Impedance of carrier injection at the metal-organic interface mediated by surface states in electron-only tris(8-hydroxyquinoline) aluminium (Alq(3)) thin layers

Capacitance spectra of thin (< 200 nm) Alq(3) electron-only devices have been measured as a function of bias voltage. Capacitance spectra exhibit a flat response at high frequencies (> 10(3) Hz) and no feature related to the carrier transit time is observed. Toward low frequencies the spectra reach a maximum and develop a negative excess capacitance. Capacitance response along with current-voltage (J-V) characteristics are interpreted in terms of the injection of electrons mediated by surface states at the metal organic interface. A detailed model for the impedance of the injection process is provided that highlights the role of the filling/releasing kinetics of energetically distributed interface states. This approach connects the whole capacitance spectra to the occupancy of interface states, with no additional information about bulk trap levels. Simulations based on the model allow to derive the density of interface states effectively intervening in the carrier injection (similar to 1.5 x 10(12) cm (2)). (C) 2008 Elsevier B.V. All rights reserved.

Preparation and thermal decomposition of copper(II), zinc(II) and cadmium(II) chelates with 8-hydroxyquinoline

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Thermal behaviour of intercalated 8-hydroxyquinoline (oxine) in montmorillonite clay

The composite montmorillonite-8-hydroxyquinoline (Swy-1-8-HQ) was prepared by two different processes and studied by using thermogravimetric analysis (TG/DTG and DSC), as well as helpful techniques as fluorescence in the UV-visible region and X-ray diffraction. The composites developed fluorescent appearance, however with quantum poor efficiency and they exhibited distinct TG and DSC thermal behavior. The fluorescence data of spectra associated to the TG/DT curves allowed to suggest that the 8-HQ was present in the composites in two different circumstances: 1 - intercalated in the interlayer spaces (Swy-1-8-HQ2), rigidly associated to the Substrate feasible as a monolayer with the aromatic rings parallel to the silica layer; and/or, 2 - adsorbed on the Surface (Swy-1-8-HQ1), either as a bilayer formation or tilting of the molecules to the silicate layer sheet. All results confirmed above are in agreement with X-ray diffraction patterns, once the interlayer space increases when 8-HQ is incorporated. The experimental results confirm the formation of the composites in agreement with the method used in the preparation.

Thermal behavior of the Ti(IV), Zr(IV) and Pb(II) complexes with 5-nitro-8-hydroxyquinoline

Ti(IV), Zr(IV) and Pb(II) complexes with 5-nitro-8-hydroxyquinoline (5-NQ) were obtained by precipitation in acetone/ammonium solution medium. The compounds TiO(C9H5N2O3)(2).0.5H(2)O, ZrO(C9H5N2O3)(2)2H(2)O and Pb(C9H5N2O3)(2) were characterized by Elemental Analysis, X-ray Diffratometry and Infrared Absorption Spectrometry and their thermal behavior followed by TG/DTA. This present study intends to show the variations in the thermal behavior of the compounds and in the composition and/or structure of final oxide residues, in different atmospheres and heating rates.

Structural and vibrational study of 8-hydroxyquinoline-2-carboxaldehyde isonicotinoyl hydrazone: a potential metal-protein attenuating compound (MPAC) for the treatment of Alzheimer's disease

A comprehensive structural and vibrational study of the potential metal-protein attenuating compound 8-hydroxyquinoline-2-carboxaldehyde isonicotinoyl hydrazone is reported. X-ray diffraction data, as well as FT-IR and Raman frequencies, were compared with the respective theoretical values obtained from DFT calculations. Theory agrees well with experiment. In this context, an attempt of total assignment concerning the FT-IR and Raman spectra of the title compound was performed, shedding new light on previous partial assignments published elsewhere.

Design and synthesis of near-IR luminescent mesoporous materials covalently linked with tris(8-hydroxyquinolinate) lanthanide(III) complexes

By using the bifunctional ligand, 8-hydroxyquinoline-functionalized organosilane (Q-Si), the new mesoporous material Q-MCM-41 covalently bonded with 8-hydroxyquinoline was synthesized. Through the ligand exchange reaction, the new near-infrared (NIR) luminescent mesoporous LnQ(3)-MCM-41 (Ln = Er, Nd, Yb) materials were prepared by linking the lanthanide quinolinate complexes to the ordered mesoporous Q-MCM-41 material. The LnQ(3)-MCM-41 materials were characterized by powder X-ray diffraction and N-2 adsorption/desorption, and they all show the characteristic mesoporous structure of MCM-41 with highly uniform pore size distributions.

Near-infrared emission from novel tris(8-hydroxyquinolinate)lanthanide(III) complexes-functionalized mesoporous SBA-15

A novel mesoporous material covalently bonded with 8-hydroxyquinoline (HQ) was synthesized (designated as Q-SBA-15). The 5-formyl-8-hydroxyquinoline grafted to.(3-aminopropyl)triethoxysilane, that is, alkoxysilane modified 8-hydroxyquinoline (Q-Si), was used as one of the precursors for the preparation of the Q-SBA-15 material. On the basis of the other function of the Q-Si of coordinating to lanthanide (Ln) ions, for the first time, the LnQ(3) complexes (Ln = Er, Nd, Yb) have been covalently bonded to the SBA-15 materials.

Efficient, Scalable, and Solvent-free Mechanochemical Synthesis of the OLED Material Alq(3) (q=8-Hydroxyquinolinate)

The aluminum complex Alq(3) (q = 8-hydroxyquinolinate), which has important applications in organic light-emitting diode materials, is shown to be readily synthesized as a pure phase under solvent-free mechanochemical conditions from Al(OAc)(2)OH and 8-hydroxyquinoline by ball milling. The initial product of the mechanochemical synthesis is a novel acetic acid solvate of Alq(3), and the alpha polymorph of Alq(3) is obtained on subsequent heating/desolvation of this phase. The structure of the mechanochemically prepared acetic acid solvate of Alq(3) has been determined directly from powder X-ray diffraction data and is shown to be a different polymorph from the corresponding acetic acid solvate prepared by solution-state crystallization of Alq(3) from acetic acid. Significantly, the mechanochemical synthesis of Alq(3) is shown to be fully scalable across two orders of magnitude from 0.5 to 50 g scale. The Alq(3) sample obtained from the solvent-free mechanochemical synthesis is analytically pure and exhibits identical photoluminescence behavior to that of a sample prepared by the conventional synthetic route.

Sensing hazardous metal ions using a fluoroionophore calix[4]arene species containing two 8-oxyquinoline groups

The interaction of a calix[4]arene-based species containing two 8-oxyquinoline chromophore pendants with hazardous metal ions has been investigated using optical absorption and fluorimetric techniques. In the presence of Hg(2+), Cd(2+), and Pb(2+) ions, there is only a small decrease of the calixarene absorption band at 283 nm. The main changes are associated with the absorption band of the 8-oxyquinoline group at 315 nm, undergoing a systematic bathochromic shift to above 350 nm. In addition, a systematic decrease of the oxyquinoline emission at lambda(em) = 392 nm (lambda(exc) = 315 nm) has been observed. These observations are consistent with the coordination of the metal ions to the quinoline groups attached to the calixarene ligand, providing a useful fluoroinophore species for analytical purposes.

Dehydration and volatilization non isothermic kinetic of the solid state aluminium 8-hydroxyquinolinate

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Synthesis and thermal study of the barium complexes with 8-hydroxyquinolinate derivatives

In this present work, barium ion was reacted with different ligands which are 5,7-dibromo, 5,7-dichloro, 7-iodo and 5-chloro-7-iodo-8-hydroxyquinoline, in acetone/ammonium hydroxide medium under constant stirring and the obtained compounds were as follows: (I) Ba[(C9H4ONBr2)(2)].1.5H(2)O; (II) Ba[(C9H4ONCl2)(OH)]. 1H(2)O; (III) Ba[(C9H5ONI)(2)]. 1H(2)O and (IV) Ba[(C9H4ONICl)(2)]. 5H(2)O, respectively. The compounds were characterized by elemental analysis, infrared absorption spectrum (IR), inductively coupled plasma spectrometry (ICP), simultaneous thermogravimetry-differential thermal analysis (TG-DTA) and differential scanning calorimeter (DSC).The final residue of the thermal decomposition was characterized as orthorhombic BaBr2 from (I); the intermediate residue, as a mixture of orthorhombic BaCO3 and BaCl2 and cubic BaO and the final residue, as a mixture of cubic and tetragonal BaO and orthorhombic BaCl2 (II); the intermediate residue, as orthorhombic BaCO3 and as a final residue, a mixture of cubic and tetragonal BaO from (III); and the intermediate residue, as a mixture of orthorhombic BaCO3 and BaCl2 and as a final residue, a mixture of cubic and tetragonal BaO and orthorhombic BaCl2 from (IV).

Attainment of lead titanate - Through the thermal decomposition of coprecipitated 8-hydroxyquinolinate precursors

Crystalline PbTiO3 was obtained through the thermal decomposition of 8-hydroxyquinolinate of lead(II) and that of titanium(IV), which was monitored by TG/DTG/DTA under different atmospheric conditions and with varying heating rates. The compound was prepared from adding 8-hydroxyquinoline solution in the solution of metallic ions Pb(II):Ti(IV) (1:1) Linder constant stirring at 3degreesC, having the pH adjusted to 10. The results of these investigations show that different thermal behavior related to the precursor occurred and also the consequent formation of residues which have different crystallinities. No carbonate residues from the thermal decomposition could be determined by XRD and IR. Only PbTiO3 was observed and confirmed by DSC at 470degreesC, temperature lower than the tetragonal-cubic transition.

Sublimation/volatilisation kinetics of 8-hydroxyquinolines and their nitro-derivatives

5-Nitro-8-hydroxyquinoline (B) and 5,7-dinitro-8-hydroxyquinoline (C) were obtained from nitration of 8-hydroxyquinoline (A) and purified in acetone medium and under heating in which the formation of (B) or (C) depends on the amount of HNO3 added. TG curves present mass loss in only one step before and after the melting point (T-m=76 degreesC (A) and 180 degreesC (B)) in different proportions as a function of the heating rate, characterising the sublimation and the volatilisation processes, respectively. The thermal stability of the compounds follow the order: A (77 degreesC)

Thermal behaviour of Tin(II) complex with 8-hydroxyquinolinate in the solid state

Tin(II) complexes with 8-hydroxyquinolinate in solid state have been obtained by adding aqueous ammonium to a solution containing stannous chloride and 8-hydroxiquinoline in medium of HCl and acetone up to pH 5 and 9, respectively. The products obtained show the same composition, Sn(C9H6ON)(2); however there are some differences regarding both the thermal behaviour in an oxidant atmosphere and morphology. These products were characterised by elemental and complexometric analysis, TG and DTA curves, infrared and X-ray diffractometry. TG curves show, above 448 K, the partial oxidation on air atmosphere of Sn(II) complexes to Sn(IV) complexes, SnO(C9H6ON)(2). This behaviour does not depend only on pH in which the compounds were obtained but also on the heating rate in TG curves. Sn(II) complexes volatilise almost completely on nitrogen atmosphere and partially on air atmosphere depending on the oxidation degree of the compound.

Synthesis and thermal study of magnesium complexes with 8-hydroxyquinolinate derivatives

Magnesium ion was reacted with 5,7-dibromo-, 5,7-dichloro-, 7-iodo- and 5-chloro-7-iodo-8-hydroxyquinoline, in acetone/ammonium hydroxide medium under constant stirring to obtain (I) Mg[(C9H4ONBr2)(2)].2H(2)O; (II) Mg[(C9H4ONCl2)(2)].3H(2)O; (III) Mg[(C9H5ONI)(2)].2H(2)O and (IV) Mg[(C9H4ONICl)(2)].2.5H(2)O complexes. The compounds were characterized by elemental analysis, IR spectra, ICP, TG-DTA and DSC.Through thermal decomposition residues were obtained and characterized, by X-ray diffractometry, as a mixture of hexagonal MgBr2 and cubic MgO to the (I) compound at 850degreesC; cubic MgO to the (II), (III) and (IV) compounds at 750, 800 and 700degreesC, respectively.