Extraction behavior of ion-pairs of azo-dye cations and their analytical applications

The extraction of ion-pairs of monovalent organic acid anions and inorganic anions with 4-(4-diethylaminophenylazo)-N-alkylpyridinium cation (azo-dye cation) is described. The alkyl groups studied were methyl, ethyl, propyl, butyl and benzyl groups. The ion association, distribution and extraction constants for the ion-pairs were determined from partition equilibrium studies. These azo-dye cations can extract chelate anions containing sulfonic acid groups into chloroform. The cobalt complex of 2-nitroso-1-naphthol-4-sulfonic acid is extracted quantitatively into chloroform with the propyl derivative as a 1:3 Co: dye complex; measurement of the absorbance of the extracted ion-pair provides a very sensitive determination of cobalt, the apparent molar absorptivity in chloroform being 1.66 × 10⁵ l mol^-1 cm^-1 at 566 nm. The methyl derivative is suitable for cation extraction of monovalent anions such as the complex nickel anion of 4-chloro-2-nitroso-1-naphthol, and anionic surfactants. The possibilities for application of these azo-dye cations in extraction-spectrophotometric determinations are very large.     

Synthesis and characterization of the free ligand 5,6:13,14-dibenzo-9,10-benzo(15-crown-5)-2,3-bis(hydroxyimino)-7,12-dioxo-1,4,8,11-tetraazacyclotetradecane and its mono and tri nuclear complexes

The novel (E,E)-dioxime 5,6:13,14-dibenzo-9,10-benzo(15-crown-5)-2,3-bis(hydroxyimino)-7,12-dioxo-1,4,8,11-tetraazacyclotetradecane (H₂L) has been synthesized by the reaction of 4′,5′-diaminobenzo(15-crown-5) with N,N′-bis(2-carbomethoxyphenyl)diaminoglyoxime (1). Only mononuclear Co^III and Ru^II complexes with a metal/ligand ratio of 1:2 have been isolated. The cobalt(III) complex bridged with BF₂⁺ is achieved with H-bonded cobalt(III) complex and borontrifluoride ethyl ether complex. The reaction of BF₂ bridged cobalt(III) complex with bis(benzonitril)palladium(II) chloride gives a trinuclear complex. The structures of dioxime and its complexes are proposed according to elemental analyses, ¹H and ¹³C-NMR, IR and mass spectral data.     

Extraction and spectrophotometric determination of zinc in coal fly ash and pond sediments with 2-[2-(3,5-dibromopyridyl)azo]-5-dimethylaminobenzoic acid

An extraction-spectrophotometric method is described for the determination of traces of zinc with 2-[2-(3,5-dibromopyridyl)azo]-5-dimethylaminobenzoic acid. The reagent forms a stable, blue 1:2 zinc/reagent complex that can be extracted into chloroform. The apparent molar absorptivity of the zinc(II) complex is 1.26 × 10⁵ l mol^?1 cm^?1 at 610 nm in chloroform. The reagent is relatively selective; interferences from cobalt, copper and nickel can be masked with dimethylglyoxime and aluminium and iron with a mixture of sodium fluoride and triethanolamine. The method is applied to the determination of zinc in coal fly ash and pond sediments with good precision and accuracy.     

Thiobarbituric acid-reacting substances derived from autoxidizing linoleic and linolenic acids

Seven pyridylazo dyes containing the m-tolylenediamine group were synthesized and their analytical potential for the determination of cobalt was studied spectrophotometrically. The molar absorptivities and selectivity of these reagents increased compared with those of PADAB. Cobalt(II) and 3,5-diCl-PADAT (5-[(3,5-dichloro-2-pyridyl)azo]-2,4-diaminotoluene) at pH 3 form a complex which is very stable even in the presence of strong mineral acids. The complex has two absorption maxima at 548 and 590 nm in hydrochloric acid (2.4 M) solution. The color is very stable and the system conforms to Beer's law; the optimal range for measurement in a 1-cm cell is 0.01–0.4 p.p.m. cobalt. In practice, this color reaction is specific. The molar absorptivity is 1.38 ·10⁵ 1 mol^-1 cm^-1 at 590 nm. The sensitivity is 0.00042 μg Co cm^-2 at 590 nm for log I₀/I= 0.001. The method was applied to the determination of cobalt in steel and waspaloy.     

Spectrophotometric studies on complexation reactions of some water-soluble 5-nitro-2-pyridylhydrazones with cobalt. Spectrophotometric and derivative spectrophotometric determination of trace cobalt with 2-benzimidazolyl-3-sulphophenylmethanone 5-nitro-2-pyridylhydrazone

The complexation reactions of four water-soluble hydrazones, 2-quinolyl-3-sulphophenylmethanone 5-nitro-2-pyridylhydrazone, 3-sulphophenyl-2-thiazolylmethanone 5-nitro-2-pyridylhydrazone (STNPH), 2-benzothiazolyl-3-sulphophenylmethanone 5-nitro-2-pyridylhydrazone and 2-benzimidazolyl-3-sulphophenylmethanone 5-nitro-2-pyridylhydrazone (BISNPH), with cobalt(II) were studied spectrophotometrically. These hydrazones react with cobalt(II) to form stable 1:2 (metal:ligand) complexes, except for STNPH, which forms a 1:1 complex, with high molar absorptivities. A sensitive and selective spectrophotometric method for the determination of cobalt with BISNPH has been developed. The cobalt(II)-BISNPH complex is formed quantitatively in the pH range 2.7–9.4 and oxidized rapidly to give the corresponding cobalt(III) complex with an absorption maximum at 517 nm. Beer's law is obeyed over the range 0.02–1.0 μg ml^?1 and the apparent molar absorptivity of the cobalt(III) complex is 6.65 × 10⁴ l mol^?1 cm^?1 at 517 nm. The method was applied to the determination of cobalt in iron and steel samples with satisfactory results. The sensitivity is increased 11-fold by use of second-derivative spectrophotometry.     

Reaction of a diphenylacetylenecobalt complex with alkyl diazoacetates

The diphenylacetylene-cobalt complex, η⁵-C₅H₅Co(PPh₃)(PhCCph) (I) reacted with alkyl diazoacetates (II, alkyl = methyl, ethyl, and t-butyl) at room temperature to give two isomers of the mononuclear cobalt complex, η⁵-C₅H₅Co- (PhC₂Ph)(CHCO₂R)₂ (III and IV) and two isomers of the dinuclear cobalt complex [η⁵-C₅H₅Co(PhC₂Ph)(CHCO₂R)]₂ (V and VI).The complexes III and IV are diene complexes, syn,syn- and syn,anti- (dialkyl 2,3-diphenylmuconate)-η⁵-cyclopentadienylcobalt, respectively. The structure of Vb (R = C₂H₅) was determined by X-ray diffraction as η-[1–3-η³ : 1,4,5-μ³- 1,6-bis(ethoxycarbonyl)-2,3,4,5-tetraphenylhexa-2,4-diene-1,1-diyl]bis(η⁵-cyclopentadienylcobalt)(CoCo. The complex VI is the bis(η³-allyl)cobalt complex, μ-[1–3-η³ : 4–6η³-1,6-anti,anti-bis(alkoxycarbonyl)-2,3,4,5,-tetraphenylhexa- 1,3,5-triene]bis(η⁵-cyclopentadienylcobalt)(CoCo) according to its ¹H NMR spectrum.The formation of these products was rationalizes in terms of a cobaltacyclobutene intermediate.     

The new method for the determination of cobalt in sea water by solvent extraction with 2-nitroso-5-diethylaminophenol

Cobalt in sea waters can be determined spectrophotometrically by means of 2-nitroso-5-diethylaminophenol after extraction of the complex into 1,2-dichloro-ethane. No preliminary concentration is needed. Interferences are prevented by masking or by stripping from the organic phase. The method is applicable over the range 0–0.24 μg Co 1^-1 when 1–1 or 2–1 samples are taken. The relative standard deviation is 4% for 0.15 μg Co 1^-1. The stability of cobalt in sea water samples is discussed.     

Spectrophotometry Determination of Cobalt after Extraction of its Ternary Complex with 3-(4-Phenyl-2-Pyridyl)-5,6-Diphenyl-1,2,4-Triazine and Tetraphenylborate into Molten Naphthalene

The reaction of 3-(4-phenyl-2-pyridyl)-5,6-diphenyl-1,2,4-triazine (PPDT) and tetraphenylborate (TPB) with cobalt (II) has been studied to determine the optimum conditions for the extraction and quantitative spectrophotometry determination of this metal. The ternary complex is extracted into molten naphthalene at pH 3.6–7.4. The solid naphthalene containing the cobalt associated complex is separated by filtration and dissolved in acetonitrile. Beer's law is obeyed in the concentration range 8–140 μg cobalt in 10 ml of acetonitrile solution. The molar absorptivity and sensitivity are 4.2×10³ l·mol^?1·cm^?1 and 0.01408 μg/cm², respectively. The other factors such as pH, amounts of reagents and naphthalene, shaking and standing times, and the effect of diverse ions are studied. The method has been applied to the determination of cobalt in iron steel alloys.     

Synthesis and spectrophotometric study of 2-[2-(3,5-dibromopyridyl,)azo] -5-dimethylaminobenzoic acid as an analytical reagent: Determination of nickel

2-[2-(3,5-Dibrornopyridyl)azo]-5-dimethyIam;nobenzoic acid (3,5-diBr-PAMB) has been synthesized and its potential for the spectrophotometric determination of metals studied. It reacts sensitively with nickel, cobalt, iron and copper, and is particularly useful for nickel. The apparent molar absorptivity in chloroform is 1.50 × 10⁵ l mol^-1 cm^-1 and the Sandell sensitivity is 0.4 ng Ni cm^-2. Nickel reacts with 3.5-diBr-PAMB at pH 4–10; at pH 4–7 the complex can be extracted into chloroform to give a stable purple solution. The optimal calibration range is 0.04–0.4 ppm Ni. Only Cu, Co, Fe, Pd and V interfere seriously but Pd, Cu and V can be masked by thiourea.     

[(R)-2-Methyl-1,4,7-triazacyclononane] [1,1,1-tris(aminomethyl)ethane]-cobalt(III) and some Mono[(R)-2-methyl-1,4,7-triazacyclononane]-cobalt(III) Complexes

Summary [(R)-2-Methyl-1,4,7-triazacyclononane][1,1,1-tris(aminomethyl)ethane]cobalt(III) has been prepared and separated into two isomers which show weak Cotton effects in the¹A₁¹T₁ region (d-electron transition) compared with that of bis[(R)-2-methyl-1,4,7-triazacyclononane]cobalt(III). The effect is comparable to that of tetraammine[(R)-1,2-diamino propane]cobalt(III). The circular dichroism spectra of the mono complex change markedly upon addition of sodium sulphate. The chelate rings are more flexible in the mono than in the bis complex. Some other related mono[(R)-2-methyl 1,4,7-triazacyclononane]cobalt(III) and [(R)-2-methyl-1,4,7 triazacyclononane][1,1,1-tris(aminomethyl)ethaneI nickel (II) complexes have also been prepared and characterized.     

Extraction-spectrophotometric determination of trace iron (II) in sea water with 2-[2-(3,5-dibromopyridyl)azo]-5-diethylaminobenzoic acid

An extraction-spectrophotometric method is described for the determination of traces of iron(II) with 2-[2-(3,5-dibromopyridyl)azo]-5-diethyl-aminobenzoic acid. The reagent forms a stable and blue 12 iron/reagent complex that can be extracted into chloroform. The apparent molar absorptivity of the iron(II) complex is 1.09 × 10⁵ 1 mol^–1 cm^–1 at 624 nm in chloroform. The reagent is relatively selective; interferences from cobalt, copper, nickel and vanadium can be removed by using dimethylglyoxime and EDTA. The method is applied to the determination of iron (II) in sea water and aluminium alloys with good precision and accuracy.     

Spectro photometric determination of cobalt(ii) with 2,2'-dipyridyl-2-pyridylhydrazone

A spectrophotometric study of the cobalt(II) complex of a new reagent, 2,2'-dipyridyl-2-pyridylhydrazone (DPPH) is presented. A water-soluble yellow-orange complex is formed in the pH range 3–11, and shows maximal absorbance at 480 nm with a molar absorptivity of 3.2·10⁴ l mol^-1 cm^-1 ; Beer's law is obeyed over the range 0.25–3.75 p.p.m. of cobalt. This complex is very stable and on addition of perchloric acid only a bathochromic shift takes place from 480 nm to 500 nm. This complex is stable even in the presence of 20% perchloric acid and shows a molar absorptivity of 4.2 ·10⁴ l mol^-1 cm^-1 ; Beer's law is obeyed over the range 0.15–2.00 p.p.m. of cobalt. A new method of determining trace amounts of cobalt is proposed, which possesses the advantages of high sensitivity and very high selectivity.     

Cobalt complexes based on hyperbranched salicylaldimine ligands as catalyst precursors for ethylene oligomerization

Three hyperbranched salicylaldimine ligands with tetradecyl as core, with hexadecyl as core and with octadecyl as core were synthesized in good yields. These ligands were reacted with cobalt chloride hexahydrate to form three complexes ( C1 – C3 ). The compounds were characterized using Fourier transform infrared, ¹H NMR, mass and UV spectroscopies and thermogravimetric and differential thermal analyses. The catalytic properties of the hyperbranched cobalt complexes were evaluated for ethylene oligomerization. The effects of solvent and reaction parameters (Al/Co molar ratio, temperature and reaction pressure) on ethylene oligomerization were studied using the cobalt complex C3 as pre‐catalyst and methylaluminoxane (MAO) as co‐catalyst. Under these conditions ([Co] = 5 μmol, Al/Co = 500, 25 °C, 0.5 MPa ethylene, 30 min), the catalytic activity of complex C3 in toluene was 1.85 × 10⁵ g (mol Co)⁻¹ h⁻¹ and the selectivity for C₈₊ oligomers was 55.72%. The complex structure also had a significant influence on both the catalytic activity and selectivity. All three cobalt complexes, activated with MAO, showed moderate activities towards ethylene oligomerization and the activity of cobalt complex C1 was up to 1.99 × 10⁵ g (mol Co)⁻¹ h⁻¹. The kinds of metal center of complexes (cobalt complex C1 and nickel complex with tetradecyl as core) and their catalytic properties were investigated in detail under the same conditions.     

A rapid spectrophotometric method for the determination of cobalt in industrial, environmental, biological, pharmaceutical and soil samples using bis(5-bromosalicylaldehyde)orthophenylenediamine

A very simple, ultra-sensitive and fairly selective spectrophotometric method is presented for the determination of cobalt at trace levels using bis(5-bromosalicylaldehyde)orthophenylenediamine (BBSOPD). The method is based on the reaction of nonabsorbent BBSOPD in a slightly acidic (0.001–0.0025 M H₂SO₄ or pH 3.4–4.0) and 50% N,N-dimethylformamide media with cobalt(II) to produce a highly absorbent orange colored chelate-product with an absorption maximum at 473 nm. The reaction is instantaneous and the absorption remains stable for 24 h. The average molar absorption coefficient and Sandell’s sensitivity were found to be 5.84 × 10⁴ l mol^-1 cm^-1 and 9.0 ng cm^-2 of cobalt(II), respectively. Linear calibration graphs were obtained for 0.02–4.0 mg l^-1 of Co(II). The stoichiometric composition of the chelate is 1:1 (Co(II):BBSOPD). A large excess of over 50 cations, anions and complexing agents do not interfere in the determination. The method was successfully used for the determination of cobalt in several standard reference materials (steels and alloys), environmental waters (potable and polluted), biological samples (human blood and urine), pharmaceutical and soil samples and solutions containing both cobalt(II) and cobalt(III) as well as some complex synthetic mixtures. The method has high precision and accuracy.     

Study on the solid phase extraction and spectrophotometric determination of cobalt with 5-(2-benzothiazolylazo)-8-hydroxyquinolene

A highly sensitive, selective and rapid method for the determination of cobalt based on the rapid reaction of cobalt(II) with 5-(2-benzothiazolylazo)-8-hydroxyquinolene BTAHQ and the solid phase extraction of the Co(II)-BTAHQ complex with C18 membrane disks were developed. In the presence of pH = 6.4 buffer solution and cetylpyridenium chloride (CPC) medium, BTAHQ reacts with cobalt to form a deep violet complex with a molar ratio of 1:1 (cobalt to BTAHQ). This complex was enriched by the solid phase extraction with C18 membrane disks. An enrichment factor of 100 was obtained by elution of the complex from the disks with a minimal amount of isopentyl alcohol. In isopentyl alcohol medium, the molar absorptivity of the complex is 2.42 × 10⁵ L mol⁻¹ cm⁻¹ at 658 nm. Beer’s law is obeyed in the range of 0.01–0.38 μg mL⁻¹ in the measured solution. The relative standard deviation for 11 replicate samples of 0.20 μg mL⁻¹ level is 1.37%. The detection and quantification limits reach 3.1 and 9.7 ng mL⁻¹ in the original samples. This method was applied for the determination of cobalt in biological, water, soil and pharmaceutical preparation samples with good results.     

配合物[Co(qina)2(DMSO)2]的结构及其对乙酸-1-萘酯水解的催化研究

合成了配合物[Co(qina)₂(DMSO)₂]单晶, 其中, qina^－为喹哪啶酸根, DMSO为二甲基亚砜. 配合物为单斜晶系, P2(1)/C空间群, 2个qina^－配体以氮原子和氧原子与Co(II)离子螯合配位, 2个DMSO以氧原子与Co(II)离子轴向配位, 形成规则的八面体构型配合物, 分子之间存在π-π堆积弱相互作用. 该配合物可显著提高乙酸-1-萘酯的水解速率, 在配合物浓度和萘酯浓度各为1.0×10^－4和3.0×10^－5 mol•L^－1条件下, 酯的水解速率提高460倍.     

Application of the Suzuki reaction to the asymmetric desymmetrisation of 1,2- and 1,3-disubstituted bulky cobalt metallocenes

Reaction of (η⁵-cyclopentadienyl)(η⁴-tetraphenylcyclobutadiene)cobalt with Hg(OAc)₂ (2.3 equiv) in 1:1 MeOH/CH₂Cl₂ followed by the addition of LiCl resulted in the formation of (η⁵-1,2-dichloromercuricyclopentadienyl)(η⁴-tetraphenylcyclobutadiene)cobalt (33%) and its 1,3-isomer (6%). Following conversion into their corresponding diiodides these compounds were desymmetrised by Suzuki reactions with ArB(OH)₂ employing [(R)-BINAP]PdCl₂, with the highest ee of 24% being obtained for (η⁵-1-iodo-3-(2-methoxyphenyl)cyclopentadienyl)(η⁴-tetraphenylcyclobutadiene)cobalt.     

Le dosage spectrophotometrique du cobalt dans le fer de tres haute purete

A spectrophotometric study of the cobalt-β-nitroso-α-naphthol complex between 200 and 350 nm showed the existence of a very sensitive absorption maximum at 308 nm. Utilization of this wavelength allows cobalt in the range 10^-6–10^-5 g to be determined with good precision. The proposed method is very suitable for the determination of cobalt in high-purity iron.     

Spectrophotometric determination of cobalt(II) with 2-(3′-sulfobenzoyl)pyridine benzoylhydrazone

A simple method has been described for the Spectrophotometric determination of cobalt(II) with 2-(3′-sulfobenzoyl)pyridine benzoylhydrazone (SBPBH). In aqueous solution, cobalt(II) reacts with SBPBH to form a yellow complex, which is not destroyed even by the addition of 3.8 M perchloric acid. The absorption maximum of the complex in 1.5 M perchloric acid medium was found to be 400 nm; the molar absorptivity was 2.17 × 10⁴ liters mol⁻¹ cm⁻¹. The proposed method is fairly selective and has been applied to the determination of cobalt in standard alloy steel samples.     

Dispersive liquid–liquid microextraction and spectrophotometric determination of cobalt in water samples

A new simple and rapid dispersive liquid–liquid microextraction has been applied to preconcentrate trace levels of cobalt as a prior step to its determination by spectrophotometric detection. In this method a small amount of chloroform as the extraction solvent was dissolved in pure ethanol as the disperser solvent, then the binary solution was rapidly injected by a syringe into the water sample containing cobalt ions complexed by 1-(2-pyridylazo)-2-naphthol (PAN). This forms a cloudy solution. The cloudy state was the result of chloroform fine droplets formation, which has been dispersed in bulk aqueous sample. Therefore, Co-PAN complex was extracted into the fine chloroform droplets. After centrifugation (2 min at 5000 rpm) these droplets were sedimented at the bottom of conical test tube (about 100 µL) and then the whole of complex enriched extracted phase was determined by a spectrophotometer at 577 nm. Complex formation and extraction are usually affected by some parameters, such as the types and volumes of extraction solvent and disperser solvent, salt effect, pH and the concentration of chelating agent, which have been optimised for the presented method. Under optimum conditions, the enhancement factor (as the ratio of slope of preconcentrated sample to that obtained without preconcentration) of 125 was obtained from 50 mL of water sample, and the limit of detection (LOD) of the method was 0.5 µg L^?1and the relative standard deviation (RSD, n = 5) for 50 µg L^?1 of cobalt was 2.5%. The method was applied to the determination of cobalt in tap and river water samples.