Uranyl ion complexes with long chain aminoalcoholbis(phenolate) [O,N,O,O′] donor ligands

The reaction between uranyl nitrate hexahydrate and phenolic ligand precursor [(N,N-bis(2-hydroxy-3,5-dimethylbenzyl)-4-amino-1-butanol) · HCl], H₃L1 · HCl, leads to a uranyl complex [UO₂(H₂L1)₂] (1a) and [UO₂(H₂L1)₂] · 2CH₃CN (1b). The ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-4-amino-1-butanol)H₃L2 · HCl], H₃L2 · HCl, yields a uranyl complex with a formula [UO₂(H₂L2)₂] · CH₃CN (2). The ligand [(N,N-bis(2-hydroxy-3,5-dimethylbenzyl)-5-amino-1-pentanol) · HCl], H₃L3 · HCl, produces a uranyl complex with a formula [UO₂(H₂L3)₂] · 2CH₃CN (3) and the ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-5-amino-1-pentanol) · HCl], H₃L4 · HCl, leads to a uranyl complex with a formula [UO₂(H₂L4)₂] · 2CH₃CN (4). The ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-6-amino-1-hexanol) · HCl], H₃L5 · HCl, leads to a uranyl complex with a formula [UO₂(H₂L5)₂] · 4toluene (5). The complexes 1–5 are obtained using a molar ratio of 1:2 (U to L) in the presence of a base (triethylamine). The molecular structures of 1a, 1b, 3, 4 and 5 were verified by X-ray crystallography. All complexes are neutral zwitterions and have similar centrosymmetric, mononuclear, distorted octahedral uranyl structures with the four coordinating phenoxo ligands in an equatorial plane. In uranyl ion extraction studies from water to dichloromethane with ligands H₃L1 · HCl–H₃L5 · HCl, ligands H₃L1 · HCl, H₃L4 · HCl and H₃L5 · HCl are the most effective ones.     

Aminoalkylbis(phenolate) [O,N,O] donor ligands for uranyl(VI) ion coordination: Syntheses,structures, and extraction studies

The syntheses of five new aminoalkylbis(phenolate) ligands (as hydrochlorides) and their uranyl complexes are described. The reaction between uranyl nitrate hexahydrate and phenolic ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-1-aminopropane) · HCl], H₂L1 · HCl, forms a uranyl complex [UO₂(HL1)₂] · 2CH₃CN (1). The ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-1-aminobutane) · HCl], H₂L2 · HCl, forms a uranyl complex with a formula [UO₂(HL2)₂] · 2CH₃CN (2). The ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methyl benzyl)-1-aminohexane) · HCl], H₂L3 · HCl, yields a uranyl complex with a formula [UO₂(HL3)₂] · 2CH₃CN (3) and the ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-cyclohexylamine) · HCl], H₂L4 · HCl, yields a uranyl complex with a formula [UO₂(HL4)₂] (4). The ligand [(N,N-bis(2-hydroxy-5-tert-butyl-3-methylbenzyl)-benzylamine) · HCl], H₂L5 · HCl, forms a uranyl complex with a formula [UO₂(HL5)₂] · 2MeOH (5). The molecular structures of 1, 2′ (2 without methanol), 3, 4 and 5 were verified by X-ray crystallography. The complexes 1–5 are neutral zwitterions which form in a molar ratio of 1:2 (U to L) in the presence of a base (triethylamine) and bear similar mononuclear, distorted octahedral uranyl structures with the four coordinating phenoxo ligands forming an equatorial plane and resulting in a centrosymmetric structure for the uranyl ion. In uranyl ion extraction studies from water to dichloromethane with ligands H₂L1 · HCl–H₂L5 · HCl, the ligands H₂L2 · HCl and H₂L4 · HCl are the most effective ones.     

Simultaneous enzymatic kinetic determination of pesticides, carbaryl and phoxim, with the aid of chemometrics

A sensitive and selective enzymatic kinetic method for the simultaneous determination of mixtures of carbaryl and phoxim pesticides was researched and developed. It was based on the inhibitory effect of the pesticides on acetylcholinesterase (AChE), and the use of 5,5′-dithiobis(2-nitrobenzoic) acid (DTNB) as a chromogenic reagent for the thiocholine iodide (TChI) released from the acetylthiocholine iodide (ATChI) substrate. The DTNB-thiocholine reaction was investigated by a spectrophotometric-kinetic approach. The complex rate equation for the formation of the chromogenic product, P, was solved under certain experimental conditions, which enabled the absorbance (A_P, at λ_max = 412 nm) from the mixtures of the two pesticide inhibitors to be directly related to their concentrations provided the absorbance additivity was followed. The spectra were measured for mixtures of carbaryl and phoxim at different concentrations, and at t = 904 s, T = 35 °C, pH = 7.5, c_ATChI = 0.14, and c_AChE = 0.10 mg mL⁻¹. The detection limits of the enzymatic kinetic spectrophotometric procedures for the determination of the carbaryl and phoxim were 4.7 and 0.59 μg L⁻¹, respectively.Calibration models for chemometrics methods, such as principal component regression (PCR), partial least squares (PLS) and radial basis function-artificial neural network (RBF-ANN) were constructed and verified with synthetic samples of the mixtures of the two pesticides. The best performing model was based on the RBF-ANN method yielding at approximately 10 ppb analyte concentrations, %RPE_T (carbaryl = 5.2; phoxim = 6.5), %Recovery (approx.105%) and %RPE_T (6.5). Various spiked town-water samples produced recoveries in the range of 98.8-103% for each pesticide.     

Crosslinking, thermal properties and relaxation behaviour of polyisoprene under high-pressure

The transient hot-wire method has been used to measure the thermal conductivity κ and heat capacity per unit volume ρc_p of untreated (virgin) and crosslinked cis-1,4-poly(isoprene) (PI) in the temperature range 160-513 K for pressures p up to 0.75 GPa. The results show that the crosslinking rate of the polymer chains becomes significant at ∼513 K on isobaric heating at 0.5 GPa changing PI into an elastomeric state within 4 h without the use of crosslinking agents. The crosslinked PI and untreated PI have about the same κ = 0.145 Wm⁻¹ K⁻¹ and c_p = 1.81 kJ kg⁻¹ K⁻¹ at 295 K and 20 MPa, but different relaxation behaviours. Two relaxation processes, corresponding to the segmental and normal modes, could be observed in both PI and crosslinked PI but these have a larger distribution of relaxation times and become arrested at higher temperatures (∼10 K) in the latter case. The arrest temperature for the segmental relaxation of untreated and crosslinked PI, for a relaxation time of ∼1 s, are described well by the empirical relations: T(p) = 209.4 (1 + 4.02 p)^0.31 and T(p) = 221.3 (1 + 2.33 p)^0.40 (p in GPa and T in K), respectively, which thus also reflects the pressure variations of the glass transition temperatures.     

Syntheses, structures and Raman spectra of Cd(BF4)(AF6) (A = Ta, Bi) compounds

The compounds, Cd(BF₄)(TaF₆) and Cd(BF₄)(BiF₆), have been synthesized and characterized by single-crystal X-ray diffraction and Raman spectroscopy. Both isostructural compounds crystallize in the monoclinic P2₁/c space group with a = 8.2700(6) Å, b = 9.3691(6) Å, c = 8.8896(7) Å, β = 94.196(3)°, V = 686.94(9) Å³ for Cd(BF₄)(TaF₆) and a = 8.3412(8) Å, b = 9.4062(8) Å, c = 8.9570(7) Å, β = 93.320(5)°, V = 701.58(11) Å³ for Cd(BF₄)(BiF₆). Eight fluorine atoms (4 BF₄⁻ + 4 AF₆⁻) form a surrounding around the cadmium atom in the shape of distorted square antiprism. These compounds are not isostructural with mixed-anion analogues of Ca, Sr, Ba and Pb studied earlier.     

Vibrational spectra and structural parameters of some XNCO and XOCN (X = H, F, Cl, Br) molecules

Ab initio calculations with full electron correlation by the perturbation method to second order and hybrid density functional theory calculations by the B3LYP method utilizing the 6-31G(d), 6-311+G(d, p), and 6-311+G(2d, 2p) basis sets have been carried out for the XNCO and XOCN (X = H, F, Cl, Br) molecules. From these calculations, force constants, vibrational frequencies, infrared intensities, Raman activities, depolarization ratios, and structural parameters have been determined and compared to the experimental quantities when available. By combining previously reported rotational constants for HNCO, ClNCO and BrNCO with the ab initio MP2/6-311+G(d, p) predicted structural values, adjusted r₀ parameters have been obtained. The r₀ values for BrNCO are: r(BrN) = 1.857(5); r(NC) = 1.228(5); r(CO) = 1.161(5) Å; BrNC = 117.5(5) and NCO = 172.3(5)°. For ClNCO the determined r₀ parameters are in excellent agreement with the previously determine r_s values, whereas those for HNCO the HNC angle is larger with a value of 126.3(5)° compared to the previous reported value of 123.9(17)°. However, considering the relatively large uncertainty in the value given initially the two results are in near agreement. Structural parameters are also estimated for FNCO and XOCN (X = H, F, Cl, Br). The centrifugal distortion constants have been calculated and are compared to the experimentally (XNCO: X = H, Cl, Br) determined values. Predicted values for the barriers of linearity are given for both the XNCO (X = H, F, Cl, Br) molecules and the results were compared to the corresponding isothiocyanate molecules. The predicted frequencies for the fundamentals of the XNCO molecules compare favorably to the experimental values but some of the predicted intensities differ significantly from those in the observed spectra. The two OCN bends for HOCN have been assigned and the frequencies for the two corresponding fundamentals of DOCN are predicted.     

Synthesis,molecular and supramolecular structure,spectroscopy and electrochemistry of a dialkoxo-bridged diuranyl(VI) compound

The synthesis, molecular and supramolecular structure, spectroscopy and electrochemistry of a dialkoxo-bridged diuranyl(VI) compound [(UO₂)₂(L)₂(dimethylformamide)₂] (1) derived from the Schiff base ligand H₂L, obtained on condensation of 3-methoxysalicylaldehyde with 2-aminoethanol, have been described. The compound has been characterized by IR, UV–Vis, NMR and mass spectra, as well as by single crystal X-ray structure determination. The title compound crystallizes in the monoclinic P2₁/n space group with the following unit cell parameters a = 10.5713(2) Å, b = 11.9895(2) Å, c = 12.9372(2) Å, β = 102.773(3)° and Z = 2. The structure of 1 reveals that it is a dialkoxo-bridged dinuclear compound of uranium(VI) containing two deprotonated ligands, [L]²⁻, two dimethylformamide (dmf) molecules and two UO₂²⁺ centers. The coordination geometry around the uranium(VI) center is distorted pentagonal bipyramidal; two uranyl oxygens occupy the axial positions, while the basal pentagonal plane is defined by a phenoxo oxygen, two bridging alkoxo oxygens, one imine nitrogen, and one dmf oxygen. Three C–H?O type hydrogen bonds involving one uranyl oxygen, two dmf hydrogens and the imine hydrogen link the dinuclear units into a two-dimensional network. The ESI-MS spectrum of 1 in dimethylsulfoxide exhibits two peaks at m/z = 464.17 and 927.26, which are assignable to [(UO₂)₂L₂H]⁺ (60%) and [(UO₂)₂LH]⁺ (100%) cations, respectively. Cyclic voltammetric measurements of 1 reveal that the uranium(VI) center is reduced quasireversibly at E_1/2 = −1112 mV with ΔE_P = 97 mV.     

New N,N-amino-diphosphonate-containing methacrylic derivatives, their syntheses and radical copolymerizations with MMA

Hydroxy-amino-diphosphonates HO-C_n-NH₂, with 2 ? n ? 11, have been successfully synthesized via the Kabachnick-Field reaction at 70 °C with high yields. These hydroxy compounds are then reacted with methacryloyl chloride to lead to novel amino-diphosphonate methacrylates MAC_nNP₂ (with 2 ? n ? 11). These highly pure methacrylate monomers were obtained with yields higher than 75%. Radical copolymerizations of MAC_nNP₂ (with 2 ? n ? 11) with MMA have been conducted and the r₁ values (related to MAC_nNP₂) are in the range of 1.1-1.3, and r₂ values (related to MMA) about 0.8; this shows that the diphosphonate groups are statistically bonded to the methacrylic backbone.     

Crystal growth, structure determination, and optical properties of new potassium-rare-earth silicates K3RESi2O7 (RE=Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu)

Single crystals of K₃RESi₂O₇ (RE=Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) were grown from a potassium fluoride flux. Two different structure types were found for this series. Silicates containing the larger rare earths, RE=Gd, Tb, Dy, Ho, Er, Tm, Yb crystallize in a structure K₃RESi₂O₇ that contains the rare-earth cation in both a slightly distorted octahedral and an ideal trigonal prismatic coordination environment, while in K₃LuSi₂O₇, containing the smallest of the rare earths, lutetium is found solely in an octahedral coordination environment. The structure of K₃LuSi₂O₇ crystallizes in space group P6₃/mmc with a=5.71160(10) Å and c=13.8883(6) Å. The structures containing the remaining rare earths crystallize in the space group P6₃/mcm with the lattice parameters of a=9.9359(2) Å, c=14.4295(4) Å, (K₃GdSi₂O₇); a=9.88730(10) Å, c=14.3856(3) Å, (K₃TbSi₂O₇); a=9.8673(2) Å, c=14.3572(4) Å, (K₃DySi₂O₇); a=9.8408(3) Å, c=14.3206(6) Å, (K₃HoSi₂O₇); a=9.82120(10) Å, c=14.2986(2) Å, (K₃ErSi₂O₇); a=9.80200(10) Å, c=14.2863(4) Å, (K₃TmSi₂O₇); a=9.78190(10) Å, c=14.2401(3) Å, (K₃YbSi₂O₇). The optical properties of the silicates were investigated and K₃TbSi₂O₇ was found to fluoresce in the visible.     

Unsaturation in trinuclear cobalt carbonyl compounds of the type ECo3(CO)n (E = CH,CF, P,As; n = 9, 8, 7, 6) with Co3E tetrahedrane structures

Theoretical studies on the known trinuclear cobalt carbonyl derivatives ECo₃(CO)₉ (E = CH, CF, P, As) predict structures with carbonyl groups bridging each edge of the Co₃ triangle in contrast with experiment where structures with all terminal carbonyl groups are found in all cases. However, the energy differences are predicted to be rather small ranging from 4 ± 2 kcal/mol for FCCo₃(CO)₉ to 10 ± 3 kcal/mol for AsCo₃(CO)₉. The global minima for the unsaturated ECo₃(CO)_n (n = 8, 7, 6) derivatives generally have two (for n = 8) or three (for n = 7 and 6) carbonyl groups bridging the edges of the Co₃ triangle. However, structures with all terminal carbonyl groups are also found in all cases as well as higher energy structures in which one of the carbonyl groups bridges all three cobalt atoms. The fluoromethinyl derivatives FCCo₃(CO)_n (n = 9, 8, 7) are anomalous since their unbridged structures or structures with a carbonyl group bridging all three cobalt atoms are closer in energy to the doubly or triply bridged global minima than is the case for the other ECo₃(CO)_n derivatives.     

Singlet-triplet energy separations in divalent five-membered cyclic conjugated C5H3X, C4H3SiX, C4H3GeX, C4H3SnX, and C4H3PbX (X = H, F, Cl, and Br)

Singlet-triplet energy gaps in cyclopenta-2,4-dienylidene, as well as its 2- or 3-halogenated derivatives, are compared and contrasted with their sila, germa, stana, and plumba analogues; at HF/6-31G* and B3LYP/ 6-311++G(3df, 2p) levels of theory. Energy gaps (ΔG_t-s), between triplet (t) and singlet (s) states, appear linearly proportional to: (i) the size of the group 14 divalent element (M = C, Si, Ge, Sn and Pb), (ii) the angle ∠C-M-C, and (iii) the ΔG_(LUMO-HOMO) of the singlet state involved. The magnitude of ΔG_t-s, for each 2- and/or 3-substituted species studied, increases with an order of: carbenes < silylenes < germylenes < stanylenes < plumbylenes. This order reverses for the barriers of the ring puckering. The puckering occurs with more ease for every singlet, compared to its corresponding triplet form.Regardless of the group 14 element (M) employed, every 3-halo-substituted species is more stable than the corresponding 2-halo-substituted isomer. For M = Pb, Sn and/or Ge; 3-halo-substituted species have higher ΔG_t-s than their corresponding 2-halo-substituted analogues. For M = Si, similar ΔG_t-s are found for 2- and 3-halogenated isomers. For M = C, 3-halo-substituted species have lower ΔG_t-s than their corresponding 2-halo-substituted analogues.Every cyclic singlet has a larger ∠C-M-C angle, than its corresponding cyclic triplet state, except for 3-halosilacyclopenta-2,4-dienylidenes where triplet has a larger ∠C-M-C angle than its corresponding singlet state.     

Predicting percent composition of blends of biodiesel and conventional diesel using gas chromatography-mass spectrometry, comprehensive two-dimensional gas chromatography-mass spectrometry, and partial least squares analysis

The percent composition of blends of biodiesel and conventional diesel from a variety of retail sources were modeled and predicted using partial least squares (PLS) analysis applied to gas chromatography-total-ion-current mass spectrometry (GC-TIC), gas chromatography-mass spectrometry (GC-MS), comprehensive two-dimensional gas chromatography-total-ion-current mass spectrometry (GCxGC-TIC) and comprehensive two-dimensional gas chromatography-mass spectrometry (GCxGC-MS) separations of the blends. In all four cases, the PLS predictions for a test set of chromatograms were plotted versus the actual blend percent composition. The GC-TIC plot produced a best-fit line with slope = 0.773 and y-intercept = 2.89, and the average percent error of prediction was 12.0%. The GC-MS plot produced a best-fit line with slope = 0.864 and y-intercept = 1.72, and the average percent error of prediction was improved to 6.89%. The GCxGC-TIC plot produced a best-fit line with slope = 0.983 and y-intercept = 0.680, and the average percent error was slightly improved to 6.16%. The GCxGC-MS plot produced a best-fit line with slope = 0.980 and y-intercept = 0.620, and the average percent error was 6.12%. The GCxGC models performed best presumably due to the multidimensional advantage of higher dimensional instrumentation providing more chemical selectivity. All the PLS models used 3 latent variables. The chemical components that differentiate the blend percent compositions are reported.     

Structure and magnetism of mono-, di-, and trinuclear benzoato cobalt(II) complexes

Three cobalt(II) - benzoato (bz) complexes have been prepared and structurally characterized. In the mononuclear complex trans-[Co(bz)₂(H₂O)₂(nca)₂] the benzoato ligand is unidentate (nca = nicotinamide). The dinuclear complex [(μ₂-bz)₄{Co(qu)}₂] is a structural analog of the copper acetate (qu = quinoline) where four bidentate benzoato ligands link two cobalt(II) pentacoordinate centers. The trinuclear complex of the composition [Co₃(bz)₆(inca)₆] contains a central hexacoordinate {(bz)₂Co(inca)₂(bz)₂} unit in which the bidentate benzoato ligands held the central and peripheral cobalt(II) centers (inca = iso-nicotinamide); the peripheral hexacoordinate {(bz)Co(inca)₂<} units contain the terminal benzoato ligand in its bidentate function. The magnetic susceptibility data down to T = 2 K and the magnetization data up to B = 7 T reveal a considerable magnetic anisotropy due to the single-ion zero-field splitting.     

Solubilities of betulin in chloroform + methanol mixed solvents at T = (278.2, 288.2, 293.2, 298.2, 308.2 and 313.2) K

Experimental solubilities of betulin in mixed solvents of chloroform (1) + methanol (2) were determined at T = (278.2, 288.2, 293.2, 298.2, 308.2 and 313.2) K. The solubilities of betulin in mixed solvents of chloroform (1) + methanol (2) increase with increasing of temperature. The curves of solubility versus solvent composition on solute-free basis went through a maximum. Experimental data of solubilities were correlated with a three-parameter equation. In addition, three crystals of betulin obtained in different compositions of chloroform (1) + methanol (2) mixtures were characterized by scanning electron microscope (SEM) and differential scanning calorimetry (DSC).     

Co(III) complexes of the type [(L)Co(O2CO)] (L = tripodal tetraamine ligand): Synthesis,structure, DFT calculations and Co NMR

The syntheses and characterisation of the Co(III) complexes [(L)Co(O₂CO)]ClO₄ (L = a tripodal tetraamine ligand = baep, abap, uns-penp, dppa, trpn) are reported. Geometric isomers are possible for all but the trpn complex, owing to the non-equivalence of the three arms on the tripodal ligand, and both NMR and X-ray crystallography are used to identify the single isomer formed. X-ray crystal structures of the complexes [(L)Co(O₂CO)]ClO₄ · xH₂O (L = baep, x = 0.5; L = abap, x = 0; L = uns-penp, x = 1; L = dppa, x = 0; L = trpn, x = 1) are reported; little variation is observed in the geometry of the carbonate chelate ring while significant lengthening of bonds and expansion of angles involving the cobalt ion occurs as the number of six-membered chelate rings in the complex cations increases. ⁵⁹Co NMR chemical shift data for the complexes show the expected linear relationship between λ_max, the wavelength of the lowest energy d–d transition, and γ, the magnetogyric ratio of the ⁵⁹Co nucleus. An excellent correlation between Δ, the d orbital splitting parameter, and δ(⁵⁹Co) also exists for these complexes. Rate data for the acid hydrolysis of [(L)Co(O₂CO)]⁺ (L = uns-penp, dppa) in 1.0 M HClO₄ differ by two orders of magnitude, and this is attributed to the differing steric accessibility of the endo O atoms in each complex. DFT calculations on the complexes reproduce the isomeric preferences, UV–Vis and ⁵⁹Co NMR spectroscopic data well, provided that solvent effects are included.     

Overpressured layer chromatographic determination of aflatoxin B1, B2, G1 and G2 in red paprika

Determination of aflatoxin B1 and total aflatoxin (B1 + B2 + G1 + G2) in red paprika powder is described using column chromatographic sample clean-up, overpressured layer chromatography (OPLC) separation and fluorescence densitometric evaluation. Two OPLC methods were developed for separation of the four aflatoxins. The detection limit and quantification limit of aflatoxins in red paprika were 0.5 and 1 μg/kg in both methods, respectively. Recovery experiment was carried out with sample containing 1.74 μg/kg aflatoxin B1 and 3.56 μg/kg total aflatoxins measured by European standard HPLC method. Mean recovery amounted to 78.5% (SD 16.1%, n = 5) for aflatoxin B1 and 81.8% (SD 17.1%, n = 5) for total aflatoxins in the case of method 1. It was 105.3% (SD 10.7%, n = 5) for aflatoxin B1 and 97.4% (SD 18.6%, n = 5) for total aflatoxins using the method 2. Despite of that the Hungarian climate is not proper for the toxin production of moulds high aflatoxin B1 contaminated red paprika purchased from the market was found, which may originate from mixing of imported paprika containing very high level toxin with Hungarian one.     

Rare earth metal rich magnesium compounds RE4NiMg (RE=Y, Pr-Nd, Sm, Gd-Tm, Lu)—Synthesis, structure, and hydrogenation behavior

The rare earth metal rich compounds RE₄NiMg (RE=Y, Pr-Nd, Sm, Gd-Tm, Lu) were synthesized from the elements in sealed tantalum tubes in an induction furnace. All compounds were investigated by X-ray diffraction on powders and single crystals: Gd₄RhIn type, space group F4¯3m, Z=16, a=1367.6(2) pm for Y₄NiMg, a=1403.7(3) pm for Pr₄NiMg, a=1400.7(1) pm for Nd₄NiMg, a=1386.5(2) pm for Sm₄NiMg, a=1376.1(2) pm for Gd₄NiMg, a=1362.1(1) pm for Tb₄NiMg, a=1355.1(2) pm for Dy₄NiMg, a=1355.2(1) pm for Ho₄NiMg, a=1354.3(2) pm for Er₄NiMg, a=1342.9(3) pm for Tm₄NiMg, and a=1336.7(3) pm for Lu₄NiMg. The nickel atoms have trigonal prismatic rare earth coordination. These NiRE₆ prisms are condensed via common edges to a three-dimensional network which leaves voids for Mg₄ tetrahedra and the RE1 atoms which show only weak coordination to the nickel atoms. The single crystal data indicate two kinds of solid solutions. The RE1 positions reveal small RE1/Mg mixing and some compounds also show Ni/Mg mixing within the Mg₄ tetrahedra. Y₄NiMg and Gd₄NiMg have been tested for hydrogenation. These compounds absorb up to eleven hydrogen atoms per formula unit under a hydrogen pressure of 1 MPa at room temperature. The structure of the metal atoms is maintained with only an increase of the lattice parameters (ΔV/V≈22%) if the absorption is done at T<363 K as at higher temperature a decomposition into REH₂-REH₃ hydrides occurred. Moreover, the hydrogenation affects drastically the magnetic properties of these intermetallics. For instance, Gd₄NiMg exhibits an antiferromagnetic behavior below T_N=92 K whereas its hydride Gd₄NiMgH₁₁ is paramagnetic down to 1.8 K.     

HPLC-UV and HPLC-MSn multiresidue determination of amidosulfuron, azimsulfuron, nicosulfuron, rimsulfuron, thifensulfuron methyl, tribenuron methyl and azoxystrobin in surface waters

The paper presents a new HPLC method, with UV and MSⁿ detection, for the determination of seven pesticides, including the sulfonylurea herbicides amidosulfuron, azimsulfuron, nicosulfuron, rimsulfuron, thifensulfuron methyl, tribenuron methyl, and the fungicide azoxystrobin characterised by a methoxyacrilate structure. The methodology consists of a preconcentration/SPE (solid phase extraction) step and HPLC-UV (240 nm detection wavelength)-MSⁿ analysis. Under the optimised conditions and after a 1000/1 preconcentration factor, the limits of detection were lower than 14.5 ng L⁻¹ for UV detection and lower than 8.1 ng L⁻¹ for MS detection. The limits of quantification were lower than 48.3 ng L⁻¹ in UV detection and than 26.9 ng L⁻¹ in MSⁿ detection. The analysis of two samples, spiked with a mixture of the pesticides at threshold level concentrations, gave more than 60% recovery.     

Measuring molecular force fields: Terahertz,inelastic neutron scattering,Raman, FTIR,DFT, and BOMD molecular dynamics of solid l-serine

A vibrational analysis of polycrystalline l-serine is provided using experimental terahertz, FTIR, Raman and inelastic neutron scattering (INS) spectra, calculated INS spectra – and Born–Oppenheimer molecular dynamics (BOMD) simulations from which the power spectra for the electronegative elements are compared to the THz spectra. Corrections are made to density functional theory (DFT) calculations for van der Waals interactions. Assignments and potential energy distributions are included for all 3N = 336 normal modes of an eight molecule supercell, including those for 48 non-bonded whole molecule translating and rotating vibrations, of which three are acoustic modes, usually not considered. Calculated and observed frequencies differ by an average 3 cm⁻¹ (s = 4). The INS spectrum of these modes below 100 cm⁻¹, calculated from energy second derivatives, show a remarkable similarity to the experimental 10 K spectra. The calculated low frequency modes are insensitive to small changes in cell parameters and geometry. THz intensities are represented by power spectra and not calculated explicitly. Nevertheless, power spectra of 13 ps BOMD trajectories at classical temperatures of 20 K, 400 K, and 500 K are markedly similar to the experimental terahertz spectra at 77 K and 298 K. Calculations on a serine crystal supercell 2 × 2 × 2 molecules deep appear to include, in a crude but fortuitously accurate way, enough of the principle out of phase dispersion to yield a match with experimental frequencies and intensities.     

Chemical bonding in EuTGe (T=Ni, Pd, Pt) and physical properties of EuPdGe

EuPdGe was prepared from the elements by reaction in a sealed tantalum tube in a high-frequency furnace. Magnetic susceptibility measurements show Curie-Weiss behavior above 60 K with an experimental magnetic moment of 8.0(1)μ_B/Eu indicating divalent europium. At low external fields antiferromagnetic ordering is observed at T_N=8.5(5) K. Magnetization measurements indicate a metamagnetic transition at a critical field of 1.5(2) T and a saturation magnetization of 6.4(1)μ_B/Eu at 5 K and 5.5 T. EuPdGe is a metallic conductor with a room-temperature value of 5000±500 μΩ cm for the specific resistivity. ¹⁵¹Eu Mössbauer spectroscopic experiments show a single europium site with an isomer shift of δ=−9.7(1) mm/s at 78 K. At 4.2 K full magnetic hyperfine field splitting with a hyperfine field of B=20.7(5) T is observed. Density functional calculations show the similarity of the electronic structures of EuPdGe and EuPtGe. T-Ge interactions (T=Pd, Pt) exist in both compounds. An ionic formula splitting Eu²⁺T⁰Ge²⁻ seems more appropriate than Eu²⁺T²⁺Ge⁴⁻ accounting for the bonding in both compounds. Geometry optimizations of EuTGe (T=Ni, Pt, Pd) show weak energy differences between the two structural types.