Infrared spectra of the ammonium ion in ammonium metavanadate NH4VO3

The ND stretching modes of isotopically dilute NH₃D⁺ ions in NH₄VO₃ are in agreement with the predicted splitting into C_s, C_s and C₁(2) components under C_s site symmetry for the NH⁺₄ ion. The three bands observed represent the three NH bonding distances in the crystal, and the position, shape and low temperature behaviour of each band confirms the existence of two types of hydrogen bonding in NH₄VO₃. The low temperature infrared modes of NH⁺₄ and ND⁺₄ in NH₄VO₃ and ND₄VO₃, respectively, can be assigned under space group Pbcm. Temperature dependence of these modes also reflects the presence of both normal and bifurcated hydrogen bonds in NH₄VO₃.     

IR-spectral investigation of the structure of glasses in the Fe2O3-V2O5 system

The structure of glasses in the Fe₂O₃-V₂O₅ system in the 0–50 mol% Fe₂O₃ range is studied by IR-spectroscopy. It is found that the introduction of Fe₂O₃ favours the transformation of the VO₅-groups into VO₄ ones. This effect may be shown with the aid of IR-spectra, owing to the fact that these glasses are characterized by two high-frequency bands at 1020 and 930 cm^–1. The first is determined by the vibrations of the short V=O nonbridging bonds in the VO₅-groups, while the second is assigned to the vibrations of the V—O-bonds in deformed VO₄-tetrahedra.

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IR-spektroskopische Strukturuntersuchung von Gläsern des Systems Fe₂O₃-V₂O₅

Zusammenfassung Die Struktur von Gläsern des Systems Fe₂O₃-V₂O₅ in dem Bereich von 0–50 Molprozent Fe₂O₃ wurde mit Hilfe der IR-Spektroskopie untersucht. Zusatz von Fe₂O₃ begünstigt die Umwandlung der VO₅- in VO₄-Gruppen. Das kann in den IR-Spektren durch zwei Banden bei 1020 und 930 cm^–1 festgestellt werden. Die erste wird durch Schwingungen der kurzen V=O-Nichtbrücken-bindungen in den VO₅-Gruppen verursacht, die zweite wird auf Schwingungen der V—O-Bindungen in dem deformierten VO₄-Tetraeder zurückgeführt.

     

Dioxofluoro-oxalato-vanadat: ein fünffach koordiniertes,monomeres Komplexion des Vanadins(V)

Dioxofluorooxalatovanadate: a Monomeric, Fivefold Coordinated Complex Ion of Vanadium(V) (NH₄)₂VO₂F(C₂O₄) crystallises in the space group P2₁/c with 4 formula units per unit cell and a = 11.362(2), b = 9.503(2), c = 7.190(1) Å und β = 96.02(2)°. 1046 reflection data were refined to R = 0.038. In the complex anion vanadium is trigonal bipyramidally coordinated by two terminal oxygen atoms in cis position, fluorine and a bidentate oxalate ion. The coordination polyhedron is highly distorted. The very short bonds in the dioxo-group forming an angle of 107.5° have lengths of 1.617(4) and 1.614(4) Å. The V—O (oxalate) distances are 2.016(4) and 2.031(4) Å, the V—F distance is 1.893(3) Å. The vibrations ν_as VO₂ and ν_sVO₂ are observed at 930 and 948 cm^?1, respectively. The remaining bands of the vibrational spectra are also assigned.     

Die Infrarotspektren einiger Orthovanadate mit Apatitstruktur

The infrared spectra (4000–300 cm^?1) of orthovanadates with apatite structure, of the formula M₅(VO₄)₃X (M = Ca, Sr, Ba and X = F, Cl, Br) are measured and interpreted. The influence of the cations and of the halogen anions about the internal vibrations of the VO ions is discussed.     

Vibrational spectra and infrared dichroism of tetraphenyl-silane,Ph4Si. II.

Vibrational spectra of Ph₄Si have been studied from 600 to 20 cm^?1 in solution, in the melt and in the crystalline state. The assignments proposed for the substituent sensitive benzene ring vibrations, for the skeletal bending modes and ring librations have been supported by polarized IR and Raman measurements. The crystal spectra are interpreted on the basis of the S₄ site symmetry of the molecules in the crystal. Two skeletal bending and four ring librational modes are supposed to appear below 120 cm^?1, in the range of the lattice vibrations.     

全光谱白光发光二极管用Eu3+掺杂Ca2KZn2(VO4)3黄色荧光粉的制备及光学性能

基于蓝光芯片激发黄色荧光粉或近紫外芯片激发三基色荧光粉构建的白光发光二极管(WLED)在青光区域呈现明显的凹口,导致白光的色彩性能不够理想。为了弥补这一缺陷,实现全光谱白光,我们设计了Eu³⁺掺杂Ca₂KZn₂(VO₄)₃黄色荧光粉,其发射波长范围为400~750 nm。在387 nm激发下,在所制荧光粉中可同时获得来自VO₄^3-基团和Eu³⁺的发射光。Eu³⁺在Ca₂KZn₂(VO₄)₃基质中的最佳掺杂浓度(物质的量分数)为0.05,且VO₄^3-基团向Eu³⁺的能量传递效率达到64.9%。基于变温的发射光谱,揭示了所制荧光粉的热稳定性并发现VO₄^3-基团和Eu³⁺的激活能分别为0.538和0.510 eV。此外,将所制黄色荧光粉与商用蓝色荧光粉和近紫外芯片进行封装整合,得到可发射暖白光的WLED器件,其色温和显色指数分别为3843 K和85.8。     

Vibrational anharmonicity constants for PuF6

The fundamental vibrations of PuF₆ cluster in two distinct group-vibrational, near-local modes at 589±50 cm^?1 for the stretching modes and 195 ± 15 cm^?1 for the bending modes. This clustering results in a corresponding “bunching up” of the density of states. One of the consequences of this behavior is that “hot band” absorption intensity pools into stronger absorption features appearing shifted at regular intervals from the fundamental. This observed structure in the 16μm region for PuF₆ has been interpreted to yield values for two empirical anharmonicity constants X_3j (j = 1, 2, 3) and X_3k (k = 4, 5, 6).     

Infrared spectra of the ammonium ion in ammonium hexavanadate (NH4)2V6O16

The infrared bands of the NH⁺₄ and ND⁺₄ groups in (NH₄)₂V₆O₁₆ and its deuterated analogue can be assigned with a fair amount of certainty at 90 K under the space group P2₁/m(C²_2h). The ND stretching modes of isotopically dilute NH₃D⁺ ions in the crystal are in agreement with the predicted splitting into C_s, C_s and C₁(2) components. The frequencies, shapes and temperature dependence of these modes suggest that both normal and bifurcated hydrogen bonds are formed. The latter closely resembles corresponding bonds in NH₄VO₃, but the normal hydrogen bonds are not as strong as the similar bonds in NH₄VO₃. This can be expected as NH⁺₄ ions are dynamic in character in (NH₄)₂V₆O₁₆ and remain so down to temperatures of 90 K.     

Vibrational spectra of tellurates with the garnet structure

The IR and Raman spectra of tellurates Ln₃Te₂Li₃O₁₂ (Ln=Pr…Lu, Y), Ca₃Te₂Zn₃O₁₂ and Na₃Te₂M³⁺₃O₁₂ (M³⁺ = Al, Ga, Fe) with the garnet structure are presented and discussed on the basis of a group theoretical analysis, and of ⁶Li—⁷Li isotopic frequency shifts. The assignment of the high-frequency bands to stretching vibrations of the TeO₆ octahedra is only an approximation whose validity depends on the nature of the tetrahedral cation (Li, Zn or M³⁺) and of the symmetry properties of the vibrations: cationic mass effects play an important role in the antisymmetric, IR-active vibrations, whereas the bonding forces are the determining factor in the totally symmetric, Raman active vibrations. For the Na₃Te₂M³⁺₃O₁₂ garnets, the (TeO₆) internal modes approximation is unacceptable since the stretching frequencies of the TeO₆ and M³⁺O₄ groups are of the same order of magnitude. No detailed assignments are available for the medium-frequency bands: they are due in part to the bending vibrations of the TeO₆ octahedra, but the contribution of the tetrahedral cation Zn²⁺ or M³⁺ to this region of the spectrum remains largely unknown. The translational frequencies of the dodecahedral Ln³⁺ cations have been identified in the low frequency region (below 250 cm⁻¹) by comparison of the frequencies of the Ln and Y garnets.     

Direct Oxidation of Benzene to Phenol by Dioxygen over Nano-vanadium Oxide

Reducing regents, such as ascorbic acid, are needed for vanadium‐containing catalysts to catalyze the direct oxidation of benzene to phenol by dioxygen. Quadrivalent vanadium species, reduced from quinquevalent vanadium species, can activate dioxygen to produce active oxygen species, which is important for the reaction. The key step is to prepare more V⁴⁺‐containing catalysts. Here, VO_X‐C₁₆‐A was prepared in an acidic medium to produce more V⁴⁺ species. The results of XPS and XRD studies confirmed that the vanadium species in VO_X‐C₁₆‐A was mainly V⁴⁺ ions. The results of XRD and electron diffraction patterns revealed that VO_X‐C₁₆‐A consisted of tetragonal VO₂ and monoclinic VO₂. Morphology observations display that the VO_X‐C₁₆‐A is made of nanorod. Investigations into the performances of the catalysts showed that VO_X‐C₁₆‐A was reusable, producing a 1.9% conversion of benzene without reducing agent.     

Hexametavanadates M<Stack><Subscript>4</Subscript><Superscript>+</Superscript></Stack>M<Superscript>2+</Superscript>(VO<Subscript>3</Subscript>)<Subscript>6</Subscript>: Thermal stability and luminescent characteristics

Rhombohedral hexametavanadates K₄Sr(VO₃)₆, K₄Ba(VO₃)₆, Rb₄ Ba(VO₃)₆, and Cs₄Ba(VO₃)₆ melt incongruently in the temperature range of 491 to 600°C. Cooling of peritectic melts yields mixtures of compounds typical of M₂⁺O-M²⁺O-V₂O₅ systems, far from equilibrium and depending on the cooling kinetics. The vanadate Cs₄Ba(VO₃)₆ undergoes reversible polymorphic transformation at 360°C. All compounds show broad-band luminescence with a maximum of the luminescence spectrum at 490–590 nm with three types of excitation. The vanadates K₄Sr(VO₃)₆ and Rb₄Ba(VO₃)₆ show the highest luminescence intensity at room temperature. The latter is also most efficient at liquid nitrogen temperatures. The luminescence spectra depend on the excitation of vanadates. Three hypotheses were put forward to interpret this finding. The nature of luminescence is attributed to the relaxation of electronic excitation in [VO₄]³⁻ structural tetrahedra present in the vanadates. The performance characteristics of luminophores were determined. These luminophores may be promising as X-ray luminescent screens, radioluminescence indicators, and light-emitting diode devices.     

Neutron inelastic scattering spectra of strongly hydrogen bonded acid oxalates NaHC2O4, KHC2O4 and LiHC2O4

Neutron inelastic scattering spectra of NaHC₂O₄, KHC₂O₄ crystals at 80 K have been recorded in the 2200-200 cm^?1 range. The lithium acid salt was also studied at different temperatures. NIS spectra are compared to the corresponding infrared and Raman spectra and an assignment is proposed. Two strong bands near 1500 and 1100 cm^?1 are assigned to δ(OH) and γ(OH) vibrations, respectively, while five weak bands below 900 cm^?1 are associated with skeletal modes, mainly bending vibrations. The OH stretching vibration is not observed and is believed to be hidden by other bands; the peak intensity must be low because of its band width which is of the order of a few hundreds wavenumbers.     

Vibrational spectroscopic characterization of the phosphate mineral hureaulite – (Mn,Fe)5(PO4)2(HPO4)2·4(H2O)

This research was done on hureaulite samples from the Cigana claim, a lithium bearing pegmatite with triphylite and spodumene. The mine is located in Conselheiro Pena, east of Minas Gerais. Chemical analysis was carried out by Electron Microprobe analysis and indicated a manganese rich phase with partial substitution of iron. The calculated chemical formula of the studied sample is: (Mn_3.23, Fe_1.04, Ca_0.19, Mg_0.13)(PO₄)_2.7(HPO₄)_2.6(OH)_4.78. The Raman spectrum of hureaulite is dominated by an intense sharp band at 959 cm⁻¹ assigned to PO stretching vibrations of HPO₄²⁻ units. The Raman band at 989 cm⁻¹ is assigned to the PO₄³⁻ stretching vibration. Raman bands at 1007, 1024, 1047, and 1083 cm⁻¹ are attributed to both the HOP and PO antisymmetric stretching vibrations of HPO₄²⁻ and PO₄³⁻ units. A set of Raman bands at 531, 543, 564 and 582 cm⁻¹ are assigned to the ν₄ bending modes of the HPO₄²⁻ and PO₄³⁻ units. Raman bands observed at 414, and 455 cm⁻¹ are attributed to the ν₂ HPO₄²⁻ and PO₄³⁻ units. The intense A series of Raman and infrared bands in the OH stretching region are assigned to water stretching vibrations. Based upon the position of these bands hydrogen bond distances are calculated. Hydrogen bond distances are short indicating very strong hydrogen bonding in the hureaulite structure. A combination of Raman and infrared spectroscopy enabled aspects of the molecular structure of the mineral hureaulite to be understood.     

The First Neutral Dinuclear Vanadium Complex Comprising VO and VO2 Cores: Synthesis,Structure, Electrochemical Properties,and Catalytic Activity

A neutral dinuclear vanadium complex containing both oxido and dioxidovanadium cores with hydrazone based ligand, [VO(OCH₃)(CH₃OH)(HL)VO₂] ( 1 ) {H₄L = bis[(E)‐N′‐(5‐bromo‐2‐hydroxybenzylidene)]‐carbohydrazide}, was synthesized and fully characterized by X‐ray crystallography and spectroscopic methods (IR, UV/Vis, NMR). The ligand acts as a trinegative hexadentate N₃O₃ donor ligand to form a dinuclear complex and during the reaction V⁴⁺ is oxidized to V⁵⁺. The coordination polyhedra are a VO₅N distorted octahedron for the mono‐oxidovanadium core and a VO₃N₂ trigonal bipyramid for the dioxidovanadium core. The results of catalytic reactions indicate that 1 is a highly active catalyst in the clean epoxidation reaction of cis‐cyclooctene using aqueous hydrogen peroxide in acetonitrile. Cyclic voltammetric experiments of 1 in DMSO reveal two quasi‐reversible peaks due to the VO³⁺–VO²⁺ and VO₂⁺–VO₂ couples.     

Multiphoton ionization of VOCl3

VOCl₃ is studied by resonance-enhanced multiphoton ionization in the region 430 to 440 nm. Mass spectrometric detection reveals the production of both V⁺ and VO⁺ with the molecular ion having the larger intensity. The V⁺ ion current spectrum shows sharp atomic resonance peaks while the VO⁺ spectrum is structureless.     

Ternary VO-ligand-surface complexes on boehmite and noncrystalline aluminosilicates

Electron spin resonance (ESR) spectroscopy was used to characterize the ligand environment of VO²⁺ absorbed on boehmite and noncrystalline aluminosilicates. Boehmite possessed a relatively low capacity to chemisorb VO²⁺ at discrete sites at low pH, a fact attributed to the chemical inactivity of the dominant (020) surfaces of the mineral. The chemisorbed cation is rigidly bound by one or two surface oxyanions. Chemisorption on allophane produced slightly different ESR parameters for VO²⁺, a possible consequence of the participation of silanol groups in the metal-surface bond. Evidence for ternary surface complexes was seen upon the addition of phosphate to the VO²⁺-surface complexes, with changes occurring in the ESR spectrum of bound VO²⁺. Oxalate also appeared to perturb the ligand environment of sorbed VO²⁺, but other anionic species had little or no effect. The experimental results point to the coadsorption of a vanadyl-phosphate complex, in which both the VO²⁺ and the PO₄³⁻ are chemisorbed to surface Al atoms. The ESR spectra of VO²⁺ in model phosphate compounds are used to establish the effect of PO₄³⁻ coordination with VO²⁺ on the spectral parameters.     

Ternary VO2+-ligand-surface complexes on boehmite and noncrystalline aluminosilicates

Electron spin resonance (ESR) spectroscopy was used to characterize the ligand environment of VO²⁺ absorbed on boehmite and noncrystalline aluminosilicates. Boehmite possessed a relatively low capacity to chemisorb VO²⁺ at discrete sites at low pH, a fact attributed to the chemical inactivity of the dominant (020) surfaces of the mineral. The chemisorbed cation is rigidly bound by one or two surface oxyanions. Chemisorption on allophane produced slightly different ESR parameters for VO²⁺, a possible consequence of the participation of silanol groups in the metal-surface bond. Evidence for ternary surface complexes was seen upon the addition of phosphate to the VO²⁺-surface complexes, with changes occurring in the ESR spectrum of bound VO²⁺. Oxalate also appeared to perturb the ligand environment of sorbed VO²⁺, but other anionic species had little or no effect. The experimental results point to the coadsorption of a vanadyl-phosphate complex, in which both the VO²⁺ and the PO₄³⁻ are chemisorbed to surface Al atoms. The ESR spectra of VO²⁺ in model phosphate compounds are used to establish the effect of PO₄³⁻ coordination with VO²⁺ on the spectral parameters.     

Single crystal Raman study of potassium oxalate monohydrate,K2C2O4. H2O,and potassium oxalate monodeuterate,K2C2O4. D2O

Raman spectra of poly crystalline and single crystal K₂C₂O₄. H₂O and K₂C₂O₄. D₂O have been recorded at room temperature. From an earlier neutron diffraction study it is known that the space group is C⁶₂h. The water molecule occupies a C₂ site and the oxalate ion a C₁ site. The assigned water vibrations show small factor group splitting between g modes (Raman active) and u modes (IR active). The internal oxalate vibrations are found to have wavenumbers in good agreement with those reported from Raman studies of other oxalates.     

Infrared and Raman spectra of magnesium ammonium phosphate hexahydrate (struvite) and its isomorphous analogues. IX: Spectra of protiated and partially deuterated cubic magnesium caesium phosphate hexahydrate

Infrared and Raman spectra of cubic magnesium caesium phosphate hexahydrate, MgCsPO₄·6H₂O (cF100), and its partially deuterated analogues were analyzed and compared to the previously studied spectra of the hexagonal analogue, MgCsPO₄·6H₂O (hP50). The vibrational spectra of the cubic and hexagonal dimorphic analogues are similar, especially in the regions of HOH stretching and bending vibrations. In the difference IR spectrum of the slightly deuterated analogue (<5% D), one distinctive band appears at 2260 cm⁻¹ with a small shoulder at around 2170 cm⁻¹, but only one band is expected in the region of the OD stretchings of isotopically isolated HDO molecules. The small weak band could possibly result from second-order transitions (a combination of HDO bending and some libration of the same species) rather than statistical disorder of the water molecules. By comparing the IR spectra in the region of external vibrations of water molecules of the protiated compound recorded at RT (room temperature) and at LNT (liquid nitrogen temperature) and those in the series of the partially deuterated analogues, it can be stated with certainty that the bands at 924 and 817 cm⁻¹ result from librations of water molecules, rocking and wagging respectively. And the band at 429 cm⁻¹ can be safely attributed to a stretching Mg–O_w mode. In the ν₃(PO₄) and ν₄(PO₄) region in the infrared spectra, one band in each is observed, at 995 and 559 cm⁻¹, respectively. In the region of the ν₁ modes, in the Raman spectrum of the protiated compound, one very intense band was observed at 930 cm⁻¹ which is only insignificantly shifted to 929 cm⁻¹ in the spectrum of the perdeuterated compound. The band at 379 cm⁻¹ in the Raman spectrum could be assigned to the ν₂(PO₄) modes. With respect to the phosphate ion vibrations, the comparison between the two polymorphic forms of MgCsPO₄·6H₂O and their deuterated compounds shows that ν₁(PO₄) and ν₃(PO₄) appear at lower wavenumbers in the cubic phase than in the hexagonal phase. These data are in full agreement with the lower repulsion potential at the cubic lattice sites compared with that for the hexagonal lattice sites.