Reactions of magnesium formate on supports

Thermal decomposition of supported magnesium formate has been studied by gas chro-matography.The reaction paths of decomposition of supported magnesium formate depend on thenature of the supports.For Mg(HCO_2)_2/HZSM-5,the zeolite behaves as a dehydration catalyst togive CO and H_2O at lower temperatures;when the zeolite is modified by phosphorus,the methanationreaction will be partly restrained.In the case of Mg(HCO_2)_2/AC,strong adsorption of CO_2 leadsto the formation of the shoulder peak of CO_2 at higher temperatures,however,CH_4 disappears aftermodified by phosphorus.For Mg(HCO_2)_2/Al_2O_3,the dehydrogenation of HCO_2~- takes place on thesurface of Al_2O_3.The decomposition of Mg(HCO_2)_2 on SiO_2 in hydrogen yields two peaks of COand only one appears after modified by phosphorus.When Mg(HCO_2)_2 decomposes on MgO,the firstpeak of CO_2 arises from the reaction of surface Mg~(2+) with HCO_2~- from dissociated Mg(HCO_2)_2.     

Kinetics of decomposition of alkylammonium salts

The thermogravimetric curves of di-n-propylammonium, di-iso-propylammonium, di-n-butylammonium and di-iso-butylammonium chlorides showed similar profiles, characterized by mass loss in only one stage, corresponding to decomposition of compounds. The following thermal stability order was obtained: [Bu₂ ⁿNH₂]Cl>[Pr₂ ⁿNH₂]Cl>[Pr₂ ⁱNH₂]Cl>[Bu₂ ⁱNH₂]Cl. The values of activation energy for non-isothermal data obtained by Ozawa and Coats-Redfern integral methods were in agreement and stability order obtained by thermogravimetry were reproduced in both methods. The decomposition reactions of [Pr₂ ⁿNH₂]Cl, [Pr₂ ⁱNH₂]Cl and [Bu₂ ⁱNH₂]Cl were better described by A3 model and [Bu₂ ⁿNH₂]Cl by A2 model. This revised version was published online in August 2006 with corrections to the Cover Date.     

The steric and electronic effects of aliphatic fluoroalkyl groups

Ab initio calculations were performed on 18 fluorinated and unfluorinated alcohols at the B3LYP and HF levels with the 6-311G^∗∗ basis set. Molar volumes of the alcohols were computed at each level and averaged to produce a scale of relative size. From this, various isosteric replacements of potential use in drug design were suggested: ethyl by FCH₂CH₂ or HCF₂CH₂, propyl by CF₃CH₂, isopropyl by CF₃(CH₃)CH or (FCH₂)₂CH, isobutyl or t-butyl by (CF₃)₂CH, and 3-methyl-2-butyl by CF₃(CH₃)₂C. Calculation of the charge on oxygen and the Wiberg index of the CO bond allowed an electronegativity scale to be constructed for the fluoroalkyl groups. Electronegativity decreased in the order: (CF₃)₃C>(CF₃)₂CH>C₂F₅CH₂>CF₃CH₂>CH₃(CF₃)₂C>HCF₂CH₂>CF₃(CH₃)CH>(FCH₂)₂CH>FCH₂CH₂>CF₃(CH₃)₂C. This ranking agreed with literature acid dissociation data for the alcohols studied.     

Synthesis and characterisation of new triple halide-bridged mixed valence binuclear complexes of ruthenium and osmium

Several isomers of the type [M₂Cl₅L₄] (M = Ru, L = AsPh₃, As(p-tol)₃, As(p-PhCl)₃, PEt₂Ph, PMe₂Ph; L₂ = Ph₂As(CH₂)₂AsPh₂; M = Os, L = PPh₃, AsPh₃) have been synthesised by various routes and characterised by magnetic, ESR and electrochemical measurements, and for [(PEt₂Ph)Cl₂RuCl₃Ru(PEt₂Ph)₃] by X-ray structural analysis.     

Effect of oxide additives on radiolytic decomposition of potassium nitrate

Gamma-ray induced decomposition of binary mixtures of potassium nitrate with 90, 70, 50, 30 and 10 mol% SiO₂, Al₂O₃, MnO₂, V₂O₅, La₂O₃, CeO₂, Sm₂O₃, Eu₂O₃, Gd₂O₃ and Dy₂O₃ has been studied at different doses up to 500 kGy. Radiolytic decomposition of the nitrate is affected by the concentration of the oxide in the binary mixture as well as by the absorbed dose. The enhancement is up to 10³ times at 90 mol% of the additive.G(NO₂ ⁻) values calculated on the basis of electron fraction of the nitrate decrease with the increasing concentration of the nitrate. A comparison ofG(NO₂ ⁻) for 90 mol% oxides shows decreasing trend as Gd₂O₃>Sm₂O₃≈Dy₂O₃> Eu₂O₃>CeO₂>Al₂O₃>V₂O₅>SiO₂>MnO₂. ESR and TL measurements suggest the formation of radical species which interact with the radical species of nitrate causing enhanced decomposition by energy transfer mechanism.     

Computer-assisted study of characteristics of water clusters in the presence of nitrogen dioxide

The interaction of IR radiation with water clusters that have absorbed NO₂ molecules is studied by the molecular dynamics method in terms of the polarizable model. Induced dipole moments of H₂O and NO₂ molecules diminish during the addition of one to six NO₂ molecules to (H₂O)₅₀ cluster. The integral intensity of IR absorption by a system consisting of (NO₂) _i (H₂O)₅₀ heteroclusters with 1 ≤ i ≤ 6 decreases, whereas the power of heat emission rises as compared with an (H₂O) _n system. The decrease in the IR absorption and the increase in the IR emission by water clusters with the capture of NO₂ molecules are nonmonotonic. The absorption of NO₂ molecules by water clusters causes a noticeable reduction in the intensity of the first peak and the confluence of the fourth and fifth peaks in the Raman spectrum.     

Stages of thermal decomposition of sodium oxo-salts of sulphur

Thermal behaviour of sodium oxo-salts of sulphur: Na₂SO₄, Na₂S₂O₇, Na₂S₂O₆, Na₂SO₃, Na₂S₂O₅, Na₂S₂O₄, Na₂S₂O₃, Na₂S₃O₆ and of sulphides Na₂S and Na₂S₂ was studied on heating up to 1000°C. The experiments were performed with anhydrous compounds obtained from commercial products by recrystallisation and dehydration. The stage mechanisms of decomposition of anionic sub-lattices of the salts have been proposed basing on the Górski’s morphological classification of simple species. The thermal stability and the stage decomposition mechanisms were correlated with the structure and the potential chemical properties of the salt anions. The thermal decomposition processes were studied by means of thermal analysis, and the decomposition products were identified by means of X-ray phase analysis.     

Synthesis and molecular structure of solvated hydride complexes of aluminium and di-η5-cyclopentadienylyttrium

A series of hydride complexes of di-η⁵-cyclopentadienyl-yttrium and -aluminium solvated by a Lewis base, viz. Cp₂YAlH₄NEt₃ (I), Cp₂YAlH₄THF (II), Cp₂YAlH₄OEt₂ (III) and (Cp₂YAlH₄)₂OEt₂ (IV), (Cp = η⁵-cyclopentadienyl) was synthesized. An X-ray study of compounds I and IV was performed, yielding the coordinates of the heavy atoms. The positions of the hydrogen atoms were determined accordingly from the IR data and also by comparison with the analogous hydridohalide complexes (Cp₂YCl)₂AlH₃L. The structures of I and IV may be represented by the following formulae: [(η⁵-C₅H₅)₂Y(μ₃-H)AlH₂NEt₃]₂ (I) and {[(η⁵-C₅H₅)₂Y]₂(μ₃-H)}[(μ₂-H)₂AlH₂][(μ₂-H)₂AlHOEt₂] (IV).     

Preparation of nanocrystalline BiFeO3 and kinetics of thermal process of precursor

The Bi₂Fe₂(C₂O₄)₅·5H₂O was synthesized by solid-state reaction at low heat using Bi(NO₃)₃·5H₂O, FeSO₄·7H₂O, and Na₂C₂O₄ as raw materials. The nanocrystalline BiFeO₃ was obtained by calcining Bi₂Fe₂(C₂O₄)₅·5H₂O at 600 °C in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, FT-IR, X-ray powder diffraction, and vibrating sample magnetometer. The data showed that highly crystallized BiFeO₃ with hexagonal structure [space group R3c(161)] was obtained when the precursor was calcined at 600 °C in air for 1.5 h. The thermal process of the precursor in air experienced five steps which involved, at first, the dehydration of an adsorption water molecule, then dehydration of four crystal water molecules, decomposition of FeC₂O₄ into Fe₂O₃, decomposition of Bi₂(C₂O₄)₃ into Bi₂O₃, and at last, reaction of Bi₂O₃ and Fe₂O₃ into hexagonal BiFeO₃. Based on Starink equation, the values of the activation energies associated with the thermal process of Bi₂Fe₂(C₂O₄)₅·5H₂O were determined. Besides, the most probable mechanism functions and thermodynamic functions (ΔS ^≠, ΔH ^≠, and ΔG ^≠) of thermal processes of Bi₂Fe₂(C₂O₄)₅·5H₂O were also determined.     

Influence of the nature of organic components in dinuclear copper(II) pivalates on the composition of thermal decomposition products

Tetrabridged dinuclear complexes ((2-NH₂)C₅H₄N)₂Cu₂(μ₂-OOCCMe₃)₄ (2·С₆Н₆) and ((3-NH₂)C₅H₄N)₂Cu₂(μ₂-OOCCMe₃)₄ (3) and the cocrystallization product ((4-NMe₂)C₅H₄N)₂Cu(η²–OOCCMe₃)₂·2((4-NMe₂)C₅H₄N)₂Cu₂(μ₂-OOCCMe₃)₄ (4) were synthesized by the reaction of the polymer [Cu(OOCCMe₃)₂]_n (1) with aminopyridine ligands (L) of different nature (Cu: L = 1:1) in С₆Н₆. The solid-state thermal decomposition of these compounds was studied by differential scanning calorimetry and thermogravimetry, and their electrochemical behavior was investigated by cyclic voltammetry. All newly synthesized complexes were studied by X-ray diffraction, the magnetic properties of the complexes were investigated, and ESR measurements were performed.     

The √t law in solid-phase reactions. Analysis of the hypothesis on rate constant distribution

The reaction C₂H₅ + O₂ → C₂H₅O₂ in glassy methanol-d₄ and the H-atom abstraction by CH₃, C₂H₅, and n-C₄H₉ radicals in C₂H₅OH + C₂D₅OH and CD₃CH₂OH + C₂D₅OH glassy mixtures have been studied by electron spin resonance. The analysis of the dependence of the reaction rates on the concentration of O₂ (oxidation) and C₂H₅OH, CD₃CH₂OH (H-atom abstraction) has shown that the √t law is not conditioned by the existence of regions characterized by different rate constants.     

Heat of formation of Benzophenone Oxide

The heat of formation of benzophenone oxide, Ph₂CO₂, was measured using photoacoustic calorimetry. The enthalpy of the reaction Ph₂CN₂ + O₂ → Ph₂CO₂ + N₂ was found to be ?48.0 ±0.8 kcal mol^?1 and ΔH_f(Ph₂CN₂) was determined by measuring the reaction enthalpy for Ph₂CN₂ + EtOH → Ph₂CHOEt + N₂ (?53.6 ±1.0 kcal mol^?1). Taking ΔH_f(PhCHOEt) = ?10.6 kcal mol^?1 led to ΔH_f(Ph₂CN₂) = 99.2 ± 1.5 kcal mol^?1 and hence to ΔH_f(Ph₂CO₂) = 51.1 ± 2.0 kcal mol^?1. The results imply that the self-reaction of benzophenone oxide i.e., 2Ph₂CO₂ → 2Ph₂CO + O₂ is exothermic by ?76.0 ±4.0 kcal mol^?1.     

Inactivation of Bacillus subtilis Spores Using Various Combinations of Ultraviolet Treatment with Addition of Hydrogen Peroxide

This study aims at comparing the inactivation of Bacillus subtilis spores by various combinations of UV treatment and hydrogen peroxide (H₂O₂) addition. The combinations included sequential (UV–H₂O₂, H₂O₂–UV) and simultaneous (UV/H₂O₂) processes. Results showed that B. subtilis spores achieved a certain inactivation effect through UV treatment. However, hardly any inactivation effect by H₂O₂ alone was observed. H₂O₂ had a significant synergetic effect when combined with UV treatment, while high irradiance and H₂O₂ concentration both favored the reaction. When treated with 0.60 mm H₂O₂ and 113.0 μW/cm² UV irradiance for 6 min, the simultaneous UV/H₂O₂ treatment showed significantly improved disinfection effect (4.13 log) compared to that of UV–H₂O₂ (3.03 log) and H₂O₂–UV (2.88 log). The relationship between the inactivation effect and the exposure time followed a typical pseudo‐first‐order kinetics model. The pseudo‐first‐order rate constants were 0.478, 0.447 and 0.634 min^?1, for the UV‐H₂O₂, H₂O₂–UV and UV/H₂O₂ processes, respectively, further confirming the optimal disinfection effect of the UV/H₂O₂ process. The disinfection could be ascribed to the OH radicals, as verified by the level of para‐chlorobenzoic acid (pCBA).     

Influence of heat treatment on the phase transition of ZrMo<Subscript>2</Subscript>O<Subscript>8</Subscript> and photocatalytic activity

ZrMo₂O₇(OH)₂·2H₂O was obtained from ZrOCl₂·2H₂O and Na₂MoO₄·2H₂O by a coprecipitation method. The phase and structural changes occurred during the heat-treatment of ZrMo₂O₇(OH)₂·2H₂O were investigated by XRD, IR and XPS analysis. The sequence of phase transformation can be divided into three stages: (1) transformation of ZrMo₂O₇(OH)₂·2H₂O to orthorhombic LT-ZrMo₂O₈ up to 300°C; (2) obtaining of mixture of both polymorphs of ZrMo₂O₈: cubic and trigonal at 400°C; (3) conversion to single trigonal (α) ZrMo₂O₈ above 450°C. The microstructure of the obtained trigonal (α) ZrMo₂O₈ was observed by scanning electron microscopy (SEM). The particle sizes were below 0.5 μm. The specific surface area was measured by modified BET method. The photocatalytic activity of the obtained trigonal (α) ZrMo₂O₈ powders was investigated by degradation of a model aqueous solution of Malachite Green (MG) upon UV-light irradiation.     

Chemical characterization of plasma-polymerized films from acetylene and nitrogen-containing mixtures and their ethanol vapor sensitivity

In this study, plasma-polymerized thin films were prepared from plasma enhanced chemical vapor deposition (PECVD) of acetylene (C₂H₂), acetylene/nitrogen (C₂H₂/N₂), or acetylene/ammonia (C₂H₂/NH₃). When N₂ or NH₃ was mixed with C₂H₂ in the feed, the films were identified to contain all elements of the mixture and the properties of the films were implied by the C–H bonds and nitrogen functionalities. As shown by X-ray photoelectron spectroscopy (XPS) the [N]/[C] atomic ratio varies by changing the mixture composition and reaches a maximum of 0.12 for mixing C₂H₂ with NH₃. It is found that the resistance of the thin film sensors prepared from C₂H₂, C₂H₂/N₂, and C₂H₂/NH₃ is distinctly decreased by over 2 orders of magnitude by the adsorption of ethanol vapor.     

Crystal structure of L-leucinium tetrafluoroantimonate(III)

The crystal structure of L-leucinium tetrafluoroantimonate(III) of the composition (C₆H₁₄NO₂)SbF₄ (orthorhombic symmetry: a = 6.1459(6) Å, b = 14.994(1) Å, c = 24.789(2) Å, Z = 8, P 2₁2₁2₁ space group) synthesized for the first time is determined. The (C₆H₁₄NO₂)SbF₄ structure represents a new structure type of tetrafluoroantimonate(III). It is formed by (C₆H₁₄NO₂)+ cations and chain complex [Sb₂F₈]_n ²ⁿ anions composed of Sb₂F₈ dimers linked into chains by bridging F atoms. The Sb₂F₈ dimers consist of SbF₃ and SbF₅ groups bound by bridging fluoride atoms of the SbF₅ group. Chains in the structure are linked by N-H…F, N-H…O, and O-H…F hydrogen bonds into a three-dimensional framework.     

Characterization of some new alkali metal molybdate hydrates by thermal and X-ray methods

Preparation and characterization of four new hydrated alkali metal molybdates Na₂Mo₄O₁₃·6H₂O, K₂Mo₄O₁₃·3H₂O, Rb₂Mo₄O₁₃·2H₂O and Cs₂Mo₄O₁₃·2H₂O are described. The compounds were prepared by crystallizing the solution obtained by dissolving MoO₃ and corresponding alkali metal carbonates A₂CO₃ or molybdate A₂MoO₄ in stoichiometric amount in distilled water. The hydrated molybdates were characterized by thermal (TG/DTA) and X-ray diffraction (XRD) methods. The number of water molecules in the compounds were determined from their TG /DTA curves recorded in air and identification of their dehydration products was done by XRD. The cell parameters of the compounds were obtained by indexing their XRD patterns. Attempt to prepare the corresponding hydrated compound of lithium was not successful. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis and structure of bilayered manganites based on Ca3Mn2O7 with the simultaneous substitution of calcium by lanthanum and strontium

A tetragonal (space group I4/mmm) solid solution La_2-2x (Ca_1-y Sr_y)_{1 + 2x} Mn₂O₇ based on the Raddlesden-Popper phase (n = 2), which is formed by the simultaneous substitution of calcium in Ca₃Mn₂O₇ by strontium and lanthanum, is synthesized by high-temperature annealing of La₂O₃, Mn₂O₃, CaCO₃, and SrCO₃ mixtures (1500°C, air). The concentration area of the solid solution in the scheme is a pentagon, whose corners correspond to the manganites Ca₃Mn₂O₇, Ca_0.75Sr_2.25Mn₂O₇, La_0.2Sr_2.8Mn₂O₇, La_1.6Sr_1.4Mn₂O₇, and LaCa₂Mn₂O₇.     

Morphology control of TiO2 through hydrothermal synthesis method using protonic tetratitanate

Fibrous TiO₂ and plate-like TiO₂ were obtained through the hydrothermal synthesis method by using two kinds of protonic tetratitanate (H₂Ti₄O₉), prepared by ion exchange of K₂Ti₄O₉ and HCl, or milled K₂Ti₄O₉ and HCl, respectively. The product made by hydrothermal treatment of H₂Ti₄O₉ without milling in water consisted of anatase TiO₂ and retained the fibrous morphology of the precursor but with fine crystals attached on the surface, formed by the in?situ topotactic transformation reaction and dissolution and recrystallization. On the other hand, TiO₂ prepared with H₂Ti₄O₉ obtained through ion exchange of milled K₂Ti₄O₉ and HCl had plate-like shape, namely retaining the morphology of nanosheets of H₂Ti₄O₉ through an in?situ transformation process. Under ultraviolet irradiation, 70% methyl orange degradation by TiO₂ nanosheets was about 3.3 times higher than that by fibrous TiO₂. The higher surface area, higher pore volume, and smaller particle size led to the higher photocatalytic activity of the TiO₂ nanosheets.     

Synthesis,characterization, and some electrocatalytic properties of heteromultinuclear FeI/RuII Clusters

A series of new heteromultinuclear Fe^I/Ru^II clusters are described. The complexes (η⁶-arene)RuFe₂S₂(CO)₆ (arene = p-cymene 1 , C₆Me₆ 2 ) and Fe₂[μ-S (Cp*Ru)(CO)₂]₂(CO)₆ (Cp* = η⁵-C₅Me₅) ( 3 ) were prepared by the reduction reactions of (μ-S)₂Fe₂(CO)₆ with 2 equiv of LiHBEt₃, followed by treatment (μ-SLi)₂Fe₂(CO)₆ with ruthenium-arene complexes Ru₂(μ-Cl)₂Cl₂(η⁶-arene)₂ or Cp*Ru (CO)₂Cl in 22–33% yields. Further reactions of 1 and 2 with 1 equiv of triphenylphosphine in the presence of the decarbonylating agent Me₃NO·2H₂O, afforded the corresponding monophosphine-substituted Fe^I/Ru^II complexes (η⁶-arene)RuFe₂S₂(CO)₅(Ph₃P) (arene = p-cymene 4 , C₆Me₆ 5 ) in 75% and 78% yields. While treatment of parent complex 1 or 2 with 1 equiv of diphosphine Ph₂PCH₂PPh₂ (dppm) in xylene at reflux temperature resulted in the formation of the diphosphine-bridged RuFe₂S₂(CO)₉ derivate RuFe₂S₂(CO)₇(dppm) ( 6 ). The possible pathway for the formation was proposed. Two isomers of novel macrocyclic complexes involve the (η⁶-arene) Ru-bridged quadruple-butterfly Fe/S clusters [{μ-S (CH₂)₃S-μ}{(μ-CS₂)Fe₂(CO)₆}₂]₂[(η⁶-arene)Ru]₂ (arene = p-cymene 7a and 7b , C₆Me₆ 8a and 8b ) were isolated by reactions of two μ-CS₂-containing dianion [{μ-S (CH₂)₃S-μ}{(μ-S=CS)Fe₂(CO)₆}₂]²⁻ with [Ru₂(μ-Cl)₂Cl₂(η⁶-arene)₂], in which the propylene groups are attached to two S atoms by ee and ea types of bonds respectively. All the new complexes 1 – 8 have been characterized by elemental analysis, spectroscopy, and particularly for 1 – 6 , 7b and 8a by X-ray crystallography. In addition, the electrochemical properties of representative complexes 1 – 4 and 6 have been investigated.