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  • 1
    Electronic Resource
    Electronic Resource
    Solid state electrochemistry, X-ray powder diffraction, magnetic susceptibility, electron spin resonance, Mössbauer and diffuse reflectance spectroscopy of mixed iron(III)-cadmium(II) hexacyanoferrates (1999)
    Springer
    Journal of solid state electrochemistry 3 (1999), S. 264-276 
    Details
    ISSN: 1433-0768
    Keywords: Key words Solid state electrochemistry ; Mössbauer ; Magnetic susceptibility ; X-ray powder diffraction ; Iron(III)-cadmium(II) hexacyanoferrates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Coprecipitates of CdII, KI and FeIII with hexacyanoferrate ions [Fe(CN)6]4− have been studied by solid-state electrochemistry (voltammetry of immobilized microparticles), magnetic susceptibility measurements, X-ray powder diffraction, electron spin resonance, Mössbauer and diffuse reflectance spectroscopy. Most suprisingly, all experimental results point to the formation of a continuous series of complex mixed phases without the formation of phase mixtures. Although CdII and FeIII ions differ too much in their ionic radii to allow the formation of simple substitution mixed hexacyanoferrates, they are capable of forming different kinds of complex insertion and substitution mixed crystals because of the zeolitic structure of both the iron and the cadmium hexacyanoferrate. Low cadmium concentrations can be found in the zeolitic cavities of iron hexacyanoferrate (Prussian blue), and they start to widen the lattice and facilitate, at higher concentrations, the direct substitution of high-spin iron(III) ions by cadmium ions. In cases of an excess of cadmium, the formation of cadmium hexacyanoferrate with iron(III) ions in the interstitials of the zeolitic structure is observed. These mixed phases show strong charge transfer bands in the visible range and have the appearance of “diluted” Prussian blue. For the first time, this indicates that the charge transfer between the carbon-coordinated low-spin iron(II) ions and the high-spin iron(III) ions can also occur when the latter are situated in the cavities of a host hexacyanoferrate. In Prussian blue the interstitial iron(III) ions are responsible for a very strong charge transfer interaction between the low-spin iron(II) ions and the nitrogen-coordinated high-spin iron(III) ions. Upon substitution of the very small amount of interstitial iron(III) ions in Prussian blue by potassium and cadmium ions the Kubelka-Munk function diminishes by more than 30%, indicating a tremendous decrease in iron(III)-iron(II) interaction.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100080050157
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  • 2
    Electronic Resource
    Electronic Resource
    Synthese und Strukturuntersuchungen von Ba2H[α-FeO4W12O36] · 26 H2O (1991)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 594 (1991), S. 191-201 
    Details
    ISSN: 0044-2313
    Keywords: Dibarium-α-dodecawolframatoferrate(III)-26-hydrate ; synthesis ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Structure Studies of Ba2H[α-FeO4W12O36] · 26 H2OThe heteropolyanion compound Ba2H[α-FeO4W12O36] · 26 H2O (I) crystallizes in the tetragonal space group P4n2 with the lattice parameters a = 12.398(6), c = 18.721(6) Å; Z = 2; Dx = 4.128 g · cm-3. The structure was solved on a twinned crystal from 1029 observed reflections and refined to an index R of 7.6%. The calculations were done by means of a modified ORFLS-programme by Eitel and Bärnighausen. The heteropolyanion [α-FeO4W12O36]5- has the well known α-Keggin structure. The average distance of the four central oxygen atoms to the FeIII position (0, 0, 0) is 1.84 Å. The angles ∢ O—Fe—O are 112.3° (4X) and 103.9 (2X), respectively, which leads to an disphenoidal distortion of the FeO4 tetrahedron.The powder and single crystal ESR spectra of I show the anisotropy of the FeIII fine structure transition 1/2 ↔ -1/2. The Mößbauer spectra confirm the tetragonal distortion of the central FeO4 tetrahedron (quadrupole splitting Δ ≈ 0.50 mm · s-1).
    Notes: Die erstmalig in einkristalliner Form dargestellte Heteropolyanionenverbindung Dibarium-α-dodekawolframatoferrat(III)-26-Hydrat, Ba2H[α-FeO4W12O36] · 26 H2O (I), kristallisiert tetragonal mit den Gitterkonstanten a = 12,398(6), c = 18,721(6) Å; Z = 2; Dx = 4,128 g α cm-3. Für den vorliegenden Inversionszwilling mit einem Heteropolyanion vom α-Keggin-Typ wurde zur Verfeinerung der Kristallstruktur in der Raumgruppe P4n2 ein von Eitel und Bärnighausen modifiziertes ORFLS-Programm benutzt (R-Wert 7,6%). Der mittlere Abstand der vier zentralen Sauerstoffatome zur FeIII-Position (0, 0, 0) beträgt 1,84 Å. Die Winkel ∢ O—Fe—O weichen mit 112,3(4X) bzw. 103,9°(2X) deutlich von 109,5° ab, wodurch das Tetraeder zu einem tetragonalen Disphenoid verzerrt wird.Die Mößbauer-Spektren von I weisen eine deutliche Quadrupolaufspaltung von Δ; ≈ 0,50 mm · s-1 auf, die durch die Asymmetrie in der Umgebung von FeIII hervorgerufen wird. Damit in Übereinstimmung zeigen die EPR-Spektren sowohl für Pulver als auch für einen Einkristall von I ein Signal bei g ≃ 2, das im wesentlichen aus dem Feinstrukturübergang 1/2 ↔ - 1/2 des FeIII-Ions herrührt und eine deutliche Anisotropie aufweist.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19915940122
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  • 3
    Electronic Resource
    Electronic Resource
    Das erste KEGGIN-Anion mit tetraedrischer. Kupfer(II) - Sauerstoff-Koordination: [α-Cu0,4(H2)0,6O4W12O36]6- (1993)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 619 (1993), S. 961-968 
    Details
    ISSN: 0044-2313
    Keywords: CuII heteropolyanion ; tetrahedral copper(II)-oxygen coordination ; IR, Raman, UV, 183W/1H NMR, ESR data ; crystal structure ; Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The First KEGGIN-Anion with Tetrahedral Coordination of Copper(II)-Oxygen: [α-Cu0,4(H2)0.6O4W12O36]6-The solution of the CuII-containing heteropolyanion was prepared starting from an aqueous solution of Na2WO4, adjusting to pH 5-6 by adding slowly a solution of Cu(NO3)2 in HNO3. The addition of the corresponding amount of N(CH3)4Br to the concentrated solution led to the crystallization of the greenish-yellow mixed crystals (TMA)6[α-Cu0.4(H2)0.6O4W12O36] · 9 H2O. After repeated recrystallization it has been investigated by chemical, spectroscopic (IR/Raman, UV, 183W/1H-NMR, ESR) and X-ray diffraction methods (monoclinic; space group P21; a = 13.117(4), b = 21.466(4), c = 13.223(3) Å, β = 91.60°; Z = 2; Dc = 3.041 g · cm-3; R = 8.0%). The distances of the four “tetrahedral” oxygen atoms to the position (0, 0, 0) range from 1.67 to 1.93 Å. The alternative occupation of the central KEGGIN position with copper(II) and two protons, respectively, accounts for the different distances. The prepared solid solution represents the first example for the tetrahedral copper(II)-oxygen coordination in any heteropolyanion compound.
    Notes: Durch Ansäuern einer wäßrigen Na2WO4-Lösung mit HNO3 auf einen pH-Wert von 5 bis 6 und anschließendes langsames Hinzutropfen einer HNO3-sauren Cu(NO3)2-Lösung bildet sich ein CuII-haltiges Heteropolyanion, von dem nach Zugabe einer entsprechenden Menge von N(CH3)4Br gelblich-grünes (TMA)6[α-Cu0,4(H2)0,6O4W12O36] · 9 H2O auskristallisiert. Es wurde aus Wasser mehrfach umkristallisiert und anschließend mittels chemischer Analyse sowie spektroskopischer (IR/Raman, UV, 183W/1H-NMR, ESR) und röntgenographischer Methoden (monoklin; P21; a = 13,117(4), b = 21,466(4), c = 13,223(3) Å, β = 91,60°; Z = 2; Dc = 3,041 g · cm-3; R = 8,0%) untersucht. Um den Ursprung der Elementarzelle sind 4 O2- stark verzerrt tetraedrisch (Abstände: 1,67-1,93 Å) angeordnet. Die alternierende Besetzung der zentralen Position des Heteropolyanions mit Kupfer(II) bzw. zwei Protonen ist für die stark unterschiedlichen Abstände verantwortlich. Der synthetisierte Mischkristall enthält das erste Heteropolyanion, für das ein tetraedrisches Cu2+ O4-Koordinationspolyeder zweifelsfrei nachgewiesen werden konnte.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19936190526
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