The quinaldic acid based charge transfer (CT) complexes with the ionic counterpart of furan (QCFC), thiophene (QCTC) and pyridine-2-carboxylic acid (QCPC) were prepared and successfully characterized ...by 1H NMR, 13C NMR, FT-IR spectroscopic techniques. In addition, the QCFC was characterized by Dept-135 and 2D NMR (Cosy, HQSC and HMBC) techniques. The electrical conductivity of synthesized CT complexes has also been investigated. The in vitro anti-inflammatory and antidiabetic activities were studied and the results were compared with reference drugs. The QCFC exhibited better anti-inflammatory and antidiabetic activity than QCTC and QCPC. Good stability under physiological conditions was observed for the CT complexes synthesized. The molecular docking studies were also performed with an α-amylase enzyme (1HNY.pdb) to identify the probable binding site of the complexes. All the CT complexes have similar binding score and the QCFC showed 4 hydrogen bonding interactions with α-amylase enzyme. Also, the 3D structure of the complexes was optimized using the Gaussian09 W program and DFT calculations were performed to find the significant regions that are necessary for enzyme inhibition.
The quinaldic acid based charge transfer complexes with the ionic counterpart of furan, thiophene and pyridine-2-carboxylic acid were prepared and characterized by spectroscopic techniques. The CT complexes showed very good anti-inflammatory, antidiabetic activity and stability. The molecular docking and DFT calculations were performed in order to support the biological activity. Display omitted
•CT complexes of Quinaldic acid were designed and synthesized.•DFT and molecular docking studies were developed to explain biological activity.•QCFC showed potent anti-inflammatory and antidiabetic activity.•All the complexes have similar binding score.•QCFC showed 4 hydrogen bonding interactions with α-amylase enzyme.
Although enzyme mimics have been widely developed, limited catalytic efficiency is still a bottleneck, especially under neutral condition. Herein, we reported the bioactive quinaldic acid (QA) ...significantly boosted the peroxidase-like activity of Co2+ in the presence of bicarbonate (HCO3−). With 2,2′-azino-bis-(3-ethylbenzothiazoline-6-sulphonate) (ABTS) as the substrate, the catalytic activity of Co2+ (1 μM) was increased by over 300 times upon adding 100 μM QA. The formed Co2+ complex had much higher turnover number (5.52 min−1) than that of cobalt-based nanozymes (0.011–0.51 min−1) in decomposing H2O2. Based on this system, ultrasensitive colorimetric methods for the detection of Co2+, bicarbonate and urease activity were achieved with limits of detection of 4.6 nM, 40 μM and 0.00125 U/mL, respectively. For the first time, this work established an ultrasensitive method for the detection of urease activity by activating a peroxidase-like mimic with the produced HCO3−.
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•Quinaldic acid boosts the peroxidase-like activity of Co2+ by over 300 times.•The formed Co2+ complex acts as a robust peroxidase mimic.•This system allows for ultrasensitive detection of Co2+, HCO3− and urease activity.•Urease activity was detected by activating the peroxidase mimic with HCO3−.•A mechanism for this effective catalytic system was proposed.
Interaction of U(VI) and Np(VI) with quinaldic acid in the presence of various inorganic (nitrate, chloride, bromide, perrhenate, selenate, sulfate) and organic (dipicolinic acid) counter-ions ...allowed obtaining a series of complexes where quinaldic acid presents in the zwitterionic form. Determination of stability constants has shown that the complexation with quinaldic acid in solution occurs via coordination of the carboxylic group.
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Interaction of U(VI) and Np(VI) with quinaldic acid in the presence of various inorganic (nitrate, chloride, bromide, perrhenate, selenate, sulfate) or organic (dipicolinic acid) counter-ions allowed obtaining a series of complexes where quinaldic acid presents in the zwitterionic form. In all compounds, except one complex, quinaldic acid acts as a monodentate ligand and coordinates metal centers via one of the carboxylic oxygen atoms. In all these cases, isolated molecular complexes are formed. In contrast, uranyl sulfate exhibits 2D layered structure where both sulfate-ions and molecules of quinaldic acid function as linkers. Determination of stability constants for 1:1 complexes has shown that the complexation of U(VI) and Np(VI) with quinaldic acid in solution likely occurs via coordination of the carboxylic group. Prevalence of the zwitterionic form and the coordination via carboxylic group both in solution and solid-state is unexpected taking into account similarity in structures of quinaldic and picolinic acids.
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By means of the reaction of lanthanide chlorides with quinaldic (quinoline-2-carboxylic, HQA) acid in an aqueous-ethanolic medium in the presence of pyridine, the following complexes ...were obtained: the known binuclear Nd2(QA)6(H2O)6·3H2O (1) one and the novel compounds built of binuclear dicationic and mononuclear anionic moieties Ln2(QA)4(H2O)42+Ln(QA)4(H2O)ˉ2·2EtOH·6H2O (Ln = Gd (2), Dy (3), Er (4), Yb (5)), as well as the anionic mononuclear one, Hpy2+Er(QA)4ˉ·4H2O (6). The complexes 2–5 were characterized by dc and ac magnetic measurements. Complex 3 exhibits the properties of a single-molecule magnet (SMM) in a zero static field with remagnetization barrier (Δeff/kB) of 82 K, while the other complexes display the properties of field-induced SMMs with the Δeff/kB values of 24, 19, and 33 K for the complexes 2, 4, and 5, respectively.
•The novel quinolinium 2-Carboxylate 2-Chloroacetic acid crystal was synthesized (compound 1).•The compound 1 structure has been determined by single X-ray diffraction analysis and characterized by ...1HNMR, 13CNMR, FTIR spectroscopy.•Theoretical calculations were done using density functional theory (DFT).•The sample has three hydrogen bonding interactions with the α-amylase enzyme.•Compound 1 shows a good antidiabetic activity.
In the present work, quinaldic acid and chloroacetic acid are used to synthesize Quinolinium 2-Carboxylate 2-Chloroacetic acid (compound 1). Conventionally, the crystal structure of the sample is determined by the single crystal X-ray diffraction method. 1H NMR, 13C NMR, FT-IR, and UV-–visible spectral studies are also carried out to confirm the crystal structure of compound 1. In this respect, compound 1 exhibits inhibitory activity against 1HNY, as evidenced by the molecular docking study. The in silico biological activities are studied, and the results are correlated with the reference drug. Since the molecular structures are optimized, DFT calculations are implemented to find the significant regions for enzymatic activities. The binding affinity values are found for compound 1, which formed an interaction with 1HNY. As evident from the MEP maps, the negative regions are localized over the carboxyl group and are suitable for antidiabetic activity.
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The Density Functional Theory (DFT) and ab initio (HF and MP2) calculations were performed on the quinoline molecule (QL) and its derivatives, namely quinaldine (QLD) and quinaldic acid (QLDA) to ...investigate their possible role as corrosion inhibitors for mild steel in acidic medium. Calculations were done for non-protonated and protonated forms in vacuo and in water. Some quantum chemical parameters were calculated and discussed in order to provide insight into the reactivity and selectivity of the molecules. The performance of the different calculation methods were also compared with available experimental data. The results show that DFT/B3LYP basis set is adequate in describing the geometry and quantum chemical parameters of the studied systems. Both experimental and theoretical results established that QLDA has the highest inhibition efficiency. A comparison in the trends of the quantum chemical parameters in water solution and in vacuo shows minimal influence of the solvent effects.
The inhibiting effect of several organic compounds on the corrosion of 2024 aluminium alloy in neutral chloride solution was investigated in the present work. The candidates were selected based on ...the assumption that effective inhibitors should form highly insoluble complexes with components of AA2024. Along with organic complexing agents, the salts of rare-earth elements were included into screening electrochemical impedance spectroscopy (EIS) test for getting comparative data. Results of EIS analysis revealed three most effective organic inhibitors: salicylaldoxime, 8-hydroxyquinoline and quinaldic acid. Their anti-corrosion performance was additionally investigated via dc polarization, as well as localized techniques: scanning electron microscopy coupled with energy dispersive spectroscopy (SEM/EDS), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy coupled with scanning Kelvin probe (SKPFM). Localized measurements at exactly the same microdimensional zones of the alloy before and after immersion into 0.05
M sodium chloride solution allowed tracing the evolution of the Volta potential, chemical composition, surface topography and formation of corrosion products on the surface and intermetallic inclusions during the corrosion tests. The results show that the quinaldic acid, salicylaldoxime and 8-hydroxyquinoline provide anti-corrosion protection for AA2024 forming a thin organic layer of insoluble complexes on the surface of the alloy. Inhibiting action is the consequence of suppression of dissolution of Mg, Al and Cu from the corrosion active intermetallic zones.
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•Complexes (Ni(quin-2-c)2(H2O)2•2H2O, Fe(quin-2-c)2(H2O)2, Cr(quin-2-c)2(H2O)2 were synthesized from aqueous solutions of metal salts, quinaldic acid, and semicarbazide.•Three ...structures are obtained and confirmed by X-ray crystallographic analysis.•The chemical bond study occurred using the quantum theory of atoms in molecules.•The newly synthesized complexes are deemed to be effective NLO materials.
Complexes (Ni(quin-2-c)2(H2O)2•2H2O, Fe(quin-2-c)2(H2O)2, Cr(quin-2-c)2(H2O)2 were synthesized from aqueous solutions of metal salts, quinaldic acid, and semicarbazide. In the crystal structure of the first complex, the nickel atom is chelated by the deprotonated quinaldic acid molecule through the oxygen atom of the carboxyl group, and the heterocyclic nitrogen atom, as well as two water molecules, are coordinated. The other two water molecules are located in the outer sphere. In the structure of the iron and chromium complexes, the metal atoms have a similar complex formation but do not have water molecules in the outer sphere. In all compounds, quinaldic acid acts as a bidentate ligand to form five-membered metallocycles. The electronic structure properties were investigated through theoretical modeling using the B3LYP method at the 6–31 + G(d,p) computational level. Density functional theory (DFT) was employed in quantum chemistry simulations to refine proposed structures and explore the characteristics of frontier orbitals via analysis of frontier molecular orbitals (FMOs). These computations facilitated the identification of specific sites on the surface of molecules by generating molecular electrostatic potential maps and provided insights into the structural and reactive properties. Hirshfeld surface analysis was conducted to examine intermolecular interactions, revealing a prevalence of H⋅⋅⋅H interactions.
The interest in indole dearomatization, which serves as a useful tool in the total synthesis of related alkaloid natural products, has recently been renewed with the intention of developing new ...methods efficient in both yield and stereoselective control. Here, we report an enzymatic approach for the oxidative dearomatization of indoles in the asymmetric synthesis of a variety of furoindolines with a vicinal quaternary carbon stereogenic center. This approach depends on the activity of a flavin‐dependent monooxygenase, TsrE, which is involved in the biosynthesis of bicyclic thiopeptide antibiotic thiostrepton. TsrE catalyzes 2,3‐epoxidation and subsequent epoxide opening in a highly enantioselective manner during the conversion of 2‐methyl‐indole‐3‐acetic acid or 2‐methyl‐tryptophol to furoindoline, with up to >99 % conversion and >99 % ee under mild reaction conditions. Complementing current chemical methods for oxidative indole dearomatization, the TsrE activity‐based approach enriches the toolbox in the asymmetric synthesis of products possessing a furoindoline skeleton.
An enzymatic approach for oxidative indole dearomatization is reported. TsrE, a flavin‐dependent monooxygenase involved in the biosynthesis of bicyclic thiopeptide antibiotic thiostrepton, catalyzes 2,3‐epoxidation and subsequent epoxide opening during the conversion of 2‐methyl‐indole‐3‐acetic acid or 2‐methyl‐tryptophol to furoindoline, with up to >99 % conversion and >99 % ee under mild reaction conditions.
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