Synthesis and spectral characterization of dioxouranium (VI) complexes of salicylhydrazine and acetone salicylhydrazone

Dioxouranium(VI) complexes of the types UO₂LSO₄ and UO₂L₂SO₄ (where L=SH, ASH) have been prepared from reaction of uranyl sulphate with salicylhydrazine (SH) and acetone salicylhydrazone (ASH) and characterized by conventional chemical and physical measurements. Infrared and Raman spectra indicate thatmono- andbis-complexes contain six-and seven-coordinate uranium atom respectively with all the ligand atoms arranged in an equatorial plane around the linear uranyl group. The infrared spectra (4000-200 cm⁻¹) reveal that both SH and ASH act as neutral bidentate ligands coordinating through a carbonyl oxygen and primary amine/azomethine nitrogen atoms. The sulphato group coordinates to the uranyl ion as bidentate chelating ligand and terminal monodentate ligand in mono- and bis-complexes respectively.     

Raman spectra of overheated sulfur vapor

Our thermodynamic study allows to confirm the selective observation with a blue exciting line (457.9 or 476.5 nm) of the resonance Raman spectra of the S₃ molecule. The extinction coefficient of the maximum λ = 395 nm of its absorption spectrum ε = 2100 1 mole⁻¹ cm⁻¹ is quite lower than that previously reported. The resonance Raman spectra of ³²S₃ and ³⁴S₄ may be explained with three normal frequencies and confirm the bent C_2v geometry of this molecule in perfect agreement with the structure of the parent anions, S⁻₃ and S²⁻₃.     

New dioxouranium(VI) complexes with tridentate dibasic Schiff bases containing ONO donor sets

Summary Several new dioxouranium(VI) complexes with the tridentate dibasic Schiff bases derived from salicylaldehyde, 5-chloro-, 5-bromo-, 5-nitro-, 3,5-dichloro-, 4-methoxy-, 5-methoxy- and 3-ethoxysalicylaldehyde and 2-hydroxy-1-naphthaldehyde ando-aminobenzyl alcohol, have been synthesized from uranyl acetate dihydrate and the Schiff base in methanol. The complexes are of the type UO₂(AAA). MeOH (where AAAH₂ = a tridentate dibasic Schiff base). The complexes have been characterized by elemental analyses, i.r. and electronic spectra, conductance, magnetic susceptibility and molecular weight measurements. Thev (U=O) stretching frequency of the complexes occurs atca. 900 cm^–1 and the U-O distance is 1.74Å. The complexes are monomers, diamagnetic and octahedral.     

A combined spectroscopic and light scattering study of hydrolysis of uranium(VI) leading to colloid formation in aqueous solutions

This study mainly focuses hydrolysis reactions of uranium(VI) under an ambient atmosphere leading to colloid formation in near neutral solution using light scattering, UV–Vis and FTIR-ATR studies. UV–Vis and IR spectrum was recorded for uranyl solution at different pH range. U(VI) hydrolyzed colloids were detected and it was confirmed by the appearance of a band at 941 cm^?1 in the IR spectra. Light scattering measurements were performed on colloidal U(VI) solutions formed at pH range of 7–8. The average particle diameter was determined as 32–36 nm using dynamic light scattering. Well defined colloidal species are formed with no considerable change in particle size with increasing U(VI) concentration. The weight average molecular weight of colloidal species was predicted as 763 Da by Debye plot. The second virial coefficient (A₂) was found to be ?0.1139 ml g^?1 Da. The present study confirms that behaviour of U(VI) contradicts conventional Zr(IV), Th(IV) and Pu(IV) solution chemistry. U(VI) polymerization is less extensive and in neutral solutions it forms only oligomers with 2–3 uranyl units.     

Raman studies of uranyl nitrate and its hydroxy bridged dimer

In this paper, the authors report Raman spectra obtained on imidazolium di-μ-hydroxybis[dioxobis-(nitrato)uranium(VI)], (UO₂(NO₃)₂(OH))₂.2C₃H₅N₂ (IUNH). An assignment of the Raman bands is made by comparing the spectrum of IUNH with those of uranyl nitrate hexahydrate (UNH) and imidazole (IMID). The electron charge transfer from the imidazole ring to the uranyl ion has been empirically determined.     

1064-nm-excited Fourier transform Raman studies of bacteriochlorophyll-a in solid films and in a blue-green mutant of Rhodobacter sphaeroides

1064-nm-excited Fourier transform Raman spectra of bacteriochlorophyll-a (BChl) in various solid films and in chromatophores from a blue-green mutant of Rhodobacter sphaeroides have been obtained. The observed Raman spectra are free from high fluorescence backgrounds and sample degradation. The observed intensities seem to be enhanced because of a pre-resonant effect between the exciting radiation at 1064 nm and the Q_y absorption at 770–870 nm of BChl. The spectral features are substantially different from the Soret and Q_x resonance Raman spectra extensively investigated so far; several bands in the wavenumber region lower than 1200 cm⁻¹ are particularly enhanced in the Q_y pre-resonance Raman spectra. Bands due to both the C₂O and C₉O stretches appear at 1700–1620 cm⁻¹, providing structural information on these carbonyl groups. In the CC stretching region (1620–1490 cm⁻¹), the correlation between band positions and the co-ordination number of central magnesium, which was previously found in the Soret-excited Raman spectra, is preserved in the Q_y, pre-resonance Raman spectra as well. The relative intensities of strong bands in the 1200–1000 cm⁻¹ region appear to be useful for characterizing the BChl state. By using these advantages of the Q_y, pre-resonance Raman spectra, molecular interactions and arrangements of BChl in hydrated films and in the B870 light-harvesting complex of R. sphaeroides are discussed.     

Vibrational spectroscopy of a crystallographically unsettled uranyl carbonate: Structural impact and model

Room-temperature vibrational and photoluminescence (PL) spectra of a natural, rare hydrated calcium copper uranyl carbonate mineral, voglite (Ca₂Cu(UO₂)(CO₃)₄·6H₂O) are recorded and discussed in details. Vibrational spectroscopy gives information about the structure of voglite, which is still missing due to its unknown crystallographic features. By comparison with other uranyl carbonates and sulfates, a strong Raman line occurring at 834 cm⁻¹ is assigned to the ν₁(UO₂)²⁺ symmetric stretching vibration rather than to the ν₂(CO₃)²⁻ out-of-plane bending vibration. The ν₃(UO₂)²⁺ antisymmetric stretching vibration is tentatively identified at 897 cm⁻¹ from infrared (IR) spectroscopy. Several well resolved bands found at 1074,1092, 1381, 1566 cm⁻¹ in the Raman and 1046, 1114, 1145, 1376, 1426, 1510, 1561 cm⁻¹ in the IR are ascribed to symmetric and antisymmetric stretching motions of the carbonate units. The presence of all these intense vibrational bands points to different CO bond lengths. The infrared water band is well structured, suggesting a few different OH moieties in the crystal. Original micro-PL spectra show a manifold of vibronic features whose energy spacing is close to the frequency of the symmetric OUO stretching vibration and confirms the uranium origin of the most intense Raman band. The study suggests that voglite structure has no inversion centers, a low symmetry, and contains molecular units similar to those of the parent phases, andersonite or liebigite, like uranyl tricarbonate clusters (UTC). The existence of these UTCs in voglite is confirmed by density functional theory calculations. A new assignment of all vibrational modes is proposed.     

Effect of substituants on the structure of dioxouranium(VI) complexes of 7-carboxaldehyde-8-hydroxyquinoline and some of its Schiff bases

Summary A series of dioxouranium(VI) complexes with 7-carboxaldehyde-8hydroxyquinoline (oxine) and with some of its Schiff bases, LH, have been prepared and characterized by elemental analyses, electronic and vibrational spectral studies. All complexes except those of the oxine have the [UO₂L₂] · EtOH, stoichiometry (n=0, 1, 2 or 4). The uranyl complexes of the oxine have the formula [UO₂L₂(LH)]. The i.r. spectra reveal all ligands to be monobasic bidentate chelating agents coordinated to the uranium(VI)via the enolized phenolic OH and aldehydic oxygen or azomethine nitrogen atom. The force constant f_U-o (mdyn Å) and the bond length r_U-o (Å) of the U-O bond are also calculated and related to the electronic properties of thep-substituents.     

Complex formation of uranium(VI) with 4-hydroxy-3-methoxybenzoic acid and related compounds

Summary The complex formation of uranium(VI) with 4-hydroxy-3-methoxybenzoic acid as well as with benzoic acid and 4-hydroxybenzoic acid was studied. In aqueous solution weak carboxylic 1 : 1 complexes, are formed in which the carboxyl group is bidentately coordinated to the metal atom. The logarithmic stability constants of these complexes regarding the reaction of the uranyl ion with the single charged anion of the respective ligands are 2.78±0.02, 2.68±0.04, and 2.71±0.04 at an ionic strength of 0.1 mol/l (NaClO₄) and at 25 °C. Bis(4-hydroxy-3-methoxybenzoato)dioxouranium(VI) was obtained as a crystalline compound if the concentrations of the starting components for the synthesis are increased. The monoclinic compound has a reflections-rich X-ray powder diffraction pattern. The lattice constants are a = 13.662(9) ?, b = 21.293(7) ?, c = 11.213(3) ?, b = 107.49(4), and V = 3111(2) ?.³     

Different level of fluorescence in Raman spectra of montmorillonites

The paper presents the study of selected montmorillonite standards by Raman spectroscopy and microscopy supported by elemental analysis, X-ray powder diffraction analysis and thermal analysis. Dispersive Raman spectroscopy with excitation lasers of 532 nm and 780 nm, dispersive Raman microscopy with excitation laser of 532 nm and 100× magnifying lens, and Fourier Transform-Raman spectroscopy with excitation laser of 1064 nm were used for the analysis of four montmorillonites (Kunipia-F, SWy-2, STx-1b and SAz-2). These mineral standards differed mainly in the type of interlayer cation and substitution of octahedral aluminium by magnesium or iron. A comparison of measured Raman spectra of montmorillonite with regard to their level of fluorescence and the presence of characteristic spectral bands was carried out. Almost all measured spectra of montmorillonites were significantly affected by fluorescence and only one sample was influenced by fluorescence slightly or not at all. In the spectra of tested montmorillonites, several characteristic Raman bands were found. The most intensive band at 96 cm⁻¹ belongs to deformation vibrations of interlayer cations. The band at 200 cm⁻¹ corresponds to deformation vibrations of the AlO₆ octahedron and at 710 cm⁻¹ can be assigned to deformation vibrations of the SiO₄ tetrahedron. The band at 3620 cm⁻¹ corresponds to the stretching vibration of structural OH groups in montmorillonites.     

Spectrophotometric Determination of U(VI) with Rifampicin in Soil Samples

A validated spectrophotometric method has been developed for the determination of uranyl ion in soil samples. The method is based on the complexation reaction between uranyl ion and rifampicin in methanol‐water medium at room temperature. The method is followed spectrophotometrically by measuring the absorbance at 375 nm. Under the optimized experimental conditions, Beer's law is obeyed in the concentration range of 1.35–20.25 μg mL^‐1 with apparent molar absorptivity and Sandell's sensitivity of 8.0 × 10³ L mol^‐1cm^‐1 and 0.042 μg/cm²/0.001 absorbance unit, respectively. The interference of a large number of anions and cations has been investigated and the optimized conditions developed have been utilized for the determination of uranium(VI) in soil samples. The three sigma detection limit (n = 9) for uranyl ion was found to be 0.20 μg mL^‐1. The proposed method was successfully applied to the determination of uranyl ion in soil samples.     

Far infrared and low frequency gas phase Raman spectra,vibrational assignment,and conformational stability of 1-chloro-2-methylpropane and 1-bromo-2-methylpropane

The Raman (3200—10cm⁻¹) and infrared (3200—50 cm⁻¹) spectra of gaseous and solid 1-chloro-2-methylpropane and 1-bromo-methylpropane, as well as the Raman spectra of the liquids, have been recorded and assigned. The gauche asymmetric torsion of the 1-chloro-2-methylpropane molecules has been observed at 110 cm⁻¹ in the Raman spectrum of the gas. For the 1-bromo-2-methylpropane molecule, both the trans and gauche asymmetric torsions have been observed at 106.70 and 103.94 cm⁻¹, respectively, along with three additional transitions for the gauche conformer. From these data, the asymmetric potential function for the bromide molecules to V₁ = —493 ±16, V₂ = 595 ± 18, and V₃ = 2006 ± 6 cm⁻¹ with the trans conformer being more stable than the gauche conformer by 44 ± 20 cm⁻¹. The trans form is found experimentally to be more stable in the liquid phase by 30 ± 14 cm⁻¹ (83 ± 40 cal mol⁻¹). From the relative intensities, in the Raman spectra, of the CCl stretches measured as a function of temperature, the gauche conformer of the chloride molecules to be 167 ± 71 cm⁻¹ (479 ± 203 cal mol⁻¹) more stable than the trans conformer in the gas phase, and 73 ± 10 cm⁻¹ (208 ± 29 cal mol⁻¹) more stable in the liquid phase. The methyl torsions for the gauche and trans conformers of both molecules are tentatively assigned in the gas phase and the barriers have been calculated. The results of this study are compared with previous studies on these molecules.     

Etude vibrationnelle de la phase II des hydrogénodisulfates de triammonium, (NH4)3H(SO4)2 et (ND4)3D(SO4)2

The i.r. and Raman spectra of room temperature phase (phase II) of (NH₄)₃H(SO₄)₂ and (ND₄)₃D(SO₄)₂ as polycrystalline samples and single crystals have been investigated between 4000 and 30 cm⁻¹. An assignment of internal and external modes is given in terms of group frequencies and symmetry types. This crystal contains non-centrosymmetric dimers (SO₄HSO₄)³⁻ where sulphate ions are associated by strong asymmetric OH … O hydrogen bonds; they are characterized by two strong Raman bands at 1078 and 966 cm⁻¹, and a νOH frequency at about 1250 cm⁻¹. The acidic proton is statistically disordered around the crystallographic symmetry centre while all of the NH⁺₄ ions show an important dynamical orientational disorder.     

Vibrational spectra of the charge transfer complexes between organic sulfides and iodine

I.r. spectra of the charge transfer complexes between nine organic sulfides (as well as diethylselenide) with iodine were recorded between 1500 and 400 cm⁻¹ in CS₂ and CCl₄ solutions and in the region 600-50 cm⁻¹ in C₆H₁₂ and C₆H₆ solutions. Raman spectra of the complexes were recorded below 600 cm⁻¹. For each system, i.r. and Raman bands in the 200-160 cm⁻¹ were assigned to the II stretching mode of the complex. Additional i.r. bands below 160 cm⁻¹, absent in Raman, were ascribed to intermolecular SI stretching vibrations. The integral intensities of these bands were determined and correlated with the thermodynamic functions. Some Raman active fundamentals of 1,4-dithiane became i.r. active in the iodine complex in accordance with a break down of the C₂h symmetry. A force constant calculation was carried out for the dimethylsulfide-iodine complex and simplified calculations of the three point mass models were made for all the systems.     

Analyse vibrationnelle infrarouge et Raman du benzosélénophène et du benzotellurophène

Infrared (4000-200 cm⁻¹; vapour solid and solution dissolved in inert and proton acceptor solvents) Raman (4000-100 cm⁻¹, solid and solution) spectra of benzoselenophene and benzotellurophene have been recorded. A complete attribution of the fundamental vibrations is proposed. The fundamental vibration wavenumbers evolution for a series of monoheteroatomic benzoheterocycles C₈H₆X with X = O, S, Se and Te is analysed.     

Raman scattering study of calcium hexaboride

We report significant difference in the Raman spectra of two different kinds of CaB₆ single crystals grown from boron purity 99.9% (3N) or 99.9999% (6N), respectively. Our Raman spectra of CaB₆ (3N), which are similar to those of previous measurement [N. Ogita, S. Nagai, N. Okamoto, M. Udagawa, F. Iga, M. Sera, J. Akimitsu, S. Kunii, Phys. Rev. B 68 (2003) 224305], show peaks at 781.3 cm⁻¹ (T_2g), 1140.1 cm⁻¹ (E_g), and 1283.5 cm⁻¹ (A_1g). The E_g mode shows a characteristic double-peak feature due to an additional weak broad peak centered at 1156.0 cm⁻¹. However, the Raman spectra of CaB₆ (6N) show sharp peaks at 772.5 cm⁻¹ (T_2g), 1137.9 cm⁻¹ (E_g), and 1266.6 cm⁻¹ (A_1g). The peak frequencies are down shifted as much as 17 cm⁻¹. In addition, no additional peak feature is observed for the E_g mode so that the mode is symmetric in the case of CaB₆ (6N). The X-ray powder diffraction patterns for both CaB₆ (3N) and CaB₆ (6N) show that the lattice parameters are essentially the same. The majority of the impurity in the 99.9% (3N) boron is assessed to be C. Thus we prepared Ca(B_0.995C_0.005)₆, CaB₆ (6N) doped with C, and looked for the difference in the Raman spectra. The Raman spectra of Ca(B_0.995C_0.005)₆ are nearly identical to those of CaB₆ (6N), indicating that the difference in the Raman spectra of CaB₆ (3N) and CaB₆ (6N) is not due to C impurity. However, presence of impurity, even if small amount, seems to be enough to trigger local-structure changes to lower symmetry inducing the difference in Raman spectra of CaB₆ (3N) and CaB₆ (6N).     

Vibrational assignments for trimethylene oxide and several deuterated analogues

Complete vibrational assignments below about 1400 cm⁻¹ are presented for trimethylene oxide and its deuterated derivatives β-d₂, α, α′-d₄, d₆, and α-d₂, on the basis of the i.r. vapour phase spectra and the spectra of the solids at 15 K as thin films and in argon matrices, and the Raman spectra of the vapours and liquids. Previously reported assignments for the CH stretching, CH₂ scissoring, and the ring puckering vibrations, as well as preliminary assignments for the CD stretching modes, are included for comparison.     

Vibrational spectroscopic studies of uranyl complexes in aqueous and non-aqueous solutions

Vibrational spectra have been obtained for aqueous solution of uranyl-perchlorates, -fluorides, -chlorides, -acetates and -sulphates over a range of solution composition with added anions. We have prepared [Buⁿ₄N][UO₂Cl₄], [Me₄N][UO₂Cl₄], [Prⁿ₄N][[UO₂(NO₃)₃], [Buⁿ₄N][UO₂(NO₃)₃], with the expectation that the large cation would give a better approximation to vibrational frequencies of the free anion and would allow measurements in non-coordinating solvents. As the perchlorate is not coordinated to [UO₂]²⁺ in aqueous solution the expected structure is a solvated cation [UO₂(OH₂)₅]²⁺ with characteristic infrared 962.5, 253 and 160 cm⁻¹ and Raman 874 and 198 cm⁻¹ bands. The formation of weak, solvated [UO₂X]⁺ complexes (X=F, Cl) has been established with frequencies at 908, 827, 254, 380 cm⁻¹ and 956, 871, 254 and 222 cm⁻¹ for [UO₂F]⁺ and [UO₂Cl]⁺, respectively. Bidentate NO₃ coordination has been established for solid and dissolved (in CH₂Cl₂) [R₄N][UO₂(NO₃)₃] (R=Prⁿ, Buⁿ). Aqueous solutions of UO₂(NO₃)₂ and Cs[UO₂(NO₃)₃] show no clear evidence that bidentate or monodentate nitrate is present. Both unidentate and bidentate linkage of acetate-uranyl were established for acetate complexes in aqueous solutions. For the uranyl sulphate system, monodentate sulphate coordination is the major mode at low SO₄:U ratios, and even at a ratio of 3:1 there is very little free sulphate.     

Preparation of carbon coated Fe3O4 nanoparticles for magnetic separation of uranium

Uranium(VI) was removed from aqueous solutions using carbon coated Fe₃O₄ nanoparticles (Fe₃O₄@C). Batch experiments were conducted to study the effects of initial pH, shaking time and temperature on uranium sorption efficiency. It was found that the maximum adsorption capacity of the Fe₃O₄@C toward uranium(VI) was ∼120.20 mg g⁻¹ when the initial uranium(VI) concentration was 100 mg L⁻¹, displaying a high efficiency for the removal of uranium(VI) ions. Kinetics of the uranium(VI) removal is found to follow pseudo-second-order rate equation. In addition, the uranium(VI)-loaded Fe₃O₄@C nanoparticles can be recovered easily from aqueous solution by magnetic separation and regenerated by acid treatment. Present study suggested that magnetic Fe₃O₄@C composite particles can be used as an effective and recyclable adsorbent for the removal of uranium(VI) from aqueous solutions.     

Phases of tetraphosphorus triselenide analysed by magic angle spinning 31P NMR and Raman spectroscopy,and the Raman spectrum of tetraphosphorus tetraselenide

The local environments of the cage molecules in the phases of P₄Se₃ are analysed with ³¹P MAS-NMR and Raman spectroscopy.The ³¹P MAS-NMR spectra of the orientationally ordered α and α′,-phases have different chemical shifts for the apical P atom (α: 68.0, 86 and 88.0 ppm; α′: 75.8 ppm), but similar chemical shifts for the basal P atoms (α: −58.8 ppm, α′: −60.0 ppm).When either α or α′-P₄Se₃ is heated above 358 K, the resulting β-P₄Se₃ has a well-resolved, liquid-like spectrum, indicating extensive molecular re-orientation. The slowly quenched β-phase shows a remnant β-phase mixed with the α-phase as well as P₄Se₄. A rapidly quenched sample of β-P₄Se₃ also shows a small remnant β-phase in the α-phase, but also a new phase with sharp resonances at 12.5, 3.6, 0.1 and −12 ppm. These are probably due to a P₄Se₄ phase which may be orientationally disordered.The Raman spectrum of P₄Se₃ heated above the α-β phase transition temperature shows a disappearance of the lattice modes and the 373 cm⁻¹ mode as previously reported, but also shows some decomposition to P₄Se₄. The β-phase reverts into the α-phase on quenching, with only weak remnant bands attributable to P₄Se₄. The bands of P₄Se₄ become more prominent as the temperature of the β-phase is raised, but above the β-∂ phase transition they are less prominent.The Raman spectrum of P₄Se₄ is reported. The strongest band is at 350 cm⁻¹, with the next strongest band at 185 cm⁻¹. The spectra indicate that the dominant isomer is the selenium analogue of α-P₄S₄ (D_2h), confirming previous ³¹P MAS-NMR studies.