IR-Spektren des p-Methylbenzamidoxims

Zusammenfassung Die IR-Spektren des p-Methylbenzamidoxims (pMB), des O-Benzoyl-pMB und des deuteriertenpMB (ND₂, OD) wurden in festem Zustand und in Lösung untersucht. Die Moleküle der festen und der gelösten Verbindungen sind durch Wasserstoffbindungen O–H...O verbrückt. Die Absorption der Valenzschwingungen der NH₂-Gruppe liegt im Bereichv _as=3505–3520 cm^–1,v _s=3370–3416 cm^–1. Die Valenzschwingungen der freien OH-Gruppe sind bei 3620 cm^–1 (in CCl₄), die der verbrückten OH-Gruppen—bei 3160–3280 cm^–1. Die KraftkonstantenF _NH, der N–H-Abstand und die Änderung der Positivladung am Stickstoffatom q wurden aus den IR-Daten berechnet.

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IR-spectra of p-methyl benzamidoxime

The IR-spectra of p-methyl benzamidoxime (pMB), O-benzoyl-pMB and deuteratedpMB (ND₂, OD) were studied in the solid state and in solution. The molecules of the solid and of the dissolved compounds are bridged by hydrogen bondings O–H...O. The absorption of the valence vibrations of the group NH₂ are found to be in the rangev _as=3505–3520 cm^–1 andv _s=3370–3416 cm^–1. The valence vibrations of the free OH-group are found to be at 3620 cm^–1 (in CCl₄) and those of the bridged OH-groups at 3160–3280 cm^–1. The force constantsF _NH, the distance between the atoms N–H, and the change of the positive charge of the nitrogen atom q were calculated from IR-data.

     

Binding energy of 2p3/2 electrons of titanium in titanium oxide layers synthesized by molecular lamination method

A variation has been found in the binding energy of the 2p_3/2 electrons of titanium in titanium oxide layers obtained by the molecular lamination method. With increasing number of synthesized monolayers, as a result of the decrease in the relative quantity of oxygen atoms in the film and the relative content of hydroxyl groups in this quantity of oxygen atoms, the effective charge on the titanium atom is lowered in comparison with a monolayer film, as manifested in a decrease of the binding energy of the titanium 2p_3/2 electrons, down to the value characteristic for titanium in bulk titanium oxide.Lensovet Leningrad Technological Institute, Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 27, No. 6, pp. 722–726. November–December, 1991. Original article submitted January 22, 1990.     

IR study of the peculiarities of the stabilization of the NH4Na-Y zeolite structure during its hydrothermal dealumination

The variations in the structure of deep-level calcinated NH₄Na-Y zeolite (68 % NH₄ ⁺, Si/Al = 2.56) at 873 K (stage I of the hydrothermal dealumination) as a result of ammonation and subsequent calcination in water vapor at 973 and 1023 K (stageII) were studied using the IR spectra of zeolite framework vibrations. It was shown that ammonation of the product of stageI promotes the formation of linear disiloxane bonds and extra-framework =Al^VI-OH species identified by absorption at 482, 1196 cm^–1, and 524, 612, 829 cm^–1. The ammonation is also accompanied by an increase in the excessive negative framework charge (ENFC), which is manifested in the high-frequency (HF) shift of the bands that have maxima in thev _as (TO₄) region and equals 10 cm^–1, and also by a decrease in the unit cell parameter (a ₀) by 0.14 Å. The decrease in both the ENFC anda ₀ for the products of stageII, v _as (TO₄) = 10–20 cm^–1 and a ₀ = 0.07–0.14 Å, is due to the formation of nonlinear disiloxane bonds and non-framework aluminum hydroxide species identified by the absorption bands at 478, 1173 cm^–1 and 530, 615, 835 cm^–1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 660–664, April, 1993.     

Structural analysis of water adsorbed in silica gel

The melting point, T _f of water in a pore decreases as the surface area to pore volume ratio of the pore decreases. Analysis of water absorbed in the pores of silica gels using differential scanning calorimetry (DSC) and dielectric relaxation spectroscopy (DRS) shows that the thickness of the bound, non-freezing water layer adjacent to the pore surface increases as its temperature increases, but that it is independent of the surface silanol concentration, [Si_sOH]. In contrast, the thickness decreases as the cylindrical pore radius r _H decreases. Thus, the increase in the bound water thickness from 0.45 nm for gels with r _H =1.2 nm to 1.2 nm for gels with r _H =7.5 nm is due to the increase from –53°C to –7°C of the temperature (e.g., the melting point T _f ) at which the bound water thickness was measured, and not due to the increase in t _H or the decrease in [Si_sOH]. The T _f of bulk water measured in a DSC was –0.3°C. The boiling point T _v of bulk water measured in a DSC was 81.3°C. T _v increased to 94°C in 7.5 nm pores and to 109°C K in 1.2 nm pores.     

Comparative FT infrared study of structural changes occuring on dealumination of zeolite Na-Y with ethylenediaminetetraacetic or hydrochloric acid

IR lattice vibration spectra were used to monitor the changes in the structure of zeolite Na-Y upon its dealumination with ethylenediaminetetraacetic acid (EDTA) or with HCl. The terminal Si-O(H,Na) bonds thus formed (which are detectable by characteristic absorbance at v 900–950 cm^–1) are energetically less uniform when EDTA has been used as the dealuminating agent. This inhomogeneity is connected with the local deformations of zeolite structure which result in lowering the symmetry of silicon-oxygen tetrahedra. As a consequence, two novel bands appear at v 1090 cm^–1 and 1200 cm^–1 in addition to the fundamental absorption bands, v_as (TO₄) (T = Si, Al), at 1030 cm^–1 and 1145 cm^–1. A mechanism of dealumination is proposed, which takes into account the topochemical peculiarities involved in the chelation of the framework aluminum ions with EDTA.Translated fromIzyestiya Akademii Nauk. Seriya Khimicheskay, No. 2, pp. 284–287, February, 1993.     

Organosilicon Amidophosphates and Their Eu and Er Complexes in Solutions and Films: Spectral and Luminescence Properties

Fluorescence and fluorescence excitation spectra of phosphorus-containing organosilicon ligands O = PX₂NHR (X = NMe₂, OPh; R = CH₂CH₂CH₂Si(Oet)₃ and their Eu(III) complexes in acetonitrile solutions and in films are studied. In UV region (285–420 nm), bis(dimethylamido)triethoxysilylpropylamidophosphate (X = NMe₂) and diphenyltriethoxysilylpropylamidophosphate (X = OPh) exhibit two emission bands, whose position and intensity depend on the nature of substituents at the phosphorus atom. The Eu complexes show the ligand and the cation luminescence. The emission bands of coordinated ligands are shifted to long-wave region. The cation luminescence appears as three or four bands due to f-f transitions from the excited ⁵ D ₀ level to the lower ⁷ F _1–4 levels. The most intense transition is ⁵ D ₀ → ⁷ F ₂. The emission band in a region of 420 nm appears in solutions and films prepared from both pure ligands and their Eu(III) complexes. This band is due to luminescence of spatially crosslinked nanoparticles of sesquioxane structure. The intensity ratio of the Eu³⁺ emission bands changes when going from solutions to films, the emission intensity increases in a range of 420 nm. Films containing incorporated Er complexes with amidophosphates show intense luminescence of a matrix at 430 nm and a series of weak narrow bands due to the Er³⁺ cation at 550–700 nm.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 7, 2005, pp. 550–558.Original Russian Text Copyright © 2005 by Semenov, Cherepennikova, Klapshina, B. Bushuk, S. Bushuk, Douglas.     

The infrared spectra (600-140 cm−1 of the imidazole,pyrazine and pyrimidine adducts of cobalt(II), nickel(II) and zinc(II) acetylacetonates

Summary The complexes M(acac)₂(imidazole)₂ (M = Co or NO and [M(acac)₂B]_n (M = Co, Ni or Zn; B = pyrazine or pyrimidine) have been prepared and their i.r. spectra determined over the 600–140 cm^–1. range. The metal-oxygen and metal-nitrogen stretching frequencies, (M-O) and v(M-N), are assigned on the basis of the band shifts induced by deuteriation of the adducted base and by substitution of the metal ion. Three or fourv(M-O) bands are observed within the 600-200 cm^–1 range. The twov(M-O) bands of higher frequency are considered to the coupled with internal ligand modes. TwovM-N) bands are observed within the 280–170 cm^–1. range. The metal-ligand stretching frequencies are in good agreement with the values previously established for these vibrations in the [M(imidazole)₆]²⁺ and Ni(acac)₂(pyridine)₂ complexes.     

Density functional study on electronic and optical properties of C (or N)-doped cubic cerium dioxide

Density functional calculations were performed on electronic and optical properties of C (or N)-doped cubic cerium dioxide (CeO₂). When O is replaced by C (or N) in CeO₂, obvious band-gap (E_g) reduction is observed. Meanwhile, it is interesting to find that the substitutional doping of C (or N) in CeO₂ obviously increases the O 2p–Ce 4f transition intensity and also the refractive index. The increase in the O 2p–Ce 4f transition intensity on going from undoped, N-doped and C-doped CeO₂ was related to the covalent character of the Ce–O bond. Compared with the undoped CeO₂, the C (or N)-doped CeO₂, with steep absorption peaks at lower energy, can be used for visible-light absorption applications.     

Study of intermolecular interactions in the equilibrium catalytic transesterification of esters

The interaction of alcohols ROH with esters PhCOOR (R = Me,n-Bu,n-C₇H₁₅) in binary mixtures and in solutions in non-polar solvents (CCl₄, cyclohexane) was studied over a wide temperature range by Fourier IR spectroscopy. Even with a great excess of alcohol (up to 3000-fold molar excess), two bands are observed in the region ofv(CO) vibrations. The low-frequency band, which is down-shifted by 15–20 cm^–1 with respect to thev(CO) band in the absence of alcohol, corresponds to ester molecules bonded by hydrogen bonds of the C=O...HO type. The high-frequency band is up-shifted by 3–5 cm^–1 with respect to the esterv(CO) band. The discreteness of the shift, which is confirmed by the appearance of an isobestic point, indicates that an H-complex of yet another type is formed between the alcohol and the ester. The analysis of the data available allows one to conclude that complex formation involves the alkoxyl oxygen atom of the ester. The enthalpies of formation were determined forn-BuOH H-bonds with the esters and with the transesterification catalysts, i.e., As(OBu)₃, B(OBu)₃, and Ti(OBu)₄.Part 3 — see ref.1Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 709–713, April, 1993.     

Determination of the stoichiometry of semiconductor systems of the type CdvHg1?vSe and CdxHg1?xTe by X-ray fluorescence spectrometry

Summary Semiconductors of the composition Cd _v Hg_1–v Se and Cd _x Hg_1–x Te are gaining growing industrial interest. The energy gap between the bands of such systems depends significantly on the magnitude of the mole fractions v and x. X-ray fluorescence analysis of acid solutions of these crystals is a simple and precise procedure to determine the stoichiometry. Sample preparation, calibration series and results are discussed.

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Bestimmung der Stöchiometrie von Halbleitersystemen des Typs Cd_vHg_1–vSe und Cd_xHg_1–xTe, durch Röntgenfluorescenz-Spektrometrie

Zusammenfassung Halbleiter der Typen Cd _v Hg_1–v Se und Cd _x Hg_1–x Te gewinnen zunehmend industrielles Interesse. Der Energieabstand der Bänder in solchen Systemen hängt entscheidend von der Größe der Molenbrüche v und x ab. Ein einfaches und sicheres Analysenverfahren zur Ermittlung der Stöchiometrie ist die Röntgenfluorescenzanalyse von sauren Lösungen dieser Kristalle. Die Probenvorbereitung, Eichreihen und Resultate werden diskutiert.

Delegated to Central Institute of Analytical Chemistry, Nuclear Research Establishment (KFA), Jülich, FRG.     

Isothiocyanatooxomolybdenum(V) dithiocarbamates

Summary Isothiocyanatooxomolybdenum(V) complexes, [MoO-(NCS)(R₂dtc)₂] (R=ethyl or dibenzyl; R₂=piperidinyl or 4-morpholinyl) have been prepared and characterized. The i.r. spectral bands at 2020 cm^–1 are assigned tov(CN) which suggest that thiocyanate coordinates through nitrogen. The bands at 930, 1500 and 960 cm^–1 are attributed tov(MoO),v(CN) andv(CS), respectively, and indicate the presence of the MoO³⁺ moiety and a bidentate dithiocarbamate group. The e.p.r. and electronic spectral data together with magnetic moment values (1.69 B.M.) suggest the presence of one unpaired electron. The complexes are monomeric. The thermal decomposition behaviour of the complexes is reported.     

Rotational analysis of the v7,v11 (a′,a″) pair of bands of the infrared spectrum of the deuterium substituted propynal molecule C2H-CDO

The mid-infrared spectrum of the v₇,v₁₁ (a′,a″) pair of bands of the deuterium substituted propynal molecule C₂H-CDO was recorded at a resolution of about 0.08 cm⁻¹. An analysis of the pair of bands was completed using the method of simulation of the observed bands with synthetic spectra taking into account the effects of second order Coriolis interactions between the energy levels of the two bands. Best fit values for the changes in the rotational constants (A″ − A′), (B″ − B′) and (C″ − C′), the second order Coriolis constant ζ_7,11 and the δ_7,11 = v₁₁ − v₇ constant have been derived.     

Photochemical properties of peroxo complexes of titanium,intermediate products in the photocatalytic liquid-phase oxidation of alcohols

A study has been made of the photochemical reactions of titanium(IV) peroxo complexes formed in the reaction of titanium tetrachloride with hydrogen peroxide in alcoholic solutions and which are characterized by intense charge transfer bands at 360–425 nm. Irradiation of the solutions with light of = 254 nm leads to the decomposition of the titanium(IV) peroxo complexes, the formation of titanium(III) compounds, as well as the oxidation of the alcohol to aldehyde. In the irradiated frozen solutions associated complexes of titanium(III), organic free radicals formed from the alcohol molecule, as well as peroxy radicals have been identified by EPR. Irradiation with light corresponding to the longwave band of the peroxo complexes leads to their decomposition but titanium(III) compounds and alcohol oxidation products are not formed in this case. In irradiated frozen solutions the formation of paramagnetic titanium(IV) complexes containing the fragment Ti...O ₂ has been established, as well as other paramagnetic particles identified tentatively as coordinated Ti...O ₂ ^· radicals or radical pairs. It is shown that the decomposition of hydrogen peroxide in the presence of titanium(IV) compounds is photocatalytic.Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 24, No. 1, pp. 67–74, January–February, 1988.     

Determination of ZnO(0001) surface termination by x‐ray photoelectron spectroscopy at photoemission angles of 0° and 70°

We present an XPS method to determine the termination of the ZnO(0001) surface. By measuring O 1s and Zn 2p_3/2 core‐level x‐ray photoelectron spectra at photoemission angles of 0° and 70° and comparing the intensity ratio (I_O1s/I_Zn2p3)_θ=0/(I_O1s/I_Zn2p3)_θ=70, the Zn and O termination can be distinguished. Calculations show that these two terminations have intensity ratios differing by ～17%. This difference is not affected by a contamination layer provided that the contamination layer thickness is the same for these two differently terminated surfaces. Although this determination method prefers a clean ZnO(0001) surface (in situ measurement), it seems also feasible for surfaces with known contamination layer thickness (ex situ measurement). We have measured ex situ ZnO(0001)‐Zn, ZnO(000&1macr;)‐O single crystals and an epitaxial ZnO film deposited on Al₂O₃(0001). The measured intensity ratios of the first two samples agree with the calculated values for a 0.2 and 0.26 nm contamination layer, respectively. The intensity ratio and the O 1s contamination component intensity of the epitaxial ZnO film are close to those of the ZnO(0001)‐Zn single crystal thus pointing at Zn termination of the film. Copyright © 2004 John Wiley & Sons, Ltd.     

Contact-angle,ellipsometric, and spin-diffusion solid-state nuclear magnetic resonance spectroscopic investigations of copolymeric stationary phases immobilized on SiO<Subscript>2</Subscript> surfaces

SiO₂ surfaces—silica gel particles and silica wafers—were modified by covalently immobilizing three poly(ethylene-co-acrylic acid) copolymers, (–CH₂CH₂–)_x[CH₂CH/(CO₂H)–]_y, with different chain lengths and mass fractions of acrylic acid. ¹³C solid-state NMR spectroscopy on the modified silica gel particles revealed both mobile gauche and rigid trans aligned alkyl chains in the copolymers. For copolymers attached to silica wafers via a 3-aminopropyltriethoxysilane spacer molecule, ellipsometric measurements revealed a mean value of the layer thickness distribution of 6.5 and 4.3 nm, respectively, for the more acidic and the shorter copolymers with mobile alkyl chains mostly in the gauche conformation. For the longest and least acidic copolymer with more rigid trans ordered alkyl chains, however, a mean phase thickness of 10.6 nm was found. When this copolymer was immobilized via a 3-glycidoxypropyltrimethoxysilane spacer molecule we measured a mean layer thickness of 9.9 nm. A model of the surface morphology of this immobilization strategy was derived using spin-diffusion ¹³C NMR measurements on the corresponding modified silica. It was thereby proven that the trans and gauche-aligned alkyl chains occur in distinct domains of certain sizes on the silica surface. The surface polarity of all modified silica wafers was also investigated by measurement of contact-angle.     

Verfeinerung der Kristallstruktur von Te2O3(SO4)

The crystal structure of ditellurium(IV)-trioxide sulfate, Te₂O₃(SO₄)—space group Pmn2₁–C _2v ⁷ ;a=8.879 (2),b=6.936 (2),c=4.646 (4) Å,Z=2—has been determined and refined by least-squares, using three-dimensionalX-ray data (1188 independent reflexions) to a final R-value of 6.3%.The crystal structure comprises puckered tellurium(IV)—oxygen layers in which the tellurium atoms are linked together by three oxygen bridges (Te–O 1.907, 1.945, 2.011 Å). The SO₄ groups are arranged between these layers. Two oxygen atoms of each SO₄ group are bonded to two adjacent tellurium atoms of one layer [Te–O(S) 2.270 Å] and the tellurium atoms show a (3+1) coordination. A third oxygen atom of the SO₄ group is in weak interaction with two adjacent tellurium atoms of the same layer (Te–O 2.603 Å) whereas the fourth oxygen atom has distances of 2.866 Å to two adjacent tellurium atoms of the next layer and effects a very weak interaction between the

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Mit 3 Abbildungen

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Herrn Prof. Dr.R. Kieffer zu seinem 70. Geburtstag gewidmet.     

Determination of traces of bismuth by quenching of solid-substrate room-temperature phosphorescence from morin-labeled silicon dioxide nano-particles

Silicon dioxide nano-particles, diameter 50 nm, containing morin (morin–SiO₂) have been synthesized by the sol–gel method. They emit strong and stable room-temperature phosphorescence (SS-RTP) on filter paper as substrate, and bismuth can quench the intensity of the SS-RTP. On this basis a new morin–SiO₂ solid-substrate room-temperature phosphorescence-quenching method has been established for determination of traces of bismuth. Reduction of phosphorescence intensity (I_p) is directly proportional to the concentration of bismuth in the working range 0.16–14.4 ag spot^–1 (sample volume 0.40 L spot^–1, corresponding to the concentration range 0.40–36.0 fg mL^–1). The regression equation of the working curve is I_p=14.86+5.279×[Bi³⁺] (ag spot^–1) (n=6, r=0.9982). The detection limit of this method is 0.026 ag spot^–1 (corresponding to a concentration of 6.5×10^–17 g mL^–1).This sensitive, reproducible and accurate method has been used for successful analysis of real samples.     

Structure of Cobalt Hexacyanoferrate Films Synthesized from a Complex Electrolyte

Films of cobalt hexacyanoferrate (CHCF) are produced under potentiodynamic conditions (E= –0.25 to 0.6 V, v= 0.05 V s^–1) from a 2 mM K₃Fe(CN)₆+ 2 mM Na₃Co(NO₂)₆+ 0.5 M Na₂SO₄solution. According to scanning electron microscopy, the thick CHCF film initially obtained during the synthesis has a heavily porous structure unusual for films of hexacyanoferrates of transition metals, the size of its crystallites is 200–600 nm. A thinner film has a more compact structure and its crystallites are smaller. The X-ray diffraction pattern for a reduced film shows rhombohedral distortion of the fcc lattice with parameters a= 1.035 nm and = 91.43°. The patterns for partially and completely oxidized films nicely fit an fcc crystalline lattice typical for hexacyanoferrates (ais 1.006 and 0.993 nm, respectively). The assumption that both hexacyanoferrate and cobalt ions are electroactive in this particular case is confirmed by the IR and X-ray photoelectron spectroscopy techniques.     

Nitrosonium nitrate: A simple cryogenic preparation and phase transitions

A simple method is suggested for the preparation of pure nitrosonium nitrate (NO⁺ NO ₃ ^– ) thin films, by deposition of nitrogen dioxide from the gas phase onto a cold tip under specified conditions and subsequent warming up of the layer. Fourier-transform infrared spectra were used for its characterization and to determine its purity. The NO⁺ NO ₃ ^– solid thus formed was found to be stable up to 230 K. Raman examination of temperature cycling effects on thev(NO⁺) band and on the phonon region of the thin films indicates one amorphous and two crystalline phases. Amorphous-crystalline and crystalline-crystalline transition temperatures are reported.     

Photoelectrochemical oxidation behavior of methanol on highly ordered TiO2 nanotube array electrodes

The highly ordered titanium dioxide nanotube array (HOTDNA) electrodes were prepared in hydrofluoric acid solution by electrochemical anodic oxidation technique on a pure titanium sheet. The HOTDNA electrodes were characterized by X-ray diffraction, SEM microscopy, and UV–vis spectra. It has shown high density, well ordered and uniform titanium dioxide nanotube array film covered on these electrodes and the TiO₂ structure depending on the heating condition, the anatase phase of TiO₂ appeared when heating to 500 °C. The photoelectrochemical characteristics of methanol in 0.5 M Na₂SO₄ on the HOTDNA electrodes were investigated. The cyclic voltammetry, photocurrent-time and open-circuit photopotential response of methanol on the HOTDNA electrode were represented and significant photogenerated current was observed upon illumination in the UV regions with the light of 253.7 nm central wavelength. The effect of variables such as light intensity, applied potential, and methanol concentration on the photoelectrochemical response was investigated. It was found that the photocurrent was greatly influenced by these factors.