Thin-layer gel chromatography of 8-hydroxyquinoline metal complexes

Gel chromatographic behavior of 8-hydroxyquinoline (oxine, abbreviated HOx) complexes of zinc, copper, aluminum, gallium and indium has been investigated on thin layers of Styragel 60A and Merckogel OR-PVA 2000 mostly in chloroform and p-dioxan media. Except for the stable Cu(Ox)₂, the other oxinates exhibit either hydration or decomposition in gel-solvent-solute systems, which leads to strong retention or tailing on gel layers. An excess of 8-hydroxyquinoline present in solvents allows the oxinates to be stabilized, so that well-defined compact spots come out and migrate. For the Zn(Ox)₂ the formation of a self-adduct is strongly suggested on the basis of gel chromatographic behavior. Elution with the solvent containing pyridine also yields evidence of the adduct formation of zinc oxinate-nitrogen base.     

Synthesis and photoluminescence properties of 8-hydroxyquinoline derivatives and their metallic complexes

Three new 8-hydroxyquinoline derivatives, i.e. 5-[(4-styryl-benzylidene)-amino]-quinolin-8-ol (1), 5-[(4-bromo-2-fluoro-benzylidene)-amino]-quinoline-8-ol (2) and 2-[2-(9-ethyl-9H-carbazol-2yl)-vinyl]-quinolin-8-ol (3), and their metallic complexes were synthesized and identified by ultraviolet-visible (UV-Vis), ¹H nuclear magnetic resonance (¹H NMR), Fourier transform infrared spectrometer (FTIR), mass spectrometry (MS) spectra and elemental analyses. Their fluorescence properties were studied by photoluminescence, which indicated that the luminescence wavelength of 5-and 2-substitued-8-hydroxyquinoline derivatives shifted to red in comparison with that of 8-hydroxyquinoline. Meanwhile, the fluorescence lifetime of 2-[2-(9-ethyl-9H-carbazol-2yl)-vinyl]-quinolin-8-ol and its zinc complex showed long lifetime in benzene solution. __________ Translated from Chinese Journal of Organic Chemistry, 2007, 27(3): 402–408 [译自: 有机化学]     

Synthesis,characterization and photoluminescence of 8-oxyquinolinato organoboron complexes derived from pyrazole

A one-pot protocol was developed for the synthesis of a series of luminescent heteroleptic diaryldiborinic complexes containing the central aryl ring bonded to two boron atoms substituted with pyrazole and complexed with 8-hydroxyquinoline. The luminescent properties of these compounds were measured. In dilute solutions they exhibited an emission at ca. 513 nm with quantum yields of 22–27% which are typical for borinic 8-hydroxyquinoline complexes. The only exception was the complex containing the bithiophene scaffold, for which no fluorescence was observed. The obtained pyrazole-based complexes show improved solubility and thermal stability with respect to their phenyl analogues. The experimental UV–vis absorption and emission data are supported by theoretical calculations of the frontier molecular orbitals, revealing the aromatic linker to quinolinato ligand excitation mechanism.     

Structural basis of DNA folding and recognition in an AMP-DNA aptamer complex: distinct architectures but common recognition motifs for DNA and RNA aptamers complexed to AMP

Background: Structural studies by nuclear magnetic resonance (NMR) of RNA and DNA aptamer complexes identified through in vitro selection and amplification have provided a wealth of information on RNA and DNA tertiary structure and molecular recognition in solution. The RNA and DNA aptamers that target ATP (and AMP)' with micromolar affinity exhibit distinct binding site sequences and secondary structures. We report below on the tertiary structure of the AMP-DNA aptamer complex in solution and compare it with the previously reported tertiary structure of the AMP-RNA aptamer complex in solution.Results: The solution structure of the AMP-DNA aptamer complex shows, surprisingly, that two AMP molecules are intercalated at adjacent sites within a rectangular widened minor groove. Complex formation involves adaptive binding where the asymmetric internal bubble of the free DNA aptamer zippers up through formation of a continuous six-base mismatch segment which includes a pair of adjacent three-base platforms. The AMP molecules pair through their Watson-Crick edges with the minor groove edges of guanine residues. These recognition G·A mismatches are flanked by sheared G·A and reversed Hoogsteen G·G mismatch pairs.Conclusions: The AMP-DNA aptamer and AMP-RNA aptamer complexes have distinct tertiary structures and binding stoichiometries. Nevertheless, both complexes have similar structural features and recognition alignments in their binding pockets. Specifically, AMP targets both DNA and RNA aptamers by intercalating between purine bases and through identical G·A mismatch formation. The recognition G·A mismatch stacks with a reversed Hoogsteen G·G mismatch in one direction and with an adenine base in the other direction in both complexes. It is striking that DNA and RNA aptamers selected independently from libraries of 10¹⁴ molecules in each case utilize identical mismatch alignments for molecular recognition with micromolar affinity within binding-site pockets containing common structural elements.     

Structure and photophysical properties of a dimeric Zn(II) complex based on 8-hydroxyquinoline group containing 2,6-dichlorobenzene unit

A novel 2-substituted-8-hydroxyquinoline ligand (E)-2-[2-(2,6-dichlorophenyl)ethenyl]-8-hydroxyquinoline (HL) was synthesized and characterized by ESI-MS, NMR spectroscopy, and elemental analysis. Using solvothermal method, a dimeric complex (ZnL₂)₂ (1) was fabricated by self-assembly of Zn(II) ions with ligand HL. X-ray structural analysis shows that 1 exhibits a binuclear core, which is bridged by two 8-hydroxyquinoline rings. The supramolecular structure of 1 features a lamellar solid constructed by aromatic stacking interactions, Cl?Cl interactions and nonclassical C–H?Cl hydrogen bonds derived from 2,6-dichlorophenyl group of the ligand HL. The aggregation behavior of zinc salts and HL in solutions was investigated with a variety of techniques, including ¹H NMR, UV–vis, and photoluminescence (PL). In addition, we also studied the photophysical properties of compound 1 by UV–vis and PL. The experimental results show that the complex 1 emits yellow luminescence in the solid state.     

Synthesis,crystal structure,and properties of a tetrairon cluster based on 2-methyl-8-hydroxyquinoline

The synthesis, structure, and magnetic properties of a tetrairon(III) complex [Fe₄(μ₂-O)₂Cl₄(L)₄]·0.5H₂O (1, L = 2-methyl-8-hydroxyquinoline), which was prepared under solvothermal conditions and characterized by IR spectra, elemental analysis, TG, and single-crystal X-ray crystal diffraction, are presented. Each Fe center adopts a distorted trigonal bipyramid geometry and is coordinated with three oxygen atoms, one nitrogen atom, and one chlorine atom. Each 2-methyl-8-hydroxyquinoline is coordinated to two Fe^III ions with μ₂-η²:η¹ coordination mode. The magnetic properties of the complex are dominated by antiferromagnetic exchange interactions.     

The Homogeneity Range of Crystalline Tris(8-hydroxyquinoline)gallium

An experimental procedure has been developed for constructing p _i –T diagrams (partial vapor pressure of the ligand-forming component–temperature) for luminescent metal complexes with symmetric organic ligands. The partial 8-hydroxyquinoline vapor pressure–temperature diagram has been constructed for tris(8-hydroxyquinoline)gallium electrophosphor (Gaq₃) in the temperature range 300–617 K at 8-hydroxyquinoline vapor pressures 10^–3–10⁴ Pa, where the homogeneity ranges of different Gaq₃ polymorphs have been determined. Structure-sensitive properties of crystalline materials can be tailored by changing synthesis conditions within the homogeneity range of a phase.     

Preparation and Characterization of Novel Asymmetrical Schiff-Base Ligands Derived from 2-methyl-7-formyl-8-hydroxyquinoline and their Metal Complexes

Two novel asymmetrical Schiff-base ligands, H₂L¹ and H₂L², were prepared by reacting two half-unit Schiff-base compounds with 2-methyl-7-formyl-8-hydroxyquinoline. The two half-unit Schiff-base compounds were initially prepared by condensing dimedone with either ethylenediamine or p-phenylenediamine, respectively. Both ligands are dibasic and contain two sets of NO coordinating sites. Twelve metal complexes were obtained by reacting both ligands with Cu(II), Ni(II), Co(II), Mn(II), Fe(III), VO(IV) cations. The ligands and their metal complexes were characterized by elemental analysis, IR, UV-Vis, ESR and mass spectra, also magnetic moments of the complexes were determined. Visible spectra of the complexes indicated distorted octahedral geometries around the metal cations. ESR spectra indicated mononuclear and dinuclear structures of the complexes of ligands H₂L¹ and H₂L², respectively. Magnetic moments of the complexes were rather low compared with those expected for octahedral geometries and indicated polymeric linkage of the metal complex molecules within their crystal lattices. The insolubility of the metal complexes in most organic solvents support the polymeric structures.     

Disorder and intermolecular interactions in a family of tetranuclear Ni(II) complexes probed by high-frequency electron paramagnetic resonance

High-frequency electron paramagnetic resonance (HFEPR) data are presented for four closely related tetranuclear Ni(II) complexes, [Ni(hmp)(MeOH)Cl]4.H2O (1a), [Ni(hmp)(MeOH)Br]4.H2O (1b), [Ni(hmp)(EtOH)Cl]4.H2O (2), and [Ni(hmp)(dmb)Cl]4 (3) (where hmp(-) is the anion of 2-hydroxymethylpyridine and dmb is 3,3'-dimethyl-1-butanol), which exhibit magnetic bistability (hysteresis) and fast magnetization tunneling at low temperatures, properties which suggest they are single-molecule magnets (SMMs). The HFEPR spectra confirm spin S = 4 ground states and dominant uniaxial anisotropy (DSz(2), D < 0) for all four complexes, which are the essential ingredients for a SMM. The individual fine structure peaks (due to zero-field splitting) for complexes 1a, 1b, and 2 are rather broad. They also exhibit further (significant) splitting, which can be explained by the fact that there exists two crystallographically distinct Ni 4 sites in the lattices for these complexes, with associated differences in metal-ligand bond lengths and different zero-field splitting (ZFS) parameters. The broad EPR lines, meanwhile, may be attributed to ligand and solvent disorder, which results in additional distributions of microenvironments. In the case of complex 3, there are no solvate molecules in the structure, and only one distinct Ni 4 molecule in the lattice. Consequently, the HFEPR data for complex 3 are extremely sharp. As the temperature of a crystal of complex 3 is decreased, the HFEPR spectrum splits abruptly at approximately 46 K into two patterns with very slightly different ZFS parameters. Heat capacity data suggest that this is caused by a structural transition at 46.6 K. A single-crystal X-ray structure at 12(2) K indicates large thermal parameters on the terminal methyl groups of the dmb (3,3-dimethyl-1-butanol) ligand. Most likely there exists dynamic disorder of parts of the dmb ligand above 46.6 K; an order-disorder structural phase transition at 46.6 K then removes some of the motion. A further decrease in temperature (<6 K) leads to further fine structure splittings for complex 3. This behavior is thought to be due to the onset of short-range magnetic correlations/coherences between molecules caused by weak intermolecular magnetic exchange interactions.     

Thermodynamic Data for the Formation of 1:1 and 2:1 Complexes of α,ω-Diamino Dihydrochlorides with 18-Crown-6 in Aqueous Solution

Calorimetric titrations are used to study the interactions between the crown ether 18-crown-6 and several α,ω-diamino dihydrochlorides in aqueous solution. These complexes are formed by ion-dipole interactions between the positively charged nitrogen atoms and the oxygen donor atoms of the crown ether. Depending on the experimental conditions, the formation of 1:1 or 2:1 complexes (ligand:diamines) can be studied. The solvation of the ligand and the amines are responsible for the observed thermodynamic values. The number of water molecules released during the reaction were calculated from the determined reaction entropies. Formation of 1:1 complexes distorts the solvation shell around the molecules. As a result, the number of solvent molecules released during the formation of the 2:1 complexes is slightly smaller than the number released from formation of the 1:1 complex. No experimental evidence is observed for the formation of complexes between one crown ether and two protonated amino groups.     

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.     

Synthesis,structures, thermal behaviour,luminescence and magnetic properties of lanthanide complexes constructed from 2,6-dimethylbenzoic acid and 5,5′-dimethyl-2,2′-bipyridine

Six new lanthanide complexes, with the formula [La(2,6-DMBA)₃(5,5′-DM-2,2′-bipy)(H₂O)]₂ (1) and [Ln(2,6-DMBA)₃(5,5′-DM-2,2′-bipy)]₂ (Ln = Tb(2), Dy(3), Ho(4), Pr(5), Nd(6)) (2,6-DMBA = 2,6-dimethylbenzoate, 5,5′-DM-2,2′-bipy = 5,5′-dimethyl-2,2′-bipyridine) have been successfully synthesized and characterized. These title complexes have three different structural types. The structure of complex 1(type I) contains coordination water molecules, and the coordination number is 8. The coordination numbers of complexes 2–4 and 5–6 are 8 and 9, showing a distorted square antiprism geometry and distorted monocapped square anti-prismatic geometry, respectively. However they have the same general formula and they can be all assembled into the same 1D, 2D supramolecular structures via the C-H···O hydrogen bonding interactions, which is interesting in previous lanthanide complexes. The complexes were analyzed by TG-DSC/FTIR. In addition, the visible light luminescence experiments of Tb (III) complex was carried out, and the characteristic luminescence behavior of strong green color was shown. And the fluorescence lifetime and intrinsic quantum yield were calculated. The magnetic properties of complexes 2–4 were also studied, and the results showed that complex 3 and complexes 2, 4 have ferromagnetic interactions and antiferromagnetic interactions, respectively.     

1D and 3D supramolecular structures exhibiting weak ferromagnetism in three Cu(II) complexes based on malonato and di-alkyl-2,2’-bipyridines

Three new Cu(II) complexes composed of malonato (mal), methylmalonato (memal), 4,4′-di-tert-butyl-2,2′-bipyridine (tbpy) and 5,5′-dimethyl-2,2′-bipyridine (mebpy) ligands, Cu(H₂O)(mal)(tbpy) (1), Cu(H₂O)(memal)(tbpy) (2) and Cu₄(H₂O)₄(memal)₄(mebpy)₄·11H₂O (3) were synthesized by simple one-pot solution reactions at ambient conditions. Single-crystal X-ray diffraction analyses reveal that the Cu(II) ions exhibit a distorted five-coordinate square pyramidal geometry. These three complexes display supramolecular arrays due to hydrogen-bonding interactions. Complexes 1 and 2 show 1-D supramolecular structures; 1 forms a double-ion chain, unlike 2, which only generates a single-ion chain. In 3, there are two identical monomers in the asymmetric unit with Z″ = 2; its high number of noncoordinated water molecules, along with hydrogen-bonding interactions between aqua ligand and memal ligand, generate a supramolecular tetramer, which mimics to produce a 3-D supramolecular framework. Besides this fascinating and yet uncommon crystallographic phenomenon in 3, the structural differences found in these complexes arise from the substituted groups in the malonato dianion and in the bipyridine ligands. These compounds exhibit weak ferromagnetic-exchange interactions.     

Aromatic properties of 8-hydroxyquinoline and its metal complexes

Chelatoaromaticity (aromaticity of chelate complexes) has been recently recognized as an important property influencing the stability of chelate compounds. In this paper, aromaticity of various forms of 8-hydroxyquinoline (anion, neutral molecule, zwitterion and cation) as well as its chelate complexes with magnesium and aluminium ions are investigated. Aromatic properties of these compounds are analyzed using several aromaticity indices based on energetic, geometric, magnetic and electronic physical manifestations of this phenomenon. Results of performed calculations have shown different aromatic properties for the two rings (pyridine and benzene) occurring in the studied ligand. Aromaticity of these rings in metal complexes of 8-hydroxyquinoline is significantly higher than that in corresponding ligand anion. This means that during complexation the aromaticity of the ligand increases and the chelatoaromatic effect stabilizes the studied metal complexes. In contrast, metallocyclic rings of studied metal complexes have non-aromatic properties, and, consequently, the metallocyclic ring is not stabilized by chelatoaromaticity. We conclude that, in the complex, every 8-hydroxyquinoline unit and the metal ion are separated p-electronic systems.      

调控发光波长: 新型2-取代8-羟基喹啉衍生物金属锌配合物的合成与特性研究

设计合成了2-[(2'-芴基)-乙烯基]-8-羟基喹啉(6)、2-[(2'-菲基)-乙烯基]-8-羟基喹啉(7)及其金属锌配合物8和9; 用UV-Vis, FT-IR, ESI-MS, ¹H NMR和元素分析确认了化合物6和7的结构; 并用四甲基偶氮唑盐微量酶反应比色法(MTT法)研究了其调控骨髓间质干细胞增殖的作用, 结果表明, 化合物6和7对干细胞有明显的增殖作用. 用FT-IR, FAB-MS和元素分析表征了金属锌配合物结构, 光致发光光谱测试结果表明, 化合物8的发光峰值为602 nm, 发黄光; 化合物9的发光峰值为628 nm, 发橙红色光.     

Interactions of binuclear copper(II) complexes with S-substituted thiosalicylate derivatives with some relevant biomolecules

Abstract

Interactions of copper(II) complexes which contain S-alkyl derivatives of thiosalicylic acid (alkyl?=?methyl, ethyl, propyl and butyl; aryl?=?benzyl), marked as 1–5, with guanosine-5′-monophosphate (5′-GMP) and calf thymus DNA (CT-DNA) were studied. Kinetics of substitution reactions of 1–5 with 5′-GMP and CT-DNA were investigated under pseudo-first-order conditions at 310 K and pH = 7.2 in 25?mM Hepes buffer using stopped-flow method. All complexes have high affinity toward studied bio-molecules. Additionally, interactions with CT-DNA were followed by absorption spectroscopy and fluorescence quenching measurements. The results indicate that complexes bind to DNA exhibiting high binding constants (K_b = 10⁴ M^?1). During the examination of competitive reactions with ethidium bromide (EB), results showed that complexes can replace EB-bound DNA. In addition, a new crystal structure of the binuclear Cu(II) complex with S-substituted thiosalicylate derivative has been reported. In the present series of Cu(II) complexes the crystal structure is the first example of a complex comprising an S-aryl derivative of thiosalicylate ligand. Through comparative study of structural properties of six molecules from four crystal structures we examined the structural variations, potentially important for biological activity of these complexes.     

Differential Pulse Polarographic Determination of Gallium and Niobium in Samples After Preconcentration of Their Quinolin-8-Olate Complexes on Microcrystalline Naphthalene

Abstract

Gallium and niobium react with quinolin-8-ol to form water insoluble complexes which are quantitatively adsorbed on microcrystalline naphthalene from the large volume of their aqueous solutions in the pH range of 3.5 - 8.2 and 6.2 - 9.4, respectively. After filtration, the metal complexes were desorbed with 10 ml of HCl (1M for Ga and 11 M for Nb) and determined by using a differential pulse polarograph (DPP). The dissolved oxygen is removed by adding a few milliliters of 4% NaBH₄ solution in the case of gallium. The detection limits are 0.04 ppm for gallium and 0.05 ppm for niobium at the minimum instrumental settings (signal to noise ratio = 2). The linearities are maintained in the concentration range 0.1 - 5.0 ppm for gallium and 0.4 - 6.0 ppm for niobium with correlation factors of 0.9997 and 0.9996 and relative standard deviations of 0.81 and 0.95%, respectively.

Characterization of the electroactive process included an examination of the degree of reversibility. Various parameters such as the effect of pH volume of aqueous phase, reagent and naphthalene concentrations and the interference of a large number of anions and cations on the estimation of these elements were studied in detail. The method is found to be highly selective, fairly sensitive, rapid, simple and economical. It has been applied for the trace determination of gallium and niobium in various standard alloys and may be applied safely for the analyses of complex materials like environmental samples and ores.

     

Sensitive spectrophotometric determination of gallium with bromopyrogallol red in the presence of surfactants

Gallium in the presence of surfactants (NTGE and CTA) forms with BPR a violet ternary complexes with λ_max at 615 and 625 nm, respectively, with molar absorptivities of 7.0 × 10⁴ and 1.3 × 10⁵ liters mol^?1 cm^?1. These complexes can be advantageously used for the determination of gallium. The molar ratio of gallium to BPR, which is 1:1 in the binary complex, increases to 1:3 in the ternary complex. The presence of surfactants changes the number of BPR molecules bonded to gallium. This is the main factor in the increase in color intensity. Numerous metals interfere. Gallium can be separated by extraction of gallium from 7 M hydrochloric acid with diisopropyl ether.     

A simple oxidation procedure for biological material prior to analysis for mercury

The stability constants of aluminium(III), gallium(III), indium(III) and scandium(III) with 8-hydroxyquinoline and its 2-methyl derivative have been determined by potentiometric titration, with computation by the SCOGS program. In contrast to previous work, the results show that protonated species occur in several of the equilibria. The constants are discussed in terms of the nature of metal-to-ligand bonding in the complexes. X-ray photoelectron spectroscopy of the ligand coordinating atoms in the solid complexes confirms the significantly increased covalency of the gallium—oxygen bond compared to the same bond in the aluminium complex.