Optical bands of dodecanuclear compounds H4PVMo11O40·yH2O with Keggin structure. Semiclassical vibronic model

Klokishner, Sophia; Melsheimer, Jörg; Jentoft, Friederike C.; Schlögl, Robert

doi:10.1039/b312753b

Cited by 15 publications

(19 citation statements)

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“…First, the spectra of the reference minerals malachite, rosasite, and aurichalcite are calculated and the simulated spectra are compared to respective experimental data. The modeling of the spectra is based on a microscopic approach − that takes into account the geometric structure of the copper centers in the minerals − and allows separation of the contributions of different copper species to the total spectra of a mineral. In the second stage, the spectra of the synthetic minerals and catalyst precursors are simulated using the individual spectra of the Cu species in the reference minerals, and on this basis a conclusion is made on their probable composition.…”

Section: Introductionmentioning

confidence: 99%

Cation Ordering in Natural and Synthetic (Cu_1–xZn_x)₂CO₃(OH)₂ and (Cu_1–xZn_x)₅(CO₃)₂(OH)₆

et al. 2011

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In the present paper we report combined experimental and theoretical studies of the UV-vis-NIR spectra of the mineral compounds malachite, rosasite, and aurichalcite and of the precursor compounds for Cu/ZnO catalysts. For the copper species in the minerals the crystal field splitting and the vibronic coupling constants are estimated using the exchange charge model of the crystal field accounting for the exchange and covalence effects. On this basis the transitions responsible for the formation of the optical bands arising from the copper centers in minerals are determined and the profiles of the absorption bands corresponding to these centers are calculated. The profiles of the absorption bands calculated as a sum of bands of their respective Cu species are in quite good agreement with the experimental data. In agreement with crystal chemical considerations, the Zn ions were found to be preferentially located on the more regular, i.e., less distorted, octahedral sites in zincian malachite and rosasite, suggesting a high degree of metal ordering in these phases. This concept also applies for the mineral aurichalcite, but not for synthetic aurichalcite, which seems to exhibit a lower degree of metal ordering. The catalyst precursor was found to be a mixture of zincian malachite and a minor amount of aurichalcite. The best fit of the optical spectrum is obtained assuming a mixture of contributions from malachite (0% Zn) and rosasite (38% Zn of [Zn + Cu]), which is probably due to the intermediate Zn content of the precursor (30%).

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Section: Introductionmentioning

confidence: 99%

Cation Ordering in Natural and Synthetic (Cu_1–xZn_x)₂CO₃(OH)₂ and (Cu_1–xZn_x)₅(CO₃)₂(OH)₆

et al. 2011

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“…The appearance of two bands is explained by either a difference in the energies of this transition within W 3 O 13 triads and between triads or specifics of the energy-level distribution of W ions in different oxidation states [1,4]. Recent theoretical calculations [16] suggest that the presence of several bands may also be due to different energies of W 5+ → W 6+ electronic transitions for protonated and unprotonated WO 6 octahedra.…”

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confidence: 98%

Structure and photochromic properties of poly(vinylalcohol)/phosphotungstic acid nanocomposite films

Sushko

Третинников

2010

J Appl Spectrosc

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Poly(vinylalcohol)/phosphotungstic acid (PVA/PWA) nanocomposite films were studied using Fourier-transform infrared and electron absorption spectroscopy. It was found that entrapping PWA into PVA leads to the formation of hydrogen bonds between OH groups of PVA and bridging oxygen atoms of PWA. Terminal oxygen atoms of PWA do not participate in hydrogen-bonding interactions with the polymer. Exposure of the nanocomposite film to UV radiation results both in the photo-induced transfer of protons from PVA to PWA with their attachment to the bridging oxygen atoms of PWA and in the formation of a PVA-PWA complex with the participation of deprotonated oxygen atoms of PVA and the terminal oxygen atoms of PWA. The UV irradiation causes the films to turn blue and a band of d-d transitions of W 5+ ions (480 nm) and two bands of intervalence W 5+ → W 6+ charge-transfer transitions (740 and 1250 nm) to appear in their electronic spectrum.Introduction. Phosphotungstic acid (PWA) is one of many heteropolyacids, which in turn include a variety of polyoxometalates (POM) that are nanoclusters based on transition metal oxides [1]. POM have a broad spectrum of important practical applications including chemical catalysis, membrane and sensor technologies, electrochemical fuel elements, and medicine [2]. These compounds exhibit photochromic properties (reversibly acquire or change color under the action of UV radiation). This enables them to be viewed as promising materials for optical and opto-electronic technologies and information recording and storage media [3]. Lately the number of publications dedicated to studies of hybrid nanomaterials obtained by dispersion of POM nanoclusters in matrices of organic polymers has been increasing rapidly [4-9]. Our goal was to prepare materials combining the advantages of polymers (low specific weight with high mechanical strength, thermal stability, long service life, and ease of fabrication into the required shape) and the photochromic properties of POM incorporated into them. The photochromic additive must be highly dispersed in the polymeric matrix in order to obtain polymer/POM nanocomposites. This is possible only if strong non-bonding interactions occur between the polymer and POM molecules. In practice, this is achieved by using polymers such as polyvinyl alcohol (PVA) [4,5,7], polyvinylpyrrolidone [6], polyacrylamide [8], and dextran [9]. However, strong nonbonding interactions between the polymer and POM can affect the structure of the polymeric matrix and/or the POM nanoclusters and cause substantial changes in the overall properties of the material, including its photochromic properties. Therefore, detailed studies of the molecular structure and non-bonding interactions in these materials with respect to their photochromic properties are needed in order to fabricate polymer/POM hybrid nanocomposites with given and controlled photochromism.The goal of our work was to study the structure and photochromic properties of PVA/PWA nanocomposite films using IR and electronic absorption s...

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“…The dopant ions represent centers of small radii, and it is sufficient to account for interaction of these ions with ions of their first coordination sphere. − Later, we calculate the operators of the crystal field and electron–vibrational interaction in this approximation assuming that the point charge of the oxygen ligands is equal to 2 e .…”

Section: Crystal Field Splittings and Vibronic Interaction Of Mn3+ Ionsmentioning

confidence: 99%

Redox Properties of Manganese-Containing Zirconia Solid Solution Catalysts Analyzed by In Situ UV–Vis Spectroscopy and Crystal Field Theory

et al. 2011

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The optical absorption spectra of manganese-promoted sulfated zirconia, a highly active alkane isomerization catalyst, were found to be characterized by oxygen-to-manganese charge-transfer transitions at 300-320 nm and d-d transitions of manganese ions at 580 and 680 nm. The latter were attributed to Mn(4+) and Mn(3+) ions, which are known to be incorporated in the zirconia lattice. The oxygen surroundings of these ions were modeled assuming a substitutional solid solution. The crystal field splittings, vibronic coupling constants, and oscillator strengths of the manganese ions were calculated on the basis of a cluster model that considers the manganese center as a complex with the adjacent ions of the lattice as ligands. The ratio of Mn(3+) to Mn(4+) ions was determined using the spectra and the model, and the relative concentrations of Mn(2+), Mn(3+), and Mn(4+) ions were determined with the help of the average valence known from X-ray absorption data in the literature. The redox behavior of manganese-promoted sulfated zirconia in oxidizing and inert atmosphere was elucidated at temperatures ranging from 323 to 773 K.

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Optical bands of dodecanuclear compounds H₄PVMo₁₁O₄₀·yH₂O with Keggin structure. Semiclassical vibronic model

Cited by 15 publications

References 47 publications

Cation Ordering in Natural and Synthetic (Cu_1–xZn_x)₂CO₃(OH)₂ and (Cu_1–xZn_x)₅(CO₃)₂(OH)₆

Cation Ordering in Natural and Synthetic (Cu_1–xZn_x)₂CO₃(OH)₂ and (Cu_1–xZn_x)₅(CO₃)₂(OH)₆

Structure and photochromic properties of poly(vinylalcohol)/phosphotungstic acid nanocomposite films

Redox Properties of Manganese-Containing Zirconia Solid Solution Catalysts Analyzed by In Situ UV–Vis Spectroscopy and Crystal Field Theory

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Optical bands of dodecanuclear compounds H4PVMo11O40·yH2O with Keggin structure. Semiclassical vibronic model

Cited by 15 publications

References 47 publications

Cation Ordering in Natural and Synthetic (Cu1–xZnx)2CO3(OH)2 and (Cu1–xZnx)5(CO3)2(OH)6

Cation Ordering in Natural and Synthetic (Cu1–xZnx)2CO3(OH)2 and (Cu1–xZnx)5(CO3)2(OH)6

Structure and photochromic properties of poly(vinylalcohol)/phosphotungstic acid nanocomposite films

Redox Properties of Manganese-Containing Zirconia Solid Solution Catalysts Analyzed by In Situ UV–Vis Spectroscopy and Crystal Field Theory

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Optical bands of dodecanuclear compounds H₄PVMo₁₁O₄₀·yH₂O with Keggin structure. Semiclassical vibronic model

Cation Ordering in Natural and Synthetic (Cu_1–xZn_x)₂CO₃(OH)₂ and (Cu_1–xZn_x)₅(CO₃)₂(OH)₆

Cation Ordering in Natural and Synthetic (Cu_1–xZn_x)₂CO₃(OH)₂ and (Cu_1–xZn_x)₅(CO₃)₂(OH)₆