Precipitation of metal 8-hydroxyquinolates from homogeneous solution—II Thorium

A comparison has been made of the precipitation of thorium with 8-hydroxyquinoline by the direct method of addition of reagent and by precipitation from homogeneous solution by generation of the reagent from 8-acetoxyquinoline. The latter reagent produces a thorium precipitate with superior physical characteristics. Separation studies using cerium^III as a diverse ion also indicate the superiority of the method using 8-acetoxyquinoline. Further studies of thorium 8-hydroxyquinolate, precipitated by either method, indicate that ignition to thorium oxide is a reliable way to conclude the determination. Methods involving weighing or brominating the 8-hydroxyquinolate generally furnish erroneous results.     

Stability constants of uranium(VI) and thorium(IV) complexes formed with 8-hydroxyquinoline and its 5-sulfonic acid derivative

In this study, the stability constants of uranium(VI) and thorium(IV) complexes formed with 8-hydroxyquinoline (8-HOQ) and its 5-sulfonic acid (8-HOQ-5-SO₃H) derivative have been determined using the Irving-Rossotti method, computing the Calvin-Bjerrum pH-titration data. As a result, it is determined that the thorium(IV) complexes are considerably more stable than the corresponding uranium(VI) complexes. On the other hand, the complexes formed between 8-HOQ-5-SO₃H and uranium(VI) or thorium(IV) are less stable than the corresponding 8-HOQ complexes.     

Liquid-liquid extraction of Th4+ and UO 2 2+ by LIX-26 and its mixtures

Solvent extractions of thorium(IV) and uranium(VI) by a commercially available chelating extractant LIX-26 (an alkylated 8-hydroxyquinoline) or 8-hydroxyquinoline, benzoic or salicylic acid, dipentyl sulphoxide (DPSO) and their mixtures with butanol as modifier in benzene/methylisobutyl ketone (MIBK) as the diluent have been studied. Extraction of uranium(VI) by 10% LIX-26 and 10% butanol in benzene becomes quantitative at pH 5.0. The pH 0.5 values for the extraction of thorium(IV) and uranium(VI) are 4.95 and 3.35, respectively. Quantitative extraction of thorium(IV) by the mixture of 0.1 M oxine and 0.1 M salicylic acid in methylisobutyl ketone was observed at pH 5.0. The influence of concentration of various anions on the extraction of Th⁴⁺ by mixtures of LIX-26 and benzoic acid has been studied. Studies on extraction of thorium(IV) and uranium(VI) by mixtures of LIX-26 (HQ) and DPSO show that the extracted species are possibly of the type [ThQ₂/DPSO/₂/SCN/₂] and [UO₂Q₂/DPSO/], respectively.     

The role of salts derived from benzilic acid and quinolines in the adsorption of some actinides Part I: Characterization of the adsorbers

The salt of the 8-hydroxyquinoline and benzilic (diphenylglycolic) acid was prepared and incorporated into active charcoal in order to have an adsorber able to concentrate actinides dispersed in natural waters before quantitative or radiochemical analysis. The formation and the characterization of this adsorber, (adsorber B), was compared with another system containing benzilic salt of the substituted quinoline, 2-methyl, 8-hydroxyquinoline, (adsorber R). The adsorption ability of the adsorbers B and R was compared with a third product (adsorber G), prepared by incorporating benzilic acid with d-glucosamine into the charcoal. In this case, d-glucosamine gives a better stability to the system, as otherwise the benzilic acid could partially be dissolved into the water system at equilibrium, during the adsorption experiments. The dissociation acid constants of all the considered components were measured, in order to have some information on the adsorption mechanism. The compound formed during the adsorption on the prepared adsorbers with uranium, thorium, and samarium were separately analyzed and identified by means of IR and NMR. The role of the components in the adsorption was evidenced. This revised version was published online in July 2006 with corrections to the Cover Date.     

8-hydroxyquinoline monomer, water adducts, and dimer. Environmental influences on structure, spectroscopic properties, and relative stability of cis and trans conformers

The low fluorescence quantum yield of 8-hydroxyquinoline cannot be correctly interpreted without knowing the form that such a compound assumes in different environments. The commonly accepted emission-quenching excited-state proton transfer can follow different reaction paths if 8-hydroxyquinoline is dimeric or monomeric or if it exists in the form of cis and trans conformers; in this light, the knowledge of the compound form in a particular environment is basic. We have performed a spectroscopic and computational investigation aimed at the determination of the form of 8-hydroxyquinoline in different solvents. UV-vis, fluorescence, and IR spectral features have been assigned by ab initio computations based on the density functional theory and time-dependent density functional theory; the density functional theory and MP2 computations have been applied to the determination of the relative stability of the dimeric and monomeric cis and trans forms of 8-hydroxyquinoline in different solvents. Molecular dynamics computations have been used to determine the compound behavior in water solutions. According to our results, 8-hydroxyquinoline shows a clear preference for the cis conformation (as dimer or monomer), but, in water solutions, a small fraction of the trans conformation is also present.     

Chloromethylation of 8-hydroxyquinoline

The reaction of formaldehyde on a hydrochloric acid solution of 8-hydroxyquinoline, in the presence of hydrochloric acid gas, gave a chloromethyl derivative which is probably 7-chloromethyl-8-hydroxyquinoline hydrochloride. This compound is readily converted into the 7-hydroxymethyl derivative in alkaline solution. The 7-chloromethyl compound has been investigated as an analytical reagent for metal ions in acid solutions.     

The 1:3 uranium(VI)-8-hydroxyquinoline compound: its composition and thermal conversion into bis(8-hydroxyquinolinato)dioxouranium(VI)

Evidence is provided to show that in the red compound formed between uranium(VI) and 8-hydroxyquinoline, the ligand-to-uranium ratio is slightly lower than 3:1, at least when the compound is prepared by a widely accepted procedure. Competition between 8-hydroxyquinoline and other ligands such as water or ammonia is probably responsible for the non-stoichiometry. Further, it is shown that a procedure frequently used for the thermal conversion of the red compound into bis(8-hydroxyquinolmato)dioxouranium(VI) yields a compound in which the ligand-to-uranium ratio is less than 2:1. Conditions which lead to the thermal preparation of the stoichiometric bis compound are described.     

8-Hydroxyquinoline-substituted boron-dipyrromethene compounds: synthesis, structure, and OFF-ON-OFF type of pH-sensing properties

A series of four novel 8-hydroxyquinoline-substituted boron-dipyrromethene derivatives, namely 4,4-difluoro-8-(5-(8-hydroxyquinoline))-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene (1), 4,4-difluoro-8-(5-(8-hydroxyquinoline))-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (2), 4,4-difluoro-8-(5-azastyryl-(8-hydroxyquinoline))-3,5-dimethyl-4-bora-3a,4a-diaza-s-indacene (3), and 4,4-difluoro-8-(5-azastyryl-(8-hydroxyquinoline))-1,3,5,7-tetramethyl-4-bora-3a,4a-diaza-s-indacene (4), have been synthesized and characterized by a series of spectroscopic methods. The molecular structures of 1 and 2 have been determined by single-crystal X-ray diffraction analyses. The two methyl substituents attached at C-1 and C-7 positions of boron-dipyrromethene (Bodipy) in compound 2 was revealed to prevent the free rotation of the 8-hydroxyquinoline (8-HQ) moiety, resulting in an almost vertical 8-HQ-Bodipy configuration of this compound. This is obviously different from those for 1 with the dihedral angle between 8-hydroxyquinoline and Bodipy moieties of 65.44 and 66.79° due to the lack of methyl substituents in the latter compound. The intense fluorescence from the Bodipy subunit of these compounds was revealed to gradually get diminished along with either decreasing or increasing the pH value under acidic and basic conditions, respectively, in particular for 1, 2, and 4 because of the photoinduced intramolecular electron transfer from excited Bodipy moiety to 8-HQ unit and just an opposite process. This renders these compounds the first OFF-ON-OFF type of pH-dependent fluorescent sensors. Nevertheless, both the intrinsic fluorescence of these compounds and their fluorescent quenching properties along with the change in the pH value have been found to depend on the steric configuration as well as the linking group between 8-hydroxyquinoline and Bodipy moieties, revealing the effect of molecular structure on their fluorescence properties.     

The absorption spectrum and dissociation constants of 4-hydroxybenzthiazole

The absorption spectra of 4-hydroxybenzthiazole and the parent compound, benzthiazole, have been determined in acidic, basic and neutral solutions, and compared with the corresponding absorption spectra of 8-hydroxyquinoline and quinoline. The dissociation constants of 4-hydroxybenzthiazole obtained by a spectrophotometric method as well as a potentiometric method, show that it is a stronger acid and a weaker base than 8-hydroxyquinoline.     

8-羟基喹啉存在下水相(两相)中合成取代水杨酸二茂钛配合物

在8-羟基喹啉存在下,分别采用水相法和两相法简便合成了5种取代水杨酸二茂钛配合物,并用元素分析、IR及 1H NMR等手段对配合物进行了结构表征,发现配合物中均不含8-羟基喹啉配体,而是形成以取代水杨酸为双齿配体的六元杂环化合物.用电子吸收光谱分别对两相反应体系(H2O/CHCl3)的水相和有机相进行了动态监测,发现8-羟基喹啉首先通过两相界面与有机相中的二氯二茂钛形成水溶性的过渡性配合物,然后该过渡性配合物再与有机相中的取代水杨酸作用形成了目标配合物.     

Technology of Preparing 8-Hydroxy-5-nitroquinoline

An efficient, two stage method is proposed for the preparation of 8-hydroxy-5-nitroquinoline based on the nitrosation of 8-hydroxyquinoline and subsequent oxidation of the nitroso derivative using nitric acid. The conditions for the nitrosation and oxidation of the 8-hydroxyquinoline (concentration of nitric acid, temperature, and reaction time) were optimized. A method for purifying the target compound is presented. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1204–1207, August, 2005.     

Mechanochemical Modification of 5-Nitro-8-hydroxyquinoline with Cellulose, Pectin, and β-Cyclodextrin

The physicochemical consequences of mechanical treatment of 5-nitro-8-hydroxyquinoline with natural polymers cellulose, pectin, and -cyclodextrin were studied in order to improve its properties. It was found that particle sizes of the medicinal compound in the agglomerated mechanical-composite materials increased. The particle-size increase of the medicinal compound was avoided by adding a third component differing from 5-nitro-8-hydroxyquinoline by the acid-base properties and containing calcium carbonate.     

Preparative,infrared and thermogravimetric studies of three scandium 8-hydroxyquinolinates

The preparation of 3 scandium 8-hydroxyquinolinates is reported. Two were prepared by precipitation from homogeneous solution using 8-hydroxyquinoline generated by hydrolysis of 8-acetoxyquinoline, and the third by a solid-phase reaction. The first precipitate was obtained at pH 6.5 as a lemon-yellow compound with the composition ScQ₃.HQ (Q == C₉H₆NO). The second chelate was obtained at pH 8.8 as a bright-yellow compound of composition (ScQ₃)₂.HQ. The third scandium 8-hydroxyquinolinate was obtained by a solid-phase reaction between the lemon-yellow compound ScQ₃.HQ and 8-hydroxyquinoline. The orange compound has the composition (ScQ₃)₂.3HQ. Infrared spectra and pyrolysis curves indicated that the 3 chelates have very similar structures.     

A Novel Family of Cage-like (CuLi,CuNa, CuK)-phenylsilsesquioxane Complexes with 8-Hydroxyquinoline Ligands: Synthesis,Structure, and Catalytic Activity

The first examples of metallasilsesquioxane complexes, including ligands of the 8-hydroxyquinoline family 1–9, were synthesized, and their structures were established by single crystal X-ray diffraction using synchrotron radiation. Compounds 1–9 tend to form a type of sandwich-like cage of Cu₄M₂ nuclearity (M = Li, Na, K). Each complex includes two cisoid pentameric silsesquioxane ligands and two 8-hydroxyquinoline ligands. The latter coordinates the copper ions and corresponding alkaline metal ions (via the deprotonated oxygen site). A characteristic (size) of the alkaline metal ion and a variation of characteristics of nitrogen ligands (8-hydroxyquinoline vs. 5-chloro-8-hydroxyquinoline vs. 5,7-dibromo-8-hydroxyquinoline vs. 5,7-diiodo-8-hydroxyquinoline) are highly influential for the formation of the supramolecular structure of the complexes 3a, 5, and 7–9. The Cu₆Na₂-based compound 2 exhibits high catalytic activity towards the oxidation of (i) hydrocarbons by H₂O₂ activated with HNO₃, and (ii) alcohols by tert-butyl hydroperoxide. Studies of kinetics and their selectivity has led us to conclude that it is the hydroxyl radicals that play a crucial role in this process.     

The role of salts derived from benzilic acid and quinolines in the adsorption of some actinides

The adsorption conditions of uranium, neptunium, thorium, europium on the adsorbers containing the benzylate salts of the 8-hydroxyquinoline (adsorber B), and of 2-methyl- 8-hydroxyquinoline (adsorber R), were prepared, supported onto charcoal and compared with an adsorber, containing the benzylic acid, (G), stabilized with d-glucoseamine, and adsorbed onto charcoal as well. Thorium, protoactinium, and europium are adsorbed nearly completely from aqueous solutions at a large pH range, even in low acid medium, whereas uranium and neptunium are completely adsorbed only from basic solutions of pH 9. The actinides are preferentially adsorbed with respect to other ions, which are present in natural waters, such as calcium or magnesium. This feature make the analysis of most actinides in natural waters easily to be performed without changing the pH of the original system. The uranium (neptunium) analysis indeed may be accomplished after adjusting the original pH to a fairly basic value (about to 9). The adsorption experiments from real samples showed that the analysis of the actinides dispersed in natural water systems may be successfully performed after previous concentration on the adsorbers prepare. This revised version was published online in July 2006 with corrections to the Cover Date.     

5-Methyl-7-nitroso-8-hydroxyquinoline and its sensitivity and selectivity towards certain metallic ions

5-Methyl-7-nitroso-8-hydroxyquinoline (5-methyl-7-nitroso-oxine), hitherto undescribed, has been prepared and tested for its sensitivity and selectivity towards various metallic ions at differing pH's. The metals tested include cadmium, ferrous and ferric iron, mercurous and mercuric mercury, lead, nickel, cobalt, thallous thallium, cerous and cerie cerium, copper, chromium, aluminium, zinc, magnesium, vanadium (as vanadate) and gallium. This reagent is comparatively “unsclective” in that it chelates with all the above metals under the conditions employed, and therefore closely follows the behaviour of the parent compound, 8-hydroxyquinoline (oxine). Its average sensitivity is somewhat greater than that of the parent compound, and it shows its greatest sensitivity with. divalent mercury.     

5,7''''-(亚甲胺基)-二-8-羟基喹啉的合成及其理论研究

以4-甲基苯磺酸作催化剂、用三乙胺调节pH值约为9的条件下,由5-甲酰基-8-羟基喹啉和5-氨基-8-羟基喹啉合成了新的5,7'-(亚甲胺基)-二-8-羟基喹啉,利用IR,UV,1HNMR,MS确认了分子结构,比较研究了其光致发光特性,运用Gaussian98量子化学程序包,采用B3LYP密度泛函(DFT)的方法,在6-31G(d,p)水平上对分子的几何构型进行结构优化;并对目标化合物的稳定结构通过计算预测其振动光谱,计算结果与实验值基本相符.     

Synthesis of the analytical ligand 2-tert.-butyl-8-hydroxyquinoline

Two methods for the synthesis of 2-tert.-butyl-8-hydroxyquinoline are described. One involves a direct reaction of the parent compound with tert.-butyl-lithium, and the other is based on a cyclization reaction of o-aminophenol with 3-chloro-4,4-dimethylpent-2-enal. Physical data confirming the structure of the compound are presented.     

Theoretical Study of Haloacetonitrile Anions: CH2XCN- (X=F,Cl)

Haloacetonitrile anions CH2XCN- (X=F, Cl) were studied by HF-SCF, Becke3-LYP, and MP2 methods together with the Dunning's basis set aug-cc-PVTZ. The vertical electron attachments to the neutral are endothermic. The geometrically optimized CH2FCN- is mainly a valence-bounded anion and CH2FCN-→CH2CN+F- is a nonadiabatic dissociation. This theoretical study in good agreement with the experimental results shows that the Becke3-LYP method is reasonable in describing the electronic structures of anions and dissociative attachment dynamics, while significant differences between MP2 and Becke3-LYP results are shown for the dissociation potential curves of CH2ClCN-→CH2CN+Cl-.2,70-(Ethylene)-bis-8-hydroxyquinoline was optimized with DFT/B3LYP and ab initio HF methods, so ionization potential and electron affinity could be determined. Absorption spectrum was calculated by ZINDO and TD-DFT. CIS method was used to calculate the S1 excited states of the compound and afterwards the emission spectrum was computed. When the solvent effect was taken into account, the computed results show encouraging agreement with known experimental data. The results of analyzing the relationship between the energies and absorption spectra indicate that the ability to transporting electrons is strengthened compared with 8-hydroxyquinoline and that absorption and emission spectra are red-shifted. The intramolecular reorganization energy of tris(2,70-(ethylene)-bis-8-hydroxyquinoline)-aluminum implies its electron transporting property is worse than tris(8-hydroxyquinoline)-aluminum. The predicted maximum emission wavelength is red-shifted compared with tris(8-hydroxyquinoline)-aluminum.     

5,7′-(亚甲胺基)-二-8-羟基喹啉的合成及其理论研究

以4-甲基苯磺酸作催化剂、用三乙胺调节pH值约为9的条件下, 由5-甲酰基-8-羟基喹啉和5-氨基-8-羟基喹啉合成了新的5,7′-(亚甲胺基)-二-8-羟基喹啉, 利用IR, UV, ¹H NMR, MS确认了分子结构, 比较研究了其光致发光特性, 运用Gaussian 98量子化学程序包, 采用B3LYP密度泛函(DFT)的方法, 在6-31G(d,p)水平上对分子的几何构型进行结构优化; 并对目标化合物的稳定结构通过计算预测其振动光谱, 计算结果与实验值基本相符.