Squaramide catalyzed α-chiral amine synthesis

Enantiomerically pure α-chiral amines, have been commonly utilized as resolving agents and chiral auxiliaries and are currently found in 40% of active pharmaceutical ingredients. Hence, development of highly stereoselective metal-free protocols regarding atom-economy and large-scale applications becomes a major issue. In this respect, chiral bifunctional H-bonding squaramides have been successfully applied for both amine synthesis and functionalization of amines in the last decade. This survey summarizes asymmetric synthesis of chiral amines by various carbon-carbon and carbon-nitrogen bond formation with squaramide catalysis as a particular focus of interest.     

The alignment of nematic liquid crystal by the Ti layer processed by nonlinear laser lithography

It is well known that the alignment of liquid crystals (LCs) can be realised by rubbing or photoalignment technologies. Recently, nonlinear laser lithography (NLL) was introduced as a fast, relatively low-cost method for large area nano-grating fabrication based on laser-induced periodic surface structuring. In this letter for the first time, the usage of the NLL as a perspective method of the alignment of nematics was presented. By NLL, nanogrooves with about 0.92 μm period were formed on Ti layer. The nanostructured Ti layer (NSTL) was coated with oxidianiline-polyimide film with annealing of the polymer followed without any further processing. Aligning properties of NSTLs were examined with combined twist LC cell. The dependencies of the twist angle of LC cells and azimuthal anchoring energy (AE) of layers on scanning speed and power of laser beam during processing of the Ti layer were the focus of our studies as well. The maximum azimuthal AE, obtained for pure NSTL, is comparable with photoalignment technology. It was found that the deposition of polyimide film on NSTL leads to the gain effect of the azimuthal AE. Also, atomic force microscopy (AFM) study of aligning surfaces was carried out.     

Asymmetric organocatalytic direct Mannich reaction of acetylacetone and isatin derived ketimines: Low catalyst loading in chiral cinchona-squaramides

A highly enantioselective synthesis of 3-amino-2-oxindoles by direct Mannich reaction between acetylacetone and N-carbamoyl isatin ketimine has been described herein. Corresponding chiral adducts were obtained in high yields (up to 98%) and with excellent enantioselectivities (up to?>99% ee) by very low (1?mol%) catalyst loading of 2-adamantyl substituted bifunctional cinchona-squaramide.     

Descriptive statistics and risk assessment for the control of seasonal pollutant effects of <Superscript>210</Superscript>Po and <Superscript>210</Superscript>Pb in coastal waters (Çanakkale,Turkey)

²¹⁰Po is absorbed into the human body by seafood intake. Especially, mollusks and mussels are known to have much higher ²¹⁰Po concentration than fish among various other types of seafood and are consumed in large quantities in Aegean Sea. ²¹⁰Po and ²¹⁰Pb radionuclide concentrations are obtained in the Mediterranean mussel (Mytilus galloprovincialis) and in the sediment samples collected from the Çanakkale. The activity concentrations of ²¹⁰Po and ²¹⁰Pb are counted using alpha spectrometry. Activity concentrations of ²¹⁰Po and ²¹⁰Pb in mussels are in the ranged of 227 ± 11–540 ± 38 and 17 ± 4–48 ± 5 Bq kg^?1 dw (dry weight), for sediments the ranges are 23 ± 6–41 ± 3 and 15 ± 3–44 ± 1 Bq kg^?1 dw, respectively. Additionally, annual committed effective dose are calculated due to consumption mussel in Çanakkale coastal region. The highest effective doses of ²¹⁰Po and ²¹⁰Po are found as 3187 and 56 μSv, respectively. Finally, risk analysis assessment is recommended to determine the pollutant effects of radionuclides. The risk fractions at the concentrations are easily determined with this evaluation process. This methodology has made a great contribution to risk assessments.     

Three novel Cu(II), Cd(II) and Cr(III) complexes of 6−Methylpyridine−2−carboxylic acid with thiocyanate: Synthesis,crystal structures,DFT calculations,molecular docking and α-Glucosidase inhibition studies

Novel complexes of 6?methylpyridine?2?carboxylic acid and thiocyanate {[Cu(NCS)(6-mpa)₂], (1); [Cd(NCS)(6-mpa)]_n, (2); [Cr(NCS)(6-mpa)₂·H₂O], (3)} were synthesized, and their structures were characterized by XRD analysis, FT–IR and UV–Vis spectroscopic techniques. The inhibitory activities of the synthesized complexes (1–3) on α-glucosidase were determined by using genistein reference compound. Furthermore, the optimized geometry and vibrational harmonic frequencies for the complexes 1–3 were obtained by DFT/HSEh1PBE/6–311G(d,p)/LanL2DZ level. Electronic spectral properties were examined by using TD-DFT/HSEh1PBE/6–311G(d,p)/LanL2DZ level with CPCM model. Additionally, major contributions to the electronic transitions were determined via Swizard program. The refractive index, linear optical and non?nonlinear optical parameters of the complexes 1–3 were investigated at HSEh1PBE/6–311G(d,p) level. The docking studies of the complexes 1–3 to the binding site of the target protein (the template structure S. cerevisiae isomaltase are fulfilled. Lastly, natural bond orbital analysis was used to investigate inter- and intra-molecular bonding and interaction among bonds.     

A kinetic study on methylation of naphthalene over Fe/ZSM-5 zeolite catalysts

2,6-Dimethylnaphthalene is an important dimethylnaphthalene isomer which can be used in the production of polyethylene naphthalate. The novelty of this study is to reveal Langmuir–Hinshelwood and Eley–Rideal reaction rate equations for the methylation of naphthalene over Fe/ZSM-5 zeolite catalysts besides the proposed reaction rate equation. To investigate the kinetics and mechanisms of naphthalene methylation, the methylation experiments were carried out in a gas–solid catalytic fixed-bed reactor in the presence of Fe/ZSM-5 zeolite catalysts at two different temperatures (450 and 500 °C) and five different weight hourly space velocities (0.5, 1.0, 1.5, 2.0, 2.5, 3.0 h^?1). A naphthalene:methanol:1,2,4-trimethyl benzene mixture having a 1:3:10 molar ratio was used as a feed stream. The methylation products were identified by using GC–MS. For the methylation kinetics of naphthalene, the reaction rates depending on the naphthalene and methanol concentration were determined. Furthermore, the effects of temperature and weight hourly space velocity on the conversion of naphthalene, the selectivity of 2,6-dimethylnaphthalene, and the ratio of 2-methylnaphthalene/1-methylnaphthalene were determined. The results of this study demonstrate that the Langmuir–Hinshelwood reaction mechanism for naphthalene methylation is more compatible at 450 °C and the Eley–Rideal reaction mechanism at 500 °C. Moreover, in addition to 2,6-dimethylnaphthalene, other dimethylnaphthalene and tri-methylnaphthalene isomers were formed in the methylation of naphthalene. The conversion of naphthalene reached approximately 70%. Moreover, the highest selectivity of 2,6-dimethylnaphthalene was almost 40%. The ratios of 2-methylnaphthalene/1-methylnaphalene demonstrate that the methylation of naphthalene to 2-methynaphthalene is much higher than to 1-methynaphthalene.     

Electrochemical Determination of Copper(II) in Water Samples Using a Novel Ion-Selective Electrode Based on a Graphite Oxide–Imprinted Polymer Composite

A novel copper(II)-selective electrode based on graphite oxide/imprinted polymer composite was developed for the electrochemical monitoring of copper(II) (Cu²⁺) ions. The electrode exhibited highly selective potentiometric response to Cu²⁺ with respect to common alkaline, alkaline earth and heavy metal cations. The composite composition studies indicated that the most suitable composite composition performing the most promising potentiometric properties was 20.0% ionophore (Cu²⁺-ion imprinted polymer), 10.0% paraffin oil, 5.0% multiwalled carbon nanotubes, and 65.0% graphite oxide. The fabricated electrode exhibited a linear response to Cu²⁺ over the concentration range of 1.0?×?10^??6–1.0?×?10^??1?M (correlation coefficient of 0.9998) with a sensitivity of 26.1?±?0.9?mV decade^??1. The detection limit of the fabricated electrode was determined to be 4.0?×?10^??7?M. The electrode worked well in the pH range of 4.0–8.0. The electrode had stable, reversible and fast potentiometric response (3?s). In addition, the electrode had a lifetime of more than 1 year. The analytical applications of the proposed electrode were performed using as an indicator electrode for the potentiometric titration of Cu²⁺ with ethylene diamine tetraacetic acid solution and for the determination of Cu²⁺ of spiked river, dam, and tap water samples. The obtained results for potentiometric titration and water samples were satisfactory.     

Novel pyridine-derived platinum complexes

Pyridine-derived platinum(II) complexes with the general formula [PtCl₂L₂] (L¹: 3,5-dimethylpyridine, L²: 2-amino-5-bromopyridine, L³: 4-(4-nitrobenzyl)pyridine) were synthesized. Characterization of the synthesized complexes was made via FT-IR, UV–Vis, ¹H-NMR and ¹³C-NMR techniques. While the thermal behavior of the complexes was investigated via DTA/TG combined system, their kinetic parameters were investigated by using Flynn–Wall–Ozawa (FWO) and Kissinger–Akahira–Sunose (KAS) methods. The activation energy of the decomposition kinetics of the complexes was calculated to be 196.5–31.7 kJ mol^?1 for FWO and 203.4–29.2 kJ mol^?1 for KAS. The cytotoxic effect of the complexes against the colon cancer cell line (DLD-1), which is one of the most common types of cancer observed both in humans and animals, was investigated. The complexes showed high cytotoxicity on DLD-1. In particular, [PtCl₂L ¹₂ ] complex was found to be the most effective compounds against colon cancer cell line during the 24 h incubation period. According to these results, the pyridine-derived platinum(II) complexes would contribute to oncologic treatment as chemotherapeutic agents.

     

Poly(glycidylmethacrylate-co-vinyl ferrocene)-grafted iron oxide nanoparticles as an electron transfer mediator for amperometric phenol detection

An amperometric phenol biosensor was constructed by using poly(glycidylmethacrylate-co-vinyl ferrocene) grafted iron oxide nanoparticles for detection of different phenolic compounds (catechol, aminophenol, phenol, p-cresol, pyrogallol). The poly(glycidylmethacrylate-co-vinyl ferrocene) and nanoparticles were characterized by Fourier transform infrared (FT-IR), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The copolymer grafted iron oxide nanoparticles and Horseradish peroxidase (HRP) were covalently attached on gold (Au) electrode surface. The effect of pH, temperature and characteristic features such as; reusability and storage stability were studied. The electrode showed good response time within ～3 s. The electrocatalytic response showed a linear dependence on the phenolic compounds concentration ranging from 0.5 to 17.0 mM.