Synthesis, characterization and properties of some divalent metal(II) complexes: their electrochemical, catalytic, thermal and antimicrobial activity studies

In this study, we synthesized the amine compound 2-(2-aminoethyliminomethyl)phenol (H(3)A) as the starting material, and then we prepared the polydentate Schiff base ligands from the reactions of the amine compound (H(3)A) with phtaldialdehyde (H(2)L), 4-methyl-2,6-di-formlyphenol (H(3)L(1)) and 4-t-butyl-2,6-di-formylphenol (H(3)L(2)) in the ethanol solution. Moreover, the complexes Cd(II), Cu(II), Co(II), Ni(II), Zn(II) and Sn(II) of the ligands H(2)L, H(3)L(1) and H(3)L(2) have been prepared. All compounds have been characterized by the analytical and spectroscopic methods. In addition, the magnetic susceptibility and molar conductance measurements have been made. The catalytic properties of the mono- and binuclear Co(II) and Cu(II) complexes have been studied on the 3,5-di-tert-butylcatechol (3,5-DTBC) and ascorbic acid (aa) as a substrate. The oxidative C-C coupling properties of the Co(II) and Cu(II) complexes have been investigated on the sterically hindered 2,6-di-tert-butylphenol (dtbp). The antimicrobial activity properties of the ligands and their mono- and binuclear complexes have been studied against the bacteria and fungi. The results have been compared to the antibacterial and fungi drugs. The TGA curves show that the decomposition takes place in three steps for all complexes. Electrochemical properties of the complexes Cu(II) and Ni(II) have been investigated for the first time in acetonitrile by cyclic voltammetry.     

Two-layered Au@Ag Bimetallic Nanocomposites-poly (L-Met) Platform for Highly Sensitive Chlorpheniramine Maleate Detection

The two-layered bimetallic Au@Ag and poly(L-methionine) (Au@Ag/p-L-met) sensor was newly developed for the electrochemical determination of chlorpheniramine maleate (CPM). After electropolymerization of L-met, bimetallic surfaces were prepared by electrodeposition of Au@Ag nanoparticles on the p-L-met/PGE. The surface characterization was carried out by scanning electron microscopy (SEM), Energy Dispersive X-ray spectroscopy (EDX), Cyclic Voltammetry (CV) and Electrochemical impedance spectroscopy (EIS). The sensor shows good electrocatalytic activity, high sensitivity, wide linear range (0.87–600.0 μM) and a low detection limit (0.26 μM) by using Differential pulse voltammetry (DPV). The sensor was used to determine CPM in pharmaceutical samples with satisfactory results.     

Ovalbumin mediated synthesis of Mn3O4

By using Mn²⁺ and Mn³⁺ salts, and freshly extracted ovalbumin, Mn₃O₄ nanocrystals have been synthesized successfully. The X-ray diffraction results indicated that the synthesized nanoparticles have only the spinel structure without the presence of any other phase impurities. As the ovalbumin–water mixture was highly basic, the process did not require any use of base to increase the pH where hydrolysis took place. A gel formed where water soluble ovalbumin proteins served as a perfect matrix for entrapment of metal ions (Mn²⁺ and Mn³⁺). Upon heat treatment, the dried gel precursor decomposed into nanocrystalline Mn₃O₄. The discrepancy between the crystallite size from XRD and particle size SEM analysis reveals polycrystalline nature of the synthesized particles with this route. EPR analysis of Mn₃O₄ shows a narrow and symmetric line indicating the absence of hyperfine splitting.     

Synthesis and Electrochemical and In Situ Spectroelectrochemical Characterization of Chloroindium(III) and Chloromanganese(III) Phthalocyanines Bearing 4‐((4′‐Trifluoromethyl)phenoxy)phenoxy Substituents

The synthesis of novel tetra‐substituted manganese and indium phthalocyanines was achieved by cyclotetramerization of corresponding phthalonitrile derivative. The new compounds have been characterized by using UV‐vis, IR, ¹H NMR and mass spectroscopic data. Spectroelectrochemical characterization of an indium phthalocyanine complex was performed for the first time in this paper and its electrochemical and spectroelectrochemical responses were compared with manganese phthalocyanine, bearing a redox active metal center. Electrochemical and spectroelectrochemical measurements exhibit that incorporation of redox active metal ion, Mn^III, instead of In^III into the phthalocyanine core extends the redox capabilities of the complex including the metal‐based reduction couples of the metal center and affect the aggregation behavior of the complexes. Presence of molecular oxygen in the electrolyte system affects the voltammetric and spectroelectrochemical responses of the phthalocyanines due to the interaction between the complexes and molecular oxygen. MnPc and InPc formed µ‐oxo species and this reaction changed the electrochemical and optic responses of the complexes, which are desired properties for sensor and electrocatalytic applications of a material. An in situ electrocolorimetric method has been applied to investigate the color of the electro‐generated anionic and cationic forms of the complexes for possible electrochromatic applications and for clarify the interaction mechanism of the MnPc with molecular oxygen.     

Antimycobacterial and antioxidant activities of reserpine and its derivatives

In view of the attributed medicinal properties of reserpine, a number of acyl reserpine derivatives were prepared and tested for antimycobacterial activity against Mycobacterium tuberculosis, strain H(37)Rv and antioxidant activities. The results indicated that in the case of antimycobacterial activity, 10 out of 18 derivatives caused more inhibition than that caused by reserpine itself. The results of antioxidant activity revealed that acylation in benzene ring of reserpine decreases the percentage inhibition of DPPH in all the derivatives compared to the parent compound (1).     

An observation on the periodic solutions to nonlinear physical models by means of the auxiliary equation with a sixth-degree nonlinear term

It is a fact that in auxiliary equation methods, the exact solutions of different types of auxiliary equations may produce new types of exact travelling wave solutions to nonlinear equations. In this manner, various auxiliary equations of first-order nonlinear ordinary differential equation with distinct-degree nonlinear terms are examined and, by means of symbolic computation, the new solutions of original auxiliary equation of first-order nonlinear ordinary differential equation with sixth-degree nonlinear term are presented. Consequently, the novel exact solutions of the generalized Klein–Gordon equation and the active-dissipative dispersive media equation are found out for illustration purposes. They are also applicable, where conventional perturbation method fails to provide any solution of the nonlinear problems under study.     

Raman spectra of ionic liquids: a simulation study of AlF3 and its mixtures with NaF

Theoretical Raman spectra of the melts of NaF/AlF3 mixtures have been obtained from computer simulations in order to examine how the Raman spectra reflect the coordination structure around the Al3+ ions. The Raman spectra, both polarized and depolarized, are calculated from a model for the dependence of the polarizability of the system on the ionic coordinates which was inspired by electronic structure calculations of the polarizabilities of ions in a condensed-phase environment. The shapes of the spectra and their evolution with composition in the mixtures conform remarkably well to those seen experimentally, and we discuss the relationship between the bands seen in the spectra and the vibrational modes of the AlFn(3-n) coordination complexes which are found in the melts. Finally, we calculate quantities which relate to the degree of cross-linking between these coordination complexes and their lifetimes.     

Organic and inorganic ion-exchange beads as indicators in redox and precipitation titrations

Resin beads in the Fe(III) or p-dimethylaminobenzylidene-rhodanine form are used as indicators in precipitation titrations with K(3)Fe(CN)(6), and Ag(+). Resin beads with dipheny lamine adsorbed on them can be used as indicators in cerimetric titrations. They have some advantages over conventional indicators.     

Synthesis and optimization of permselective polymer (polyindoline) film

A polyindoline permselective polymer film was readily synthesized by an electrochemical polymerization of indoline in an aqueous solution of KCl at a potential of 0.4 V vs Ag/AgCl. The amperometric responses of the polyindoline film-coated platinum electrodes to electroactive (ascorbic acid, oxalic acid and hydrogen peroxide) and non-electroactive (lactose, sucrose and urea) substances were measured at a potential of 0.7 V. Effects of various variables such as film thickness, concentrations of monomer and electrolyte, and pH on the permselective behavior of the polymeric membrane were systematically investigated and the optimal values were determined. It was found that permselective polyindoline-coated electrodes prepared in this one-step procedure permitted hydrogen peroxide oxidation while it prevented interference due to oxidizable species such as ascorbic acid and oxalic acid. As a result, it is believed that this polymeric membrane, owing to its permselective character, can be used as the protective material in the construction of hydrogen peroxide-based biosensors. Received: 10 November 1997 / Accepted: 27 January 1998