8-hydroxyquinoline Complexes Research Articles

A novel dichromate-sensitive fluorescent nano-chemosensor using new functionalized SBA-15

A novel fluorescence nano-chemosensor for Cr 2O 7 2− anion has been developed by assembly of fluorescent aluminum complex of 8-hydroxyquinoline (AlQ x ) within the channels of modified SBA-15. SBA-SPS-AlQ x shows a fluorescence emission at 486 nm. The observed remarkable fluorescence of SBA-SPS-AlQ x quenches in presence of Cr 2O 7 2− anion. The results showed that this fluorescent nano-material can be a useful chemo-sensor for determination of dichromate anions in aqueous solutions. The linear detecting range of fluorescent nano-chemosensor for Cr 2O 7 2− anion was 0.16–2.9 μmol L −1. The lowest limit of detection (LDL) was also found to be 0.2 ng mL −1 in aqueous solutions. SBA-SPS-AlQ x showed selectively and sensitively fluorescent quenching response toward Cr 2O 7 2− ion in comparison with I 3 −, NO 3 −, CN −, CO 3 2−, Br −, Cl −, F −, H 2PO 4 − and SO 4 2− ions, which was because of the higher stability of its inorganic complex with dichromate ion.

A novel permanganate-sensitive fluorescent nano-chemosensor assembled with a new 8-hydroxyquinoline-functionalized SBA-15

A novel fluorescence nano-chemosensor for MnO4− anion has been developed by assembly of fluorescent aluminum complex of 8-hydroxyquinoline (8-HQ) within the channels of modified SBA-15 (SBA-SPS-QAl). The ordered porous structure of SBA-15 is still retained after hybridization by chemosensor material. A remarkable fluorescent quenching of SBA-SPS-QAl was attributed to the effect of MnO4− anion. The linear detecting range of the hybrid mesoporous chemosensor is 0.16–4.6μmolL−1 of MnO4− anion and the lowest detection limit is 0.2ngmL−1 in the aqueous solution. SBA-SPS-QAl showed a selective and sensitive fluorescent quenching response toward MnO4− ion in comparison with N3−, NO3−, CN−, HCO3−, Cl−, F−, H2PO4−, SO42−, Cr2O72−, IO3− and I− ions, which was because of the higher stability of its inorganic complex with permanganate anion.

In situ route to novel fluorescent mesoporous silica nanoparticles with 8-hydroxyquinolinate zinc complexes and their biomedical applications

Novel luminescent mesoporous silica nanoparticles (MSNs) containing zinc 8-hydroxyquinolinate complexes were prepared by in situ formation route of metal complex in channels of MSNs. The MSNs functionalized with or without mercapto groups had a diameter of 80–170 nm and high surface area (>1010 m 2/g). The 8-hydroxyquinolinate (Hq) was introduced into MSNs containing-zinc ions to form the metalloquinolates by in situ route. The metalloquinolates formed in the channels of MSNs were determined as a single coordination mode (Znq). The novel Znq-MSNs exhibit different optical properties as compared with that obtained by direct chemical adsorption of Znq 2. Especially, the mercapto-modified MSNs exhibited the strong and stable fluorescent emission at about 500 nm in the pH range of 3–10. The obtained fluorescent MSNs were used in the in vitro researches of controlled release for ibuprofen and the imaging for human cervical cancer cells (HeLa).

Vibrational spectra of the Ga(III) complexes with oxine and clioquinol

The FTIR and FT-Raman spectra of the gallium(III) complexes of 8-hydroxyquinoline (oxine) and 5-chloro-7-iodo-8-hydroxyquinoline (clioquinol), were recorded and briefly discussed by comparison with the spectra of the uncoordinated ligands and with some related species.

Uncertainty estimation for the determination of Fe, Pb and Zn in natural water samples by SPE-ICP-OES

In this paper we estimate measurement of uncertainty for determination of Fe, Pb and Zn in natural water samples by solid-phase extraction and inductively coupled plasma optical emission spectrometry (SPE-ICP-OES). The procedure is based on the retention of analytes in the form of 8-hydroxyquinoline (8-HQ) complexes on a mini column of XAD-4 resin and subsequent elution with nitric acid. The influence of various analytical parameters including the amount of solid phase, pH, elution factors (concentration and volume of eluting solution), volume of sample solution, and amount of ligand on the extraction efficiency of analytes was investigated. To estimate the uncertainty of analytical result obtained, we propose assessing trueness by employing spiked sample. Two kinds of bias (proportional bias and constant bias) estimated. We applied Nested design for calculating proportional bias and Youden method to calculate the constant bias. The results we obtained for proportional bias are calculated from spiked sample...

Novel polymeric metal complexes as dye sensitizers for Dye-sensitized solar cells based on poly thiophene containing complexes of 8-hydroxyquinoline with Zn(II),Cu(II) and Eu(III) in the side chain

Novel polymeric metal complexes as dye sensitizer for dye-sensitized solar cells (DSSCs) based on poly thiophene containing complexes of 8-hydroxyquinoline with Zn(II),Cu(II), and Eu(III) in the side chain have been synthesized according to the Stille coupling method and characterized by FTIR, GPC, and Elemental analysis. The UV–vis absorption spectroscopy, photoluminescence spectroscopy, cyclic voltammetry, and the applications in dye-sensitized solar cells (DSSCs) are also determined and studied. The DSSCs fabricated by PZn(Q) 2- co-3MT, PCu(Q) 2- co-3MT, and PEu(Q) 3- co-3MT exhibit good device performance with a power conversion efficiency of up to 0.56%, 0.78%, and 1.16%, respectively, under simulated AM 1.5 G solar irradiation (100 mW/cm 2). They possess excellent stabilities and their thermal decomposition temperatures are 340 °C, 400 °C, and 540 °C, respectively, indicating polymeric metal complexes are suitable for the fabrication processes of optoelectronic devices.

Structural and photophysical properties of trianionic nine-coordinated near-IR emitting 8-hydroxyquinoline-based complexes

Two building blocks, 2-(1H-tetrazol-5-yl)quinoline-8-ol (8-hydroxyquinoline-2-tetrazole) (H(2)hqt) and 8-hydroxyquinoline-2-carboxylic acid (H(2)hqa) provide convenient dianionic tridentate O,N,N- and O,N,O-chelating units containing the 8-hydroxyquinoline chromophore. These ligands form tris-chelate tris-anionic complexes [Ln(hqa)(3)]K(3) and [Ln(hqt)(3)]K(3) in water at pH = 12. At lower pH partially protonated species are formed. The Nd(III), Yb(III) and Er(III) complexes of hqa, and hqt and the partially protonated complex [Nd(H(1/2)hqa)(3)](2)(Et(3)NH)(3).Et(3)NHOTf have been crystallised from methanol solution. The X-ray crystal structure ([Nd(hqa)(3)]K(3).7MeOH(∞)·MeOH, [Er(hqa)(3)]K(3).4MeOH(∞)·3MeOH and [Nd(hqt)(3)]K(3).5MeOH(∞)·MeOH) show a helical arrangement of both ligands with an "anti" geometry for hqa and a "syn" geometry for hqt. Only tris-chelate complexes are formed in water and 0.04 M methanol solutions for both ligands. A "syn" geometry is found for the partially protonated dimeric complexes which is preserved in methanol solution. A statistical distribution of "anti" and "syn" species is found for [Ln(hqa)(3)]K(3) complexes in solution while the major solution geometry of [Ln(hqt)(3)]K(3) complexes is "syn". Sizable near-IR emission quantum yields were measured for the [Ln(hqa)(3)]K(3) complexes in solid state (0.06%, 0.18%, 0.0051% for Nd(III), Yb(III) and Er(III) respectively) and in methanol (0.063%, 0.28%, 0.0019% for Nd(III), Yb(III) and Er(III) respectively). All the values of quantum yields obtained for the hqt complexes are 5-17% higher than those measured for the hqa complexes. The trianionic complexes present a high solubility in organic and aqueous solvents and a good resistance to ligand dissociation compared to neutral tris 8-hydroxyquinoline complexes.

Visible Light Sensitization of TiO2 Surfaces with Alq3 Complexes

We combine ab initio DFT molecular dynamics simulations and quantum dynamics propagation of transient electronic excitations to investigate visible light sensitization of TiO2-anatase surfaces by covalent attachment of derivatized aluminum tris-(8-hydroxyquinoline) (Alq3) complexes. Hydroxylated arylquinoline and benzoquinoline ligands are introduced as robust anchoring groups to form Alq3/TiO2 molecular assemblies. We show that photoexcitation of the resulting surface complexes with visible light triggers ultrafast interfacial electron injection into the TiO2 host substrate. Furthermore, we show that derivatization of the Alq3/TiO2 surface complexes with oligothiophenes should hinder electron−hole pair recombination after photoinduced interfacial electron transfer. These findings are particularly relevant to the development of molecular based photo-optic devices based on the general class of metaloquinolate complexes Mq3, with q = 8-hydroxyquinoline and M = Al, Zn, Ga, and In, which have already attracted significant interest in the development of new technologies.

Spectrophotometric and Thermodynamic Studies of Charge Transfer Complexes of 8-Hydroxyquinoline with π Acceptor p-Nitrophenol in Different Solvents

The charge transfer complexes of the donor 8-hydroxyquinoline (8HQ) with π acceptor p-nitrophenol (PNP) have been studied spectrophotometrically in various solvents. The results indicate the formation of CTC in less Polar solvent to be more and also λCT shifted to longer wavelength with increased polarity. The stoichiometry of the complex was found to be 1:1 by straight line method between donor and acceptor with maximum absorption bands. The data are discussed in terms of molar extinction coefficient (ϵCT), equilibrium constant (Formation constant), resonance energy (RN), free energy (ΔGo), ionization potential (ID), and oscillator strengths (f). The results indicate the formation constant (KCT) for the complex to be dependent of the nature of electron acceptors, donors, and polarity of solvents.

Spectrophotometric and spectroscopic studies of complexation of 8-hydroxyquinoline with π acceptor metadinitrobenzene in different polar solvents

The complexation of electron donor–acceptor complexes of 8-hydroxyquinoline (8HQ) and metadinitrobenzene (MNB) have been studied spectrophotometrically and thermodynamically in different polar solvent at room temperature. A new absorption band due to charge transfer (CT) transition is observed in the visible region. A new theoretical model has been developed which take into account the interaction between electronic subsystem of 8HQ and MNB. The results indicate the extent of charge transfer complexes (CTCs) formation to be more in less polar solvents. Stoichiometry of the complex was found to be 1:1 by straight line method and 1H NMR between donor and acceptor at the maximum absorption bands. Ionization potential ( I D) and resonance energy ( R N) were determined from the CT transition energy in different solvents. The formation constants of the complexes were determined in different polar solvents from which Δ G° formation of the complexes was estimated and also extinction coefficient of the charge transfer complex (CTC) was calculated. Oscillator strength, transition dipole strengths and maximum wavelength of the CTC ( λ CT) in various solvents and IR spectra of the CTC have also been discussed. It has been observed that all parameters described above changed with change in polarity and concentration of donor.

A Density Functional Theory Study of the Topology of the Charge Density of Complexes of 8-Hydroxyquinoline with Mn(III), Fe(III), and Co(III)

By use of the quantum theory of atoms in molecules, it was found that the electronic charge distribution rho(r) of the metal atoms in Mn(III), Fe(III), and Co(III) complexes of 8-hydroxyquinoline (8HQ) showed eight nonbonded concentrations in their valence shell that were located at the corners of a cube and a depletion region was located in each of its six faces. Coordination was such that regions of charge concentration of the ligands matched the depletion ones of the metal. The O- and N-metal bonds showed low rho(r(c)) values at the bond critical point r(c) and low and positive ones for its Laplacian indicating that they were dative bonds of close shell type with a degree of covalency. Most changes in rho(r) were located around the N and O atoms of 8HQ directly involved in dative bonds. By use of the delocalization index delta(C(A),C(B)) only for C-C bonds, it was found that coordination increased the aromaticity of most of them. The most important changes in rho(r) were found in the C-H bonds were a noticeable increase in bond strength was obtained upon coordination.

Effect of substituting groups on electronic spectra and second-order nonlinear optical properties of 8-hydroxyquinolinate metal complexes

Geometry optimization of target complexes were performed at the level of B3LYP/ LanL2DZ/6-31G*, and their absorption spectra and the second nonlinear optical properties were calculated at the TD-B3LYP/LANL2DZ/6-31++G** level and B3LYP/LANL2DZ/6-31++G** level, respectively. The results indicate that the introduction of conjugated substituting groups of electron-donor and conjugated substituting groups of strong electron-accepter makes maximal absorption wavelength red-shifted and blue-shifted, respectively. The introduction of conjugated substituting groups resultes in obvious increase of second nonlinear optical properties for IrQ3 complexes. The electronic transfer belongs to intra-ligand charge transfer （LLCT） for AgQ complexes, and LLCT mixed with partially metal-to-ligand charge transfer for PtQ2 and IrQ3 complexes. There is no effect of substituting groups on transition properties for AgQ, PtQ2 and IrQ3 complexes.

Influence of Zn–Cd substitution: Spectroscopic and theoretical investigation of 8-hydroxyquinoline complexes

It is now well known that zinc is crucial for the synthesis of nucleic acids and, consequently, for cellular division. However, 67Zn, the NMR-detectable isotope, is one of the isotopes most poorly studied by NMR. The strategy used for NMR studies is the substitution of Zn by 113Cd. In this work, we employed 13C, 113Cd NMR (CPMAS), X-ray and DFT calculation in order to evaluate the Zn–Cd substitution using 8-hydroxyquinoline like prototype compound. Our results show that there are strong structural and electronics effects are involved in the substitution.

Rare-earth metal 8-hydroxyquinolinate complexes as materials for organic light-emitting diodes

Rare-earth metal 8-hydroxyquinolinates (q) were studied as emission layers for organic light-emitting diodes. Compounds Dyq3, Tbq3, and Smq3 possess weak electroluminescence due to the emission of the ligand, and the electroluminescence of Hoq3, Tmq3, and Ybq3 is due to electronic transitions of the lanthanide ion. The best electroluminescence characteristics were demonstrated by Scq3 and Yq3. The power efficiency of the organic light emitter based on ITO/TPD/Scq3/Yb (ITO is tin-alloyed indium oxide, TPD is N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine) is 2.6 lm W−1 at a luminance of the device of 300 cd m−2.

Preparation of cobalt and nickel complexes of 8-hydroxyquinoline with nanobelt structure via one-step, low-heating, solid-state reactions

Two nano-structural complexes, bis-(8-hydroxyquinoline) cobalt and bis-(8-hydroxyquinoline) nickel, have been prepared by one-step, low-heating, solid-state reaction, a simple, safe, economical and environmentally-friendly method. TEM and SEM images show that the complexes are composed of nanobelts with width ranging from 100 to 300 nm and a length of up to 1 µm. The technique offers a new way for fabricating coordination compounds with one-dimensional nanostructure.

Uncertainty Estimation for the Determination of Ni, Pb and Al in Natural Water Samples by SPE-ICP-OES

In this paper we propose uncertainty estimation for the analytical results we obtained from determination of Ni, Pb and Al by solidphase extraction and inductively coupled plasma optical emission spectrometry (SPE-ICP-OES). The procedure is based on the retention of analytes in the form of 8-hydroxyquinoline (8-HQ) complexes on a mini column of XAD-4 resin and subsequent elution with nitric acid. The influence of various analytical parameters including the amount of solid phase, pH, elution factors (concentration and volume of eluting solution), volume of sample solution, and amount of ligand on the extraction efficiency of analytes was investigated. To estimate the uncertainty of analytical result obtained, we propose assessing trueness by employing spiked sample. Two types of bias are calculated in the assessment of trueness: a proportional bias and a constant bias. We applied Nested design for calculating proportional bias and Youden method to calculate the constant bias. The results we obtained for proportional bias are calculated from spiked samples. In this case, the concentration found is plotted against the concentration added and the slop of standard addition curve is an estimate of the method recovery. Estimated method of average recovery in Karaj river water is: (1.004±0.0085) for Ni, (0.999±0.010) for Pb and (0.987±0.008) for Al.

Radioiodinated magnetic targeted carriers (131I-MTC)

Magnetically targeted drug delivery by particulate carriers is an efficient method of delivering drugs to localized disease sites, such as tumors. Thus, high concentrations of carrier molecules such as therapeutic radiopharmaceuticals can be achieved near the target site without any toxic effects to normal surrounding tissue. In this study, magnetic targeting carriers (MTC) were radioiodinated with 131I using three different methods (1) 131I was directly bound onto MTC, (2) an iron complex of 8-hydroxyquinoline (8-OHQ) has been absorbed onto magnetic microspheres. The iodogen method was performed for the iodination of the complexes. (3) 8-OHQ was radioiodinated before chelating with Fe. Reaction parameters were investigated in order to optimize the final properties of the labeled MTC. The best labeling yield and the best stability were obtained when 8-OHQ was chelated before the radioiodination. Binding efficiency was found to be 99.58%. The labeling of the MTC with 131I was undertaken to allow for therapy with 131I-labeled MTC with simultaneous imaging.

Analysis of metal ions in crude oil by reversed-phase high performance liquid chromatography using short column

In this study a rapid, simultaneous analysis of V, Ni, Fe and Cu in crude oil was achieved by high performance liquid chromatography using 10 cm length reversed-phase C18 column. Since the amount of metal ions is at a very low level, in this work, solvent extraction of metals by a ligand such as 8-hydroxyquinoline from acidic media was investigated with some modification to previous procedures. Average extraction recoveries were 99, 85, 94 and 96 for V, Ni, Fe and Cu, respectively. The proposed method was successfully applied to the crude oil which was obtained from Koshk area in southern Iran. Fast analysis of metal ion in reversed-phase short column was achieved with methanol/water (55/45, v/v) and the detection limits measured as three times the background noise were obtained. Also it was shown that if small amount of 8-hydroxyquinoline was added to the mobile phase, the peak height and the peak symmetry were improved. A typical chromatogram for the separation of the 8-hydroxyquinoline complexes of V (V), Ni (II), Fe (III) and Cu (II) in crude oil was obtained in less than 4 min.

Radiolytic and cellular reduction of a novel hypoxia-activated cobalt(III) prodrug of a chloromethylbenzindoline DNA minor groove alkylator

Metabolic reduction can be used to activate prodrugs in hypoxic regions of tumours, but reduction by ionising radiation is also theoretically attractive. Previously, we showed that a cobalt(III) complex containing 8-hydroxyquinoline (8-HQ) and cyclen ligands releases 8-HQ efficiently on irradiation in hypoxic solutions [Ahn G-O, Ware DC, Denny WA, Wilson WR. Optimization of the auxiliary ligand shell of cobalt(III)(8-hydroxyquinoline) complexes as model hypoxia-selective radiation-activated prodrugs. Radiat Res 2004;162:315–25]. Here we investigate an analogous Co(III) complex containing the potent DNA minor groove alkylator azachloromethylbenzindoline (azaCBI, 1 ) to determine whether it releases 1 on radiolytic and/or enzymatic reduction under hypoxia. Monitoring by HPLC, the azaCBI ligand in the Co(III)(cyclen)(azaCBI) complex ( 2 ) slowly hydrolysed in aqueous solution, in contrast to the free ligand 1 which readily converted to its reactive cyclopropyl form. Irradiation of 2 (30–50 μM) in hypoxic solutions released 1 with yields of 0.57 μmol/J in formate buffer and 0.13 μmol/J in human plasma. Using bioassay methods, cytotoxic activation by irradiation of 2 at 1 μM in hypoxic plasma was readily detectable at clinically relevant doses (≥1 Gy), with a estimated yield of 1 of 0.075 μmol/J. Release of 1 from 2 was also observed in hypoxic HT29 cultures without radiation, with subsequent conversion of 1 to its O-glucuronide. Surprisingly, overexpression of human cytochrome P450 reductase in A549 cells did not increase the rate of metabolic reduction of 2 , suggesting that other reductases and/or non-enzymatic reductants are responsible. Thus the cobalt(III) complex 2 is a promising prodrug capable of being activated to release a very potent cytotoxin when reduced by either ionising radiation or cells under hypoxic conditions.

Fabrication and photoluminescence of molecular hybrid films based on the complexes of 8-hydroxyquinoline with different metal ions via sol–gel process

A kind of monomer (abbreviated as HQ-TESPI) was prepared by modifying 8-hydroxyquinoline (abbreviated as HQ) with 3-(triethoxysilyl)-propyl isocyanate (abbreviated as TESPI) through the hydrogen transfer nucleophilic addition in this study. Then the monomer was used to coordinate with the metal ions (Al 3+, Zn 2+, Eu 3+, Tb 3+) according to the complexation theory. On the other hand, the monomer was simultaneously used to occur hydrolysis and condensation together with tetraethoxysilane (abbreviated as TEOS) to form silica-based organic–inorganic hybrid thin films (abbreviated as Al-HQ-TESPI, Zn-HQ-TESPI, Eu-HQ-TESPI and Tb-HQ-TESPI, respectively) by the means of spin-coating technology. The resultant thin films showed characteristic photoluminescence originated from the modified 8-hydroxyquinolinates. The target materials exhibit strong green-colored fluorescence (Al-HQ-TESPI), cyan-colored fluorescence (Zn-HQ-TESPI) and olivine-colored fluorescence (Eu-HQ-TESPI, Tb-HQ-TESPI). These hybrid thin films can be prospected to be used in the field of photoluminescence.