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1.
A new catalytic Spectrophotometric method for the determination of trace amounts of molybdenum (VI) has been proposed. The method is based on the catalytic effect of Mo(VI) on the reduction of metanil yellow by hydrazine dihydrochloride. Under experiment condition, the linear range of determination is 20–160 ng/mL for molybdenum and the detection limit is 11.2ng/mL. The method has been used to determine trace molybdenum in bean samples with the recovery of 96.0–99.0%, with relative standard deviations of 1.50–2.53%.  相似文献   

2.
The formation of a new ternary ion-associate complex of vanadium(V) with 2,3-dihydroxynaphthalene and iodonitrotetrazolium chloride with a composition ratio of 1:2:1 is reported. The complex is quantitatively extracted from water into chloroform. The molar absorptivity (ɛ) of the extract at λ max=340 nm is 2.5 × 104 dm3/mol cm, and Beer’s law is obeyed for concentrations ranging from 0.1 to 0.9 μg/cm3 V(V). The following constants are determined: the extraction constant, the association constant, the distribution constant, and the recovery factor. The effects of foreign ions and reagents are studied. A selective and sensitive method is developed for determination of vanadium in steels.  相似文献   

3.
《Analytical letters》2012,45(3):141-152
Abstract

The complex formed between molybdenum(VI) and benzoylacetanilide in the pH range 0.6 and 1.9 has been extracted into methyl isobutyl ketone and the absorbance has been measured at 410 mμ. Quantities of 0.15 to 2.10 mg of molybdenum have been determined with a standard deviation of 0.6%. The color is stable up to 2 hours. The presence of Co2+, Ni2+, Zn2+, Mn2+, Be2+, Al3+, Cr3+, Ce4+, Th4+ or UO2+ 2 up to 100 μg causes no interference. Ordinarily, Fe3+ interferes with the determination, but when masked with 1 ml of 0.5% solution of ascorbic acid the tolerance limit is 10 mg. Thus, molybdenum can be determined in steel when present in amounts as low as 0.26%.  相似文献   

4.
1INTRoDUCTIONMolybdenumintheVandVIoxidationstatesformsaconsiderablenumberofoxocomplexes.Someofthemareactivecatalystsfortheoxidationoforganicsub-stracts[li'Allthesefactshavewidelyarousedchemists'interest.lnordertoobservetheeffectofthedonorgroupsonthedegreeofcomplexaggregationandonthecoor-dinationgeometry,thetitlecompoundwaspreparedbythereactionof(n-Bu'N)'-[Mo,O,,jwitho-mercaptophenolandthesinglecrystalswereobtained.Itcontainsa[Mo,O,j' core.Somereleventreportscanbefoundinthepreviousliter…  相似文献   

5.
A one-pot, three-component reaction of 2,3-dihydroxynaphthalene, aromatic aldehydes, and cyclic 1,3-dicarbonyl compounds in the presence of formic acid catalyst under solvent-free conditions provides access toward a new class of tetrahydrobenzo[a]xanthen-11-ones and naphthopyranopyrimidines. The scope of the process was explored under two different reaction conditions resulting in the generation of title compounds in high yields. Moreover, the key advantages of this process are cost effectiveness of catalyst, short reaction times, easy workup, and purification of products by nonchromatographic methods.  相似文献   

6.
Lubal P  Koprivová H  Sedo O  Havel J  Lis S  But S 《Talanta》2006,69(4):800-806
Spectrophotometric determination of molybdenum(VI) and tungsten(VI) with application of Artificial Neural Networks is proposed and it was applied for elemental analysis of solid polyoxometalates. Better results in comparison with previously those achieved by previous published method were demonstrated. MALDI-TOF Mass Spectrometry was tested for possible determination of molecular weight of polyoxometalates utilizing different matrices. Phenomena observed during desorption-ionisation processes are discussed. LDI-TOF MS was found to be suitable for the determination of Mo:W ratio in polyoxometalates as a rapid screening method to follow synthetic procedure.  相似文献   

7.
The formation constants of species formed in the systems H+?+?W(VI)?+?nitrilotriacetic acid (NTA) and H+?+?NTA have been determined in aqueous solution for pH?=?4–9 at 25°C and different ionic strengths ranging from 0.1 to 1.0?mol?dm?3 NaClO4, using potentiometric and spectrophotometric techniques. It was shown that tungsten(VI) forms a mononuclear 1?:?1 complex with NTA of the type WO3L3? at pH?=?7.5. The composition of the complex was determined by the continuous variations method. The complexation of molybdenum(VI) with glutamic acid was investigated in aqueous solution ranging in pH from 4 to 9, using polarimetric, potentiometric and spectrophotometric techniques. The composition of the complex was determined by the continuous variations method. It was shown that molybdenum(VI) forms a mononuclear 1?:?1 complex with glutamic acid of the type MoO3L2? at pH?=?6.0. The dissociation constants of glutamic acid and the stability constants of the complex were determined at 25°C and at ionic strengths ranging from 0.1 to 1.0?mol?dm?3 sodium perchlorate. In both complex formation reactions the dependence of the dissociation and stability constants on ionic strength is described by a Debye-Huckel type equation. Finally, a comparison has been made between the patterns of ionic strength dependence for the two complexes and the results have been compared with data previously reported.  相似文献   

8.
By using spectrophotometric and potentiometric techniques the formation constants of the species formed in the systems H^++ Mo(Ⅵ)+nitrilotriacetic acid and H^+ + nitrilotriacetic acid have been determined in aqueous solutions of propanol at 25 ℃ and constant ionic strength 0.1 molodm^-3 sodium perchlorate. The composition of the complex was determined by the continuous variation method. It was shown that molybdenum(Ⅵ) forms a mononuclear 1 : 1 complex with nitrilotriacetic acid of the type MoO3L^-3 at -lg[H^+] =5.8. The formation constants in various media were analyzed in terms of Kamlet and Taft's parameters. Linear relationships were observed when lg Ks was plotted versusp. Finally, the results were discussed in terms of the effect of solvent on complexation.  相似文献   

9.
This review describes the chemistry of 2,3-dihydroxynaphthalene and the related analogues. The synthetic routes reported to obtain the investigated structures are discussed. In addition, the reactivity and the synthesis of fused heterocyclic systems containing one or two heteroatoms are discussed. The compounds derived from 2,3-dihydroxynaphthalene are located in the basic skeleton of several natural drugs. The products were applied in the fields of polymer chemistry, physical chemistry, and medicinal chemistry. The different sections cover: methods of preparation, reactions, heterocyclic systems, macrocycles, organosilicon derivatives, coordination chemistry, and biological importance. The assessment relates to the recent reports and contains a short, targeted survey of the title compound for the past 15 years.  相似文献   

10.
The interaction of nitrilotriacetic acid (NTA) and iminodiacetic acid (IDA) with tungsten(VI) (pH 7.5) and molybdenum(VI) (pH 6.00) has been studied in aqueous solutions at 25 ℃, and different ionic strengths (0.1 相似文献   

11.
The formation of complexes between Mo(VI) and 8-hydroxy-quinoline (oxine) and four oxine derivatives were investigated by multiwavelength molecular absorption spectrometry, potentiometry, and polarography. The following pKOH- and pKNH- values of the ligands and logK 211-values of the complexes MoO2(OH)2L x (x=1 or 2) were obtained at 25° C and an ionic strength of 1M(NaClO4): 5,7-dinitro8-hydroxyquinoline 4.59, <0, 14.50; 7-nitro-8-hydroxyquinoline-5-sulfonic acid 5.34, 0.41, 15.70; 7-iodo-8-hydroxyquinoline-5-sulfonic acid 6.98, 2.62, 17.65; 8-hydroxyquinoline-5-sulfonic acid 8.33, 4.13, 18.71; and 8-hydroxyquinoline 9.62, 5.28, 19.69. A good linearity was found between logK 211 and the sum of the pK-values of the OH- and NH+-groups. The dependence of the peak current of Mo(VI)-determinations by adsorption polarography of the 7-nitro-8-hydroxyquinoline-5-sulfonate complex of Mo(VI) MoO(OH)3L can quantitatively be described at pH 0.8–2 using the corresponding pK-values and the log K311 of 18.54±0.03, determined by polarography.  相似文献   

12.
The hydrolysis of the chromate ion has been studied using a potentiometric-spectrophotometric automated titration system, titrating basic K2CrO4–KNO3 solutions with previously standarized HNO3–KNO3 solutions. The temperature was kept constant at 25°C and the ionic strengths were 0.5, 1.0 and 2.0 mol-dm–3. The resulting titration curves can be interpreted in terms of two equilibria involving the formation of HCrO 4 (aq) and Cr2O 7 2– (aq). A spectrophotometric batch study was also carried out in order to obtain the thermodynamic constant for the HCrO 4 (aq) formation as well as the spectrophotometric parameters at low ionic strengths. The proposed stoichiometric constants for the two reactions and the molar absorptivities for the three species at different wavelengths and ionic strengths are also given.  相似文献   

13.
The complexes (NH4)2[MoO2(C2H2O3)2]·H2O, (NH4)2[MoO2(C8H6O3)2] and (NH4)2[MoO3(C4H4O6)]·H2O were prepared by reaction of MoO3 with glycolic, mandelic and tartaric acids, respectively. The complexes were characterized by elemental and thermal analysis, IR spectroscopy and X-ray diffraction. Crystals of the glycolate and tartarate complexes are orthorhombic and the mandelate complex is monoclinic. Elemental and thermal analysis data showed that the glycolate and tartarate complexes are monohydrated. Hydration water is not present in the structure of the mandelate complex. IR spectra showed COO? is involved in coordination as well as the oxygen atom of the deprotonated hydroxyl group of the α-carbon. The glycolate molybdenum complexes with general formula M2[MoO2(C2H2O3)2nH2O, where M is an alkali metal and n?=?1 or ½, were also prepared and characterized. Aqueous solutions of the glycolate complex become blue and mandelate and tartarate complexes change to yellow or brown when exposed to UV-radiation.  相似文献   

14.
Two new molybdenum (VI) monophosphates CsMoO2PO4 and TlMoO2PO4 have been synthesized by solid state chemistry. Their structure were determined from single crystal X-ray diffraction studies. The frameworks MoO2PO4 delimit tunnels in which are located the univalent cations. Structural relationships between the different monophosphates of the AMoO2PO4 series with A = Ag, Na, K, Tl, Cs, are presented in which two kinds of frameworks appear owing to the size of the univalent cations.  相似文献   

15.
Summary Complex reactions between MoV.VI ando-hydroxybenzylamine-N,N,O-triacetic acid (HBATA) have been investigated in the 1–3 and 2.8–6.5 pH range by potentiometric titration at 30° C in 0.5 mol dm–3 NaCl. The equilibrium data were analyzed with the SCOGS2 and MINIQUAD programs, taking into account side reactions of MoV.VI and HBATA with hydrogen ion. The favorable reaction model comprises two complexes, (1,1,1)+ and (1,2,2), with formation constants log 111 = 14.85 ± 0.11 and log 122 = 28.51 ± 0.08 for the MoV-HBATA system and the two complexes (1,1,2)3– and (1,1,3)2– with formation constants log 112 = 17.36 ± 0.01 and log 113 = 20.60 ± 0.01 for the MoVI-HBATA system. The numbers in brackets refer to the chemical stoichiometric coefficients of molybdenum, HBATA and hydrogen ion in the complexes. The structure and coordinating behaviours of MoV and MoVI complexes are discussed. The equilibria studied for the polymerization of MoV indicates that dimeric, trimeric and tetrameric species are present at pH 1–3.  相似文献   

16.
Salicylhydroxamic acid (H3shi) is known for its strong coordination ability and multiple coordination modes, and can easily coordinate to metal cations to form compounds with five‐ or six‐membered rings, as well as mono‐, di‐ and multinuclear compounds with interesting structures having potential applications in organic chemistry, coordination chemistry, and the materials and biological sciences. A novel octanuclear nickel(II)–molybdenum(VI) heterometallic cluster based on the salicylhydroxamate ligand, namely di‐μ3‐acetato‐di‐μ2‐acetato‐di‐μ3‐hydroxido‐di‐μ3‐oxido‐tetraoxidooctakis(pyridine‐κN)bis(μ5‐salicylhydroxamato)hexanickel(II)dimolybdenum(VI) monohydrate, [Mo2Ni6(C7H4NO3)2(C2H3O2)4O5(OH)2(C5H5N)8]·H2O, (I), was synthesized by the reaction of sodium molybdate, nickel acetate and salicylhydroxamic acid in a dimethylformamide/pyridine/methanol solution at room temperature. The salicylhydroxamate(3−) (shi3−), acetate and oxide ligands adopt complicated coordination modes and link six NiII and two MoVI cations into the octanuclear heterometallic cluster. All of the metal cations exhibit octahedral coordination geometries and are connected to each other through the sharing of corners, edges or planes. The heterometallic clusters are further connected to form two‐dimensional supramolecular layers through weak C—H…O hydrogen bonds. Studies of the magnetic properties of the title compound reveal antiferromagnetic interactions between the NiII cations.  相似文献   

17.
18.
A new series of dioxouranium(VI) complexes of a potential ONNO tetradentate donor 2-aminobenzoylhydrazone of butane-2,3-dione (L1H2) have been synthesized. At pH 2·5–4·0, the donor (L1H2) reacts in the keto form and complexes of the type [UO2(L1H2)(X)2] (X=Cl, Br, NO 3 , NCS, ClO 4 , CH3COO, 1/2SO 4 2− ) are obtained. At higher pH (6·5–7), the complex of the enol form having the formula [UO2(L1)(H2O)] has been isolated. On reaction with a monodentate lewis base (B), both types of complexes yield adducts of the type [UO2(L1)(B)]. All these complexes have been characterised adequately by elemental analyses and other standard physicochemical techniques. Location of the bonding sites of the donor molecule around the uranyl ion, status of the uranium-oxygen bond and the probable structure of the complexes have also been discussed.  相似文献   

19.
We describe in this work the synthesis by the Pechini method of five Mo(VI)- and W(VI)-containing complex perovskites and their structural characterisation by HREM and XRD. The compounds studied, Ba(B2/3B1/3″)O3 (B′=In and Y; B″=W and Mo) and Sr(In2/3W1/3)O3, were obtained after firing the precursor powders for 8 h at 1200°C. Thermal analysis showed that the formation mechanism of the five perovskites is similar and implies the formation of barium carbonate and barium tungstates or molybdates of different stoichiometries as intermediate phases. Interesting enough, these similar mechanisms yield to materials of a quite different structure. Indeed, Ba(In2/3Mo1/3)O3 and Sr(In2/3W1/3)O3 were found to be disordered perovskites (unit cells: ap×ap×ap and , respectively); on the other hand, two phases coexist in the sample Ba(In2/3W1/3)O3 at the synthesis conditions: an ordered predominant phase (unit cell: 2ap×2ap×2ap) and, as a minor phase, a disordered perovskite (unit cell: ap×ap×ap). Finally, the two yttrium-containing compounds were found to be ordered perovskites (2ap×2ap×2ap).  相似文献   

20.
The reaction of bis(2-hydroxy-1-naphthaldehyde)succinoyldihydrazone with bis(acetylacetonato)dioxomolybdenum(VI) (MoO2(acac)2) in 1 : 3 molar ratio in EtOH : water mixture (95 : 5) affords a complex of composition [(MoO2)2(nsh)(H2O)2] · C2H5OH. The reaction of [(MoO2)2(nsh)(H2O)2] · C2H5OH with Lewis bases, namely pyridine, 2-picoline, 3-picoline, and 4-picoline, yields [(MoO2)2(nsh)(B)2] · C2H5OH (where B = pyridine, 2-picoline, 3-picoline, and 4-picoline). Further, when this complex was reacted with 1,10-phenanthroline and 2,2′-bipyridine in 1 : 3 molar ratio in anhydrous ethanol the binuclear complexes [(μ2-O)2(MoO2)2(H4nsh)(phen)] · C2H5OH and [(μ2-O)2(MoO2)2(H4nsh)(bpy)] · C2H5OH were obtained. All of the complexes have been characterized by analytical, magnetic moment, and molar conductivity data. The structures of the complexes have been discussed in the light of electronic, IR, 1H NMR, and 13C NMR spectroscopy.  相似文献   

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