A series of novel lanthanide polyoxometalates: condensation of building blocks dependent on the nature of rare earth cations

A series of novel lanthanide polyoxomolybdates was synthesized by reaction of lanthanide cations with the Anderson type anion (TeMo(6)O(24))(6-). The polyoxometalates K(6n)(TeMo(6)O(24))(n)[(Ln(H(2)O)(7))(2)(TeMo(6)O(24))](n)[middle dot]16nH(2)O (Ln = Eu, Gd) and K(3n)[Ln(H(2)O)(5)(TeMo(6)O(24))](n)[middle dot]6nH(2)O (Ln = Tb, Dy, Ho, Er) were characterized by X-ray structure analysis, elemental analysis and IR spectroscopy. We found that the solid-state structures of Ln/(TeMo(6)O(24))(6-) compounds are strongly dependent on the lanthanide cations, and therefore represent a rare example for different arrangements of building units depending on the nature of the rare earth cations. While the Eu(3+) and Gd(3+) cations achieve ninefold coordination by seven water molecules and two terminal oxygen atoms of the (TeMo(6)O(24))(6-) anions, the Tb(3+), Dy(3+), Ho(3+) and Er(3+) cations are coordinated by five water molecules, two terminal oxygen atoms and one molybdenum-bridging oxygen atom belonging to the (TeMo(6)O(24))(6-) anion. The europium and gadolinium substituted compounds contain infinite one-dimensional [(Ln(H(2)O)(7))(2)(TeMo(6)O(24))](n) chains; the terbium, dysprosium, holmium and erbium compounds contain infinite one-dimensional [Ln(H(2)O)(5)(TeMo(6)O(24))](n)(3n-) chains.     

Influence of Cyclodextrins on the Kinetics of Oxidation of Amino Acids and BSA by Hydrazyl Radicals

The kinetics of oxidation of amino acids (Arg, His, Lys, Phe, Thr and Tyr), a dipeptide (Gly-His), and BSA (bovine serum albumin) by two persistent water soluble free radicals of the hydrazyl type has been studied.The rate decreases in the order Arg>Lys>Tyr>Thr>HisBSAPheGly-His with bothfree radicals. Addition to the reaction mixture of - and -cyclodextrin decreases the oxidation rate, probably due to amino acidencapsulation in the cyclodextrin cavity. -Cyclodextrin protects more efficiently against oxidation than -cyclodextrin.     

The microscopic investigation of structures of moving flux lines by neutron and muon techniques

We have used a variety of microscopic techniques to reveal the structure and motion of flux line arrangements, when the flux lines in low T _c type II superconductors are caused to move by a transport current. Using small-angle neutron scattering by the flux line lattice (FLL), we are able to demonstrate directly the alignment by motion of the nearest-neighbor FLL direction. This tends to be parallel to the direction of flux line motion, as had been suspected from two-dimensional simulations. We also see the destruction of the ordered FLL by plastic flow and the bending of flux lines. Another technique that our collaboration has employed is the direct measurement of flux line motion, using the ultra-high-resolution spectroscopy of the neutron spin-echo technique to observe the energy change of neutrons diffracted by moving flux lines. The muon spin rotation (μSR) technique gives the distribution of values of magnetic field within the FLL. We have recently succeeded in performing μSR measurements while the FLL is moving. Such measurements give complementary information about the local speed and orientation of the FLL motion. We conclude by discussing the possible application of this technique to thin film superconductors.     

Neue Heteropolyanionen des M2X2W20‐Typs mit Antimon(III) als Heteroatom

New Heteropolyanions of the M₂X₂W₂₀ Structure Type with Antimony(III) as a Heteroatom The syntheses of two new heteropolyanions of the M₂X₂W₂₀ structure type are presented. They are characterized by X‐ray structure analysis and vibrational spectra. Na₆(NH₄)₄[Zn₂(H₂O)₆(WO₂)₂(SbW₉O₃₃)₂]·36H₂O (1) is monoclinic (P2₁/n) with a = 12.873(3)Å, b = 25.303(4)Å, c = 15.975(4)Å and β = 91.99(3)°. Na₁₀[Mn₂(H₂O)₆(WO₂)₂(SbW₉O₃₃)₂]·40H₂O (2) also crystallizes in the space group P2₁/n with a = 12.892(3)Å, b = 25.219(5)Å, c = 16.166(3)Å and β = 94.41(3)°. Both polyanions are isostructural to anions of this structure type containing other heteroatoms. They are built up by two β‐B‐SbW₉ fragments, which are derived from defect structures of the Keggin anion. These subÍunits are connected by two formal WO₂ groups with further stabilization by addition of two M(H₂O)₃ groups (M = Zn^II, Mn^II, Fe^III, Co^II) leading to the M₂X₂W₂₀‐type heteropolytungstates.     

Neue Heteropolyanionen des Wolframs mit Vanadium(IV) als Heteroatom

New Heteropolyanions of Tungsten with Vanadium(IV) as a Heteroatom The syntheses of two new heteropolyanions with vanadium as heteroatom are presented. They are characterized by X‐ray structure analysis and vibrational spectra. ((CH₃)₄N)₆Na₄[(VO(H₂O)₂)₂(WO₂)₂(BiW₉O₃₃)₂]·18H₂O (1) crystallises in the triclinic crystal system (P1¯) with a = 13.299(3)Å, b = 13.554(3)Å, c = 18.620(4)Å and α = 90.22(3)°, β = 91.99(3)°, γ = 119.16(3)°. Na_5.4K_6.6[(VO)₃(AsW₉O₃₃)₂]·29H₂O ( 2 ) crystallises in the hexagonal space group P6₃/mmc with a = 15.124(3)Å and c = 24.209(5)Å. The polyanion in 1 is isostructural to anions of the M₂X₂W₂₀‐typ with other heteroatoms. They are built up by two β‐B‐[SbW₉O₃₃] fragments, which are derived from defect structures of the Keggin anion. These subunits are connected by two formal WO₂ groups with further stabilisation by addition of two M(H₂O)₃ groups leading to the M₂X₂W₂₀‐type heteropolytungstates. The anion in 2 is a new example of the M₃X₂W₁₈‐type, which contains two α‐B‐[XW₉O₃₃]‐units connected via a belt of three transition metal atoms.     

Investigation of the quantitative properties of the quadrupole orthogonal acceleration time-of-flight mass spectrometer with electrospray ionisation using 3,4-methylenedioxymethamphetamine

This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd.     

Syntheses and X-ray Characterization of Novel [M4(H2O)2(XW9O34)2] n− (M=CuII, X=CuII; and M=FeIII, X=FeIII) Polyoxotungstates

Two novel examples of sandwich type heteropolyanions were synthesized and characterized by X-ray crystal structure and elemental analysis as well as infrared spectroscopy. Na₁₃[H₃Cu₄(H₂O)₂(CuW₉O₃₄)₂]39H₂O (1) and Na₉K[Fe₄(H₂O)₂(FeW₉O₃₄)₂]32H₂O (2) were prepared in aqueous solution by reaction of sodium tungstate with Fe^III and Cu^II cations, respectively. 1 crystallizes in the monoclinic space group P2₁/n (a=13.054(3) Å, b=17.729(4) Å, c=20.998(4) Å, =93.50(3)°), while 2 is triclinic, space group P¯1 (a=12.316(2) Å, b=13.716(3) Å, c=14.925(3) Å, =99.36(3)°, =104.21(3)°, =101.55(3)°). Each anion consists of two [XW₉O₃₄] ^n– moieties (X=Fe^III, n=11 (1) and Cu^II, n=12 (2)) which can be described as -B-isomers of the defect Keggin anion. These units are linked via a belt of four Fe^IIIO₆ or Cu^IIO₆ groups. Two transition metal atoms fill their octahedral coordination sphere with one additional water ligand.     

Investigation of the quantitative properties of the quadrupole orthogonal acceleration time-of-flight mass spectrometer with electrospray ionisation using 3,4-methylenedioxymethamphetamine

This paper describes the investigation of the potential of a quadrupole orthogonal acceleration time-of-flight mass spectrometer (Q-TOF) equipped with an atmospheric pressure ionisation interface for quantitative measurements of small molecules separated by reversed phase liquid chromatography. To this end, the detection limits and linear dynamic range in particular were studied in an LC/MS/MS experiment using 3,4-methylenedioxymethamphetamine standards and 3,4-methylenedioxyethylamphetamine for internal standardisation. In a second phase, the experiment was repeated with real biological extracts (whole blood, serum, and vitreous humour). A calibration for 3,4-methylenedioxymethamphetamine and its metabolite 3,4-methylenedioxyamphetamine was prepared in each of these matrices again using 3,4-methylenedioxyethylamphetamine as internal standard. The resulting quantitative data were compared with those obtained by liquid chromatography with fluorescence detection for the same extracts. The Q-TOF results revealed excellent sensitivity and a linear dynamic range of nearly four decades (2-10 000 pg on-column, r(2) = 0.9998, 1/x weighting). Furthermore, all the calibration curves prepared in biological material were superimposable, LC/MS/MS and LC-fluorescence, and the quantitative results for actual samples compared very favourably. It was concluded that the Q-TOF achieves a linear dynamic range for quantitative LC/MS/MS work exceeding that of fluorescence detection and at much better absolute sensitivity. Copyright 1999 John Wiley & Sons, Ltd.