Molybdate Groups Research Articles

Ultrasound-assisted synthesis of Dy2Mo3O12-Dy2O3 nanostructures for enhanced electrochemical hydrogen storage

Among the major challenges facing the hydrogen economy is the issue of hydrogen storage. In terms of "future energy needs", electrochemical hydrogen storage in solid-state materials is an accepted perspective that could mitigate the discontinuation of primary energy sources. In this study, we demonstrate the electrochemical properties of a complex metal oxide that contains the molybdate group, Dy2Mo3O12. Wet-chemical synthesis of nanostructured Dy2Mo3O12 is primarily carried out using ultrasound-assisted wet-chemical methods in the presence of a variety of surfactants. The structural and morphological observations of the samples confirm a pure and highly crystalline structure obtained in the presence of CTAB surfactant at 900 °C and 30 min of sonication, with an average crystalline size of 29 nm. Based on the FTIR spectrum of this sample, it can be concluded that there are significant absorptions indicating the formation of oxygen-metal bonds. The specific surface area and pore volume of the selected sample are 4.543 m2/g and 0.0284 cm3/g, respectively, demonstrating its porous structure. Electrochemical studies of this sample at various temperatures have revealed an enhanced discharge capacity (5100 mAh/g at 65 °C) with a capacity retention rate of 97%. Based on these findings, mixed metal oxides containing at least one active charge transfer species (Red./Ox.) are suitable for use in solid-state hydrogen storage devices.

Rape straw biochar enhanced Cd immobilization in flooded paddy soil by promoting Fe and sulfur transformation

Cd is normally associated with sulfide and Fe oxides in flooded paddy soil. The mechanisms of biochar enhanced Cd immobilization by promoting Fe transformation and sulfide formation are unclear. Rape straw biochar (RSB) pyrolyzed at 450 °C (LB) and 800 °C (HB) was added to Cd-contaminated paddy soil at 1% (LB1, HB1) and 2% (LB2, HB2) doses. The results showed that Fe/Mn oxide–Cd (Fe/Mn–Cd) and free Fe oxide (Fed) concentrations decreased in the first 12 days and then rose, while Fe2+ in pore water (W–Fe2+) tended to rise first and then fall. The electron transfer rate of soil in the HB2 treatment was 4.9-fold higher than that in the treatment without biochar (CK). Fe oxide reduction was enhanced by RSB, with a maximum increase in W–Fe2+ by 62.1% in HB2 on Day 12. The negative correlation between W–Fe2+ and Fed showed that Fe2+ promoted the reformatted of seconded Fe minerals after Day 12, and the Fed in the HB2 treatments increased by 31.5% in this period. RSB addition also promoted the reformation of poorly crystallized Fe oxide (Feo) by increasing soil pH, which increased by 17.2% and 15.1% on average in the LB2 and HB2 treatments, respectively, compared to CK. Compared to Day 7, the increased rate of Fe/Mn–Cd on Day 30 in RSB was approximately twice that of CK. Compared to the molybdate group, the maximum decrease in CaCl2–Cd was 29.1% in LB2 on Day 12. LB2 increased SO42− and acid-volatile sulfide concentrations by 6.9- and 4.1-fold, respectively, compared to CK. These results suggested that RSB, particularly HB, promoted more Cd adsorption in Fe minerals by increasing Fe hydroxylation and recrystallization processes. LB increased the contribution of sulfide to Cd immobility.

SYNTHESIS AND LUMINESCENCE PROPERTIES OF K0,5xBi1-0,5x(MoxV1-x)O4 SOLID SOLUTIONS

The conditions of heterovalent substitution in cationic and anionic positions of хK0,5Bi0,5MoO4 – (1-х)BiVO4 system within range of х = 0.1-0.9 with forming of К0,5xBi1-0,5x(MoxV1-x)O4 solid solutions, those possess scheelite-like type structure have been studied. All the samples of series were obtained by solid state technique. It was shown by IR spectroscopy and X-ray diffraction studies that molybdenum and vanadium occupying one crystallographic position with statistical distribution in х = 0.1–0.9 range of substitution. As result a lowering of lattice symmetry from tetragonal to monoclinic take place with increasing of molybdenum content. Charge compensation in system is realized through proportional substitution of bismuth by potassium in (К/Bi)O8 polyhedra. The data on diffuse reflectance indicate that increasing of substitution degree, x, lead to proportional increasing of band gap values from 2.33 to 2.72 eV for the semiconductors obtained. Intrinsic photoluminescence of the samples has been observed at low temperatures but is absent at room temperature. Total intensity of visible luminescence increases with increasing of molybdenum content in К0.5xBi1-0.5x(MoxV1-x)O4 solid solutions. Spectra of photoluminescence consist of wide two-component band with maxima at 620 and 705 nm, respectively. Simultaneous analysis of literature data and dependences of luminescence intensity on molybdenum content allow assumption that short-wavelength component related with centers, those formed on molybdate groups. Long-wavelength component related with vanadate groups. The wide bands at 375 and 410 nm in the photoluminescence excitation spectra were ascribed to absorption transitions in molybdate and vanadate oxyanions, respectively. The solid solutions studied can be used as hosts for luminescent ions or in elaboration of photocatalysts.

Structure, stability, and properties of phenolic fibers modified by phenyl molybdate

Phenyl molybdate-modified phenolic fibers (PMoPFs) were prepared by melt spinning from the corresponding resin which was polymerized from phenol, formaldehyde, and phenyl molybdate, followed by solution curing and then heat curing processes. The molecular structures, including characteristic groups and molecular weight, were examined by nuclear magnetic resonance, Fourier transform infrared spectroscopy, and gel permeation chromatography. The influences of the curing processes were demonstrated by mechanical properties, scanning electron microscopy, and thermogravimetric analysis characterization. PMoPF with 8 wt% molybdic acid and cured in an oven possessed a tensile strength as high as 187 MPa, initial decomposition temperature of 300°C, and a char yield under nitrogen atmosphere at 800°C as high as 66.0%, with the molybdate (MoO4 2−) groups being introduced into the phenolic main chain.

Investigation on the Structure of a LiB3O5-Li2Mo3O10 High-Temperature Solution for Understanding the Li2Mo3O10 Flux Behavior.

LiB3O5 is the most widely used nonlinear optical crystal. Li2Mo3O10 (a nominal composition) is a typical flux used to produce large-sized and high-quality LiB3O5 crystals. The structure of the LiB3O5-Li2Mo3O10 high-temperature solution is essential to understanding the flux behavior of Li2Mo3O10 but still remains unclear. In this work, high-temperature Raman spectroscopy combined with density functional theory (DFT) was applied to study the LiB3O5-Li2Mo3O10 solution structure. Raman spectra of a LiB3O5-Li4Mo5O17-Li2Mo4O13 polycrystalline mixture were recorded at different temperatures until the mixture melted completely. The solution structure was deduced from the spectral changes and verified by DFT calculations. When the mixture began to melt, its molybdate component first changed into the Li2Mo3O10 melt; meanwhile, the complicated molybdate groups existing in the crystalline state transformed into Mo3O102- groups, which are formed by three corner-sharing MoO3Ø-/MoO2Ø2 (Ø = bridging oxygen atom) tetrahedra. When LiB3O5 dissolved in the Li2Mo3O10 melt, the crystal structure collapsed into polymeric chains of [B3O4Ø2-]n. Its basic structural unit, the B3O4Ø2- ring, coordinated with the Mo3O102- group to form a MoO3·B3O4Ø2- complex and a Mo2O72- group. On the basis of the LiB3O5-Li2Mo3O10 solution structure, we discuss the LiB3O5 crystal growth mechanism and the compositional dependence of the solution viscosity.

Synthesis and photoluminescence studies of one dimensional Sm2MoO6 nanofibers derived from electrospinning process

A combined sol–gel and electrospinning process was employed to synthesize one-dimensional nanofibers of samarium molybdate (Sm2MoO6). X-ray diffraction (XRD), scanning electron microscopy (SEM), photoluminescence (PL) and CIE chromaticity studies were used to characterize the resulting samples. XRD studies revealed the formation of crystalline phase of nanofibers on annealing. SEM analyses indicate that the fibers were of uniform size with length of 10–100μm. Due to the efficient energy transfer from host molybdate groups to Sm3+, Sm2MoO6 phosphors show their strong characteristic emission on exciting the molybdate group. The emission colors of Sm2MoO6 nanofibers are in the orange red region hence suggests its potential applications in fluorescent lamps and field emission displays (FEDs).

A structural study of D-mannitolatodimolybdate(VI) complexes in aqueous solution

The structure of the D-mannitolatodimolybdate(VI) complex has been determined by means of large angle X-ray scattering (LAXS) in aqueous solution at two pH values, 2.0 and 5.5. The two complexes have in principle the same structure in aqueous solution, two face-sharing molybdate(VI) octahedra connected to one D-mannitol ligand, as previously observed in the solid state. In the deprotonated form of the complex, pH 5.5, the D-mannitol ligand has lost a proton and as a result the Mo⋅⋅⋅Mo distance is 0.054Å shorter than the protonated form, pH 2.0. This indicates that it is a proton on an oxygen shared by molybdate groups that leaves the complex at deprotonation and forces the molydate(VI) octahedra even closer to each other.

Synthesis and optimum luminescence of doughnut-shape undoped and doped CaMoO4.

In this work, we report the size and shape-controlled synthesis of CaMoO4 nanocrystals with an aim of investigate their structural, electronic, and luminescent properties. The samples were carefully characterized by X-ray diffraction, transmission electron microscopy, Fourier transformed infrared spectroscopy, UV-vis diffuse reflectance spectroscopy, and luminescence spectroscopy. It is found that when MoO4(2-) and Ca2+ were mixed at relatively low temperature (in ice salt bath), the reaction produces a uniform population of microparticles with an interesting "doughnut" shapes. Due to the low temperature, the process of crystal nucleus is slow enough to for separated growth. The intensity of the absorption band for CaMoO4 nanocrystals was greatly enhanced with the decrease reaction temperature. The as-prepared CaMoO4 doughnut phosphors reveal a broad emission with a maximum at 500 nm, which exhibit blue-green emission. We also study the luminescent property for Eu(3+)-doped CaMoO4. As for the Eu(3+)-doped samples (initial Ca2+:Eu3+ molar ratio 20:1), it is shown that Eu3+ was substituted at Ca2+ sites in the CaMoO4 host lattice, which favors energy transition between Eu3+ ions and molybdate groups that caused the decrease of strength of the peak in emission spectra.

Luminescence spectroscopy and electronic structure of the PbMoO4 and Pb2MoO5 single crystals

Intrinsic photoluminescence (PL) and electronic structure of Pb2MoO5 single crystal are first described and compared with corresponding properties of PbMoO4 crystal. The PL properties of PbMoO4 and Pb2MoO5 crystals grown by Czochralski method are studied under the VUV synchrotron radiation excitations (3.7–14eV region of excitation photon energies) at T=8K. The electronic band structures of perfect PbMoO4 and Pb2MoO5 are calculated by the Full-Potential Linear Augmented Plane Wave method. The Pb2MoO5 crystals reveal intensive PL band in the yellow–red spectral region peaking at ∼600nm. All studied PbMoO4 samples reveal intensive PL band in the green spectral region and this band is accompanied by additional fast-decaying (τ≈3.5ns) component in the violet when the samples are grown with 30° orientation of seed with respect to the c axis. The excitation spectra of the violet component of PbMoO4 reveal complex excitation band with main peak at 6.2eV. It is assumed that the violet PL component of PbMoO4 is generated by intra-center excitations from the ground to singlet excited states 1A1–1T1,2 of the MoO42− molybdate groups located near point defects in subsurface layer of the crystal. Strong anisotropy of reflectivity spectra of PbMoO4 below 6eV is a consequence of peculiarities of the electronic structure of the crystal and reflectivity bands at ∼3.6 and ∼4.3eV are formed by band-to-band electronic transitions.

Electronic Structure and Luminescence Spectroscopy of M'Bi(MoO<sub>4</sub>)<sub>2</sub> (M' = Li, Na, K), LiY(MoO<sub>4</sub>)<sub>2</sub> and NaFe(MoO<sub>4</sub>)<sub>2</sub> Molybdates

The mechanisms of intrinsic luminescence in the set of molybdate crystals of MIMIII(MoO4)2 (MI = Li, Na, K; MIII =Bi, Y, Fe) type are revealed in complex experimental and theoretical studies. The luminescence spectroscopy under vacuum ultraviolet (VUV) synchrotron excitations is applied together with the electronic structure calculations carried out by the FLAPW method. The energy gaps (Eg) values of the crystals are determined in simultaneous analysis of diffuse reflectance and luminescence excitation spectra. It is found that the molybdate groups MoO42- play a dominant role in the processes of intrinsic luminescence in studied molybdate compounds

Electronic structure and luminescence mechanisms in ZnMoO4 crystals

Calculations of the band structure, partial densities of states and optical spectra of permittivity, reflectivity and absorption of perfect ZnMoO4 crystal were performed using the full-potential linear-augmented-plane-wave method. It is shown that the calculated reflectivity spectra reproduce the main features of corresponding experimental spectra in the fundamental absorption region. The bandgap value of ZnMoO4 is estimated as Eg = 4.3 eV. Peculiarities of luminescence excitation spectra corrected for near-surface losses and losses on reflectivity are discussed, taking into account the results of the calculations. It is found that the energy structure of the lower part of conduction band is manifested in the excitation spectra of the intrinsic luminescence. The excitation spectra in the region 4.3–8.0 eV are formed by band-to-band electronic transitions mainly within the molybdate groups MoO42−, whereas electronic states of Zn2+ cations are not directly involved into the excitation processes. It is shown that the structure of the intrinsic luminescence excitation spectrum depends on the temperature and mechanisms of the structure modification are discussed.

Gamma ray interactions with MoO3-doped lead phosphate glasses

The UV–Visible, Fourier transform infrared (FTIR) and Raman and electron spin resonance (ESR) spectra of undoped lead phosphate and MoO3-doped glassy samples have been investigated. The UV–VIS absorption spectra were re-measured after successive gamma irradiation. Before irradiation, undoped sample exhibited strong ultraviolet absorption, which was attributed to co-absorption due to trace iron impurities (mainly Fe3+ ions) and lead Pb2+ ions. With the introduction of MoO3 in progressive amounts, extra visible bands were recorded at about 400–440, 540, 750 and 870 nm. These bands are most likely correlated with the presence of Mo3+, Mo4+ and Mo5+ ions in the host glass. In the undoped specimen, gamma irradiation produced UV absorption bands that increased slightly with irradiation but no visible bands were recorded. Samples containing high MoO3 content showed some resistance to irradiation with no bands in the visible region being observed. FTIR absorption spectra of the undoped and MoO3-doped samples revealed the formation of metaphosphate and pyrophosphate structural units. Highly MoO3-doped samples exhibited additional bands due to molybdate groups. Raman and ESR spectra were in agreement with UV–VIS and IR data, indicating the presence of molybdenum ions in lead phosphate glass, as Mo3+, Mo4+ and Mo6+ with different ratios. However, such glassy systems favor the trivalent species.

Dinuclear, tetranuclear and one-dimensional pyrazine-based copper(ii) complexes: preparation, X-ray structure and magnetic properties

The preparation, crystal structures and magnetic properties of the copper(II) complexes of formula [Cu(2)(tppz)(H(2)O)(2)(CF(3)SO(3))(4)] (1), [Cu(tppz)(CrO(4))](n) x 3nH(2)O (2) and [Cu(4)(tppz)(4)(H(2)O)(4)(MoO(4))(2)](CF(3)SO(3))(4) x 7 H(2)O (3) [tppz = 2,3,5,6-tetrakis(2-pyridyl)pyrazine] are reported. Complex 1 is a dinuclear species where tppz adopts a bis-tridentate bridging mode with an intramolecular copper-copper separation of 6.5221(6) A. Each copper(II) ion in 1 has an elongated octahedral geometry with three tppz nitrogen atoms and a water molecule in the equatorial positions and two triflate oxygen atoms occupying the axial sites. Complex 2 is a uniform copper(II) chain where the copper atoms are bridged by two oxygen atoms of the chromate group (mu(1,2)-CrO(4)), the value of the intrachain metal-metal separation being 4.2614(5) A. Each copper(II) ion in 2 exhibits a somewhat distorted square pyramidal geometry with three nitrogen atoms from a tridentate tppz ligand and a chromate oxygen atom in the basal plane and an oxygen atom of a symmetry-related chromate group in the apical position. Complex 3 is a cyclic tetranuclear compound where peripheral [Cu(tppz)(H(2)O)](2+) units are connected through two molybdate groups, each one adopting the mu(1,1,2)-MoO(4) bridging mode. Regular alternating five [Cu(1) and Cu(4)] and six [Cu(2) and Cu(3)] coordinated copper(II) ions occur in 3 with distorted square pyramidal CuN(3)O(2) and elongated octahedral CuN(3)O(3) surroundings, respectively. The four copper atoms in 3 have in common the presence of a molybdate-oxygen and three tppz-nitrogen atoms in the basal [Cu(1) and Cu(4)]/equatorial [Cu(2) and Cu(3)] planes and a water molecule in the apical [Cu(1) and Cu(4)]/one axial [Cu(2) and Cu(3)] positions whereas the remaining axial position is occupied by a molybdate-oxygen [Cu(2) and Cu(3)]. The shorter intramolecular copper-copper separation is 3.371(1) A [Cu(2)...Cu(3)], the other ones varying in the range 5.537(1)-6.301(1) A. The investigation of the magnetic properties of 1-3 in the temperature range 1.9-295 K has shown the occurrence of intermediate antiferro- [J = -48.0(1) cm(-1) with H = -JS(1) x S(2) (1)], weak ferro- [J = +0.28(1) cm(-1) with H = -JSigma(i)S(i) x S(i+I) (2)] and coexistence of weak ferro- and antiferromagnetic interactions [J(1) = +2.38(2) cm(-1), J(2) = +0.56(2) cm(-1) and J(3) = -1.53(2) cm(-1) with H = -J(1) (S(2) x S(3)) + J(2) (S(1) x S(3) + S(2) x S(4)) + J(3) (S(1) x S(2) + S(3) x S(4)) (3)] between the copper(II) ions across bis-tridentate tppz (1), mu(1,2)-CrO(4) (2), di-mu(1,1)-MoO(4) and mu(1,2)-MoO(4) (3) bridges. The values of the magnetic interactions are analyzed in terms of simple orbital symmetry considerations and compared with those reported for parent systems.

Growth and photoluminescence of (00l)-oriented RMoO 4 films by chemical solution deposition

RMoO 4 (RMO, R = Ca, Sr, Ba) films were fabricated on LaAlO 3 (LAO) substrates using chemical solution deposition method. The derived RMO films are highly (00l)-orientated with good crystallization. The photoluminescence (PL) emission spectra show that the CaMoO 4 (CMO) and SrMoO 4 (SMO) films have an intrinsic broad green emission band centered at 500 nm whereas BaMoO 4 (BMO) film has a broad orange emission band resulting from the PL of molybdate group with an oxygen ion deficiency. The highly (00l)-oriented CMO film on LAO has better PL property than that of CMO film on Si substrate, which is ascribed to higher crystalline integrity and lower light scattering.

Molybdenum(VI) imido complexes: formation of [Mo(NPh)(S2CNR2)3]X and [Mo(NPh)(S2CNR2)2(μ-MoO4)]2 (R = Me, Et) from the reaction of [MoO2(S2CNR2)2] and PhNCO under aerobic conditions

Products from the thermolysis of PhNCO and [MoO2(S2CNR2)(2)] (R = Me, Et) are highly dependent upon the reaction conditions. When carried out in air, the major products are cations, [Mo(NPh)(S2CNR2)(3)](+), as shown by a crystal structure of [Mo(NPh)(S2CNEt2)(3)](2)[Mo6O19]. Under rigorously anaerobic conditions, reaction of two equivalents of PhNCO with [MoO2(S2CNR2)(2)] affords [Mo(NPh)(2)(S2CNR2)(2)] as the major product. However, chloroform solutions of the bis(imido) complexes hydrolyze in air to afford [Mo(NPh)(S2CNR2)(2)(mu-MoO4)](2), in which molybdate groups bridge between molybdenum(VI) imido-bis(dithiocarbamate) centers. These results are placed in context of our earlier studies of these reactions that lead to the formation of oxo-disulfide [MoS2(NPh)(S2CNR2)(2)] and dimeric molybdenum(V) [MoO(mu-NPh)(S2CNR2)](2) complexes, thus allowing a full picture of these transformations to be established.Heating PhNCO with [MoO2(S2CNR2)(2)] in air gives [Mo(NPh)(S2CNR2)(3)]X (R = Me, Et), but when the reaction is carried out under anaerobic conditions, [Mo(NPh)(2)(S2CNR2)(2)] initially results, chloroform solutions of which hydrolyze in air to afford [Mo(NPh)(S2CNR2)(2)(mu-MoO4)](2).

Fabrication and Luminescence Properties of One-Dimensional CaMoO4: Ln3+ (Ln = Eu, Tb, Dy) Nanofibers via Electrospinning Process

One-dimensional CaMoO(4):Ln(3+) (Ln = Eu, Tb, Dy) nanofibers have been prepared by a combination method of sol-gel and electrospinning process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL), and low voltage cathodoluminescence (CL) as well as kinetic decays were used to characterize the resulting samples. SEM and TEM analyses indicate that the obtained precursor fibers have a uniform size, and the as-formed CaMoO(4):Ln(3+) nanofibers consist of nanoparticles. Under ultraviolet excitation, the CaMoO(4) samples exhibit a blue-green emission band with a maximum at 500 nm originating from the MoO(4)(2-) groups. Due to an efficient energy transfer from molybdate groups to dopants, CaMoO(4):Ln(3+) phosphors show their strong characteristic emission under ultraviolet excitation and low-voltage electron beam excitation. The energy transfer process was further studied by the emission spectra and the kinetic decay curves of Ln(3+) upon excitation into the MoO(4)(2-) groups in the CaMoO(4):x mol % Ln(3+) samples (x = 0-5). Furthermore, the emission colors of CaMoO(4):Ln(3+) nanofibers can be tuned from blue-green to green, yellow, and orange-red easily by changing the doping concentrations (x) of Ln(3+) ions, making the materials have potential applications in fluorescent lamps and field emission displays (FEDs).

Gamma ray interaction with sodium phosphate glasses containing MoO3

Sodium metaphosphate glasses undoped and doped with varying MoO3 contents were prepared and their UV–visible, infrared and Raman spectroscopy were measured. The ultraviolet–visible absorption were remeasured after each successive gamma irradiation. The induced color centers of the intrinsic defects of the undoped and extrinsic defects due to Mo-doped glasses were characterized. The structural forming units were derived and analyzed from infrared and Raman spectroscopic evolution. Also, some sodium phosphate glasses with varying Na2O or P2O5 content and constant MoO3 were investigated. The experimental results show that the parent undoped sodium metaphosphate reveals strong ultraviolet spectra originating from the presence of trace iron impurities. Upon gamma irradiation, some UV and visible induced absorption bands are resolved which can be correlated with POHC, OHC, PEC from phosphate network and extrinsic defect due to iron impurities. The high Mo-doped glass reveals two small visible bands with increasing the Na2O content which seems to be related to polymolybdate ions. Infrared and Raman spectra show the characteristic absorption bands due mainly to metaphosphate network and molybdate groups.

Crystal structures of some crystal hydrates of binary molybdates

The structures of a series of binary molybdates with the lithium cation LiM(MoO4) · H2O (M = K+, Na+, Rb+, NH 4 + ) are analyzed and compared. Except for LiNa(MoO4) · 2H2O, in all other compounds the lithium cations have a tetrahedral coordination formed by the oxygen atoms of the water molecules and molybdate groups. The structure of LiNa(MoO4) · 2H2O was found to contain a unique coordination polyhedron of lithium, i.e., a trigonal bipyramid formed by the O atoms of the water molecules and oxo anions.

An IR and Raman study of trigonal triple molybdates M 5 I M 0.5 II Hf1.5(MoO4)6 (MI = K, Tl; MII = Ca, Sr, Ba, Pb)

The vibration spectra of triple molybdates M 5 I M 0.5 II Hf1.5(MoO4)6 (MI = K, Tl; MII = Ca, Sr, Ba, Pb) were examined. The internal vibration frequencies of molybdate groups were assigned. The double-charged cations affect the symmetric stretching (v1), bending, and translation vibration frequencies in the Raman spectra. In the IR spectra, the triply degenerate stretching vibration of the MoO4 group (∼890–720 cm−1) is split, and the splitting increases with an increase in the radius of the double-charged cation.

Structure and Some Properties of a Double Neptunyl(V) Cesium Molybdate, Cs[NpO2MoO4(H2O)

A double neptunyl(V) cesium molybdate, Cs[NpO2MoO4(H2O)], was studied by single crystal X-ray diffraction. Crystal data: rhombic system, a = 9.478(2), b = 7.900(1), c = 10.499(2) A; space group Pnna, Z = 4, d = 5.05 g cm−3, R = 0.030. The compound has a framework structure; the coordination polyhedron of the Np atom is a distorted pentagonal bipyramid with the equatorial positions occupied by four O atoms of four molybdate groups and an O atom of the coordinated water molecule. The IR and visible absorption spectra of this compound and of Cs2[(NpO2)2Mo2O8] whose structure had been determined previously were measured. The NpO 2 + stretching vibration frequencies in the IR spectra of these compounds virtually coincide. Incorporation of the O atom of the Mo-O-Mo bridge into the first coordination sphere of the neptunyl(V) ion in Cs2[(NpO2)2Mo2O8] exerts the same disturbing effect on the electronic absorption spectrum as does the cation-cation interaction with one of the O atoms acting as a bridge between two Np atoms.