The solubilities of zinc complexes of 8-quinolinol and some derivatives of 8-quinolinol

The solubilities of bis-8-quinolinolo-zinc^II, bis-2-methyl-8-quinolinolo-zinc^II and bis-5 : 7-dibromo-S-quinolinolo-zinc^II have been measured over the pH range of 4.5 to 9 at ionic strengths of 0.114 and 0.230 and at 25° and 40°. A mathematical treatment of the results gave nearly constant solubility products only when a dissolved but undissociated molecule, in addition to all of the dissociated and partly dissociated species, was considered. The relative abundance of each species of molecule in solution has been calculated.     

7-硝基-8-羟基喹啉的合成

以8-羟基喹啉为原料,经硝化和脱磺酸基保护两步反应合成了7-硝基-8-羟基喹啉,总收率69％,纯度高于99％.其结构经1H NMR,13C NMR和HR-MS确证.     

Rare earth chelates derived from 8-quinolinol

The composition and heat stabilities of trivalent lanthanide oxinates prepared by homogeneous precipitation (urea hydrolysis in the presence of acetic acid) have been studied. The products contain acetate ion; and the molar ratio oxinate/metal is less than three. Polymeric structures are proposed for these materials, Heat stability in an inert atmosphere, as determined by thermogravimetric, thermomanometric and differential thermal analyses, decreases with increasing atomic weight of the metal.     

Spectrophotometric determination of ruthenium with 8-quinolinol

A spectrophotometric method is described for the determination of 2–80 μg of ruthenium. The method involves oxidation of ruthenium to ruthenate, addition of 8-quinolinol, adjustment of the pH to 4–6.5, digestion of the complex formed at 85° for 30 min, extraction with chloroform, and measurement of absorbance at 430 nm. Almost all other metals and excess of reagent are removed by washing the extract. About 98 % of ¹⁰⁶Ru tracer was recovered.     

Thermal analysis of iron-8-quinolinol complexes

Thermal analysis studies were performed on the iron-8-quinolinol complexes Fe(Ox)₂, Fe(Ox)₃, Fe(Ox)₂(OH), Fe(Ox)(OH)₂ and Fe(Ox · HCl)₂Cl₃ (where Ox is 8-quinolinol). Mixtures of these complexes with Fe(OH)₃ and Fe₂O₃ were also investigated.

---

Zusammenfassung Thermoanalytische Untersuchungen der Eisen-8-Oxy-Chinolinkomplexe wurden für Fe(Ox)₂, Fe(Ox)₃, Fe(Ox)₂(OH), Fe(Ox)(Ox)₂ und Fe(Ox · HCl)₂Cl₃ (Ox=8-Oxy-Chinolin) durchgeführt. Gemische dieser Komplexe mit Fe(OH)₃ und Fe₂O₃ wurden ebenfalls untersucht.

---

Résumé Etude par analyse thermique de complexes du fer avec l'hydroxy-8 quinoléine: Fe(Ox)₂, Fe(Ox)₃, Fe(Ox)₂(OH), Fe(Ox)(Ox)₂ et Fe(Ox · HCl)₂Cl₃ (où Ox est l'hydroxy-8 quinoléine), ainsi que de leurs mélanges avec Fe(OH)₃ et Fe₂O₃.

---

-8- , Fe(Ox)₂, Fe(Ox)₃, Fe(Ox)₂(OH), Fe(Ox)(OH)₂ u Fe(Ox · HCl)₂Cl₃, Ox — 8- . Fe(OH)₃ Fe₂O₃.

---

---

The authors wish to thank Dr. A. Calusaru for his valuable suggestions.     

Supercritical carbon dioxide extraction equilibrium of gallium(III) with 2-methyl-8-quinolinol and 2-methyl-5-butyloxymethyl-8-quinolinol

This work performed fundamental studies for the extraction of gallium(III) with 2-methyl-8-quinolinol (HMQ) and 2-methyl-5-butyloxymethyl-8-quinolinol (HMO(4)Q) into supercritical carbon dioxide (SF-CO(2)) from a weakly acidic solution. The distribution constants of HMO(4)Q between aqueous and SF-CO(2) phases were determined at 45 degrees C, 8.6-20.4 MPa and I=0.1 M (H, Na)NO(3) (M=mol dm(-3)). At 45 degrees C and 15.7 MPa, gallium(III) was hardly extracted with HMQ into SF-CO(2), but was quantitatively extracted with HMO(4)Q in the pH range of 2.20-2.84. The extraction constant, K(ex, SF-CO(2)) (=[Ga(OH)(MO(4)Q)(2)](SF-CO(2))[H(+)](3)[Ga(3+)](-1)[HMO(4)Q](SF-CO(2))(-2)), of gallium(III) with HMO(4)Q was determined to be 10(-2.6+/-0.1) at 45 degrees C, 15.7 MPa and I=0.1 M (H, Na)NO(3), which was 63 times larger than that in heptane at 45 degrees C and 0.10 MPa. It was also found that the addition of 3,5-dichlorophenol as a synergist enhanced the extractability of gallium(III) with HMO(4)Q into SF-CO(2).     

Steric effects in tin-phenyl cleavage by substituted 8-quinolinol

A series of compounds of the type Cl₂Sn(Ox′)₂ (where Ox′ is a substituted 8-quinolinolate) have been prepared by tin-phenyl cleavage of diphenyltin dichloride at 180°C. The kinetics of the reaction have been studied with 2-methyl-8-quinolinol and diphenyltin dichloride in dimethyl sulfoxide at 192° and compared with the kinetic pattern using 8-quinolinol. Kinetics with both chelating agents follow pseudo-first order rate law: rate = (k₁ + k₂[HOx′]ⁿ[(C₆H₅)₂SnCl₂]). Both show a mass-law retardive effect with added tetramethylammonium chloride. The values of n also differ; 2 for 8-quinolinol and 1 for the 2-methyl derivative. The evidence for incursion of steric effects and the significance is considered.     

Effect of salts on the partition of 8-quinolinol

The effect of inert salts on the partition of 8-quinolinol between benzene and water was determined. For the salts investigated, the relation log K(D') = I + k(3),mu was demonstrated, as expected from the Setschenow equation. The salting out order observed is KCl > NaCl > KNO(3) > NaClO(4).     

Some solvent effects on the solvent extraction of 8-quinolinol

The distribution constants of 8-quinolinol between water and a series of substituted aliphatic hydrocarbons, at 25 degrees , are reported. The results are discussed in terms of dielectric constant and solubility parameter of the solvents. For 8-quinolinol, and possibly for its chelates, bromochloromethane, dibromomethane and chloroform seem to be about the best solvents, in that order. Among the solvents studied, chloroform shows significantly higher values than expected; the deviation may be explained as a specific interaction of the hydrogen- bonding type.     

Molybdenum (V) oxo-complexes of 2-methyl-8-quinolinol

The synthesis and structure elucidation of the dimeric or monomeric nature of several molybdenum (V) oxo-complexes of 2-methyl-8-quinolinol (2-methyloxine) have been described, and we have compared these complexes with the molybdenum (V) oxo-complexes of 8-quinolinol (oxine). These complexes, were identified by IR and electronic spectra, magnetic susceptibility, differential scanning calorimetry, thermogravimetric analysis and the analytical data. The results permit us to assign the formulae: (C₁₀H₈NO)₄Mo₂O₃, (C₁₀H₈NO)₂Mo₂O₄ and (C₁₀H₈NO)₂MoO(OH). We suggest that the low magnetic moments observed for the dimeric complexes (C₁₀H₈NO)₄Mo₂O₃ and (C₁₀H₈NO)₂Mo₂O₄ are due, at least in part to intramolecular metal-metal interactions. Monomeric molybdenum (V) species (C₁₀H₈NO)₂MoO(OH), exhibits a magnetic moment ca. 1.75 Bohr magnetons.     

The spectrophotometric determination of nitrite in water with 8-quinolinol

The method is based on the formation of a purple azoxine dye by coupling diazotized p-nitroaniline with 8-quinolinol. Beer's law is obeyed at 550 nm in the range 2–28 μg NO₂^- per 25 ml. The molar absorptivity and Sandell sensitivity are 3.88 × 10⁴ l mol^-1 cm^-1 and 0.0012 μg cm^-2, respectively.     

1H NMR study of isomerization in chlorotin(IV) ternary complexes of 8-quinolinol and 5,7-dichloro-8-quinolinol

A complete analysis of the temperature dependence (?30 to 52°C) of the ¹H NMR spectra in d-chloroform of the ternary complexes, bis-(8-quinolinato)tin(IV) dichloride and bis-(5,7-dichloro-8-quinolinato)tin(IV) dichloride has been performed. The intramolecular character of the exchange process has been established, and the spectra have been analyzed by the total lineshape method in terms of the interconversion of two isomers, the cis-cis-trans and the cis-trans-cis (with respect to Cl, N and O atoms), including the tin-proton couplings in the simulations. Arrhenius parameters of the process were E_a = 54 ± 1 and 52 + 1 kJ mol^?1, and log A = 11.8 ± 0.2 and 11.7 ± 0.3, respectively, for the two complexes. The similarity of the activation parameters obtained for both complexes indicates that the presence of bulky Cl atoms in the 8-quinolinol ring had no appreciable energetic influence on the isomerization process. Data were compared with those reported for other chlorinated hexacoordinated complexes, involving ligands other than the 8-quinolinol ring.     

Preparation of 6-Fluoro-8-quinolinol and Related 6-Fluoroquinolines

 6-Fluoro-8-quinolinol was prepared from 2-amino-5-fluorophenol by a Skraup synthesis. No synergism was observed between 5-fluoro- and 6-fluoro-8-quinolinols or between 6-fluoro- and 7-fluoro-8-quinolinols against any of the six fungi in our test system (Aspergillus niger, A. oryzae, Myrothecium verrucaria, Trichoderma viride, Mucor cirinelloides, and Trichophyton mentagrophytes) in Sabouraud dextrose broth. Unlike the fluoro-8-quinolinols, the 8-quinolinols comparably substituted with chlorine or bromine did form synergistic mixtures. This is attributed to steric factors.     

Preparation of 6-Fluoro-8-quinolinol and Related 6-Fluoroquinolines

Summary.  6-Fluoro-8-quinolinol was prepared from 2-amino-5-fluorophenol by a Skraup synthesis. No synergism was observed between 5-fluoro- and 6-fluoro-8-quinolinols or between 6-fluoro- and 7-fluoro-8-quinolinols against any of the six fungi in our test system (Aspergillus niger, A. oryzae, Myrothecium verrucaria, Trichoderma viride, Mucor cirinelloides, and Trichophyton mentagrophytes) in Sabouraud dextrose broth. Unlike the fluoro-8-quinolinols, the 8-quinolinols comparably substituted with chlorine or bromine did form synergistic mixtures. This is attributed to steric factors. Corresponding author. E-mail: clarke@fordham.edu Received May 23, 2002; accepted May 29, 2002     

Effect of pore size on the capacity of sislca-immobilized 8-quinolinol

Optimization of the pore sizes of various silica gels used as supports in the immobilization of 8-quinolinol is described. Increased capacity is observed as pore size decrease to the opt? at about 6 nm. At smaller pore sizes, steric effects appear to predominate, ? capacities decrease sharply. An explanation for these effects is proposed, it was confirmed by using molecular models.     

Solvent effect on the intramolecular hydrogen bond in 8-quinolinol N-oxide

Solvent effect on intramolecular hydrogen bond in 8-quinolinol N-oxide has been studied by IR, UV,¹H NMR and¹³C NMR spectroscopy, dipole moment measurements and quantum-mechanical calculations. The solute-solvent interactions are of local character and they vary considerably over the range of solvent under study. The results suggest that formation complexes with solvent molecules weaken the intramolecular hydrogen bond in 8-quinolinol N-oxide.     

Redox properties of 8-quinolinol and implications for its mode of action

8-Quinolinol (oxine, 8-hydroxyquinoline) is a simple aromatic alkaloid with allelopathic, antibacterial, antifungal, and cytotoxic activities. Generally, it is assumed that 8-quinolinol toxicity depends on transition metal chelation that negatively affects their availability for metalloenzymes in the cell or reactive oxygen species generation (ROS), which are formed following reduction of molecular oxygen by autoxidation of the redox active metal central atom of the 8-quinolinol complex. On the contrary, beneficial effects of 8-quinolinol and its derivatives in the medication of certain degenerative diseases are known. In this context, the activity of 8-quinolinol derivatives is attributed to their antioxidant activity following iron complex formation. To address this controversial issue, we explore the possible anti- or pro-oxidant effects of 8-quinolinol and its iron complexes in the deoxyribose degradation assay, by cyclic voltammetry and in a biological assay. The antibacterial effects of 8-quinolinol and its complex with iron were evaluated on Curtobacterium flaccumfacies and Paenibacillus amylolyticus. 8-Quinolinol showed strong antioxidant activity in the deoxyribose degradation assay. This activity may not depend exclusively on iron chelation, but probably more on the notable reducing properties of 8-quinolinol; it proved to be a more efficient antioxidant than the flavonoids catechin and quercetin. By contrast, 8-quinolinol showed no pro-oxidative effects in the deoxyribose degradation assay, both in free form and in complex with iron, as it may occur with redox cyclers. Cyclic voltammetry confirmed this too. 8-Quinolinol significantly inhibited bacterial growth and respiration. Idiosyncratically, its 50:1 mixture with iron(III) ions was less active compared with free 8-quinolinol; it even caused a U-shaped nonlinear hormetic effect on growth and failed to inhibit respiration as totally as the pure mixture; the respiration was even accelerated compared with the control as a result of lower stress. Our results support the notion that complex formation with either iron or other transition metals affects the reducing power of 8-quinolinol, but, in contrast to general assumptions, this study finds no support that complex formation with iron represents the major mode of action.