Quinoline Group Research Articles

Geometrical variations of two manganese(II) complexes with closely related quinoline-based tripodal ligands.

Structural analyses of the compounds di-μ-acetato-κ4 O:O'-bis-{[2-meth-oxy-N,N-bis-(quinolin-2-ylmeth-yl)ethanamine-κ4 N,N',N'',O]manganese(II)} bis-(tetra-phen-yl-borate) di-chloro-methane 1.45-solvate, [Mn2(C23O2)2(C23H23N3O)2](C24H20B)·1.45CH2Cl2 or [Mn(DQMEA)(μ-OAc)2Mn(DQMEA)](BPh4)2·1.45CH2Cl2 or [1](BPh4)2·1.45CH2Cl2, and (acetato-κO)[2-hy-droxy-N,N-bis(quinolin-2-ylmeth-yl)ethanamine-κ4 N,N',N'',O](methanol-κO)manganese(II) tetra-phenyl-borate methanol monosolvate, [Mn(CH3COO)(C22H21N3O)(CH3OH)](C24H20B)·CH3OH or [Mn(DQEA)(OAc)(CH3OH)]BPh4·CH3OH or [2]BPh4·CH3OH, by single-crystal X-ray diffraction reveal distinct differences in the geometry of coordination of the tripodal DQEA and DQMEA ligands to MnII ions. In the asymmetric unit, compound [1](BPh4)2·(CH2Cl2)1.45 crystallizes as a dimer in which each manganese(II) center is coordinated by the central amine nitro-gen, the nitro-gen atom of each quinoline group, and the meth-oxy-oxygen of the tetra-dentate DQMEA ligand, and two bridging-acetate oxygen atoms. The symmetric MnII centers have a distorted, octa-hedral geometry in which the quinoline nitro-gen atoms are trans to each other resulting in co-planarity of the quinoline rings. For each MnII center, a coordinated acetate oxygen participates in C-H⋯O hydrogen-bonding inter-actions with the two quinolyl moieties, further stabilizing the trans structure. Within the crystal, weak π-π stacking inter-actions and inter-molecular cation-anion inter-actions stabilize the crystal packing. In the asymmetric unit, compound [2]BPh4·CH3OH crystallizes as a monomer in which the manganese(II) ion is coordinated to the central nitro-gen, the nitro-gen atom of each quinoline group, and the alcohol oxygen of the tetra-dentate DQEA ligand, an oxygen atom of OAc, and the oxygen atom of a methanol ligand. The geometry of the MnII center in [2]BPh4·CH3OH is also a distorted octa-hedron, but the quinoline nitro-gen atoms are cis to each other in this structure. Hydrogen bonding between the acetate oxygen atoms and hydroxyl (O-H⋯O) and quinolyl (C-H⋯O and N-H⋯O) moieties of the DQEA ligand stabilize the complex in this cis configuration. Within the crystal, dimerization of complexes occurs by the formation of a pair of inter-molecular O3-H3⋯O2 hydrogen bonds between the coordinated hydroxyl oxygen of the DQEA ligand of one complex and an acetate oxygen of another. Additional hydrogen-bonding and inter-molecular cation-anion inter-actions contribute to the crystal packing.

Tuning the position of methyl groups to realize highly efficient deep-red PhOLEDs

As the promising candidates for red phosphorescent organic light-emitting diodes (PhOLEDs), aryl quinoline Ir(III) complexes have attracted enormous and continual attention. The molecular design strategy of introducing methyl group to aryl quinoline unit to tune their optoelectronic properties is reported here. The synthesis, structures, electrochemical and photophysical properties of a series of methyl-substituted aryl quinoline Ir(III) complexes were systematically studied. Red and deep-rep phosphorescent emission with the maximum wavelength from 610 nm to 646 nm were accessed by combing the electron-donating effect of the 3-methyl group to centered Ir atom and increased twist angle between phenyl unit and quinoline group induced by the 2-methyl group. Deep-red PhOLEDs with the emission peak at 620 nm, CIE coordinates of (0.68, 0.32), luminescence of 23720 cd/m2, and an EQE of 40.5% were realized.

Syntheses and properties of mononuclear cobalt-dioxolene complexes with the ancillary ligand containing bulky quinoline rings – Electronic state manipulation of the complexes by steric effect

Two types of mononuclear cobalt complexes with two ancillary ligands containing isoquinoline groups and 3, 5-di-tert-butylcatechol (3, 5-DBCat) were synthesized. The crystal structures and spectroscopic, electrochemical, and magnetic properties of these complexes and complexes with ancillary ligands containing multiple quinoline groups were compared to clarify the steric effect of quinoline derivatives around the cobalt center. In particular, a comparison of the crystal structures of the mononuclear cobalt complexes containing tris(2-quinolylmethyl)amine (tqa) and tris(3-isoquinolylmethyl)amine (isotqa) as ancillary ligands, each of which has three isoquinoline and three quinoline rings, showed that the isotqa complex was less congested than the tqa complex around the cobalt center. As a result, the tqa complex contains Co (II), whereas the isotqa complex has the stable Co (III) electronic state due to the stronger ligand field. In this report, the steric influence of ancillary ligand substituents on the electronic states of complexes is clarified from several perspectives such as spectroscopic, electrochemical and magnetic properties.

Discovery of Potent, Selective Triazolothiadiazole-Containing c-Met Inhibitors.

Herein, we report a novel series of highly potent and selective triazolothiadiazole c-Met inhibitors. Starting with molecule 5, we have applied structure-based drug design principles to identify the triazolothiadiazole ring system. We successfully replaced the metabolically unstable phenolic moiety with a quinoline group. Further optimization around the 5,6 bicyclic moiety led to the identification of 21. Compound 21 suffered from PDE3 selectivity issues and subsequent, structurally informed design led to the discovery of compound 23. Compound 23 has exquisite kinase selectivity, excellent potency, favorable ADME profile, and showed dose-dependent antitumor efficacy in a SNU-5 gastric cancer xenograft model.

Synthesis, characterization, and photophysical properties of cyclotriphosphazenes containing quinoline-4-aldehyde-p-oxyanil moieties

In the present work, a series of cyclotriphosphazenes including Schiff bases, {[N3P3(biph)2(R)2] (5), [N3P3(biph)(R)4] (6), and N3P3R6 (7) (biph = 2′,2′′-dioxy-1′,1′′- biphenyl, R = Quinoline-4-aldehyde-p-oxyanil}, were synthesized in high yields via the nucleophilic substitution reactions of quinoline-4-aldehyde-p-hydroxyanil (1) with [N3P3(biph)2Cl2] (2) and [N3P3(biph)Cl4] (3) and N3P3Cl6 (4), respectively. The structures of all products (5, 6, and 7) were defined by elemental analysis, mass spectrometry, FTIR, (1H, 13C, and 31P) NMR spectroscopies. Furthermore, the photophysical properties of these new cyclotriphosphazenes (5, 6, and 7) in different solvents and concentrations were investigated and the results were compared and discussed. The absorption characteristics of novel cyclotriphosphazene-based Schiff bases demonstrated n–π* and π–π* transitions which can be attributed to quinoline side whereas absorbance values were significantly enhanced under the same analytical conditions when the number of quinoline groups attached to the cyclotriphosphazene-core increased. As a result, the molar absorptivity of novel cyclotriphosphazene-based Schiff bases which substituted with two (5) and six quinolines moieties (7) were increased 4.43- and 11.4-fold, respectively, when compared with their precursor (1).

Photoisomerization and Energy Transfer in an Unsymmetrical Biphotochromic Dyad with a Longitudinal Shift of Photochromes—Derivatives of 3-Styrylbenzo[f]quinoline and Oxymethylene Bridging Group

Photoisomerization and Energy Transfer in an Unsymmetrical Biphotochromic Dyad with a Longitudinal Shift of Photochromes—Derivatives of 3-Styrylbenzo[f]quinoline and Oxymethylene Bridging Group

A facile gelator based on phenylalanine derivative is capable of forming fluorescent Zn-metallohydrogel, detecting Zn2+ in aqueous solutions and imaging Zn2+ in living cells

Supramolecular hydrogels are attracting soft materials with potential applications. In this study, we synthesized a facile gelator (named 2-QF) based on phenylalanine derivative with a Quinoline group. 2-QF can assemble to form hydrogels at room temperature in different colors under low pH values. Moreover, 2-QF was triggered to form a yellow metallohydrogel (2-QF-Zn) at high pH by the coordination between 2-QF and Zn2+. 2-QF-Zn metallohydrogel showed excellent multi-stimuli responsiveness, especially the reversible “on-off” luminescence switching, as induced by base/acid. In addition, at a low concentration, 2-QF can selectively and visibly identify Zn2+ through fluorescence enhancement, and can detect Zn2+ at physiological pH as a chemosensor. Remarkably, 2-QF and 2-QF-Zn exhibited an excellent biocompatibility without cell cytotoxicity, and 2-QF is able to penetrate live HeLa cells and image intracellular Zn2+ by a turn-on fluorescent response, which makes it a potential candidate for biomedical applications.

Synthesis and Photophysical Properties of a Series of Dimeric Indium Quinolinates

A novel class of quinolinol-based dimeric indium complexes (1–6) was synthesized and characterized using 1H and 13C(1H) NMR spectroscopy and elemental analysis. Compounds 1–6 exhibited typical low-energy absorption bands assignable to quinolinol-centered π–π* charge transfer (CT) transition. The emission spectra of 1–6 exhibited slight bathochromic shifts with increasing solvent polarity (p-xylene < tetrahydrofuran (THF) < dichloromethane (DCM)). The emission bands also showed a gradual redshift, with an increase in the electron-donating effect of substituents at the C5 position of the quinoline groups. The absolute emission quantum yields (ΦPL) of compounds 1 (11.2% in THF and 17.2% in film) and 4 (17.8% in THF and 36.2% in film) with methyl substituents at the C5 position of the quinoline moieties were higher than those of the indium complexes with other substituents.

A ratiometric fluorescent probe based on quinoline for monitoring and imaging of Leucine aminopeptidase in liver tumor cells

Leucine aminopeptidase (LAP) is known as an important potential biomarker for liver malignancy and it is urgent to develop an intuitive and effective method to monitor the activity of LAP in liver cancer. Although, numerous LAP fluorescent probes had been developed, it is still a challenge to detect LAP activity in liver cancer. Herein, combained with the DFT, we reported a novel galactose-appended hepatoma-specific ratiometric fluorescent probe (Gal-QL-Leu) based on quinoline group for imaging and tracing LAP in liver tumor cells. Probe Gal-QL-Leu demonstrated a obvious ratiometric characteristics, better selectivity, good biocompatibility and high sensitivity. Moreover, the selective imaging of LAP in HepG2, HCT116, A549 and HeLa cells had been achieved with probe Gal-QL-Leu, demonstrating good application prospect in the detection of LAP activity in liver tumor cells.

Synthesis, spectroscopic, DFT, HSA binding and docking studies of new 1,5-bis(4-chlorophenyl)-3-(2-(4-methylpiperazin-1-yl)quinolin-3-yl)pentane-1,5-dione

1,5-Bis(4-chlorophenyl)-3-(2-(4-methylpiperazin-1-yl)quinolin-3-yl)pentane-1,5-dione was synthesised and characterised using single-crystal X-ray Crystallography, FT-IR, 1H-NMR, 13C-NMR and UV-Visible spectroscopy. DFT calculations were performed at the B3LYP/6-311++G (d.p) level of theory in the gas phase. Frontier Molecular Orbitals (FMO) yielded HOMO-LUMO energy as: EHOMO = -6.015 eV, ELUMO = -2.525 eV and energy gap, ΔEgap = 3.490 eV. Fukui Function Analysis (FFA) indicated the reactive sites for electrophilic, and nucleophilic attack. The molecule's electrophilic addition site is 4-N in the piperazine group with a value of 0.020. The site for nucleophilic attack is both 13-C and 15-C in the quinoline group with values of 0.02 and 0.031 respectively. The biological activity was elucidated by molecular docking studies that gave a ΔG value for HSA binding of -26.44 kJ mol−1 which is approximately similar to the experimental value obtained from emission spectral data of -32.15 kJ mol−1.

CRYSTAL STRUCTURES OF QUINOLINYL PALLADIUM(II) COMPLEXES: [Pd(PPh3)2{κ1-C9H6NB}(Cl)] AND [Pd(PPh3)2Cl]2{μ,κ2-C9H6N}

A reaction of Pd(PPh3)4 (complex 1) and 2-chloroquinoline C9H6NCl in a 1:1 molar ratio produces a mononuclear [Pd(PPh3)2{κ1-C9H6NB}(Cl)] complex (complex 2) and a binuclear [Pd(PPh3)2Cl]2{μ,κ2-C9H6N} complex (complex 3). In complex 3, each of quinoline units is bridged through the carbon atom of quinoline groups to one metal center and the nitrogen atom to another metal, forming a six-membered ring with the boat-like geometry. Complexes 2 and 3 are characterized by the elemental analysis, fast atom bombardment mass spectrometry, 31P NMR spectroscopy, and single crystal X-ray diffraction.

8-Hydroxyquinoline functionalized covalent organic framework as a pH sensitive carrier for drug delivery.

A porous 8-hydroxyquinoline functionalized organic covalent framework (named COF-HQ) was synthesized. The as-prepared COF-HQ showed stable crystal structure, suitable pore size, excellent dispersibility in physiological solution and pH sensitivity, which would be employed as a potential nanocarrier for drug transport and controlled release. The drug loading experiment with 5-Fluorouracil (5-FU) as the model molecule proved that the drug loading capacity of COF-HQ was significantly improved due to the introduction of quinoline groups. The drug release profiles of 5-FU from 5-FU loaded COF-HQ (termed 5-FU@COF-HQ) under different pH showed that its release was controlled by pH owing to the pH sensitivity of conjugated nitrogen atoms from quinoline groups and CN. The in vitro hemolysis and in vivo biocompatibility experiments further verified the good biocompatibility of COF-HQ. Importantly, 5-FU@COF-HQ-treated B16F10 cell-induced tumor models showed that 5-FU@COF-HQ displayed enhanced anti-tumor efficacy than other groups. These results suggested that the drug-loading COF-HQ delivery system showed the potential for effective cancer therapy with advantages of high drug loading, good biocompatibility and the pH-sensitive release of the tumor microenvironment. Overall, our research provided a new functionalized COF-HQ drug delivery system, which further expanded the application of COFs as carriers in the field of cancer treatment.

Preparation of Benzyl Quinine-modified Monolithic Column for Reversed-phase Capillary Electrochromatography.

N-Benzylquininium chloride is a versatile functional monomer with quinoline and benzyl groups, which is beneficial for reversed-phase chromatography. In this study, a novel monolithic column with reversed-phase mode was synthesized using N-benzylquininium chloride as the monomer and 3-(acryloyloxy)-2-hydroxypropyl methacrylate as the cross-linker in a binary porogenic solvent consisting of PEG 400 and a 0.05 M sodium hydroxide aqueous solution. The alkaline solution were found to be useful for the improvement of the mechanical stability of the porous monoliths. The monolithic column showed excellent reversed-phase selectivity and various compounds, such as alkylbenzenes, phenols and polycyclic aromatic hydrocarbons, were separated successfully. The highest column efficiency was 1.75 × 105 N m-1. The relative standard deviations of the migration time for thiourea and four alkylbenzenes were all less than 5.0%, which indicates the monolithic column has good stability. The application of the monolithic column for the analysis of polycyclic aromatic hydrocarbons in spiked lake water samples illustrated its great potential for practical application.

Syntheses and crystal structures of a new pyrazine dicarboxamide ligand, N 2,N 3-bis-(quinolin-8-yl)pyrazine-2,3-dicarboxamide, and of a copper perchlorate binuclear complex.

The title pyrazine dicarboxamide ligand, N 2,N 3-bis-(quinolin-8-yl)pyrazine-2,3-dicarboxamide (H2L1), C24H16N6O2, has a twisted conformation with the outer quinoline groups being inclined to the central pyrazine ring by 9.00 (6) and 78.67 (5)°, and by 79.94 (4)° to each other. In the crystal, molecules are linked by C-H⋯O hydrogen bonds, forming layers parallel to the (10) plane, which are in turn linked by offset π-π inter-actions [inter-centroid distances 3.4779 (9) and 3.6526 (8) Å], forming a supra-molecular three-dimensional structure. Reaction of the ligand H2L1 with Cu(ClO4)2 in aceto-nitrile leads to the formation of the binuclear complex, [μ-(3-{hy-droxy[(quinolin-8-yl)imino]-meth-yl}pyrazin-2-yl)[(quinolin-8-yl)imino]-methano-lato]bis-[diaceto-nitrile-copper(II)] tris-(per-chlor-ate) aceto-nitrile disolvate, [Cu2(C24H15N6O2)(CH3CN)4](ClO4)3·2CH3CN or [Cu2(HL1-)(CH3CN)4](ClO4)3·2CH3CN (I). In the cation of complex I, the ligand coordinates to the copper(II) atoms in a bis-tridentate fashion. A resonance-assisted O-H⋯O hydrogen bond is present in the ligand; the position of this H atom was located in a difference-Fourier map. Both copper(II) atoms are fivefold coordinate, being ligated by three N atoms of the ligand and by the N atoms of two aceto-nitrile mol-ecules. The first copper atom has a perfect square-pyramidal geometry while the second copper atom has a distorted shape. In the crystal, the cation and perchlorate anions are linked by a number of C-H⋯O hydrogen bonds, forming a supra-molecular three-dimensional structure.

Spectroscopic characterization of valence tautomeric behavior in a cobalt-dioxolene complex using an ancillary ligand containing quinoline groups

Co-dioxolene complex [Co(DBCat)(pbqa)](PF6) (DBCat = 3,5-di-tert-butylcatechol, pbqa = (2-pyridylmethyl)bis(2-quinolylmethyl)amine), was prepared from methanol solution. Single crystal X-ray structural analysis revealed that the valence of the cobalt ion to be +III, as DBCat is formally a catecholate dianion, whereas the acetonitrile solution exhibits an MLCT absorption near 575 nm, suggesting it is present as hs-CoII(SQ). Of note, this MLCT band disappears with decreasing temperature. This behavior suggests that [Co(DBCat)(pbqa)](PF6) undergoes a temperature-dependent change from hs-CoII(SQ) to ls-CoIII(Cat). Magnetic susceptibility vs. temperature data for the compound displayed a gradual variation over 250 K, due to intramolecular electron transfer in the solid-state as well. [Co(DBCat)(pbqa)](PF6) demonstrates valence tautomerism due to a strong π-π interaction between the quinoline rings of the ancillary ligand. Comparison of this pbqa compound to similar Co compounds provides further evidence for these conclusions.

Cosmetic dyes as potential photosensitizers of singlet oxygen generation

Photosensitizer molecules capable of absorbing UV radiation and visible light through photochemical reactions can generate singlet oxygen (1O2). 1O2 is an oxidizing agent that can react with biomolecules causing oxidative damage. Cosmetic dyes possess chromophore groups capable of performing the absorption process of electromagnetic radiation thereby they could act as photosensitizers. The aim of this research was to evaluate the photosensitizing ability of 25 dyes used as cosmetic ingredients through photo-oxidation of ergosterol as an indirect detection method of 1O2. The presence of 1O2 was indirectly detected by ergosterol conversion into ergosterol peroxide through 1H-NMR mixture analysis. Our results showed that 9 cosmetic dyes belonging to pyrene, chlorophyll, xanthene and aminoanthraquinone groups were able to act as photosensitizers in the generation of 1O2. The photosensitizing ability of these dyes could be contradictory if they are used as cosmetic ingredients because of pro-oxidants effects caused by 1O2 and its implications in skin photoaging. On the other hand, in regard to the photosensitizing ability of the remaining dyes tested belonging to the azo, triarylmethane, hydroxyanthraquinone, quinoline and indigoid groups, these were found not capable of photosensitizing 1O2 generation, consequently their use as cosmetic ingredients wouldn't suppose an oxidation risk caused by 1O2.

Crystal structures of quinolinyl palladium(II) complexes: [Pd(PPh3)2{κ1-C9H6NB}(Cl)] and [Pd(PPh3)2Cl]2{μ,κ2-C9H6N}

A reaction of Pd(PPh3)4 (complex 1) and 2-chloroquinoline C9H6NCl in a 1:1 molar ratio produces a mononuclear [Pd(PPh3)2{κ1-C9H6NB}(Cl)] complex (complex 2) and a binuclear [Pd(PPh3)2Cl]2{μ,κ2-C9H6N} complex (complex 3). In complex 3, each of quinoline units is bridged through the carbon atom of quinoline groups to one metal center and the nitrogen atom to another metal, forming a six-membered ring with the boat-like geometry. Complexes 2 and 3 are characterized by the elemental analysis, fast atom bombardment mass spectrometry, 31P NMR spectroscopy, and single crystal X-ray diffraction.

A multi-photon fluorescent probe based on quinoline groups for the highly selective and sensitive detection of lipid droplets.

Compared to general fluorescent probes, multi-photon fluorescent probes exhibit deeper tissue penetration, lower auto-fluorescence and lower photo-toxicity in the bio-imaging field. Herein, we synthesized a series multi-photon fluorescent probe (L1-L3) based on quinolone groups. Of notably, the three-photon fluorescence of L3 significantly enhanced when L3 interacted with liposome; moreover, L3 exhibited high selectivity towards lipid droplets in living cells. Due to its large Stokes shift, high selectivity and photon-stability, L3 was successfully used in lipid droplet imaging via multi-photon fluorescence bio-imaging.

Synthesis and Optoelectronic Characterization of Perylene Diimide-Quinoline Based Small Molecules

Perylene diimide (PDI) is one of the most studied functional dyes due to their structural versatility and fine tuning of the materials properties. Core substituted PDIs are prominent n-type semiconductor materials that could be used as non-fullerene acceptors in organic photovoltaics. Herein, we develop versatile organic building blocks based on PDI by decorating the PDI core with quinoline groups. Styryl and hydroxy phenyl mono and difunctionalized molecules were prepared using mono-nitro and dibromo bay substituted PDIs by Suzuki coupling with the respective boronic acid derivatives. A novel methodology using nitro-PDI under Suzuki coupling conditions as an electrophile partner was successfully tested. Furthermore, the PDI derivatives were used for the synthesis of soluble, electron accepting small molecules combining PDI with weak electron withdrawing quinoline derivatives. The new molecules presented wide absorbance in the visible spectrum from 450 to almost 700 nm while their LUMO levels and their energy levels are in the range of −3.8 to −4.2 eV.

Synthesis, crystal structure and molecular docking studies of novel 2-(4-benzoylpiperazin-1-yl) quinoline-3-carbaldehyde

Abstract As a continuation of our research work, we have synthesized novel 2-(4-benzoylpiperazin-1-yl)quinoline-3-carbaldehyde. The structural characterization of the synthesized compound was done by spectroscopic techniques such as FT-IR, 1H NMR, 13C NMR & LCMS spectrometry and finally by X-Ray diffraction studies. In the title molecule the dihedral angle between the benzene and the quinoline ring is 64.22(4)o and the aldehyde group is twisted relative to the quinoline group by 24.96(3)o due to the presence of a bulky piperazinyl group in the ortho position. The crystal structure features C H…π interactions forming one dimensional zig-zag chains. The in silico molecular docking studies was carried out in order to know the binding mode of the synthesized compound with Dehydrosqualene synthase, Tubulin and COX-1, COX-2, as target proteins for antibacterial, anthelmintic and anti-inflammatory docking studies respectively.