Zehra Durmus

INVESTIGATIONS ON SOME HETERO-TRINUCLEAR COMPLEXES OF NICKEL(II) AND COPPER(II)

Ni(II) and Cu(II) complexes of N,N′-bis(salicylidene-1,3-diaminopropane) were prepared and found to form linear and non-linear trinuclear complexes. Elemental analyses, IR spectroscopy, thermogravimetry and X-ray diffraction techniques applied to the complexes yielded valuable information about their moleculer structures. It was observed that μ-bridges in these trinuclear complexes form through the phenolic oxygens of the ligand or through anions present in the medium. In the presence of acetate, nitrate or nitrite, μ-bridges form between a pair of atoms resulting in linear trinuclear complexes. However, the presence of chloride or bromide results in μ-bridges involving the phenolic oxygens of N,N′-Bis(salicylidene)-1,3-diaminopropane.

Liquid-membrane electrode sensitive to ammonia and aliphatic amines based on 1-[(2-oxyphenyl)iminomethly]-2-oxybenzene-O,O',N-ammin-nickel(II) complex.

In this study, an ammonia-gas-sensing liquid-state membrane electrode based on 1-[(2-oxyphenyl)iminomethyl]-2-oxybenzene-O,O,N-ammin-nickel(II) (Ni(II)-Schiff base) as an ionophore was developed. This membrane electrode gave a very good performance and exhibited linear response with near-Nernstian slope of 50.7+/-0.5 mV per decade, within a concentration range of 1.0x10(-1)-1.0x10(-3) M. The electrode performance depends on the pH of the test solution and the optimum pH range was 10.0-11.5. The effect of concentration of internal solutions in the electrode was also investigated. The selectivity properties of the electrode towards aliphatic amines at a pH value of 10.2 were investigated with the mixed-solution method. Furthermore, the response time and lifetime of the electrode prepared were determined.

Electrochemical oxidation behavior of ezetimibe and its adsorptive stripping determination in pharmaceutical dosage forms and biological fluids

Ezetimibe (EZE) is a drug that reduces plasma cholesterol levels and performs by decreasing cholesterol absorption in intestines. In this study, we examined the electrochemical behavior of EZE on a glassy carbon electrode and optimum conditions for its quantitative determination by using voltammetric methods. In addition, some electrochemical parameters such as diffusion coefficient, surface coverage of adsorbed molecules, electron transfer coefficient, standard rate constant and number of electrons were calculated by using the results of cyclic voltammetry. A tentative mechanism for the oxidation for EZE is suggested. As a result of bulk electrolysis and cyclic voltammetric experiments, an intermediate product occurred. The oxidation signal of the EZE molecule was used to develop fully validated, new, rapid, selective and simple square-wave anodic adsorptive stripping voltammetric (AdsSWV) and differential pulse anodic stripping voltammetric (AdsDPV) methods to direct determination of EZE in pharmaceutical dosage forms and biological samples. As a result of these studies, for the AdsDPV and AdsSWV techniques, linear working ranges were found to be 4.0xa0×xa010−7–7.6xa0×xa010−6 and 4.0xa0×xa010−7–6.0xa0×xa010−6 mol L−1, respectively. The detection limits obtained from AdsDPV and AdsSWV were calculated to be 1.529xa0×xa010−7 and 1.185xa0×xa010−7mol L−1, respectively. Moreover, the limit of quantification was evaluated for AdsDPV and AdsSWV methods and found to be 5.098xa0×xa010−7 and 3.951xa0×xa010−7 mol L−1, respectively. The developed methods for EZE were successfully applied to assay the drug in tablets, human blood serum and human urine.

Electrochemical Behaviors and Determinations of Some 2,5-Disubstituted Benzoxazole Compounds at the Hanging Mercury Drop Electrode

The electrochemical behaviors of N-(2-benzylbenzoxazol-5-yl)benzamide (B1), N-(2-benzylbenzoxazol-5-yl)4-nitrobenzamide (B2) and N-(2-(4-chlorobenzyl)benzoxazol-5-yl)-4-nitrobenzamide (B3) were investigated by cyclic voltammetry (CV), square wave voltammetry (SWV), differential puls voltammetry (DPV), chronoamperometry (CA) and bulk electrolysis (BE) techniques in dimethylsulfoxide (DMSO) containing 0.1 M tetrabutylammonium tetrafluoroborate (TBATFB). The number of electrons transferred and diffusion coefficients were calculated by using chronoamperometry and bulk electrolysis techniques. Standard heterogeneous rate constants for the electrochemical reduction were calculated by Klingler-Kochi technique. The data obtained showed that the quantitative determination of benzoxazoles could be done by using DPV and SWV rapidly and sensitively. For the DPV technique, linear working ranges for B2 and B3 were found to be (6.0 10-4.0 10) M and (1.0 10-2.0 10) M respectively. The corresponding ranges for these compounds found by SWV were (6.0 10-4.0 10) M and (1.0 10-2.0 10) M. The detection limits for B2 obtained from DPV and SWV were calculated to be 1.33 10 M and 1.76 10 M respectively. The detection limits with B3 deplicted to be almost the same.

Electrochemical behaviour of 3,8-difluorobenzo[c]cinnoline at mercury electrode

Voltametric and coulometric methods have been used to study the electroanalytical behaviour of 3,8-difluorobenzo[c]cinnoline. The number of electrons transferred, the wave characteristics, diffusion coefficient and reversibility of the reactions have been investigated in ethyl alcohol-BR. Adsorption of the molecule on the surface of the mercury drop electrode was analyzed and this phenomena was exploited to calculate the diffusion coefficient of 3,8-difluorobenzo[c]cinnoline. A mechanism for the electrode reaction was proposed.

{[μ‐N,N′‐Bis­(salicyl­idene)‐2,2′‐di­methyl‐1,3‐propane­di­amine](piperidine)copper(II)}di­bromo­zinc(II)

In the crystal structure of the dinuclear title compound, [CuZnBr2(C19H22N2O2)(C5H11N)], the CuII ion has a distorted square-pyramidal coordination involving two iminic N and two phenolic O atoms of the N,N′-bisxad(salicylxadidene)-2,2′-dixadmethyl-1,3-propanexaddiaminate (SALPD2− or C17H16N2O22−) ligand and one N atom of the piperidine group. The coordination around the ZnII ion is distorted tetrahedral, with two O atoms of the SALPD2− ligand and two bromide ions. The Zn—Br bond lengths are 2.3309u2005(9) and 2.3508u2005(10)u2005A. The Cu⋯Zn distance is 3.0800u2005(9)u2005A.

Syntheses, characterization of and studies on the electrochemical behaviour of ferrocenyl dithiophosphonates and 4-methoxyphenyl dithiophosphonates

GRAPHICAL ABSTRACT ABSTRACT Some 1,3-dithiadiphosphetane 2,4-disulfides (X2P2S4, X: Fc, FcLR; X: CH3O‒C6H4‒, LR) were allowed to react with alcohols to obtain dithiophosphonic acids (X(OR)PS2H). These were converted to the corresponding ammonium salts. The salts were of the structures [Fc(OR)PS2]−[NH4]+, R: 3-methyl-1-butyl- for I; 1-phenyl-1-propyl- for II; 3-pentyl- for III; 3-phenyl-1-propyl- for IV and [CH3O‒C6H4(OR)PS2]−[NH4]+, R: 3-methyl-1-butyl- for V and 1-phenyl-1-propyl- for VI. To the best of our knowledge, all the compounds except V were prepared for the first time. The compounds synthesized were characterized by elemental analysis, NMR (1H, 13C, 31P), MS, FTIR, and Raman spectroscopies. Electrochemical behaviors of I–VI at disposable pencil graphite electrode (PGE) were investigated by using cyclic voltammetry (CV) and square-wave voltammetry (SWV). Adsorption and diffusion patterns of all the compounds on the PGE were also studied. Two electroactive groups were identified in the compounds I–IV and only one in V and VI. The ferrocenyl groups of I-IV were oxidized at around 0.4 V. The same compounds display a second, more intense CV band at 0.8 V. The corresponding band for the compounds V–VI appears at around 0.6 V with a much weaker intensity. It is suggested that the ferrocenyl group introduced into the structures stabilizes the radical species formed as the product of the oxidation of the dithiophosphonato group.