An electrochemical chiral sensor based on electrochemically modified electrode for the enantioselective discrimination of D-/L-tryptophan

Journal of Solid State Electrochemistry - Chirality is a universal characteristic of natural systems and discrimination of enantiomers of a chiral molecule plays a major role particularly in...     

New Copper（Ⅱ） and Nickel（Ⅱ） Complexes of 4-Morpholinoacetophenone Thiosemicarbazone： Structural, Electrochemical and Antimicrobial Studies

4-Morpholinoacetophenone thiosemicarbazone, MAPT, and its nickel（Ⅱ） and copper（Ⅱ） complexes have been prepared and characterized by elemental analysis, magnetic susceptibility, spectral methods （FT-IR, ^1H NMR） and cyclic voltammetry. Electrochemical behaviors of the complexes have been studied by cyclic voltammetry in DMF media showing metal centered reduction processes for both of them. The redox properties, nature of the electrode processes and the stability of the complexes were discussed. [Cu（MAPT）2]Cl2 complex shows Cu（Ⅱ）/Cu（Ⅰ） couple and quasi-reversible wave associated with the Cu（Ⅲ）/Cu（Ⅱ） process. The reduction/oxidation potential values depend on the structures of complexes. Also, the antimicrobial activities of these complexes were determined against S. aureus, E. coli and B. subtilis.     

Kinetic study of copper(II) complexation with 9-ethyl-3-carbazolecarboxaldehyde-thiosemicarbazone and kinetic-spectrophotometric determination of copper(II)

The kinetics of complexation reaction of Cu(II) with 9-ethyl-3-carbazolecarboxaldehyde-thiosemicarbazone (ECCAT) has been examined spectrophotometrically. The ligand was synthesized for the first time. The complexation reaction was carried out in a DMF-water medium at 35°C. The complex has maximum absorbance at 393 nm. Kinetic and activation parameters of the complexation reaction were calculated by the Arrhenius and Eyring equations using the data obtained from investigating the effect of temperature on reaction rates under the specified conditions. We also proposed reaction rate equations. Based on the studied complexation reaction, a simple kinetic method for the spectrophotometric determination of copper(II) has been developed. The calibration graphs are linear in the concentration range 0.2–1.9 μg/mL. The species that caused interference were investigated. The text was submitted by the authors in English.     

Electrochemical Investigation of Heavy Metal Ion Transfer Across the Water/1,2‐Dichloroethane Interface Assisted by 9‐Ethyl‐3‐Carbazolecarboxaldehyde‐Thiosemicarbazone

The transfer of heavy metal ions across the polarized water/1,2‐dichloroethane (1,2‐DCE) interface assisted by 9‐ethyl‐3‐carbazolecarboxaldehyde‐thiosemicarbazone (ECCAT) in the 1,2‐DCE phase has been studied by cyclic voltammetry. Voltammetric waves of Pb(II) and Cd(II) ions were reversible and quasi‐reversible, respectively, whereas that of Hg(II) and Zn(II) ion were irreversible. The voltammogram of Cu(II) ion showed a two‐step wave, however the nature of the transfer could not be satisfactorily evaluated by analyzing the cyclic voltammetric data. When Ni(II) and Co(II) was used no peak was visible under the experimental conditions used in this study. The dependence of the half‐wave potentials of Pb(II) and Cd(II) ions on the ligand concentration reveals that their ion‐transfer is assisted by the formation of 1:3 metal‐ECCAT complex in 1,2‐DCE. The over‐all association constants of [Pb(ECCAT)₃]²⁺ and [Cd(ECCAT)₃]²⁺ complexes in DCE‐phase have been determined to be log β =14.03 and log β =15.44, respectively.     

Investigation of the Lipophilicity of 2-Benzoylpyridine-Thiosemicarbazone Based on the Ion Transfer across the Liquid/Liquid Interface

The ion transfer reaction of 2-benzoylpyridine-thiosemicarbazone (HL), which has antimicrobial and antifungal properties and anticancer activity, has been studied to determine its lipophilicity by cyclic voltammetry at the water/1,2-dichloroethane (1,2-DCE) interface. The physicochemical parameters such as standard partition coefficient (lgP_I) and the standard Gibbs energy of transfer ( ) of the protonated form of the ligand were measured as a function of pH in aqueous phase. The protonated form of the ligand exhibited reversible or quasi-reversible voltammograms at the 1,2-DCE in the range of pH 1–5. The protonation constants of the ligand, pK_a1 and pK_a2, were determined spectrophotometrically and were found to be 12.14 and 3.24, respectively. The standard Gibbs energy of transfer ( ) and the partition coefficient of neutral species (lgP_N) were also determined by the shake-flask method. The standard Gibbs energy of transfer of this compound across the water/1,2-DCE interface was evaluated as the quantitative measure of its lipophilicity. The difference between lgP_I and lgP_N was related to the degree of charge delocalization and was used to evaluate qualitatively the lipophilicity of the ligand.     

Cytotoxic effects,microbiological analysis and inhibitory properties on carbonic anhydrase isozyme activities of 2-hydroxy-5-methoxyacetophenone thiosemicarbazone and its Cu(II), Co(II), Zn(II) and Mn(II) complexes

Research on Chemical Intermediates - Metal complexes of thiosemicarbazones have been receiving considerable attention in biological applications such as antimicrobial and anticancer therapies. In...     

Facilitated Transfer of Alkali and Alkaline‐Earth Metal Ions by a Calix[4]arene Derivative Across Water/1,2‐Dichloroethane Microinterface: Amperometric Detection of Ca2+

The host–guest complexation reactions between 5,11,17,23‐tetra‐tert‐butyl‐25,27‐diethoxycarbonylmethoxy‐26,28‐dimethoxy calix[4]arene (BDDC4) and alkali and alkaline‐earth metal ions were investigated by facilitated ion transfer processes across water/1,2‐dichloroethane microinterface by using steady‐state cyclic voltammetry and differential pulse voltammetry. The obtained facilitated transfers for Li⁺, Na⁺, K⁺, Rb⁺ and Ca²⁺ were evaluated under the different experimental conditions, at the excess concentrations of metal ions with respect to BDDC4 and vice versa. The association constants having 1 : 1 stoichiometry for Li⁺, Na⁺, K⁺ and Rb⁺ in 1,2‐DCE were determined. Also, we demonstrated that BDDC4 can play an important role for the development of highly selective chemical sensor for Ca²⁺ among alkaline‐metal ions in the concentration range of 0.1–1.0 mM in aqueous solution.     

Facilitated Transfer of Alkali Metal Ions by a Tetraester Derivative of Thiacalix[4]arene at the Liquid–Liquid Interface

The facilitated transfer of alkali metal ions (Na⁺, K⁺, Rb⁺, and Cs⁺) by 25,26,27,28‐tetraethoxycarbonylmethoxy‐thiacalix[4]arene across the water/1,2‐dichloroethane interface was investigated by cyclic voltammetry. The dependence of the half‐wave transfer potential on the metal and ligand concentrations was used to formulate the stoichiometric ratio and to evaluate the association constants of the complexes formed between ionophore and metal ions. While the facilitated transfer of Li⁺ ion was not observed across the water/1,2‐dichloroethane interface, the facilitated transfers were observed by formation of 1 : 1 (metal:ionophore) complex for Na⁺, K⁺, and Rb⁺ ions except for Cs⁺ ion. In the case of Cs⁺ a 1 : 2 (metal:ionophore) complex was obtained from its special electrochemical response to the variation of ligand concentrations in the organic phase. The logarithms of the complex association constants, for facilitated transfer of Na⁺, K⁺, Rb⁺, and Cs⁺, were estimated as 6.52, 7.75, 7.91 (log β₁°), and 8.36 (log β₂°), respectively.     

Synthesis, characterization and electrochemical investigation of a novel vic-dioxime ligand and its some transition metal complexes

4-(Chloroacetyl)diphenyl ether was synthesized from chloroacetyl chloride and diphenyl ether in the presence of AlCl₃ as catalyst in a Friedel-Crafts reaction. Then, its keto oxime and dioxime derivatives were prepared. 4-phenoxy-(N-4-chlorophenylamino)phenylglyoxime (H₂L) was synthesized from 4-(phenoxy)chlorophenylglyoxime and 4-chloroaniline. Ni(II), Co(II) and Cu(II) complexes of H₂L were obtained. The mononuclear Ni(II), Co(II) and Cu(II) complexes of H₂L have a metal–ligand ratio of 1:2 and the ligand coordinates through the two N atoms, as do most of the vic-dioximes. The structure of the ligand was identified by FT-IR, ¹H NMR, ¹³C NMR, ¹³C NMR (APT) spectroscopy and elemental analysis data. The structures of the complexes were characterized on the basis of FT-IR, ICP-AES, UV-Vis, elemental analysis, magnetic susceptibility measurements, and cyclic voltammetry. The electrochemical measurements were obtained by using cyclic voltammetry in DMF solution at room temperature. The electrochemical behaviors of H₂L and its complexes showed that the redox process of H₂L has one irreversible oxidation wave, whereas the redox processes of the complexes have both oxidation and reduction waves with metal centered.