Electrodeposition of Mo-Se thin films from a sulfamatic electrolyte

Mo-Se thin films have been electrodeposited on conducting tin oxide (SnO₂) coated glass substrates from a sulfamatic solution containing Na₂MoO₄ and H₂SeO₃ under potentiostatic conditions. The deposition potential varied from –0.6 V to –0.9 V, at a deposition temperature of 20–40 °C and pH 6.5. X-ray diffraction analysis revealed that the overall composition of the films deposited is consistent with the formation of MoO₂ and MoSe₂. The lattice parameters of the as-deposited MoSe₂ are a=b=3.2340 Å and c=13.2859 Å, which fits a hexagonal structure.     

Electrochemical behavior of electrode modified with a cobalt hexacyanoferrate film: Effect of the supporting electrolyte cation

Cobalt hexacyanoferrate films are synthesized on a glassy carbon electrode with sodium, potassium, and ammonium salts in the supporting electrolyte. The electrochemical behavior of the modified electrode is studied in individual solutions of the salts and in their mixtures. The change in electrochemical properties of cobalt hexacyanoferrate agrees with an increase in the interaction of cations with the film in the series Li⁺, Na⁺, K⁺, NH ₄ ⁺ , Cs⁺. The effect of the energy of interaction between the modify ing-substance crystal lattice and counter-ions on the electrochemical processes is discussed     

Preparation of Thallium Hexacyanoferrate Film and Mixed‐Film Modified Electrodes with Cobalt(II) Hexacyanoferrate

Thallium hexacyanoferrate films have been prepared from various aqueous electrolyte solutions using consecutive cyclic voltammetry. The cyclic voltammograms recorded the direct deposition of thallium hexacyanoferrate films from the mixing of Tl³⁺ and [Fe(CN)₆]^3? ions from solutions of seven cations: Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, H⁺, and Tl⁺. An electrochemical quartz crystal microbalance (EQCM) and cyclic voltammetry were used to study the in situ growth of the thallium hexacyanoferrate films. The thallium hexacyanoferrate film shows a single redox couple with a formal potential between +0.6 V and +1.2 V, and shows a cation effect (H⁺, Li⁺, Na⁺, K⁺, Rb⁺, Cs⁺, and Tl⁺). A mixed film and a two‐layered modified electrodes composed of a thallium hexacyanoferrate film with cobalt(II) hexacyanoferrate film were prepared.     

Peculiarities of cyanide-faujasite systems incorporating transition metal ions

Fragments of the corresponding hexacyanoferrates are formed when transition metal ions replace Na⁺ in faujasite containing hexacyanoferrate(II) encapsulated in the large pores.Translated from Teoreticheskaya i Èksperimental'naya Khimiya, Vol. 30, No. 6, pp. 332–336, November–December, 1994.     

Investigations of crystalline structure of gamma-zirconium phosphate

The -crystalline form zirconium phosphate was investigated. For its lattice parameters was found:a=0.538 nm,b=0.664 nm,c=2.459 nm, =94.2° and basal spacing (d)=1.22 nm. It was determined by IR spectrophotometric method that the phosphate is present in groups of H₂PO ₄ ^– and PO ₄ ^3– of equal quantity. Two moles of crystalline water per formula unit were found where the moles are bound differently. The compound can be characterized by the following chemical formula: Zr(HPO₄)(PO₄)·2H₂O.     

Über eine neue Chi-Phase im System Kobalt-Chrom-Wolfram-Kohlenstoff

Zusammenfassung Im System Co–Cr–W–C wird eine Verbindung der Zusammensetzung Co₂₅Cr₂₅W₈C₂ beobachtet. Diese Phase kristallisiert mit -Mangan-Struktur mit dem Gitterparametera=8,892Å. An Hand von röntgenographischen Intensitätsmessungen wird die wahrscheinliche Verteilung der Atome der Elementarzelle ermittelt.

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A new chi-phase in the system cobalt-chromium-tungsten-carbon

In the system Co–Cr–W–C a compound of composition Co₂₅Cr₂₅W₈C₂ has been observed. This phase has an -manganese type structure and a lattice constanta=8.892 Å. By means of intensity measurements of X-ray diffraction lines the probable distribution of atoms on the lattice sites has been evaluated.

     

Preparation and properties of compact cubic δ-NbN1−x

Compact -NbN_1–x was prepared by heating niobium wire for several days in nitrogen at 4 MPa pressure and temperatures of 1 723 to 1 923 K. The samples obtained had compositions between NbN_0.924 and NbN_0.975±0.002 and were coarse-grained. The lattice parameter increases with the nitrogen content froma=0.43884 nm for NbN_0.924 toa=0.43913 nm for NbN_0.975. From the determination of the lattice parameters up to 1 073 K the coefficient of linear thermal expansion as a function of temperature was evaluated. The microhardness HV_0.1 decreases from 1 300±80·10⁷Nm^–2 for NbN_0.924 to 1080±60·10⁷ Nm^–2 for NbN_0.975. The occupancies of both the niobium and the nitrogen sublattices were calculated using experimental density data. The occupancy of the niobium sublattice decreases linearly with increasing nitrogen content. An extrapolation gives 2.9±0.4% vacancies in both sublattices for stoichiometric -NbN.

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Herstellung und Eigenschaften von kompaktem, kubischem -NbN_1–x

Zusammenfassung Kompaktes -NbN_1–x wurde durch mehrtägiges Erhitzen von Niobdraht in Stickstoff bei einem Druck von 4 MPa und Temperaturen von 1 273 bis 1 923 K hergestellt. Die dabei erhaltenen Proben hatten Zusammensetzungen von NbN_0.924 bis NbN_0.975±0.002 und zeigten ein grobkörniges Gefüge. Der Gitterparameter steigt mit dem Stickstoffgehalt vona=0.43884 nm für NbN_0.924 bisa=0.43913 nm für NbN_0.975 an. Von einer Bestimmung der Gitterparameter bis 1 073 K wurde der lineare thermische Ausdehnungskoeffizient erhalten. Die Mikrohärte HV_0.1 sinkt von 1 300±80·10⁷ Nm^–2 für NbN_0.924 auf 1 080±60·10⁷ Nm^–2 für NbN_0.975 ab. Die Besetzung sowohl des Niob- als auch des Stickstoffteilgitters wurde unter Verwendung von experimentell gemessenen Dichten bestimmt. Die Besetzung des Niobteilgitters fällt mit zunehmendem Stickstoffanteil linear ab. Eine Extrapolation dieser Werte ergibt für stöchiometrisches -NbN einen Leerstellenanteil von 2.9±0.4% auf beiden Teilgittern.

     

Zur Entmischung von kubischen Mehrstoffcarbiden

Zusammenfassung Die Mischungslücke in den Systemen: TiC–{ZrC, HfC} und VC-{NbC, TaC} wird im Bereich von 1200° C bis zur Temperatur des kritischen Punktes experimentell ermittelt und mit Hilfe der freien Exzeß-Enthalpie von der Form: G ^E =x(1–x) {(a ₀+a ₁ T)+(2x–1)(b ₀+b ₁ T)} berechnet.

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The miscibility gap within the systems: TiC–{ZrC, HfC} and VC—{NbC, TaC} has been experimentally determined in the region from 1200°C up to the temperature of the critical point. A calculation of the binodal curve has been carried out by means of an excess free enthalpy of the form: G ^E =x(1–x){(a ₀+a ₁ T)+(2x–1)(b ₀+b ₁ T)}.

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Disordered Crystal Structure of Bis[(2.2.2-Cryptand)Sodium] Bis[Aqua(Isothiocyanato)(μ-Isothiocyanato)Sodium] 2[Na(2.2.2-Crypt)]+ · [Na2(NCS)2(μ-NCS)2(H2O)2]2–

Crystals of bis[(2.2.2-cryptand)sodium] bis[aqua(isothiocyanato)(-isothiocyanato)sodium]: 2[Na(C₁₈H₃₆N₂O₆)]⁺ · [Na₂(NCS)₂(-NCS)₂(H₂O)₂]^2– (I) were synthesized and studied by X-ray diffraction analysis. The disordered structure of I (a = 12.715 Å, b = 10.458 Å, c = 21.767 Å, = 102.56°, space group P2₁/n) was solved by the direct method and refined by the full-matrix least-squares method in anisotropic approximation to R = 0.058 from 3896 independent reflections (CAD4 automated diffractometer, MoK ). The crystal consists of two complex ions [I¹]⁺ and [I²]^2– (molar ratio 2 : 1). The Na⁺ cation of the host–guest cation I¹ is coordinated by all eight heteroatoms (6O + 2N) of the cryptand ligand. The coordination polyhedron of this Na⁺ cation is a distorted cube. The atoms of two groups (CH₂–CH₂ and CH₂–O–CH₂–CH₂) in the cryptand ligand are disordered over two positions. The independent cation Na⁺ of the centrosymmetric binuclear complex anion I² is coordinated by one bifurcated O atom of the disordered water molecule and by three N atoms of the SCN^– ligands (including two bridging ligands). The coordination polyhedron of this Na⁺ caiotn is a distorted tetrahedron. The complex ions in the crystal structure of I are united by hydrogen bonds.     

Thermal Decomposition Mechanism, Thermodynamical and Quantum Chemical of Properties [Pb(NTO)2⋅(H2O)]

The single crystal of lead salt of 3-nitro-1,2,4-triazol-5-one (NTO), [Pb(NTO)₂(H₂O)] was prepared and its structure was determined by a four-circle X-ray diffractometer. The crystal is monoclinic, its space group is P2₁/n with crystal parameters of a=0.7262(1) nm, b=1.2129(2) nm, c=1.2268(3) nm, =90.38(2)°, V=1.0806(2) nm³, Z=4, D_c=2.97 g cm^–3, µ=157.83cm^–1, F(000)=888. The final R is 0.027. By using SCF-PM3-MO method we obtained optimized geometry for [Pb(NTO)₂H₂O] and particularly positions for hydrogen atoms. Through the analyses of MO levels and bond orders it is found that Pb atom bond to ligands mainly with its 6p_z and 6p_y AOs. The thermal decomposition experiments are elucidated when [Pb(NTO)₂H₂O] is heated, ligand water is dissociated first and NO₂ group has priority of leaving. Based on the thermal analysis, the thermal decomposition mechanism of [Pb(NTO)₂H₂O] has been derived. The lattice enthalpy and its lattice energy were also estimated.This revised version was published online in November 2005 with corrections to the Cover Date.     

Single crystals of regio-selectively substituted cellulose hetero-esters

Lamellar single crystals of some regio-selectively substituted cellulose hetero-esters: cellulose propionate diacetate (CPDA, 2,3-di-O-acetyl-6-O-propionyl cellulose), cellulose acetate dipropionate (CADP, 6-O-acetyl-2,3-di-O-propionyl cellulose), cellulose butyrate diacetate (CBDA, 2,3-di-O-acetyl-6-O-butyryl cellulose) and cellulose acetate dibutyrate (CADB, 6-O-acetyl-2,3-di-O-butyryl cellulose), have been prepared at high temperature in a mixture of dibenzyl ether andn-tetradecane. The CPDA crystals were lozenge-shaped whereas those of CADP, CBDA and CADB had a ribbon morphology. CPDA crystals gave well-resolved electron diffractograms from which the reciprocal lattice parameters a^*=0.807 nm^–1,b ^*=0.400 nm^–1 and ^*=90° could be determined. Systematic absences occurred at every odd reflection along the two orthogonal axesa ^*andb ^*. Thus, the CPDA diffraction pattern is consistent with a p_gg symmetry. For CADP, the electron diffraction pattern is consistent with a p_mg two-dimensional space group withb the unique axis along the ribbon direction. The diagram yields the reciprocal lattice parameters a^* = 0.902 nm^–1,b ^*=0.651 nm^–1 and ^*=90°. The CBDA electron diffractogram yields the following cell parameters and two-dimensional space group:a ^*=0.482 nm^–1,b ^*=0.659 nm^–1 and ^*=90°, and a p_gg symmetry; and that of CADB:a ^*=0.834 nm^–1,b ^*=0.645 nm^–1 and ^*=90°, and a p_mg symmetry.     

Electrochemical quartz crystal microbalance study for vanadium hexacyanoferrates: monitoring of film growth and ion effects during redox reactions

An electrochemical quartz crystal microbalance was employed to monitor directly the growth of vanadium hexacyanoferrate (VHF) films on platinum substrates during electrodeposition and interfacial coagulation in the solution containing sulfuric acid electrolyte, vanadium(IV) and hexacyanoferrate(III). Mass changes of the gold/crystal working electrode were correlated with cyclic voltammetry data. Effects of cations (NH₄⁺, Li⁺, Na⁺ and K⁺), anions (SO₄²⁻ and NO₃⁻) and solvent during redox reactions of the films were studied. The results show that cations were incorporated into the film during reduction and expelled from the film during oxidation. Solvent also participates in VHF electrochemistry, and its role cannot be neglected. Anions play no role in VHF electrochemistry.     

Synthesis and Electrical Properties of Lithium Metazirconate

Lithium metazirconate Li₂ZrO₃ with a monoclinic lattice is synthesized; the lattice parameters are: a = 0.5432 nm, b = 0.5427 nm, c = 0.903 nm, = 112.72°, and Z = 4. The conductivity of both the stoichiometric compound and samples rich or deficient in Li₂O near this composition is determined. The conductivity of the synthesized compound reaches 0.029 S cm^–1 at 600°C. The activation energy for the high-temperature segment is 13.8 kJ mol^–1. An abnormal behavior (abrupt jump) of the temperature dependence of the conductivity at 430°C is discovered and attributed to a phase transition. The change in the structure in this temperature domain (400 to 500°C) is corroborated by the high-temperature X-ray analysis.     

Electrodeposition of cobalt oxide films from carbonate solutions containing Co(II)–tartrate complexes

An electrochemical procedure of anodic deposition of cobalt oxyhydroxide film on a glassy carbon substrate in an alkaline medium (i.e. pH 11.6) is described. The electrodeposited film was obtained either by voltage cycling or by potentiostatic conditions using non-deaerated 0.1 M Na₂CO₃ solutions containing 40 mM tartrate ions and 4 mM CoCl₂. The effects on the film formation and growth, such as tartrate–cobalt ratio, pH, applied potential, etc. were widely evaluated. The electrodeposition process, under anodic conditions and moderately alkaline solutions, most likely involves a redox transition Co(II)→Co(III)/Co(IV) with destruction of the tartrate complex and formation of insoluble oxide/hydroxide cobalt species on the glassy carbon surface. The resulting cobalt oxyhydroxide films were characterised by cyclic voltammetry (CV) in 0.1 M NaOH solutions and by scanning electron microscopy (SEM) analysis after different strategies of preparation and various electrochemical treatments. The electrochemical activity of the deposited films was checked using various organic molecules as model compounds.     

Preparation of a cobalt hexacyanoferrate film-modified aluminum electrode by chemical and electrochemical methods: enhanced stability of the electrode in the presence of phosphate and ruthenium(III)

Modification of an aluminum electrode by means of a thin film of cobalt hexacyanoferrate (CoHCF) using electroless and electrochemical procedures is described. The modification conditions of the aluminum surface, including the electroless deposition of metallic cobalt on the electrode surface from CoCl₂+NaF solution and the chemical derivatization of the deposited cobalt to give a CoHCF film in 0.25 M KCl+0.25 M K₃[Fe(CN)₆] solution, have been determined. The modified Al electrodes prepared under optimum conditions show one or two well-defined redox couples in phosphate buffer solutions of pH 7.2, depending on the preparation procedure, due to the [Co^IIFe^III/II(CN)₆]^–/2– system. The effect of pH, alkali metal cations, and anions of the supporting electrolyte on the electrochemical characteristics of the modified electrode were studied. Diffusion coefficients of hydrated Na⁺ in the film, the transfer coefficient, and the transfer rate constant for electrons were determined. The stability of the modified electrodes under various experimental conditions was studied and their high stability in the sodium phosphate buffer solutions was confirmed. Enhanced stability was observed when the modified electrode was scanned in fresh solutions of RuCl₃ between 0 and 1 V for at least 20 cycles, due to the formation of mixed hexacyanoferrates of cobalt and ruthenium. Electronic Publication     

Die Kristallstruktur von Li4SiO4

Zusammenfassung Die Kristallstruktur des Lithiumorthosilicats wurde mittels dreidimensionaler Fourier-Synthesen und nach der Methode der kleinsten Quadrate bestimmt. Die Gitterparameter der monoklinen Elementarzelle (C _2h ² –P2₁/m) betragen:a=5,14;b=6,10;c=5,30 Å und =90,5°. Die Struktur enthält isolierte [SiO₄]-Tetraeder, welche durch [LiO _n ]-Polyeder (n=4, 5, 6) verknüpft sind. Hervorzuheben ist, daß sämtliche Lithiumlagen nur partiell besetzt sind. Als mittlerer Si–O-Abstand wurde 1,632 Å erhalten; als Mittelwerte der Li–O-Abstände für die verschiedenen Koordinationszahlen ergeben sich: 1,975 [4]; 2,099 [5] und 2,247 [6] Å.

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The crystal structure of lithium orthosilicate has been determined by means of three-dimensional Fourier syntheses and the least squares method. The lattice parameters of the monoclinic unit cell (P2₁/m–C _2h ² ) are:a=5.14;b=6.10;c=5.30 Å and =90.5°. The crystal structure contains isolated [SiO₄]-tetrahedra being connected by [LiO _n ]-polyhedra (n=4, 5, 6). The positions of the lithium atoms are partially occupied only. The average interatomic Si–O distance is found to be 1.632 Å. The averaged values for Li–O distances given for the different coordination numbers are: 1.975 [4]; 2.099 [5] and 2.247 [6] Å.

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Mit 4 Abbildungen     

Ellipsometrical measurements on porous copper films

Summary Porous films are prepared by depositing copper onto glass substrates at 77 K. The structure of the films is characterized ellipsometrically (=632.8 nm) and by means of resistivity measurements. The measured dielectric function of the porous films is=–6.5 –4.6i, a value which deviates strongly from the corresponding value of bulk copper ( _m=–18 –1.6i). A quantitative evaluation on the basis of the EMA theory yields a void concentration of about 20%. In addition, the interaction of the films with oxygen is investigated. The gas tends to penetrate into the near-surface portion of the voids.

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Ellipsometrische Messungen an porösen Kupferschichten

     

Capture of aromatic carboxylate anion through second sphere coordination: Topological complementarity of [cis-Co(en)2(N3)2] and ions

[cis-Co(en)₂(N₃)₂]C₇H₃ClNO₄·1.25H₂O (Cocnb) was synthesised and detailed packing analyses were undertaken to delineate the topological complementarity of [cis-Co(en)₂(N₃)₂]⁺ and a 2-chloro-4-nitro benzoate anion (cnb) for second sphere coordination in the crystal lattice. The complex was completely characterised by elemental analyses, spectroscopic studies (IR, UV/visible, ¹H and ¹³C NMR). The compound crystallizes in the monoclinic (space group C2/c) with a = 21.9843(18), b = 8.7959(7), c = 23.0121(18) Å, β = 116.426(1)°, V = 3984.9(6) Å³, and Z = 8. In the crystal lattice, discrete ions of [cis-Co(en)₂(N₃)₂]⁺ and cnb are arranged in A–B–A–B pattern (in both a and c directions of the lattice) forming columns of anions and cations. The anionic columns are π stacked and are involved in extensive hydrogen bonding interaction. It appears that the topological feature of [cis-Co(en)₂(N₃)₂]⁺ is conducive for generating second sphere interactions with aromatic carboxylates. This strategy may be used as a viable method for the capture of aromatic carboxylate anions.     

Concerning the absorption and emission properties of phenanthro[1,10,9,8,o,p,q,r,a]perylene-7,14-dione

Summary In contrast to hitherto published data, phenanthro[1,10,9,8,o,p,q,r,a]perylene-7,14-dione, the fundamental chromophoric system of hypericin type compounds, exhibits an absorption with a long wavelength band at 423 nm in aprotic solvents like dimethylsulfoxide (7000). Its fluorescence in these solvents is below the detection limit. In protic solvents like methanol, the long wavelength absorption is bathochromically shifted to 546 nm, and a fluorescence at 565 nm is observed. This behavior was interpreted from the reversal ofn – * and – * transitions. The data have not been recorded yet due to the very low solubility of this compound. Its monoprotonation in ground and excited states is characterized bypK _a andpK* _a values of –6 and 2; diprotonation occurs at apK _a=–7.

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Absorptions- und Emissions-Eigenschaften von Phenanthro[1,10,9,8,o,p,q,r,a]perylen-7,14-dion (Kurze Mitt.)

Zusammenfassung Im Gegensatz zu bislang publizierten Daten zeigt Phenanthro[1,10,9,8,o,p,q,r,a]perylen-7,14-dion, das fundamentale chromophore System der Hypericintyp-Verbindungen, in aprotischen Lösungsmitteln wie Dimethylsulfoxid eine Absorption mit einer langwelligen Bande bei 423 nm (7000). In diesen Lösungsmitteln ist Fluoreszenz nicht nachweisbar. In protischen Lösungsmitteln wie Methanol wird die langwellige Bande bathochrom verschoben (546 nm) und bei 565 nm tritt Fluoreszenz auf. Dieses Verhalten wurde mit der Umkehr in der Reihenfolge vonn – * und – * Übergängen interpretiert. Die Daten wurden wegen der extremen Schwerlöslichkeit dieser Verbindung bislang nicht erhalten. Die Monoprotonierung im Grund- und Anregungszustand ist durchpK _a- undpK* _a -Werte von –6 und 2 charakterisiert; die Diprotonierung tritt beipK _a=–7 ein.

     

The crystal and molecular structure of acetonitrilechlorodicyclopentadienyltitanium tetrachloroferrate(III). Some Mössbauer and X-ray photoelectron spectroscopic data

Summary The title compound crystallizes in the orthorhombic space group P2₁2₁2₁ with Z=4 and lattice parametersa=1744.2(4),b=1360.7(4),c=751.3(5) pm. An x-ray analysis shows the compound to consist of discrete (h⁵-C₅H₅)₂-Ti(Cl)NCMe⁺ cations and FeCl ₄ ^– anions. The cation has a distorted tetrahedral structure (Ti-C: 231.9-237.6 pm; Ti-Z: 203 and 204pm; Ti-Cl: 230.4 pm; Ti-N: 213.5 pm; Z-Ti-Z: 133.2°; Cl-Ti-N: 91.7° (Z: centre of cyclopentadienyl ring). The relatively short Ti-Cl bond length indicates a modest Ti-Cl -bonding contribution. The tetrachloroferrate(III) anion possesses a nearly undistorted tetrahedral geometry (Fe-Cl: 216.0–218.5 pm; Cl-Fe-Cl: 109.0–111.1°). Mössbauer and x-ray photoelectron spectroscopic data confirm the crystallographically derived structural features.