Complexation equilibria between niobium(V) and 4-(4'H-1',2',4'-triazolyl-3'-azo)-2-methylresorcinol Extraction-spectrophotometric determination of niobium in pyrochlore-bearing rocks

The complexation equilibria between niobium(V) and 4-(1'H-1',2',4'-triazolyl-3'-azo)-2-methylresorcinol has been studied by spectrophotometric methods and graphical and numerical calculation methods. The 1:2 Nb:R complex species formed at pH 6.2 ( = 2.16 x 10(4) l.mole(-1).cm(-1) at 490 nm) allows the determination of 0.15-2.50 ppm Nb. A 1:1 Nb:R complex species can be extracted into n-butanol from 0.1-1.5M hydrochloric acid ( = 1.28 x 10(4) l.mole(-1) .cm(-1) at 510 nm) and Beer's law is obeyed over the range 0.77-4.64 ppm Nb. Interferences and their elimination have been studied and the methods applied to the determination of niobium in pyrochlore-bearing ores.     

Extractive spectrophotometric determination of tungsten(VI) using 3-hydroxy-2-(2'-thienyl)-4-oxo-4H-1-benzopyran

A simple, rapid, highly sensitive and selective spectrophotometric method for the determination of tungsten(VI) in trace amounts is developed using 3-hydroxy-2-(2'-thienyl)-4-oxo-4H-1-benzopyran (HTB) as a reagent for the complexation of metal ion and extracting the 1:2 (metal:ligand) complex into dichloromethane from 0.2 M HCl solution. It obeys Beer's law in the range 0-2.8 microg Wml(-1) with molar absorptivity and Sandell's sensitivity at 415 nm as 6.45 x 10(4) L mol(-1) cm(-1) and 0.0029 microg W(VI) cm(-2), respectively. The method is free from the interference of a large number (39) of elements and handles satisfactorily the analysis of various samples of varying complexity.     

6-Chloro-3-hydroxy-2-(5'-methylfuryl)-4H-chromene-4-one as an analytical reagent for micro determination of molybdenum(VI).

6-Chloro-3-hydroxy-2-(5'-methylfuryl)-4H-chromene-4-one (CHMFC) has been used as an analytical reagent for the spectrophotometric determination of molybdenum. Molybdenum(VI) in the presence of several cations, anions and complexing agents forms a yellow 1:2 complex with CHMFC. The complex is quantitatively extractable into 1,2-dichloroethane from 1 mol dm(-3) acetic acid medium and is stable for more than 6 h. The complex shows an absorption maximum at 438 nm with a molar absorptivity of 5.36 x 10(4) dm3 mol(-1) cm(-1) and Sandell's sensitivity equal to 0.0017 microg Mo cm(-2). The method obeys Beer's law up to 1.9 microg Mo ml(-1). The relative standard deviations are 0.2% for solutions and 0.5-1.5% for solid samples. The method is simple, selective, precise and rapid, and has been satisfactorily applied to the micro determination of molybdenum in various synthetic and standard samples.     

Extraction and complex formation of niobium(V) with 3-hydroxy-2-methyl-1-(4-tolyl)-4-pyridone

The extraction of niobium(V) from aqueous hydrochloric and sulphuric acid solutions with 3-hydroxy-2-methyl-1-(4-tolyl)-4-pyridone (HY) dissolved in chloroform is described. Niobium(V) can be quantitatively extracted with HY in the form of two different complexes depending on the chloride ion concentration in the aqueous phase. At a low chloride concentration or without chloride in the aqueous phase niobium(V) is extracted with HY in the form of Nb(OH)₃Y₂ and at a high chloride concentration as a mixed Nb(OH)₃ClY complex. Niobium extraction with HY enables the separation of niobium(V) from zirconium(IV) and hafnium(IV). The formation of a mixed chloro-4-pyridone complex is also applicable for the spectrophotometric determination of niobium in the organic phase at the maximum absorption at 350 nm.     

Threshold photoionization and density functional theory studies of the niobium carbide clusters Nb3C(n) (n = 1-4) and Nb4C(n) (n = 1-6)

We have used photoionization efficiency spectroscopy to determine ionization potentials (IP) of the niobium-carbide clusters, Nb3C(n) (n = 1-4) and Nb4C(n) (n = 1-6). The Nb3C2 and Nb4C4 clusters exhibit the lowest IPs for the two series, respectively. For clusters containing up to four carbon atoms, excellent agreement is found with relative IPs calculated using density functional theory. The lowest energy isomers are mostly consistent with the development of a 2 x 2 x 2 face-centered cubic structure of Nb4C4. However, for Nb3C4 a low-lying isomer containing a molecular C2 unit is assigned to the experimental IP rather than the depleted 2 x 2 x 2 nanocrystal isomer. For Nb4C5 and Nb4C6, interpretation is less straightforward, but results indicate isomers containing molecular C2 units are the lowest in energy, suggesting that carbon-carbon bonding is preferred when the number of carbon atoms exceeds the number of metal atoms. A double IP onset is observed for Nb4C3, which is attributed to ionization from the both the lowest energy singlet state and a meta-stable triplet state. This work further supports the notion that IPs can be used as a reliable validation for the geometries of metal-carbide clusters calculated by theory.     

Synthesis and Crystal Structure of 2（1-Phenyl-3-methyl-5-chloro-1H-pyrazol-4-yl）-3-（1-naphthoylamido）-4-thiazolidinone

1INTRODUCTIONManypyrazolederivativeshavebeenreportedtoshowvariousbiologicalactivitiestobeusedasbactericide[1],fungicide[2],herbicide[3],insecticide[4]andvirucide[5]agents.Inaddition,4-thiazolidinoneplaysavitalroleowingtoitswiderangeofbiologi-calactivities…     

Extractive photometric determination of gold(III) with 1-(2',4',6'-trichlorophenyl)-4,4,6-trimethyl-(1H,4H)-2-pyrimidinethiol in presence of tri-iso-octylamine

Tervalent gold was determined spectrophotometrically as its anionic 1:4 gold-thiol complex extracted into chloroform from aqueous acidic medium (1.5M sulphuric acid) in the presence of tri-iso-octylamine. The complex exhibits maximum absorption at 480 nm (molar absorptivity 4.60 x 10(3) l.mole(-1).cm(-1)) and Beer's law is obeyed in the concentration range 5-50 microg of gold(III) per ml. The relative standard deviation and relative error, calculated from ten determinations of solutions containing 15 microg of gold(III) per ml were 1.0% and 0.8%. The method is simple, selective and reproducible. It permits separation of gold(III) from associated elements and its determination in synthetic mixtures.     

Interaction of nickel with 4-(2'-benzothiazolylazo) salicylic acid (BTAS) and simultaneous first-derivative spectrophotometric determination of nickel(II) and iron(III)

The solution properties of nickel complex with 4-(2'-benzo-thiazolylazo) salicylic acid (BTAS) have been studied by zero-order absorption spectrophotometry in 40% (v/v) ethanol at 20 degrees C and an ionic strength of 0.1 mol dm(-3) (KNO(3)). The equilibria that exist in solution were established and the basic characteristics of complexes formed were determined. A new direct spectrophotometric method for the determination of trace amounts of the nickel is proposed based on the formation of the Ni (BTAS) complex at pH 7.0. The absorption maximum, molar absorbtivity, and Sandell's sensitivity of 1:1 (M:L) complex are 525 nm, 0.6 x 10(4) l mol(-1) cm(-1) and 2.824 x 10(-9) microg cm(-2), respectively. The use of first-derivative spectrophotometry eliminates the interference of iron and enables the simultaneous determination of nickel and iron using BTAS. Quantitative determination of Ni(II) and Fe(III) is possible in the range (0.59-7.08) and (2.1-8.4) microg ml(-1), respectively with a relative standard deviation of 0.5%. The proposed method has been successfully applied to the simultaneous spectrophotometric determination of nickel and iron in steel alloys and aluminum alloys.     

4-(N,N-diethylamino) benzaldehyde thiosemicarbazone in the spectrophotometric determination of palladium

4-(N,N-diethylamino)benzaldehyde thiosemicarbazone(DEABT) is proposed as a sensitive and selective analytical reagent for the spectrophotometric determination of palladium(II). The reagent reacts with palladium (II) in a potassium hydrogen phthalate-hydrochloric acid buffer of pH 3.0, to form a yellow complex. Beer's law is obeyed in the concentration range up to 3.60 microgmL(-1). The optimum concentration range for minimum photometric error as determined by Ringbom plot method is 0.36 - 3.24 microg mL(-1). The yellow Pd(II)-DEABT complex shows a maximum absorbance at 408 nm, with molar absorptivity of 3.33 x 10(4) dm3 mol(-1) cm(-1) and Sandell's sensitivity of the complex from Beer's data, for D = 0.001, is 0.0032 microg cm(-2). The composition of the Pd(II)-DEABT complex is found to be 1:2 (M:L). The interference of various cations and anions in the method were studied. The proposed method was successfully used for the determination of Pd(II) in alloys, catalysts, complexes and model mixtures with a fair degree of accuracy.     

Tris(1-4-eta 4-anthracene)niobate(1-), the first polyaromatic hydrocarbon complex of niobium

The first tris(arene)niobium complex, [Nb(1-4-eta 4-anthracene)3]-, has been obtained by the sodium or potassium anthracene reduction of NbCl4(THF)2, structurally characterized by X-ray analysis and shown to undergo facile anthracene displacement reactions in the presence of excess CO, PF3, 1,3,5,7-cyclooctatetraene and P(OMe)3.     

1-(2-hydroxy-3-methoxybenzylideneamino)-8-hydroxynaphthalene-3,6-disulfonic acid as a reagent for the spectrophotometric determination of boron in ceramic materials

A sensitive and selective spectrophotometric method for the determination of boron is described. The method is based on the colour reaction between boron and the reagent 1-(2-hydroxy-3-methoxybenzylideneamino)-8-hydroxynaphthalene-3,6-disulfonic acid (HMOA). In a HOAc-NH4OAc buffer of pH 5.5, HMOA reacts with boron to form a 1:2 yellow complex with a maximum absorption at 423 nm. The absorbance (lambdamax = 423 nm) is linear up to 1.2 microg ml(-1) boron in aqueous solution with a repeatability (RSD) of 1.12%. The molar absorptivity and Sandell's sensitivity are 7.19 x 10(3) l mol(-1) cm(-1) and 0.0015 microg cm(-2), respectively. The limit of quantification and limit of detection were found to be 17.1 and 5.2 ng ml(-1), respectively. The interference of various ions was examined in detail. All the metal ions studied can be tolerated in considerable amounts; in particular, the tolerance limits of Fe, Al, Zn, Ca and Mg are superior to those of other reagents such as Azomethine-H and Azomethine-HR. The proposed method was applied to the determination of boron in ceramic materials with satisfactory results.     

Synthesis and Crystal Structure of 2-（4-Fluoro-2-（4-fluorophenoxy）phenyl）-1-（1H- 1,2,4-triazol-1-ylmethyl）-3-methoxy-isopropy Alcohol

The title compound 2-（4-fluoro-2-（4-fluorophenoxy）phenyl）-1-（1H-1,2,4-triazol- 1-ylmethyl）-3-methoxy-isopropy alcohol has been synthesized by the treatment of 1-[2-（4-fluoro- 2-（4-fluorophenoxy）phenyl）-2,3-epoxypropyl]-1H-1,2,4-triazole with sodium methoxide. It belongs to orthorhombic, space group P212121, with a = 9.7229（19）, b = 11.516（2）, c = 16.047（3）A, C18H17F2 N3O3, Mr = 361.35, V = 1796.7（6）A^3, Z = 4, Dc = 1.3359 g/cm^3, F（000） = 752, p = 0.106 mm^-1, the final R = 0.0329 and wR = 0.0803 for 1821 unique reflections. The dihedral angles made by the triazole ring with two benzene rings are 43.56（3） and 54.78（2）°, respectively. The intermolecular hydrogen bond in the crystal lattice plays an important role in stabilizing the structure.     

Synthesis and Crystal Structure of 2-(4-Fluoro-2-(4-fluorophenoxy) phenyl)-1-(1H-1,2,4-triazol-l-ylmethyl)-3-methoxy-isopropy Alcohol

The title compound 2-(4-fluoro-2-(4-fluorophenoxy)phenyl)-1-(1H-1,2,4-triazol-z 1-ylmethyl)-3-methoxy-isopropy alcohol has been synthesized by the treatment of 1-[2-(4-fluoro-2-(4-fluorophenoxy)phenyl)-2,3-epoxypropyl]-1H-1,2,4-tdazole with sodium methoxide. It be-longs to orthorhombic, space group P212121, with a=9.7229(19), b=11.516(2), c=16.047(3) A, C18H17F2N3O3, Mr-361.35, V=1796.7(6) A3, Z=4, Dc=1.3359 g/cm3, F(000)=752,μ=0.106 mm-1, the final R=0.0329 and wR=0.0803 for 1821 unique reflections. The dihedral angles made by the triazole ring with two benzene rings are 43.56(3) and 54.78(2)°, respectively. The intermolecular hydrogen bond in the crystal lattice plays an important role in stabilizing the structure.     

Molecular and Crystal Structure of 1-(4-Chlorophenyl)-3-(2-nitrophenyl)-1-triazene

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Li(+) ion conductivity in rock salt-structured nickel-doped Li(3)NbO(4)

Two mechanisms of doping Li(3)NbO(4), which has an ordered, rock salt superstructure, have been established. In the "stoichiometric mechanism", the overall cation-to-anion ratio is maintained at 1:1 by means of the substitution 3Li(+) + Nb(5+) --> 4Ni(2+). In the "vacancy mechanism", Li(+) ion vacancies are created by means of the substitution 2Li(+) --> Ni(2+). Solid solution ranges have been determined for both mechanisms and a partial phase diagram constructed for the stoichiometric join. On the vacancy join, the substitution mechanism has been confirmed by powder neutron diffraction; associated with lithium vacancy creation, a dramatic increase in Li(+) ion conductivity occurs with increasing Ni content, reaching a value of 5 x 10(-4) Omega(-1) cm(-1) at 300 degrees C for composition x= 0.1 in the formula Li(3-2x)Ni(x)NbO(4). This is the first example of high Li(+) ion conductivity in complex oxides with rock salt-related structures.     

Syntheses and Crystal Structures of （S）-Methyl 2-（4-R-phenylsulfonamido）-3-（1H-indol-3-yl）propanoate （R = H （1） and Cl （2））

The title compounds （S）-methyl-2-（4-R-phenylsulfonamido）-3-（1H-indol-3- yl）propanoate （R = H （1）, Cl （2）） have been synthesized and their crystal structures also have been determined by X-ray single-crystal diffraction. Compound 1 （C18H18N2O4S） belongs to orthorhombic, space group P212121 with a = 9.6348（14）, b = 11.1517（17）, c = 16.412（3） A, V = 1763.4（5） A^3, Mr = 358.40, Z = 4, De = 1.350 g/cm^3,/t = 0.209 mm^-1, F（000） = 752, R = 0.0348 and wR = 0.0714. Compound 2 （CI8H17ClN2O4S） crystallizes in orthorhombic, space group P212121 with a = 9.3128（14）, b = 10.9655（16）, c = 17.783（3） A, V = 1815.9（5） A^3, Mr = 392.85, Z = 4, De = 1.437 g/cm^3, p = 0.352 mm^-1, F（000） = 816, R = 0.0389 and wR = 0.0845. The absolute structure Flack parameters X of compounds 1 and 2 are -0.03（8） and -0.06（7）, respectively. X-ray analysis reveals that the crystal structures of these two compounds both involve two intermolecular N-H…O hydrogen bond＇s.     

Synthesis and Crystal Structure of 1＇-Methyl-4＇-（4-chlorophenyl）-1H-indole-3-spiro-2＇-pyrrolidine-3＇-spiro-4＂-（2＂-phenyloxazole）-2,5＂（3H,4＂H）-dione

The title compound （C26H20ClN3O3） has been synthesized by 1,3-dipolar cycloaddition reaction from isatin, sarcosine and （Z）-4-（4-chlorobenzylidene）-2-phenyloxazol-5（4H）-one through a one-pot procedure, and its structure was confirmed by IR, IH NMR, elemental analysis and single-crystal X-ray diffraction analysis. The crystal belongs to the triclinic system, space group PI, with a = 9.3903（19）, b = 11.398（2）, c = 12.603（3） A, α = 83.495（3）, β = 68.988（3）, γ = 67.178（3）^o, V= 1160.1（4）A^3 Z = 2, Mr= 457.90, Dc= 1.311 g/cm^3, p = 0.198 mm ^-1, F（000） = 476, the final R = 0.0489 and wR = 0.1144 for 3109 observed reflections with I 〉 2σ（I）.     

CRYSTAL AND MOLECULAR STRUCTURE OF THE HEXANUCLE-AR DIAZENIDO-OXOMOLYBDATE [(n-C_4H_9)_4N]_3[Mo_6O_(18)-(N_2C_6H_3-2,4-(NO_2)_2]

<正> Crystal of the title complex [(n-C4H9)4N]3[Mo6O18(N2C6H3-2,4-(NO2)2](Mr= 1710. 5) is orthorhombic with space group P21cn (Pna21), a = 17. 304(3), b = 17.580(2), c=24. 355(4) (?), V = 7409(2)(?)3, Z = 4, Dc=1. 60g/ cm3, μ=10. 29cm-1, F (000) = 3647. The structural solutions and refinements based on 3900 reflections (I≥3σ(I)) converged at R = 0. 0575, Rw =0. 0498. The atoms of Mo(3), Mo(4), O(1), O(5), O(9), O(11) and the [N2C6H3-2,4-(NO2)2] unit in the complex anion locate approximately in a plane about which the complex anion is nearly symmetrical.     

Synthesis, Structure and Photoluminescence of(CH3-4, 4'-H2bipy)-(HgCl4)with CH3-4, 4'-H2bipy Generated in Situ

A novel viologen(4,4'bipyridinium)-based complex(CH3-4,4'-H2bipy)(HgCl4)(1),in which the CH3-4,4'-H2bipy(MQ2+)was generated in situ,has been synthesized via hydrothermal reaction and structurally characterized.Complex 1 crystallizes in the space group P21/c of monoclinic system with four formula units in a cell:a = 8.1848(6),b = 21.809(2),c = 9.0285(6)(A),β =.107.377(1)°,V= 1538.0(2)(A)3,C11H11Cl4HgN2,Mr = 513.61,Dc = 2.218 g/cm3,S = 1.009,μ(MoKα)= 10.685 mm-1,F(000)= 956,R = 0.0360 and wR = 0.0812.The crystal structure analysis reveals that the title complex features an isolated structure based on a CH3-4,4'-H2bipy moiety and a mercury atom terminally bound by four chlorine atoms.Photoluminescence investigation reveals a strong emission in blue region,which may originate from π→π* charge-transfer interaction of the CH3-4,4'-H2bipy moiety.     

A rapid and sensitive extractive spectrophotometric determination of palladium(II) in synthetic mixtures and hydrogenation catalysts using pyridoxal-4-phenyl-3-thiosemicarbazone.

A rapid and sensitive extractive spectrophotometric method has been developed for the determination of palladium(II) in synthetic mixtures and hydrogenation catalysts using pyridoxal-4-phenyl-3-thiosemicarbazone (PPT) as an analytical reagent. The reagent forms a red-color complex with the metal at pH 3.0, which is extracted into benzene. The absorbance is measured at 460 nm. The method adheres to Beer's law up to a concentration range of 0.4-6.4 microg cm(-3). The molar absorptivity and Sandell's sensitivity are 2.20 x 10(4) dm3 mol(-1) cm(-1) and 4.85 x 10(-3) microg cm(-2), respectively. The correlation coefficient of the Pd(II)-PPT complex is 0.99, which indicates an excellent linearity between two variables. The detection limit of this method is 0.05 microg cm(-3). The instability constant of the Pd(II)-PPT complex calculated from Edmond and Birnbaum's method is 2.90 x 10(-5) and that of Asmus' method is 2.80 x 10(-5) at room temperature. The concurrent repetition of the method is checked and the relative standard deviation (RSD) (n = 5) was derived as 1.84 percent. The present method was applied to the determination of palladium(II) in synthetic mixtures and hydrogenation catalysts. The results were compared by employing an atomic-absorption spectrometer.