Sensitive voltammetric determination of paracetamol by poly (4-vinylpyridine)/multiwalled carbon nanotubes modified glassy carbon electrode

A novel glassy carbon electrode (GCE) modified with a composite film of poly (4-vinylpyridine) (P4VP) and multiwalled carbon nanotubes (P4VP/MWCNT GCE) was used for the voltammetric determination of paracetamol (PCT). This novel electrode displayed a combined effect of P4VP and MWCNT on the electro-oxidation of PCT in a solution of phosphate buffer at pH 7. Hence, conducting properties of P4VP along with the remarkable physical properties of MWCNTs might have combined effects in enhancing the kinetics of PCT oxidation. The P4VP/MWCNT GCE has also demonstrated excellent electrochemical activity toward PCT oxidation compared to that with bare GCE and MWCNT GCE. The anodic peak currents of PCT on the P4VP/MWCNT GCE were about 300 fold higher than that of the non-modified electrodes. By applying differential pulse voltammetry technique under optimized experimental conditions, a good linear ratio of oxidation peak currents and concentrations of PCT over the range of 0.02–450 μM with a limit of detection of 1.69 nM were achieved. This novel electrode was stable for more than 60 days and reproducible responses were obtained at 99% of the initial current of PCT without any influence of physiologically common interferences such as ascorbic acid and uric acid. The application of this electrode to determine PCT in tablets and urine samples was proposed.     

An efficient,rapid and facile procedure for conversion of aldoximes to nitriles using triphenylphosphine and N-halo sulfonamides

N,N,N＇,N＇-Tetrabromobenzene-1,3-disulfonamide （TBBDA）/triphenylphosphine and N,N,N＇,N＇-tetra- chlorobenzene-1,3-disulfonamide （TCBDA）/triphenylphosphine have been introduced as highly efficient systems for the versatile conversion of aldoxime derivatives into nitriles. The process reported here is operationally simple and reactions have been mildly performed in dichloromethane at room temperature.     

FACILE AND EFFICIENT METHOD FOR DEPROTECTION OF 1,3-OXATHIOLANES WITH N,N′-DIBROMO-N,N′-1,2-ETHANEDIYLBIS(p-TOLUENESULPHONAMIDE)

Aliphatic and aromatic 1,3-oxathiolanes[3pc] are readily oxidized to aldehydes and ketones in good yields under mild conditions by N,N′-dibromo-N,N′-1,2-ethanediylbis(p-toluenesulphonamide) [BNBTS].     

N,N′,N,N′-TETRABROMO-BENZENE-1,3-DISULFONYLAMIDE AS A NOVEL REAGENT FOR OXIDATIVE AROMATIZATION OF 1,3,5-TRISUBSTITUTED PYRAZOLINES UNDER HETEROGENEOUS AND SOLVENT-FREE CONDITIONS

1,3,5-Trisubstituted pyrazolines were converted to the corresponding pyrazoles in good yields under heterogeneous and solvent-free conditions by N,N′,N,N′-tetrabromo-benzene-1,3-disulfonylamide [TBBDA] at ambient temperature.     

Enhancement of azo dyes removal efficiency by using LDH/Tris/Pd catalyst: Kinetic studies

LDH/Tris/Pd (CaAl‐layered double hydroxide/tris (hydroxymethyl)aminomethane/palladium) was synthesized and appraised for its catalytic activity towards the degradation of two selected azo dyes. The decolorization of azo dyes, acid red 18 (AR 18) and reactive yellow 15 (RY 15), requires considerably small amounts of synthesized catalyst. Kinetic studies show that the catalytic decolorization of these azo dyes follows the first order kinetic model. The reported method is simple and applicable; in addition, the stable catalyst can efficiently decolorize model azo dyes with good recyclability. Therefore, LDH/Tris/Pd can be accepted as the possible component for the utilization in wastewater treatment.     

Near‐IR Absorbing Ruthenium Complexes of Non‐Innocent 6,12‐Di(pyridin‐2‐yl)indolo[3,2‐b]carbazole: Variation as a Function of Co‐Ligands

This article deals with the hitherto unexplored metal complexes of deprotonated 6,12‐di(pyridin‐2‐yl)‐5,11‐dihydroindolo[3,2‐b]carbazole (H₂L). The synthesis and structural, optical, electrochemical characterization of dimeric [{Ru^III(acac)₂}₂(μ‐L^.?)]ClO₄ ([ 1 ]ClO₄, S=1/2), [{Ru^II(bpy)₂}₂(μ‐L^.?)](ClO₄)₃ ([ 2 ](ClO₄)₃, S=1/2), [{Ru^II(pap)₂}₂(μ‐L^2?)](ClO₄)₂ ([ 4 ](ClO₄)₂, S=0), and monomeric [(bpy)₂Ru^II(HL^?)]ClO₄ ([ 3 ]ClO₄, S=0), [(pap)₂Ru^II(HL^?)]ClO₄ ([ 5 ]ClO₄, S=0) (acac=σ‐donating acetylacetonate, bpy=moderately π‐accepting 2,2’‐bipyridine, pap=strongly π‐accepting 2‐phenylazopyridine) are reported. The radical and dianionic states of deprotonated L in isolated dimeric 1 ⁺/ 2 ³⁺ and 4 ²⁺, respectively, could be attributed to the varying electronic features of the ancillary (acac, bpy, and pap) ligands, as was reflected in their redox potentials. Perturbation of the energy level of the deprotonated L or HL upon coordination with {Ru(acac)₂}, {Ru(bpy)₂}, or {Ru(pap)₂} led to the smaller energy gap in the frontier molecular orbitals (FMO), resulting in bathochromically shifted NIR absorption bands (800–2000 nm) in the accessible redox states of the complexes, which varied to some extent as a function of the ancillary ligands. Spectroelectrochemical (UV/Vis/NIR, EPR) studies along with DFT/TD‐DFT calculations revealed (i) involvement of deprotonated L or HL in the oxidation processes owing to its redox non‐innocent potential and (ii) metal (Ru^III/Ru^II) or bpy/pap dominated reduction processes in 1 ⁺ or 2 ²⁺/ 3 ⁺/ 4 ²⁺/ 5 ⁺, respectively.     

Doped Nano‐Sized Copper(I) Oxide (Cu2O) on Melamine?Formaldehyde Resin: a Highly Efficient Heterogeneous Nano Catalyst for ‘Click’ Synthesis of Some Novel 1H‐1,2,3‐Triazole Derivatives Having Antibacterial Activity

A facile and simple protocol for the 1,3‐dipolar cycloaddition of organic azides with terminal alkynes catalyzed by doped nano‐sized Cu₂O on melamine? formaldehyde resin (nano‐Cu₂O? MFR) as a new and convenient heterogeneous catalyst is described. In this method, ‘click’ cycloaddition of various structurally diverse β‐azido alcohols and alkynes in the presence of nano‐Cu₂O? MFR in H₂O/THF 1 : 2 furnished the corresponding 1,4‐disubstituted 1H‐1,2,3‐triazole adducts 1a – 1o in good to excellent yields at room temperature (Scheme and Table 3). The nano‐Cu₂O? MFR was characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD), inductively coupled plasma (ICP) analysis, and FT‐IR. The nano‐Cu₂O? MFR could be easily recovered and recycled from the reaction mixture and reused for many consecutive trials without significant decrease in activity (Table 4). The in vitro antibacterial activities of all synthesized compounds were tested on several Gram‐positive and/or Gram‐negative bacteria (Table 5). The results demonstrate the promising antibacterial activity for some of the synthesized compounds.     

A New Reaction of Isatin,Cyclic 1,3‐Diketone,and 2‐Cyanoacetamide: A Four‐Component Synthesis of Spirooxindoles

A novel reaction of isatins, 2‐cyanoacetamide, and cyclic 1,3‐diketones in ethanol was reported. The reaction gave the unexpected spirooxindole ethyl carboxylates in excellent yields and the spirooxindole carboxamide was not observed.     

Synthesis of new bicarbazole-linked triazoles as non-cytotoxic reactive oxygen species (ROS) inhibitors

Abstract

Carbazole analogs 3 and 4 and a new library of bicarbazole-linked triazoles 6–11 were prepared via new synthetic methodology. Metal-catalyzed oxidative coupling reaction was utilized for the synthesis of bicarbazole acetylene 4 and different metals (Zn⁺², Co⁺², Fe⁺³, Ni⁺², Cu⁺², Mn⁺²) as catalyst were screened. Only Fe-catalyzed reaction was found to be excellent and gave homocoupled product 4. Cu-catalyzed 1,3-dipolar cycloaddition was also utilized to install triazole moiety for the synthesis of hybrid molecules 6–11. Based on reported anti-inflammatory activity of carbazole and triazole scaffolds, all compounds were screened for their reactive oxygen species (ROS) inhibitory potential. Results from these studies revealed triazole 9 as most active compound (IC₅₀ value of 7.6?±?0.1?µg/mL on human whole blood and 2.7?±?0.09?µg/mL on isolated neutrophils) using ibuprofen as a standard. Therefore, class described herein can serve as attractive structural element for further studies on ROS inhibition.