Preparation of New Calix[4]arene-Immobilized Biopolymers for Enhancing Catalytic Properties of Candida rugosa Lipase by Sol–Gel Encapsulation

The article describes preparation of new calixarene biopolymers consisting of the immobilization of convenience calixarene derivative onto cellulose and chitosan biopolymers, and the encapsulation of these calixarene biopolymers with Candida rugosa lipase within a chemical inert sol–gel supported by polycondensation with tetraethoxysilane and octyltriethoxysilane. The catalytic properties of immobilized lipase were evaluated into model reactions employing the hydrolysis of p-nitrophenylpalmitate and the enantioselective hydrolysis of naproxen methyl esters from racemic prodrugs in aqueous buffer solution/isooctane reaction system. The resolution studies using sol–gel support have observed more improvement in the enantioselectivity of naproxen E?=?300 with Cel-Calix-E than with encapsulated lipase without calixarene-based materials. Furthermore, the encapsulated lipase (Cel-Calix-E) was still retained about 39 % of their conversion ratios after the fifth reuse in the enantioselective reaction.     

Preparation of calix[4]arene-based sporopollenin and examination of its dichromate sorption ability

The present study describes the preparation of a new calix[4]arene-based sporopollenin material and its application for the removal of Na₂Cr₂O₇ from aqueous solution. The novel calix[4]arene-based sporopollenin material was prepared via the immobilization of dihydrazine amide derivative of p-tert-butylcalix[4]arene (3) onto the modified sporopollenin. The newly prepared calix[4]arene-based sporopollenin is characterized by using different analytical techniques such as FT-IR spectroscopy, scanning electron microscope and Elemental analysis. The batch wise sorption study was carried out to optimize various experimental parameters such as the effect of sorbent dosage, pH, temperature and Cr(VI) anion concentration. It has been found that the sorption of Cr(VI) anion on calix[4]arene-based sporopollenin was highly pH dependent and maximum sorption was achieved at pH 1.5. The sorption behavior was also evaluated by Langmuir, Freundlich and Dubinin Radushkevich isotherms. The value of correlation coefficient (R ²) showed a good agreement with Freundlich isotherm model. Result of study demonstrated that calix[4]arene-based sporopollenin proved to be highly effective for the removal of Cr(VI).     

Brønsted acidic magnetic nano-Fe3O4-adorned calix[n]arene sulfonic acids: synthesis and application in the nucleophilic substitution of alcohols

Three magnetically recoverable Brønsted acidic calix[n]arene derivatives were successfully constructed by immobilizing calix[n]arene sulfonic acids onto silica-coated magnetic nanoparticles, a process, which allows calix[n]arene derivatives to acquire magnetic properties. All of the magnetically recoverable Brønsted acidic calix[n]arenes efficiently catalyze the coupling of electron-rich arenes with some alcohols in water. After separation and recovery from the reaction mixture by a simple magnet, these Brønsted acidic calix[n]arenes can be recycled many times without losing their catalytic activity.     

A triphenylamine based multi-analyte chemosensor for Hg and Cu ions in MeCN/H2O

A novel triphenylamine based oxidative chemosensor TOC was synthesized. The chromogenic and fluorogenic behaviors of TOC towards Hg²⁺ and Cu²⁺ ions in a binary mixture of MeCN/H₂O (9/1) were dramatically different. TOC displays colorimetric ‘naked eye’ recognition of Hg²⁺ and fluorogenic ‘turn on’ response towards Cu²⁺ via a unique cyclization reaction using two different detection modes. Moreover, TOCAZOL obtained from the oxidative cyclization reaction of TOC with Cu(ClO₄)₂ can be used as a selective fluorescent sensor toward Hg²⁺ ion.     

Enhanced ethanol sensing properties of WO3 modified TiO2 nanorods

Pristine and WO₃ decorated TiO₂ nanorods (NRs) were synthesised to investigate n-n-type heterojunction gas sensing properties. TiO₂ NRs were fabricated via hydrothermal method on fluorine-doped tin oxide coated glass (FTO) substrates. Then, tungsten was sputtered on the TiO₂ NRs and thermally oxidised to obtain WO₃ nanoparticles. The heterostructure was characterised by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray (EDX) spectroscopy. Fabricated sensor devices were exposed to VOCs such as toluene, xylene, acetone and ethanol, and humidity at different operation temperatures. Experimental results demonstrated that the heterostructure has better sensor response toward ethanol at 200 °C. Enhanced sensing properties are attributed to the heterojunction formation by decorating TiO₂ NRs with WO₃.     

Nafion-graphene composite film modified glassy carbon electrode for voltammetric determination of p-aminophenol

A Nafion-graphene (Nafion-GR) nanocomposite film modified glassy carbon electrode was fabricated by a simple drop-casting method, and used in the electrochemical detection of p-aminophenol (4-AP). Owing to the large surface area, good conductivity of GR and good affinity of Nafion, the sensor exhibited excellent electrocatalytic activity for the oxidation of 4-AP. The electrochemical behaviors of 4-AP on Nafion/GR film modified glassy carbon electrodes were investigated by cyclic voltammetry and differential pulse voltammetry. A calibration curve is constructed in the same matrix, urine, as the unknown samples to be analyzed. The Nafion-GR film modified electrode was linearly dependent on the 4-AP concentration and the linear analytical curve was obtained in the ranges of 0.5–200 μM with differential pulse voltammetry (DPV) and the detection limit was 0.051 μM. The Nafion-graphene nanocomposite modified electrode exhibited good reusability than pure graphene modified GCE. This procedure can be used for the determination of p-aminophenol in the presence of its degradation products and paracetamol. Finally, the proposed method was successfully used to determine p-aminophenol in local tap water samples in urine samples and pharmaceutical preparations.     

Synthesis and monoamine oxidase A/B inhibitory evaluation of new benzothiazole-thiazolylhydrazine derivatives

Abstract

In this study, a novel series of benzothiazole-thiazolylhydrazine (3a–3i) was synthesized and their structures were characterized by ¹H-NMR, ¹³C-NMR spectrometry, and mass spectroscopy. These compounds were evaluated as inhibitors of type A and type B monoamine oxidase (MAO) enzymes. The most active compound 3b (2-((2-(2-(4-(4-Nitrophenyl)thiazol-2-yl)hydrazineylidene)-2-phenylethyl)thio)benzothiazole) showed strong inhibitory activity at hMAO-A (IC₅₀ of 0.095?±?0.004?µM). Furthermore, compound 3i (2-((2-(2-(4-(2,4-dichlorophenyl)thiazol-2-yl)hydrazineylidene)-2-phenylethyl)thio)benzothiazole) showed significant inhibition profile on hMAO-A with the IC₅₀ values 0.141?±?0.006?µM.     

Synthesis of new cyclotriphosphazene derivatives bearing Schiff bases and their thermal and absorbance properties

In this study, a series of cyclotriphosphazene derivatives containing a Schiff base (3a–3d) were synthesized by the reactions of hexachlorocyclotriphosphazene (1) with bis-aryl Schiff bases ( 2a – 2d ) having different terminal groups (H, F, Cl, and Br). The products ( 3a – 3d ) were characterized by elemental and mass analyses, FT-IR, and ¹ H, ¹³ C, and ³¹ P NMR spectroscopies. Furthermore, the structure of compound 3a was also determined by X-ray crystallography. The thermal behaviors and the spectral properties of the new cyclotriphosphazene compounds ( 3a – 3d ) were investigated and the results were compared in the series.     

Synthesis,optical, and structural properties of bisphenol-bridged aromatic cyclic phosphazenes

Phenoxy- and naphthoxy-substituted bisphenol-bridged cyclic phosphazenes were synthesized in 2 steps and their thermal, photophysical, and electrochemical properties were investigated. The structures of the cyclic phosphazene compounds were determined by ESI-MS mass spectrometry and ¹ H, ¹³ C, and ³¹ P NMR spectroscopies. The photophysical studies of phenoxy- and naphthoxy-substituted bridged cyclophosphazenes were investigated by means of absorption and fluorescence spectroscopies in different solvents. Thermal and electrochemical properties of the target compounds were also studied. Furthermore, the excimer emissions through intramolecular interactions in solution and in solid state were investigated by fluorescence spectroscopy and the theoretical calculations were performed in detail using DFT.     

Spectral characterization and antibacterial effect of 2-methyl-6-(5-H-Me-Cl-NO <Subscript>2</Subscript>-1<Emphasis Type="Italic">H</Emphasis>-benzimidazol-2-yl)-phenols and some transition metal complexes

2-Methyl-6-(5-H-methyl-chloro-nitro-1H-benzimidazol-2-yl)-phenols( HL _x :x= 1-4)ligands and HL₁ complexes with Fe(NO₃)₃, Cu(NO₃)₂, AgNO₃, Zn(NO₃)₂ have been synthesized and characterized. The structures of the compounds were confirmed on the basis of elemental analysis, molar conductivity, magnetic moment, FT-IR, ¹H-and ¹³C-NMR. Antibacterial activity of the free ligands, their hydrochloride salts and the complexes were evaluated using the disk diffusion method in dimethyl sulfoxide as well as the minimum inhibitory concentration dilution method, against nine bacteria. While HL₁ ligand has not any activity, it’s Ag(I) complex show antibacterial effect toward almost to all the bacteria. Zn(II) complex has antibacterial effect on especially K. pneumoniae, S. epidermidis and S. aureus bacteria.