Oxine complexes

Solvent extraction techniques are useful in the quantitative analysis of niobium. The fluoro complexes are amenable to extraction by a wide variety of ketones. Some of the water-insoluble complexes with organic precipitants are extractable by organic solvents and colorimetry is performed on the extract. An example is the extraction of the niobium—oxine complex with chloroform (41). The extraction of the niobium—pyrocatechol violet complex with tridodecylethylammonium bromide and the extraction of niobium—pyrocatechol—sparteine complex with chloroform are examples of extractions of water-soluble complexes. Colorimetry is performed on the extract (42,43). Colorimetry may also be performed directly on the water-soluble complex, eg, using ascorbic acid and 5-nitrosahcyhc acid (44,45). 

Direct. Some radionucHdes are packaged in solution for direct sampling (qv) via a septum and injection into the patient. GalHum-67 is a marker of inflammation, infection, and various tumor types. Its half-life is 78.3 h and it is suppHed as the gallium citrate salt. Indium-111 chloride is suppHed for the labeling of white blood ceUs. The In chloride is mixed with oxine (9-hydroxyquinoline) to form a lipophilic, cationic In oxine complex, which enters the white blood ceU. The complex dissociates within the ceU, and the cationic In " ion is trapped within the ceU, owing to its charge. 

Among the most important indirect methods of analysis which employ redox reactions are the bromination procedures for the determination of aromatic amines, phenols, and other compounds which undergo stoichiometric bromine substitution or addition. Bromine may be liberated quantitatively by the acidification of a bromate-bromide solution mixed with the sample. The excess, unreacted bromine can then be determined by reaction with iodide ions to liberate iodine, followed by titration of the iodine with sodium thiosulphate. An interesting extension of the bromination method employs 8-hydroxyquinoline (oxine) to effect a separation of a metal by solvent extraction or precipitation. The metal-oxine complex can then be determined by bromine substitution. 

Dithiocarbamates and xanthates form particularly stable, neutral complexes with Cu(II), Cd(II) (and also Ni, Hg, Pb), which are membrane permeable and increase the apparent bioaccumulation of these metals [13]. In the series of sulfoxine, oxine, and chloroxine, the hydrophobicity of the neutral and the charged form, as well as of the Cu complex, increases. While the sulfoxine is not hydrophobic and does not modulate copper toxicity [220], the Cu-oxine complex is hydrophobic with an octanol-water partition constant, log Kok, of 1.7 [221] or 2.6 [222]. Chloroxine can be assumed to be even more hydrophobic, but so far its influence on uptake and toxicity has not been investigated. Uptake of Cu2+ into unilamellar liposomes was increased in the presence of 8-hydroxy-chinoline, and decreased again after adding HA [223],... 

The resulting precipitate of aluminium-oxine complex is crystalline in nature and hence can be filtered conveniently, washed with water and finally dried at 130-150°C to constant weight. 

Disadvantages There are two disadvantages of the metal-oxine-complex method, namely ... 

Discuss the theoretical and procedural aspects for the assay of Fe(III) as its Fe(III) oxinate complex. 

The acid-catalyzed aquation of iron(III)-(substituted)oxinate complexes involves iron oxygen bond breaking and concomitant proton transfer in transition state formation. The latter aspect contrasts with the much slower acid-catalyzed aquation of hydroxamates, where proton transfer seems not to take place in the transition state. Reactivities, with and without proton assistance, for various stages in dissociation of a selection of bidentate and hexadentate hydroxamates, oxinates, and salicylates are compared and discussed—the overall theme is of dissociative activation. ... 

The electrochemical behavior of Cd-oxine complexes was analyzed by square-wave stripping voltammetry [80] from the mechanistic point of view, applying the theoretical model developed previously [81-83]. Influence of ligand and reactant adsorption, and the ligand concentration on the Cd-oxine electroreduction were also examined [84] using SWV. Typical curves recorded and calculated for several Egw are shown in Fig. 5. 

The stability constants821 for the 8-hydroxyquinoline (oxine) complexes have been questioned owing to the ease with which the VIV complexes undergo oxidation, even by atmospheric o2.355,687 However, adducts [VO(oxine)2L] (L = py or other nitrogen bases) were more stable towards oxidation. The Viv oxine complex gradually turns magenta black when extracted into a nonpolar solvent, indicating formation of the Vv oxine complex in air, but in... 

Total trace metals were determined after compl xation in seawater by 8-hydroxyquinoline (8-HQ), isolation of the oxine complexes on the RPLC column, and subsequent elution by a small volume of methanol. As shown in Figure 2, the formation of 8-HQ complexes is strongly pH dependent. For the metals of interest, formation and isolation of the complexes at the typical pH of seawater (i.e., about 8) should, in principle, yield complete recovery. In practice, complete recovery is observed only in seawater sam-... 

Yersin, H. Donges, D. Nagle, J. K. Sitters, R. Glasbeek, M. Intraligand charge transfer in the Pd(II) oxinate complex Pd(qol)(2). Site-selective emission, excitation, and optically detected magnetic resonance. Inorg. Chem. 2000, 39, 770-777. 

Oxygen-containing organic solvents extract the charged forms of the reagent as ion-pairs. Some metals (Ni, Zn, U) form anionic oxine complexes, which form with basic dyes ion-associates, extractable into benzene [109]. 

Manganese has been determined in the form of ion-associates the anionic chloro-oxine complex of manganese with Rhodamine 6G, extractable into benzene (e = 7.0-10 ) [46], and the cationic complex of Mn(II) with phen, associated with the acid dye Erythrosin, and extractable into ethyl acetate (e = 1.5-10 ) [47]. 

Benzotrisfuroxan forms complexes with various organic molecules two of these, and the uncomplexed molecule, have been studied by X-ray methods. The complex with the thiophene-cyclophane (19) gave structural parameters for both molecules, but the copper oxinate complex appeared to possess a disordered orientation of the trifuroxan. The shortness of the exocyclic N—0 bond is remarkable, " as has been noted also in simple furoxans. ... 

Platelets and white blood cells (WBC) can be labeled with In to provide agents for imaging inflammatory processes and thrombi (McAfee and Thakur 1976, Keeley and Hillis 1996, Becker and Meller 2001). A weak complex is formed between the In radiometal and 8-hydroxyquinoline (oxine). Since the hn-oxine complex is weak, the metal rapidly exchanges with transferrin in the plasma. In the absence of plasma, the complex diffuses across the cell membrane and the metal binds to intracellular sites. In humans, hn-labeledWBC will accumulate at sites of inflammation and also localize in the liver and spleen. 

The emissive states of oxinate complexes which are described as IL states (see above) have apparently a considerable ILCT contribution [177, 183, 195]. Accordingly, such emissive states maybe also termed ILCT [177],e.g.,... 

ILCT in oxinate complexes is associated with the promotion of an electron from the Pt-0 bond to the nitrogen atom of the heterocyclic ligand. 

C6H4NCH=NR (R = Me, CeH40Me-/ , C.H4Me-/ , or CeH a-/ ) have been isolated, and their equilibrium constants, heats of complex formation and thermodynamic parameters obtained. The lead(iv) Schiff-base complexes (19) and (20) have also been synthesized. The reaction of BuSnClg with pentane-2,4-dione in the presence of pyridine leads to the isolation of the pyridine adduct of butyldichloro(pentane-2,4-dionato)tin(iv). Some more diaryltin dichloride-oxine complexes have been prepared. ... 

Table 3.16 Measured Absorbance for Recovered Cadmium as the Oxine Complex at an Acidic and an Alkaline pH...

Figure II.3.7b-d shows the changes in the cathodic and anodic components of the net response in the range of the quasi-reversible maximum. These currents are very sensitive to a change in frequency and allowed the evaluation of kinetic parameters of azobenzene [91], cytochrome c [92], and Cu(II)-oxine complexes [103] by fitting experimental data with theoretical curves. In addition, a theory of a two-step surface reaction was developed and applied to the kinetics of the reduction of adsorbed 4-(dimethylamino)azobenzene [104].

A third technique which is somewhat less popular but still useful is application of surface adsorption reagents. Activated car n is generally used as the carrier after conversion of the metal ion(s) of interest to a suitable form. For example, iodide in ground water has been determined by this method after conversion to silver iodide [61]. Neutral 8-hydroxyquinoline complexes have been employed in which, again, the oxine complex is collected on activated carbon [62]. Use of activated carbon is particularly useful where PIXE is being employed as the analysis technique, since the resultant sample is ideal for direct presentation to the instrument [63]. Other preconcentration methods that have been employed in this area include electrodeposition [64], precipitation chromatography [65], liquid/liquid extraction, immobilized reagents [66], plus a variety of other techniques well known to the analytical chemist. 

Vanadium ions are extracted with chloroform at pH 3.4 as a vanadium oxinate complex, the extracts evaporated, and after oxidation with nitric acid determined by atomic-absorption analysis in the presence of aluminium ions. 

Ligand replacements for which kinetic data have been reported include [Ni(dgen)] + plus edta (parallel dissociative and associative paths), [Pb(edta)] plus R-( —)-pdta, polyether complexes of lead(n) plus nitrogen macrocycles, metal(ii)-oxine complexes plus edta, and a variety of analogous reactions involving lanthanide and actinide complexes (see Chapter 10). Kinetic data are also available for ligand exchange between trien and tetren complexes of cad-mium(ii) and the edta complex of copper(ii). ... 

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