Thickness Dependent Behavior of Photoluminescence of Tris(8-hydroxyquinoline)Aluminum Film

In situ thickness dependent photoluminescence （PL） measurements of tris（8-hydroxyquinoline） aluminum（Alq3） film were performed. At the beginning of Alq3 deposition on the glass substrate, the Alq3 emission showed a sharp red-shift. Further deposition of Alq3 resulted slight red-shift, and finally tended to saturated value. The total red-shift of about 12 nm was observed for the Alq3 film thickness range from 2 to 500 nm.This red-shift was attributed to the change from the 2D to 3D exciton state with increasing Alq3 film thickness. Meanwhile, the PL intensity of Alq3 emission increased continuously, and showed a rate change at the initial deposition of Alq3 due to non-rediative decay of excitons arised from the interaction between excitons and the substrate, and finally tended to saturation with the Alq3 thickness.

Thermochemical Study on Coordination Complex of Samarium with Salicylic Acid and 8-Hydroxyquinoline

The coordination complex Sm（C7H5O2）2·（C9H6NO）, synthesized from the reaction of samarium chloride sixhydrate with salicylic acid and 8-hydroxyquinoline, was characterized with IR, elemental analysis, molar conductance, and thermogravimatric analysis. The standard molar enthalpies of solution of [ SmCl3·6H2O （s） ], [ 2C7H6O3 （s） ], [ C9H7NO （ s ） ] and [ Sm （C7H5O3） 2·（ C9H6NO ） （ s ） ] in the calorimetric solvent were determined with the solution-reaction isoperibol calorimeter at 298.15 K to be △sHm^- [ SmCl3·6H2O （s）, 298.15 K ] = - 103.98 ± 0.04 kJ·mol^-1, △sHm^- [2 C7H6O3 （s）, 298.15 K] = 16.35±0.14 kJ·mol^-1,△sHm^-[C9H7NO （s）, 298.15 K] = -6.11±0.08 kJ·mol^-1 and △sHm^-[Sm（C7H5O3）2·（C9H6NO） （s）, 298.15 K] = - 130.08 ± 0.04 kJ·mol^-1, respectively. The enthalpy was determined to be △rHm^- = 89.59 ±0.18 kJ·mol^-1 for the reaction SmCl3·6H2O（s） ＋ 2C7H6O3（s） ＋ C9H7NO（s） = Sm （C7H5O3） 2·（C9H6NO） （ s ） ＋ 3HCl （g） ＋ 6H2O （ l ）. According to the above results and the data given in literature and through Hess＇ law, the standard molar enthalpy of formation of Sin（ C7H5O3 ）2·（C9H7NO）（s） was estimated to be △rHm^- [ Sm （C7H5O3）2·（C9H6NO） （s）, 298.15 K] = - 2055.9 ± 3.03 kJ·mol^-1.

Crystal Structure and Characterization of a Binuclear Cd(Ⅱ) Quaternary Coordination Complex [Cd_2(phen)_2Q_2(BP)]_n(phen=1,10-Phenanthroline,BP = Biphenyl-4,4'-dicarboxylic acid,Q=8-Hydroxyquinoline Anion)

The structure of a binuclear cadmium（Ⅱ） quaternary complex, [Cd2（phen）2- Q2（BP）]n 1 （phen = 1,10-phenanthroline, BP = biphenyl-4,4′-dicarboxylic acid, Q = 8-hydroxy- quinoline-anion）, has been determined by X-ray crystallography and characterized by elemental analysis, IR spectrum and thermogravimetric analysis. It crystallizes in the monoclinic system, space group P21/n with a = 13.1906（18）, b = 10.9623（15）, c = 16.947（2）A, β = 111.3430（10）°, V = 2282.5（5）A^3, Z = 4, Mr = 556.85, Dc = 1.620 g/cm^3, F（000） = 1116,μ= 0.994 mm^-1 and S = 1.056. In the structure, 1D chains are connected via biphenyl-4,4′-dicarboxylic acid, 8-hydroxy quinoline anion and binuclear cadmium atoms into an infinite 1-D molecular chain architecture. Via aryl ring π-π stacking interactions a supramolecular structure is formed in 1.

Synergistic extraction of praseodymium with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester and 8-Hydroxyquinoline

The synergistic extraction of Pr^3＋ from hydrochloric medium using mixture of 2-ethylhexyl phosphonic acid mono- 2-ethylhexyl ester （P507, HL） and 8-Hydroxyquinoline （HQ） in heptane was investigated. The effect of equilibrium of aqueous acidity on extraction of Pr^3＋ was discussed. The effect of extractant concentraction, different diluents, equilibrium time and acetate ion concentration oil extraction reaction were also studied. With a method of double-logarithmic slope, composition of the extracted species on 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester and 8-Hydroxyquinoline was derived. The result shows that the synergistic extraction system not only overcomes emulsification of 8-Hydroxyquinoline, but also shows perfect capacity of synergistic extraction. The largest synergistic enhancement factor can be calculated to be 5.49 at pH 3.6 for Pr^3＋.

Bipolar resistive switching based on bis(8-hydroxyquinoline) cadmium complex:Mechanism and non-volatile memory application

Stable and persistent bipolar resistive switching was observed in an organic diode with the structure of indium-tin oxide （ITO）/bis（8-hydroxyquinoline） cadmium （Cdq2）/Al. Aggregate formation and electric field driven trapping and detrapping of charge carriers in the aggregate states that lie in the energy gap of the highest occupied molecular orbital （HOMO） and the lowest unoccupied molecular orbital （LUMO） of the organic molecule were proposed as the mechanism of the observed bipolar resistive switching, and this was solidly supported by the results of AFM investigations. Repeatedly set, read, and reset measurements demonstrated that the device is potentially applicable in non-volatile memories.

A Hydrogen Bond Stabilized 3D Network Built from Pyrazine-2,3,5,6-tetracarboxylic Acid and 8-Hydroxyquinoline

8-Hydroxyquinoline salt of pyrazine-2,3,5,6-tetracarboxylic acid [HQ]2[H2pztc]· 2H2O （1） was prepared and characterized by single-crystal X-ray diffraction, NMR, IR, TGA, elemental analysis and fluorescent measurements. Compound 1 crystallizes in orthorhombic, space group Pbcn with a = 9.953（3）, b = 15.966（3）, c = 16.081（5） A, V = 2555.5（13） A3, Z = 4, μ = 0.122 mm^-1, Dc = 1.514 Mg/m3, T= 296（2） K, C26H22N4O12, Mr = 582.48, F（000） = 1208, S = 1.006, R = 0.0448 and wR = 0.1149. Compound 1 has a three-dimensional （3D） network, in which pyra- zine-2,3,5,6-tetracarboxylic acids build up two-dimensional （2D） sheets and 8-hydroxyquinoline cations and water molecules act as pillars to connect the 2D sheets into an extended 3D network through strong intermolecular hydrogen bonding and π…π stacking interactions. Especially, a very short O-H…O hydrogen bond （O…O 2.470（2） A） between two neighboring [H2pztc] anions was observed.

Theoretical Studies on the Ground State and Excited State of 2,7′- （Ethylene）-bis-8-hydroxyquinoline

2,7′-（Ethylene）-bis-8-hydroxyquinoline was optimized with DFT/B3LYP and ab initio HF methods, so ion- ization 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 intramoleeular reor- ganization energy of tris（2,7′-（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.

Synthesis and Structural Characterization of [Co(Q)_2(H_2O)_2](Q=8-Hydroxyquinoline Ion)

The single crystal of bi（8-hydroxyquinoline） bihydrated cobalt （Ⅱ） complex, [ Co（Q）2 （H2O2 ] （Q = 8-hydroxyquinoline ion）, has been synthesized by general method and structurally characterized by single crystal X-ray diffraction. Crystal data： C18H16CoN2O4, monoclinic, C2/c, α = 1.336 2（4） nm, b = 0.941 2（3） nm, c = 1.354 3（4） nm, β= 109.672（4）°, Z = 4. In the complex, Co（ Ⅱ ） ion is six-coordinated, forming a distorted octahedron. H-bonding and π-π stacking interaction play a significant role to form and stabilize the three-dimensional structure.

ABSORPTION SPECTRA OF 4f ELECTRON TRANSITIONS OF NEODYMIUM COMPLEX WITH 8-HYDROXYQUINOLINE AND OCTYLPHENOL POLY(ETHYLENEGLYCOL)ETHER

In this paper the absorption spectra of 4f electron transitions of the neodymlum complex with 8-hydroxyquinoline and octylphenol poly(ethyleneglycol)ether have been studied. The marked intensification of the band at low octylphenol poly(ethyleneglycol)ether concentration is found normally at 575 nm, and its resolution into three sharp bands centering at 572, 580 and 584 nm. The absorbances of the absorption maxima are 3.5 (at 572 nm), 7.2 (at 580 nm) and 10.2 (at 584 nm) times greater than that of the chloride.

Preparation and Characterization of Carboxyl Functionalized Fluorescent Mesoporous Silica Nanoparticles Containing 8-Hydroxyquinolinate Zinc Complexes

Fluorescent mesoporous silica nanoparticles functionalized with carboxyl group(Znq-CMSCOOH) were successfully synthesized by in situ formation route of 8-hydroxyquinolinate zinc complexes in channels of mesoporous silica nanoparticles and post-grafting of carboxyl group on the surface. Moreover,the particle size and structural properties of Znq-CMS-COOH were characterized by transmission electron microscopy(TEM),field emission scanning electron microscopy(FE-SEM),dynamic light scattering(DLS),Fourier transform infrared spectroscopy(FT-IR),UV-vis spectrometer, fluorescence spectrometer and nitrogen adsorption-desorption measurements. The obtained results suggest that the Znq-CMS-COOH presents the uniform spherical shape with the mean diameter of about 85 nm and the obvious wormhole arrangement mesoporous. In addition, the Znq-CMS-COOH possesses green fluorescence with the emission peaks at 495 nm. So the Znq-CMS-COOH, which is beneficial to further modification and tracing, might be a great potential carrier for applying in drug delivery system in the future.

Mitigating phytotoxicity of tetracycline by metal-free 8-hydroxyquinoline functionalized carbon nitride photocatalyst

Photooxidative removal of pharmaceuticals and organic dyes is an effective way to eliminate growing micropollutants. However, photooxidation often results in byproducts as secondary hazardous substances such as phytotoxins. Herein, we found that photooxidation of common antibiotic tetracycline hydrochloride(TCH) over a metal-free 8-hydroxyquinoline(8-HQ) functionalized carbon nitride(CN) photocatalyst significantly reduces the TCH phytotoxic effect. The phytotoxicity test of photocatalytic treated TCH-solution evaluated towards seed growth of Cicer arietinum plant model endowed natural root and shoot growth.This study highlights the conceptual insights in designing of metal-free photocatalyst for environmental remediation.

Evaluating the Efficiency of Cadmium Removal by Alginate Hydrogels from Water Using 5,7-Dibromo-8-hydroxyquinoline as a Complexing Reagent

Cadmium toxicity in wastewater is a rising concern due to industries like batteries,metallurgy,electroplating,plastic stabilizers,and pigments.The quantitative detection of Cd^(2+)and its remediation from wastewater samples are of major concern from an environmental point of view.In the present work,an effective spectrophotometric method has been reported using 5,7-dibromo-8-hydroxyquinoline(DBHQ)as a complexing agent for Cd^(2+).This method has advantages like using recyclable,less toxic solvents and easy sample preparation.The limit of detection,limit of quantification,and sensitivity of the proposed method were found to be 33.30,36.70 mg L^(−1),and 2×10^(−3),respectively.The DBHQ method was validated using atomic absorption spectroscopy,and the recovery percentage was more than 98%.These results indicate that DBHQ can be effectively used for monitoring Cd^(2+)in aqueous systems.The method developed was further employed for monitoring Cd^(2+)adsorption on calcium alginate(AL)hydrogels.Batch adsorption studies were done to optimize parameters of Cd^(2+)removal using AL hydrogels,and the data obtained were used for kinetic and thermodynamic studies.Kinetic studies indicated that the pseudo-first-order model showed better fitting,and thermodynamic studies showed Freundlich-like adsorption.The maximum adsorption capacity of Cd^(2+)on AL hydrogels was found to be 56.45 mg g^(−1).The validation studies of DBHQ were performed using statistical analysis methods like t-tests and one-way variance.

Efficient Synthesis of 2-(8-Quinolinoxy)-4H-imidazolin-4-ones

The title compounds 2-(8-quinolinoxy)-4 H -imidazolin-4-ones(4) were synthesized by means of base catalytic reactions of 8-hydroxyquinoline with each of carbodiimides 2, which were obtained via aza-Wittig reactions of iminophosphoranes 1 with the corresponding aromatic isocyanates.

Ethylene Oligomerization to Low Carbon Olefins by a Zirconium Complex Incorporating 8-Quinolinolato Ligands at a Low Al/Zr Ratio

Bis(8-quinolinolato)zirconium dichloride (Ox)2ZrCl2 (Ox- = 8-quinolinolato) was found active for ethylene oligomerization with a high selectivity of 84~94% to C4~C10 olefins at 70~100C under the pressure of 1.8 MPa using Et2AlCl as a co-catalyst (Al/Zr = 60).

Conjugated 8-Hydroxylquinoline-Based Fluorescent Chemosensor for Zn^(2+) and Cd^(2+) and Bioimaging Application in Living Cells

A conjugated 8-hydroxyquinoline( 8-HQ)-based fluorescent chemosensor( 1) for Zinc ion( Zn^(2+)) and Cadmium ion( Cd^(2+)) was developed in aqueous solution and used for Zinc ion living cells bioimaging. The probe 1 was weakly fluorescent,but displayed a strong fluorescence at 580 nm with a large Stokes shift of150 nm in the presence of Zn^(2+) or Cd^(2+). This probe allows the detections of Zn^(2+) in the range of 0. 8-10 μmol/L and Cd^(2+) in the range of 0. 8-8 μmol/L,with the limit of detections of 0. 2 and 0. 6μmol/L for Zn^(2+) and Cd^(2+),respectively. The present probe was successfully used for fluorescence bioimaging of Zn^(2+) or Cd^(2+) in the living cells.

Synthesis and Crystal Structure of a Cr(Ⅲ) Dimer[Cr_2(8-hqn)_2Cl_4(H_2O)_2]·2(CH_3)_2CO (8-hqn=8-Hydroxyoxyquinolate)

The title complex [Cr2（8-hqn）2Cl4（H2O）2]·2（CH3）2CO （8-hqn = 8-hydroxyoxyquinolate） has been synthesized and characterized by single-crystal X-ray diffraction. It crystallizes in the triclinic system, space group P^-1 with a = 8.719（1）, b = 9.226（1）, c = 9.717（1） A^°, α = 71.916（2）, β= 78.072（2）, γ = 76.014（2）°, V= 713.72（15） A^°^3, Z= 1, Dc= 1.597g/cm^3, F（000） = 350 and μ（MoKa） = 1.177 mm^-1, the final R = 0.0490 and wR = 0.1055 for 1616 observed reflections with I 〉 2σ（I）. It is a dimer constructed by two monomeric units [Cr（8-hqn）Cl2（H2O）] bridged by phenoxide-like oxygen atom from 8-hydroxyoxyquinolate, where the two six-coordinated Cr（Ⅲ）atoms exhibit an octahedral coordination geometry.

Studies on synergistic solvent extraction of rare earth elements from nitrate medium by mixtures of 8-hydroxyquinoline with Cyanex 301 or Cyanex 302

Synergistic solvent extraction of rare earth elements （REEs） from nitrate medium was investigated with mixtures of 8-hydroxyquinoline （HQ） and acidic organophosphorus extractants, bis（2,4,4-trimethylpentyl） dithiophosphinic acid （Cyanex 301） and bis（2,4,4-trimethylpentyl） monothiophosphinic acid （Cyanex 302）. The extraction behavior of Cyanex 301/Cyanex 302 and their binary mixtures with HQ towards several lanthanoids （La, Nd, Sm, Tb, Ho, Tm） and yttrium （Y） was investigated. The separation ability of REEs was studied according to the various extraction effects. The extraction mechanisms for yttrium were studied with the methods of slope analysis and constant moles in the synergistic systems. The extracted compounds, the equilibrium constants, and thermodynamic functions were also determined.

Determination of Some Trace Metals in Environmental Samples by Flame AAS Following Solid Phase Extraction with Amberlite XAD-2000 Resin after Complexing with 8-Hydroxyquinoline

A procedure for preconcentration of Mn（Ⅱ）, Fe（Ⅱ）, Co（H）, Cu（Ⅱ）, Cd（Ⅱ）, Zn（Ⅱ）, Pb（Ⅱ） and Ni（Ⅱ） based on retention of their complexes with 8-hydroxyquinoline （HQ） on Amberlite XAD-2000 resin in a column was proposed for the analysis of environmental samples by flame AAS. Various parameters such as pH, eluent type, volume, concentration, flow rate and volume of sample solution, and matrix interference effect on the retention of the metal ions were investigated. The optimum pHs for the retention of metal complexes in question were about 6 except for Mn^2＋ for whose value is 8. The loading capacity of the adsorbent for these metals and their recoveries from the resin under the optimum conditions were in the range 6.82-9.26 mg·g^-1 and 95%-101%, respectively. The enrichment factor was calculated as 100 and the limit of detection was in the range 0.3-2.2 μg·L^-1 （n=20, blank＋ 3s）. The proposed enrichment method was applied to tap water, stream water and vegetable samples. The validation of the procedure was carried out by analysis of certified reference material and standard addition. The analytes were determined with a relative standard deviation lower than 6% in all samples.

Synthesis and Characterization of 8-Hydroxyquinoline Derivative Containing a Triphenylamine Unit and Its Metal Complexes

A new 8-hydroxyquinoline derivative （5） was synthesized and characterized by ESI-MS, ^1H NMR spectroscopy, elemental analysis and IR spectroscopy. The photophysical properties of compounds 5, 6 and 7 were also detemined by UV-vis and FL spectroscopy. The vibrational frequency of ligand 5 predicted by using B3LYP method is in good agreement with experimentally determined values. The compositions of the corresponding copper（Ⅱ） and zinc（Ⅱ） complexes were confirmed to be Cu（C29H21N2·O）2,H2O （6） and Zn（C29H21N2O）2,H2O （7） by elementary analysis, thermogravimetry analysis and IR spectroscopy.

Theoretical Studies on Proton Transfer Reactions of 8-Hydroxyquinoline Monomers and Dimers

Density functional theory （DFT） of quantum chemistry method was employed to investigate proton transfer reactions of 8-hydroxyquinoline （8-HQ） monomers and dimers. By studying the potential energy curves of the isomerization, the most possible reaction pathway was found. The total energy of 8-hydroxyquinoline was lower than that of quinolin-8（1H）-one, whereas the order was reversed in dimers. The findings explained the contrary experimental phenomena. The minimum reaction barrier of intramolecular proton transfer was 47.3 kJ/mol while that in dimer was only 25.7 kJ/mol. Hence it is obvious that proton transfer reactions of 8-HQ monomer have a considerable rate but it is easier to proceed for 8-HQ dimer than monomers. It implied that the hydrogen bond played an important role in depressing the activation energy of reaction. The mechanism of the tautomerization was discussed on the basis of theoretical results.