Ultrasensitive chemiluminescence detection of aM vanadium(IV) by capillary electrophoresis

Ultrasensitive chemiluminescence (CL) detection of aM vanadium(IV) in capillary electrophoresis (CE) is first reported. In this work, inclusion of the luminol in the electrophoretic carrier electrolyte avoids the loss of light signal that occurs when luminol and hydrogen peroxide are mixed in advance, as in the conventional method in CE-CL detection. The detection limit (S/N ratio=3) for V(IV) is 2.4×10⁻¹⁷ M (24 aM), which has been improved by a factor of 10⁴ as compared with that of the most sensitive metal ion detection (Co²⁺ 0.5 pM) reported previously. In addition, the separation of V(IV) and V(V) has been performed successfully.     

Reaktionen und thermisches Verhalten oxofreier Vanadium(IV)-Komplexe. Kristallstrukturen von Methoxo-oxo[thenoyltrifluoraceton-salicylhydrazonato(2−)]vanadium(V) und Methoxo-oxo[benzoylaceton-salicylhydrazonato(2−)]vanadium(V)

Reactions and Thermal Behaviour of Nonoxo Vanadium(IV) Complexes. Crystal Structures of Methoxo-oxo[thenoyltrifluoroacetone-salicylhydrazonato(2–)]vanadium(V) and Methoxo-oxo[benzoylacetone-salicylhydrazonato(2–)]vanadium(V) The persistence of non-oxo vanadium(IV) complexes in dichlormethane/methanol/water solutions was studied by UV/VIS spectroscopy. The reaction products methoxo-oxo-[thenoyltrifluoroacetone-salicylhydrazonato(2–)]vanadium(V) and methoxo-oxo[benzoylacetone-salicylhydrazonato(2–)]vanadium(V) were isolated and characterized by X-ray analysis. The thermal behaviour of non-oxo vanadium(IV) complexes was checked.     

Photochemistry of tris(pyrazolyl)borate titanium(IV) complexes

The electronic features and photochemistry of TpTiCl₃ (1) (Tp = hydrotris(pyrazol-1-yl)borate) and Tp*TiCl₃ (2) (Tp* = hydrotris(3,5-dimethylpyrazol-1-yl)borate) were studied in THF. Reactive decay of the excited states produced either (or ) and metal center Ti(III) radicals via homolytic cleavage of the Tp → Ti (Tp* → Ti) bond. Cleavage of the Tp → Ti and the Tp* → Ti bond as a primary photoprocess is shown to be consistent with LMCT Tp → Ti and Tp* → Ti excitation. TpTiCl₂(THF) (3) and Tp*TiCl₂(THF) (4) were also prepared by stoichiometric reduction of 1 and 2 with Li₃N. The THF ligand in 3 and 4 was replaced by the stable nitroxyl radical TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) to provide the new complexes TpTiCl₂(TEMPO) (5) and Tp*TiCl₂(TEMPO) (6) in which the TEMPO ligand is η¹ coordinated to Ti(IV). Photolysis of 5 and 6 generate Ti(III) and the TEMPO radical in the primary photochemical step.     

Darstellung und Eigenschaften von Vanadyl(IV)-Saccharinat

Summary The synthesis of a new vanadyl(IV)/saccharin complex is reported. Its bonding characteristics differ considerably from all known divalent metal-saccharinates. In this complex a VO(OH)⁺ moiety is coordinated to a saccharin molecule through its carbonyl oxygen and to a saccharinate ion through its deprotonated nitrogen. Two water molecules complete the coordination sphere. X-ray powder diagrams, infrared- and electronic absorption-spectra were recorded and analyzed for the characterization of the compound and its coordination properties. Besides, the magnetic susceptibility and the thermal behaviour were also investigated.

     

Structural study of C,N‐chelated monoorganotin(IV) halides

Three monoorganotin(IV) compounds of general formula L^CNSnX₃, where L^CN is a 2‐(dimethylaminomethyl)phenyl‐ group and X = Cl ( 1 ), Br ( 2 ) and I ( 3 ), were prepared and characterized using XRD and NMR techniques. Compound 1 reacts with moisture producing [(L^CN)₂HSnCl₂]⁺ [L^CNSnCl₄]^?. Compound 3 decomposes to (L^CN)₂SnI₂, SnI₂ and I₂ when heated. Compound 2 was reacted with NH₄F yielding an equilibrium of fluorine‐containing species. The major products were [L^CNSnF₅]^2? and [(L^CNSnF₃)₂(µ²‐F)₂]^2? (4a). When compound 2 was reacted with another fluorinating agent, L^CN(n‐Bu)₂SnF, an oligomeric product, [L^CNSnF₂(µ²‐F)₂]_n, was observed. Further addition of NH₄F led to subsequent formation of 4a. The structure of fluorinated products was investigated by ¹H, ¹⁹F and ¹¹⁹Sn NMR spectroscopy. Copyright © 2006 John Wiley & Sons, Ltd.     

Struktur von Bis[salicylaldehyd-2-hydroxyanilato(2—)]vanadium(IV)

Molecular Structure of Bis[salicylaldehyde-2-hydroxyanilato(2—)]vanadium(IV) By the reaction of tris(acetylacetonato)vanadium(III) with salicylaldehyde-2-hydroxyanil the non-oxo vanadium(IV) complex of this ligand was prepared. Bis[salicylaldehyde-2-hydroxyanilato(2—)]vanadium(IV) has a distorted octahedral structure. Crystallographic data see “Inhaltsübersicht”.     

Bioactive versatile azomethine complexes of organotin(IV) and organosilicon(IV)

Diorganotin(IV) and diorganosilicon(IV) derivatives of the types R₂MCl(TSCZ) and R₂M(TSCZ)₂ (where TSCZ is the anion of a thiosemicarbazone ligand, R=Ph or Me and M=Sn or Si) have been synthesized and characterized by elemental analyses, molecular weight determinations and conductivity measurements. The mode of bonding has been established on the basis of IR and ¹H, ¹³C ²⁹Si and ¹¹⁹Sn NMR spectroscopic studies. Some of the representative complexes have also been evaluated for their antimicrobial effects on different species of pathogenic fungi and bacteria in vivoas well as in vitro.The results of these investigations are reported. © 1998 John Wiley & Sons, Ltd.     

Electrochemical and Spectroscopic Behaviour of Bis(2‐mercaptopyridine‐N‐oxide)oxovanadium(IV)

The complex [VO(MPO)₂] (MPO = deprotonated 2‐mercaptopyridine N‐oxide) was synthesized and characterized by IR spectroscopy. Its electrochemical behaviour was investigated by cyclic voltammetry in different organic solvents. The V^IV/V^V and V^IV/V^III couples could be identified. The nature of the electroactive species is strongly dependent on the solvent. The results are discussed in terms of a reaction mechanism describing the characteristics of the electron transfer processes and the involved chemical reactions, and the stability of the complex in each solvent was also determined. The electronic spectra of the investigated solutions gave additional support to the proposed mechanisms.     

Adsorption of metal anions of vanadium(V) and chromium(VI) on Zr(IV)-impregnated collagen fiber

The metal anions of vanadium (V) and chromium (VI) in aqueous solution can be effectively adsorbed by Zr(IV)-impregnated collagen fiber (ZrICF). The maximum adsorption capacity of V(V) takes place within the pH range of 5.0 to 8.0, while that of Cr(VI) is within the pH range of 6.0 to 9.0. When the initial concentration of metal ions was 2.00 mmol L⁻¹ and the temperature was 303 K, the adsorption capacity of V(V) on Zr-ICF was 1.92 mmol g⁻¹ at pH 5.0, and the adsorption capacity of Cr(VI) was 0.53 mmol g⁻¹ at pH 7.0. As temperature increased, the adsorption capacity of V(V) increased, while that of Cr(VI) was almost unchanged. The adsorption isotherms of the anionic species of V(V) and Cr(VI) can be fit by the Langmuir equation. The adsorption rate of V(V) follows the pseudo-first-order rate model, while the adsorption rate of Cr(VI) follows the pseudo-second-order rate model. Furthermore, ZrICF shows high adsorption selectivity to V(V) in the mixture solution of V(V) and Cr(VI). Practical applications of ZrICF could be expected in consideration of its performance in adsorption of V(V) and Cr(VI).     

Products and kinetics of non-isothermal decomposition of vanadium(IV) oxide compounds

The kinetics of dehydration and decomposition of VOSO₄·2H₂O, VOSO₄ and VOSeO₃·H₂O was studied under non-isothermal heating on a derivatograph. The stages and products of the thermal decomposition were determined. It was proved that VOSO₄·2H₂O decomposes to V₂O₅ while VOSeO₃·H₂O − to V₂O₄. A number of kinetic models and calculation procedures were used to determine the values of the kinetic parameters characterizing the process. The parameters calculated were compared and analyzed. IR-spectra of the initial substances and the solid residue after decomposition are presented.     

Spectroscopic and Electrochemical Behavior of the Methyl and Ethyl Derivatives of Bis(acetylacetonato) oxovanadium(IV)

The infrared, Raman and electronic spectra of the oxovanadium (IV) complexes of the 3‐methyl and 3‐ethyl substituted acetylacetone were recorded and discussed in detail, in comparison with that of the bis(acetylacetonato) complex and on the basis of the known structural data of these compounds. The electrochemical behavior of the three complexes was investigated by cyclic voltammetry in DMSO solutions, and the mechanism of the involved processes is briefly discussed.     

Oxofreie Vanadium(IV)-Komplexe mit dreizähnigen diaciden Liganden. Struktur von Bis[2,2′-dihydroxy-azobenzenato(2−)]vanadium(IV)

Non-oxo Vanadium(IV) Complexes with Tridentate Diacidic Ligands. Molecular Structure of Bis[2.2′-dihydroxy-azobenzenato(2?)]vanadium(IV) By the reaction of tris(acetylacetonato)vanadium(III) with tridentate diacidic ligands non-oxo vanadium(IV) complexes of these ligands were synthesized. The complexes were characterized by mass spectrometry. Electrochemical studies show that the complexes are reversibly oxidized or reduced. Bis[2,2′-dihydroxy-azobenzenato(2?)]vanadium(IV) has a distorted trigonal-prismatic structure. Crystallographic data see ?Inhaltsübersicht”?.     

Darstellung und spektroskopische Charakterisierung von bindungsisomeren Halogenoselenocyanato-Osmaten(IV) und -Rhenaten(IV)

Preparation and Spectroscopic Characterization of Bond Isomeric Halogenoselenocyanato-Osmates(IV) and -Rhenates(IV) By oxidative ligand exchange of appropriate chloro-iodo complexes of Os^IV or Re^IV with (SeCN)₂ in CH₂Cl₂ or by heterogeneous reaction with Pb(SeCN)₂ or AgSeCN in CH₂Cl₂ the new complexes cis-[OsCl₄(NCSe)(SeCN)]^2?, tr.-[OsCl₄Br(NCSe)]^2?, tr.-[OsCl₄Br(SeCN)]^2?, [ReCl₅(NCSe)]^2?, [ReCl₅(SeCN)]^2?, tr.-[ReCl₄I(NCSe)]^2?, tr.?[ReCl₄(NCSe)(SeCN)]^2? and tr.?[ReCl₄(NCSe)₂]^2? are formed and isolated as pure compounds by ion exchange chromatography on DEAE-cellulose. The bond isomers are significantly distinguished by the frequencies of innerligand vibrations: n?_CN(Se) > n?_CN(N); n?_CSe(N) > n?_CSe(Se); δ_NCSe > δ_SeCN. The electronic spectra (10 K) of the solid salts reveal a bathochromic shift for the charge transfer bands of the Se isomers as compared with the corresponding N isomers. The intra-configurational transitions are observed for the Os^IV complexes at 600 to 2400 and for the Re^IV complexes at 500 to 1600 nm. The ⁷⁷Se nmr signals of the Os^IV bond isomers are registrated for Se binding in the region 970 to 1040 ppm, for N coordination downfield at 1540 to 1640 ppm.     

Zur Synthese von Bor-Schwefel(IV)-Stickstoff-Heterocyclen

Synthesis of Boron-Sulfur(IV)-Nitrogen Heterocycles The reaction of bis(lithio.tert.-butylamino)phenylborane with tert.-butyldichlorosulfimide and bischlorodimethylsilylsulfodiimide respectively leads to four- or eight-membered heterocycles. The disulfanebridge of one dithiazadiborolidine can be replaced by the ? N?S?N-sequence to yield a Thiatriazadiborine. ¹H, ¹¹B, ¹³C-NMR, mass spectra, and analytical data are reported and discussed.     

17O NMR spectra of some butyltin(IV) acetates

The ¹⁷O NMR spectra of ¹⁷O isotope‐enriched tributyltin(IV) acetate (1) and dibutyltin(IV) diacetate (2) were recorded in various solvents over wide temperature ranges. Only a single ¹⁷O signal was observed for both oxygen atoms of the —COOSn—groups under these experimental conditions, in both non‐coordinating and coordinating solvents. The ¹⁷O NMR spectra of tert‐butyl acetate (3) were obtained for comparison. Copyright © 2002 John Wiley & Sons, Ltd.     

Structural Studies on Dimethyltin(IV) Carboxylates

In order to correlate ¹¹⁹Sn Mössbauer parameters and structural data for dimethyltin(IV) derivatives, the molecular structures of bis(acetato)dimethyltin(IV) and bis(trifluoroacetato)dimethyltin(IV) were determined by single crystal X-ray diffration. Crystals of Me₂Sn(OOCCH₃)₂ are monoclinic, a = 26.282(4), b = 5.282(1), c = 14.434(3) Å, β = 101.17(2)°, Z = 8, space group C2/c, and those of [Me₂Sn(OOCCF₃)₂]_n are monoclinic, a = 8.444(1), b = 17.689(1), c = 15.368(1) Å, β = 93.013(9)°, Z = 8, space group Cc. The structures were solved by the Patterson method and were refined by full-matrix least-squares procedures to R = 0.025 and 0.027 (R_w = 0.023 and 0.030) for 2 298 and 4 182 reflections with I ≥ 3σ(F²), respectively.     

Kinetic studies on the reduction of a nickel (III) oxime-imine complex by sulphur(IV) and selenium(IV)

The kinetics of the reduction of [Ni^III(L¹)]²⁺ (where HL¹ = 15-amino-3-methyl-4,7,10,13-tetraazapentadec-3-en-2-one oxime) by sulphur(IV) and selenium (IV) over the regions pH 2.50–8.02 and 2.01–4.00 respectively have been investigated at 30°C. Attempts were made to evaluate the reactivity of all the reacting species, of sulphur(IV) and selenium(IV) by considering suitable pH ranges. The oxidation of SC₂·H₂O and HSO ₃ ⁻ is proposed to proceed through the formation of a hydrogen-bonded adduct. The reaction with SO ₃ ²⁻ seems to follow a direct outer-sphere route which is well supported by Marcus crossrelation calculation. The oxidation of HSeO _l3 ⁻ is ≈ 10³ times slower than that of H₂SeO₃. The kinetic data indicate that the oxidation of sulphur(IV) by [Ni^IIIL¹)]²⁺ is much more favourable as compared to the corresponding oxidation of selenium(IV).     

Synthesis, characterization and crystal structures of new bidentate Schiff base ligand and its vanadium(IV) complex: The catalytic activity of vanadyl complex in epoxidation of alkenes

The Schiff base ligand N-salicylidin-2-bromoethylimine (L) and its vanadium(IV) complex, VOL₂ (1), were synthesized and characterized by using X-ray, CHN, ¹H NMR and FT-IR methods. X-ray analysis shows the Schiff base ligand L acts as a bidentate (O, N) chelating ligand and coordinates via imine nitrogen and phenolato oxygen atoms to the V(IV) center. The coordination geometry around the V(IV) center in 1 is approximately square pyramidal, as indicated by the unequal metal-ligand bond distances and angles, with the basal plane formed by the N₂O₂ donors of the two bidentate Schiff base ligands, the two phenolato O atoms and the two imine N atoms are in the trans position. The coordination sphere of the V(IV) is completed by one oxygen atom in apical position. In the Schiff base ligand, L, there are some classical intramolecular O1-H1?N1 and non-classical intermolecular C9-H9b?O1 hydrogen bonds, while in 1, there are two non-classical intermolecular C7-H7?O3 and C8-H8b?O3 hydrogen bonds. The catalytic activity of 1 in epoxidation of cyclooctene was investigated in different conditions to obtain optimum conditions. The effects of solvent, oxidant, catalyst concentration and alkene/oxidant ratio were studied and the results showed that in CCl₄ in the presence of tert-butylhydroperoxide in 1:3 alkene/oxidant ratio, high epoxide yield was obtained. The epoxidation of alkenes was also carried out in optimized conditions that high catalytic activity and selectivity were obtained.     

Oxovanadium(IV) complexes of halogenated oxines

Summary Six VO²⁺ complexes of 8-hydroxyquinoline (oxine) and of some of its mono- and dihalogenated derivatives have been prepared. The complex of 5-chloro-oxine is very unstable and oxidizes rapidly, generating a V(V) complex of stoichiometry VO(QCl)₂OH which could also be prepared in pure form. The infrared spectra of all complexes have been recorded and are discussed in detail. The complexes containing halogenated ligands appear as polymeric species, interacting through V=O...V=O bridges. The magnetic moments, investigated at room temperature, indicate completely quenched orbital contributions. The analysis of the electronic spectra reveals very complex solution behaviour including, oxidation phenomena, ligand loss, and interaction with the solvent.

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Oxovanadium(IV)-Komplexe von halogenierten Oxinen

Zusammenfassung Sechs VO²⁺-Komplexe von 8-Hydroxyquinolin (Oxin) und einige seiner mono- und dihalogenierten Derivate wurden dargestellt. Der Komplex des 5-Chloroxins erwies sich als besonders instabil und oxidiert sehr schnell unter Bildung eines V(V)-Komplexes der Stöchiometrie VO(QCl)₂OH, welcher auch in reiner Form dargestellt werden konnte. Die Infrarotspektren aller Komplexe wurden aufgenommen und werden eingehend diskutiert. Die Komplexe mit halogenierten Liganden erscheinen als polymere Spezies, welche über V=O...V=O-Brücken wechselwirken. Die bei Raumtemperatur gemessenen magnetischen Momente zeigen die totale Abwesenheit von Orbitalbeiträgen. Die Analyse der Elektronenspektren weist auf ein besonders kompliziertes Lösungsverhalten hin, welches Oxidationsphänomene, Ligandenabspaltung und Wechselwirkung mit den Lösungsmitteln einschließt.