 6.6·10³ to 9.6·10⁴ M⁻¹ show that cyclic structure and the increase of lipid chain length are favourable on the surfactin binding affinity to POPC vesicles, whereas the rise of the number of negative charges has an opposite effect.     

Thermal Behaviour Studies on Some Heterotrinuclearpolyacids

An improved method for the synthesis of four heterotrinuclearpolyacids of the type: H_x[EM′_yM″_zO₄₀⋅nH₂O (E=P, Si; M′=Mo, W; M″=V, W) was elaborated. The studied compounds were characterized by elemental analysis, IR spectra and thermal behaviour over 20–800°C temperature range. This revised version was published online in August 2006 with corrections to the Cover Date.     

Divalent transition metal complexes of 3,5-pyrazoledicarboxylate

New divalent transition metal 3,5-pyrazoledicarboxylate hydrates of empirical formula Mpz(COO)₂(H₂O)₂, where M=Mn, Co, Ni, Cu, Zn and Cd (pz(COO)₂=3,5-pyrazoledicarboxylate), metal hydrazine complexes of the type Mpz(COO)₂N₂H₄ where M=Co, Zn or Cd and Mpz(COO)₂nN₂H₄·H₂O, where n=1 for M=Ni and n=0.5 for M=Cu have been prepared and characterized by physico-chemical methods. Electronic spectroscopic data suggest that Co and Ni complexes adopt an octahedral geometry. The IR spectra confirm the presence of unidentate carboxylate anion (Δν=ν_asy(COO^–)–ν_sym(COO^–)>215 cm^–1) in all the complexes and bidentate bridging hydrazine (ν_N–N=985–950 cm^–1) in the metal hydrazine complexes. Both metal carboxylate and metal hydrazine carboxylate complexes undergo endothermic dehydration and/or dehydrazination followed by exothermic decomposition of organic moiety to give the respective metal oxides as the end products except manganese pyrazoledicarboxylate hydrate, which leaves manganese carbonate. X-ray powder diffraction patterns reveal that the metal carboxylate hydrates are isomorphous as are those of metal hydrazine complexes of cobalt, zinc and cadmium.     

Preparation and thermal behaviour of divalent transition metal complexes of pyromellitic acid with hydrazine

Hydrazine forms two different types of complexes with divalent metal ions and pyromellitic acid (H₄pml) in aqueous medium: (i) hydrazinium complexes of formulae, (N₂H₅)₂M(pml)·xH₂O, where x = 3 for M=Ni and x = 4 for M=Co or Zn, and (N₂H₅)₂Mn(H₂pml)₂, at pH 4.5, (ii) neutral hydrazine complexes with formulae, M₂(pml)(N₂H₄) _n ·xH₂O where M=Co or Ni when n = 4 and x = 5 or 4 and M=Zn or Cd when n = 2, and x = 4 or 3 at pH 7, and M(H₂pml)(N₂H₄)·xH₂O where x = 4; M=Cu and x = 0; M=Hg, at pH 3, 7.5, respectively. All the complexes are insoluble in water, alcohol and ether. The N–N stretching frequency (990–1,007 cm⁻¹ for coordinated hydrazinium ion and 956–985 cm⁻¹ for bridged neutral hydrazine) indicates the nature of hydrazine present in the complexes. Simultaneously TG-DTA analysis indicates that hydrazinium complexes undergo dehydration and dehydrazination in a single step endothermally in the range of 289–300 °C whereas neutral hydrazine complexes undergo endothermic dehydration (~100 °C) followed by exothermic dehydrazination in the temperature range, 253–332 °C. The anhydrous metal carboxylates further decompose exothermally to leave the respective metal oxides or metal carbonates except zinc, which gives its oxalate as the end product. X-ray powder patterns indicate that even the complexes with the same formulation possess no isomorphism.     

Thermal stability of some new complexes bearing ligands with polymerizable groups

A series of new complexes with mixed ligands of the type M(4,4’-dipy)(C₃H₃O₂)₂(H₂O)_y ((1) M=Mn, y=2; (2) M=Ni, y=2; 4,4’-dipy: 4,4’-dipyridyl and C₃H₃O₂ is acrylate anion) and respectively M₂(4,4’-dipy)(C₃H₃O₂)₄(H₂O)_y ((3) M=Cu, y=0; (4) M=Zn, y=1). The modification evidenced in IR spectra was correlated with the presence of acrylate ion as unidentate in the case of complex (1) and as bidentate for others complexes. The electronic reflectance spectra showed the d–d transition for complex (1) and (2) characteristic for the octahedral surrounding while the spectrum for complex (3) have the characteristic pattern for square-pyramidal stereochemistry. The thermal behaviour steps were investigated. The thermal transformations are complex processes according to TG and DTG curves including dehydration, acrylate ion oxidative degradation and thermolysis process of aromatic amine. The final products of decomposition are the most stable metal oxides.     

Kinetic Determination of Iodide Based on its Effect on the Hydrogen Peroxide Oxidation of Triflupromazine

 A new selective, sensitive, and simple kinetic method is developed for the determination of trace amounts of iodide. The method is based on the catalytic effect of iodide on the reaction of triflupromazine (TFP) with H₂O₂. The reaction is followed spectrophotometrically by tracing the oxidation product at 498 nm within 1 min after addition of H₂O₂. The optimum reaction conditions are TFP (0.4 × 10⁻³ M), H₂SO₄ (1.0M), H₃PO₄ (2.0M), and H₂O₂ (1.6M) at 30°C. Following this procedure, iodide can be determined with a linear calibration graph up to 4.5 ng ċ cm⁻³ and a detection limit of 0.04 ng ċ cm⁻³, based on the 3 S_b criterion. The method can also be applied to the determination of iodate and periodate ions. Determination of as little as 0.2, 1.0, 2.0, and 4.0 ng ċ cm⁻³ of I⁻, IO₃ ^-, or IO₄ ^- in aqueous solutions gave an average recovery of 98% with relative standard deviations below 1.6% (n = 5). The method was applied to the determination of iodide in Nile river water and ground waters as well as in various food samples after alkaline ashing treatment. The method is compared with other catalytic spectrophotometric procedures for iodide determination.     

Kinetic Determination of Iodide Based on its Effect on the Hydrogen Peroxide Oxidation of Triflupromazine

Summary.  A new selective, sensitive, and simple kinetic method is developed for the determination of trace amounts of iodide. The method is based on the catalytic effect of iodide on the reaction of triflupromazine (TFP) with H₂O₂. The reaction is followed spectrophotometrically by tracing the oxidation product at 498 nm within 1 min after addition of H₂O₂. The optimum reaction conditions are TFP (0.4 × 10⁻³ M), H₂SO₄ (1.0M), H₃PO₄ (2.0M), and H₂O₂ (1.6M) at 30°C. Following this procedure, iodide can be determined with a linear calibration graph up to 4.5 ng ċ cm⁻³ and a detection limit of 0.04 ng ċ cm⁻³, based on the 3 S_b criterion. The method can also be applied to the determination of iodate and periodate ions. Determination of as little as 0.2, 1.0, 2.0, and 4.0 ng ċ cm⁻³ of I⁻, IO₃ ^-, or IO₄ ^- in aqueous solutions gave an average recovery of 98% with relative standard deviations below 1.6% (n = 5). The method was applied to the determination of iodide in Nile river water and ground waters as well as in various food samples after alkaline ashing treatment. The method is compared with other catalytic spectrophotometric procedures for iodide determination. Received January 19, 2001. Accepted (revised) March 12, 2001     

Film formation stages for poly(vinyl acetate) latex particles: a photon transmission study

Photon transmission technique was used to monitor the evolution of transparency during film formation from poly(vinyl acetate) (PVAc) latex particles. The latex films were prepared below the glass transition temperature (T _g) of PVAc. These films were annealed at elevated temperatures in various time intervals above the T _g of PVAc. It is observed that transmitted photon intensity (I _tr) from these films increased as the annealing temperature is increased. It is seen from I _tr curves that there are two film formation stages. These successive stages are named void closure (viscous flow) and interdiffusion. The activation energies for viscous flow (ΔH) and backbone motion (ΔE _b) were obtained by using well-defined models. The averaged values of the backbone (ΔE _b) and the viscous flow activation energies (ΔH) were found to be 188.6 and 5.6 kcal/mol, respectively. The minimum film formation (τ _M,T _M) and healing points (τ _H,T _H) were determined. Minimum film formation (ΔE _M) and healing activation energies (ΔE _H) were measured using these time–temperature pairs. ΔE _M and ΔE _H were found to be 32.5 and 28.3 kcal/mol, respectively.     

Etude des systemes CaHPO4−MHPO4−H2O (M=Sr,Ba) A 50°C

The systems CaHPO₄−MHPO₄−H₂O (M=Sr, Ba) were studied at 50°C. ForM=Sr, the series of single phases, Ca_1−xSr_xHPO₄ for 0.95<X<0.75 and Ca_xSr_1−xHPO₄ for 0.4<X<1 have been prepared. These solid solution were caracterized by their infrared spectra and their crystallographic unit cell parameters. ForM=Ba a new phase Ca₂Ba(HPO₄)₃ has been determined. It was characterized by DRX, IR, ATD and chemical analyses.

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Zusammenfassung Bei 50°C wurde das System CaHPO₄−MHPO₄−H₂O (mitM=Sr, Ba) untersucht. FürM=Sr wurden Serien von Einzelphasen erhalten: Ca_1−xSr_xHPO₄ für 0.95<X< 0.75 und Ca_xSr_1−xHPO₄ für 0.4<X<1. Diese Mischkristalle wurden anhand ihrer Infrarotspektren und ihrer kristallographischen Elementarzellenparameter charakterisiert. FürM=Ba wurde die neue Phase Ca₂Ba(HPO₄)₃ ermittelt. Sie wurde mittels DRX, IR, ATD und chemischer Analyse charakterisiert.

     

Effect of Buffer Species on the Inclusion Complexation of Acidic Drug Celecoxib with Cyclodextrin in Solution

The interaction of celecoxib (Celox) with cyclodextrins (CDs) has been investigated by phase solubility techniques. In this study, the influences of CD type, pH, buffer type, buffer concentration and temperature on the tendency of Celox to form inclusion complexes with CDs were examined. The tendency of Celox to complex with CDs is in the order HP-β-CD > β-CD > γ-CD > α-CD, where the complex formation constants (K ₁₁) were 1377, 693, 126 and 60 M⁻¹, respectively. Also ionization of the slightly acidic Celox (pK _a=9.7) was found to reduce its tendency to complex (i.e., The K ₁₁ values of Celox/β-CD in 0.05 M phosphate buffer were 976 and 210 M⁻¹ for neutral and ionized Celox, respectively). Increasing citrate and phosphate buffer concentration enhances the tendency of ionized Celox to complex with β-CD as a result of a corresponding decrease in the inherent solubility (S ₀) of the Celox anion. On the other hand, these two buffers interact differently with neutral Celox and β-CD, where increasing phosphate buffer concentration at low pH enhances the complexation of neutral Celox by lowering S ₀, while increasing citrate buffer concentration at low pH reduces complex formation as citrate buffer species, mainly citric acid, act as a solublizer and a competitor for Celox and β-CD. The contribution of Celox hydrophobicity for complex stability constitutes about 77% of the driving force for complex stability. The complex formation of neutral Celox with β-CD (ΔG ⁰=−28.6 kJ/mol) is driven by both enthalpy (ΔH ⁰=−21.7 kJ/mol) and entropy (ΔS ⁰=23.3 J/mol K) changes.     

Speciation of phytate ion in aqueous solution. Alkali metal complex formation in different ionic media

The acid–base properties of phytic acid [myo-inositol 1,2,3,4,5,6-hexakis(dihydrogen phosphate)] (H₁₂Phy; Phy^12–=phytate anion) were studied in aqueous solution by potentiometric measurements ([H⁺]-glass electrode) in lithium and potassium chloride aqueous media at different ionic strengths (0<I mol L^–13) and at t=25 °C. The protonation of phytate proved strongly dependent on both ionic medium and ionic strength. The protonation constants obtained in alkali metal chlorides are considerably lower than the corresponding ones obtained in a previous paper in tetraethylammonium iodide (Et₄NI; e.g., at I=0.5 mol L^–1, logK₃^H=11.7, 8.0, 9.1, and 9.1 in Et₄NI, LiCl, NaCl and KCl, respectively; the protonation constants in Et₄NI and NaCl were already reported), owing to the strong interactions occurring between the phytate and alkaline cations present in the background salt. We explained this in terms of complex formation between phytate and alkali metal ions. Experimental evidence allows us to consider the formation of 13 mixed proton–metal–ligand complexes, M_jH_iPhy^{(12–i–j)–}, (M⁺=Li⁺, Na⁺, K⁺), with j7 and i6, in the range 2.5pH10 (some measurements, at low ionic strength, were extended to pH=11). In particular, all the species formed are negatively charged: i+j–12=–5, –6. Very high formation percentages of M⁺–phytate species are observed in all the pH ranges investigated. The stability of alkali metal complexes follows the trend Li⁺Na⁺K⁺. Some measurements were also performed at constant ionic strength (I=0.5 mol L^–1), using different mixtures of Et₄NI and alkali metal chlorides, in order to confirm the formation of hypothesized and calculated metal–proton–ligand complex species and to obtain conditional protonation constants in these multi-component ionic media.Presented at SIMEC–02, Santiago de Compostela, 2–6 June 2002     

Solubility and Ionic Processes in the Cu X 2? MX ?H2O ( X ?=Cl?, Br?; M +=Li+, Na+, K+, NH4+, Cs+) Systems

 Solubility isotherms in the CuBr₂−MBr−H₂O (M ⁺ = Li⁺, Na⁺, Cs⁺) systems at 298.15 K were measured. The results together with other available literature data for copper chloride and bromide systems were treated by hydration analysis, and comparative discussion of ionic processes taking place in the respective saturated solutions was performed.     

Complexes of a diacetylmonoxime Schiff base of S-methyldithiocarbazate (H2damsm) with Fe(III), Ru(III)/Ru(II), and V(IV); catalytic activity and X-ray crystal structure of [Fe(Hdamsm)2]NO3·H2O

The complexes [M(Hdamsm)₂]X·H₂O (M = Fe, X = NO₃; M = Ru, X = Cl), [Ru(Hdamsm)(PPh₃)₂X′](X′ = Cl, Br), and [VO(Hdamsm)(acac)] (H₂damsm = diacetylmonoxime Schiff base of S-methyldithiocarbazate, Hacac = acetylacetone) have been prepared and characterized by spectroscopic techniques. Their redox properties were investigated by cyclic voltammetry. The X-ray crystal structure of [Fe(Hdamsm)₂]NO₃.H₂O has been determined and shows that the complex has a distorted octahedral geometry in which the Hdamsm behaves as a monoanionic NNS tridentate ligand coordinating via oxime nitrogen, hydrazinic imine nitrogen, and thiolate sulfur. The reactivity of these complexes toward oxidation of alcohols in the presence of t-BuOOH and H₂O₂ as co-oxidants is reported.     

Über Struktur und Eigenschaften der Mischfilme von Polyaminosäuren mit langkettigen aliphatischen Verbindungen

Zusammenfassung Unter Verwendung einer Filmwaage wurden Mischfilme von Polyaminos?uren und Natrium-octadecylsulfat bzw. Myristylalkohol oder Myristins?ure untersucht. Bei Molverh?ltnissen von 1∶1 und 5∶1 für die Polymereinheit und die Paraffinverbindung tritt intermolekulare Komplexbildung zwischen Poly-DL-Leucin und Octadecylsulfat ein. Die gleichen Bedingungen führen im Falle des Poly-DL-Phenylalanins nur zu einem Komplex im Molverh?ltnis 5∶1. Der Zustand des Mischfilmes wird bedeutend beeinflu?t durch ?nderung des p_H-Wertes der L?sung. In bestimmten Systemen, z. B. Poly-DL-Leucin und Myristylalkohol 4∶1, findet eine molekulare Entmischung statt. Die Resultate werden im Hinblick auf die Anordnungsm?glichkeiten der Assoziate diskutiert.

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Summary Mixed monolayers of polyaminoacids and sodium sulphate, tetradecyl alcohol or myristic acid respectively have been investigated by using a film balance. Intermolecular complexing occurs between poly-DL-leucine and sodium octadecyl sulphate at mol ratios in the monolayer of 5∶1 and 1∶1 for the polymer unit and the paraffin compound. The same condition only leads to a complex in a mol ratio of 5∶1 in the case of poly-DL-phenylalanine. Remarkable changes in the state of the mixed monolayers are influenced by variation of the p_H of the underlaying solution. Molecular decomposition occurs in definite systems, e. g. poly-DL-leucine and tetradecyl alcohol 4∶1. The results are interpreted in terms of possible configurations of the intermolecular associations.

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Herrn Dipl.-Chem.H. Fruhner und HerrnH. Stollens bin ich für die Unterstützung beim Aufbau der Me?einrichtung und FrauB. Buchmann für die Durchführung der Messungen zu Dank verpflichtet.     

Activities of δ-Al2O3-supported bimetallic Pt?NiO and Co?NiO catalysts for methane autoreforming: Oxidation studies

The methane oxidation activities of Pt−NiO and Co−NiO bimetallic catalysts have been investigated as part of a larger research program on the autothermal reforming of methane (combined methane oxidation and steam reforming) in a fluidized bed reactor. Experiments at atmospheric pressure and 783–1023 K for both catalysts showed that the reaction was more selective towards H₂ production at CH₄∶O₂ ratios greater than unity. Light-off temperature increased with decreasing CH₄∶O₂ ratios, but increase in gas velocity (beyond minimum fluidization) increased the light-off temperature. Co−NiO was as promising as the more expensive Pt−NiO catalyst for the oxidation.     

Thermodynamic properties of molybdenum-transition metal-hydrogen (nitrogen) solid solutions

Using the experimental values ΔH _H^exc and ΔS _H^exc (ΔH _N^exc and ΔS _N^exc) for solid solutions of hydrogen and nitrogen in molybdenum, we calculate the parameters ɛ_H^Mand ɛ_N^M of interaction between hydrogen (nitrogen) and molybdenum lattice doped with small additives of transition metals M; the values of the activity coefficients on hydrogen and nitrogen γ_H^M and γ_N^M, ΔH _H, ΔH _N, ΔS _H, ΔS _N; enthalpy (η_H^M and η_N^M) and entropy (σ_H^M and σ_N^M) parameters of interaction over the 1100–1300 K range for alloys of Mo_{1 − y} M _y H _x and Mo_{1 − y} M _y N _x types (y = 0.01 and 0.02; x = 0.01 and 0.02).     

Synthesis and characterization of new metal(II) complexes with formates and some nitrogen donor ligands

New mixed-ligands complexes with empirical formulae: M(2,4′-bpy)₂L₂·H₂O (M(II)Zn, Cd), Zn(2-bpy)₃L₂·4H₂O, Cd(2-bpy)₂L₂·3H₂O, M(phen)L₂·2H₂O (where M(II)=Mn, Ni, Zn, Cd; 2,4′-bpy=2,4′-bipyridine, 2-bpy=2,2′-bipyridine, phen=1,10-phenanthroline, L=HCOO⁻) were prepared in pure solid state. They were characterized by chemical, thermal and X-ray powder diffraction analysis, IR spectroscopy, molar conductance in MeOH, DMF and DMSO. Examinations of OCO⁻ absorption bands suggest versatile coordination behaviour of obtained complexes. The 2,4′-bpy acts as monodentate ligand; 2-bpy and phen as chelating ligands. Thermal studies were performed in static air atmosphere. When the temperature raised the dehydration processes started. The final decomposition products, namely MO (Ni, Zn, Cd) and Mn₃O₄, were identified by X-ray diffraction.     

4-Chlorophenol degradation by chloroperoxidase from Caldariomyces fumago

This study investigated the degradation of 4-chlorophenol (4-CP) by Caldariomyces fumago chloroperoxidase (CPO). Enzymatic oxidations were studied in reaction mixtures at pH 3.0, 4.0, and 6.0 in the presence and absence of Cl⁻ containing 3.5 IU of CPO and 4-CP and hydrogen peroxide concentrations within the range of 0.5–50 and 0.005–50 mM, respectively. Distinct patterns of products regarding color, concentration, and solubility were observed. Reaction mixtures at pH 6.0 containing 3.5 IU of CPO and 5.0 mM 4-CP and H₂O₂ (1:1 stoichiometry) showed the highest 4-CP removal of 95% and the highest formation of a dark precipitate.