Hayati Türkmen

Aqueous-phase Suzuki-Miyaura cross-coupling reactions catalyzed by Pd-NHC complexes.

Cleavage reactions of [PdBr(2)(NHC)](2) with two equiv. of pyridine derivatives (L), having one or two carboxylic acid groups [L = NC(5)H(4)-2-COOH, NC(5)H(4)-3-COOH, NC(5)H(4)-4-COOH, or NC(5)H(3)-2,6-(COOH)(2) in chloroform or DMSO, respectively, afforded the monomeric mixed ligand complexes trans-[PdBr(2)(NHC)L] (1-4) which, due to deprotonation of the carboxylic acid functionality, are water soluble in KOH. The catalytic activity of complexes 1-4 in aqueous Suzuki-Miyaura cross-coupling reactions were evaluated and compared. The dicarboxylic functionality enhances the catalyst reactivity and stability and the carboxylate derived from 4 could be easily recovered and reused for several cycles under the mild reaction conditions.

Ionic liquid intercalated clay sorbents for micro solid phase extraction of steroid hormones from water samples with analysis by liquid chromatography–tandem mass spectrometry

Clay material plays an important role in the transport and retention of many compounds in the soil, therefore, clay based sorbents are promising alternatives for selective sorption of organic pollutants. In the present work, different chain length ionic liquids (ILs) namely, 1-methyl-3-octyl-imidazolium bromide, 1-methyl-3-undecyl-imidazolium bromide and 1-methyl-3-octadecyl-imidazolium bromide were intercalated in the galleries of montmorillonite (MMT) clay. Then, this novel nanofiller surface was utilized in micro extraction of estrogenic hormones for the first time. A fast procedure where sonication-assisted emulsification microextraction combined with vortex assisted micro-solid phase extraction (μ-SPE) was developed for the LC-MS/MS analysis of estrone (E1), 17β-estradiol (E2), estriol (E3) and ethynylestradiol (EE2). The parameters related to the μ-SPE procedure namely; pH, sorbent amount, extraction solvent type and volume, sonication and vortex time, sample volume and salt effect on the extraction efficiency were screened by applying Plackett-Burmann design. The selected parameters were then optimized by using Box-Behnken design. The method was validated for the determination of estrogenic hormone residues in river water samples. Linear calibration plots were obtained for all hormones whose regression coefficients were larger than 0.98. RSD values were found less than 10% for three levels of concentration. LOD levels were calculated as; 0.012, 0.062, 0.018 and 0.693 ng L(-1) for E1, E2, E3 and EE2, respectively. Recovery values were calculated in the range of 86.9-97.7%. Considering large sample volumes required for attaining low limits of these hormones, present method provides an ease for analyst as 10 mL of the sample is adequate for achieving the same sensitivity.

A novel polythiophene – ionic liquid modified clay composite solid phase microextraction fiber: Preparation, characterization and application to pesticide analysis

This report comprises the novel usage of polythiophene - ionic liquid modified clay surfaces for solid phase microextraction (SPME) fiber production to improve the analysis of pesticides in fruit juice samples. Montmorillonite (Mmt) clay intercalated with ionic liquids (IL) was co-deposited with polythiophene (PTh) polymer coated electrochemically on an SPME fiber. The surface of the fibers were characterized by using scanning electron microscopy (SEM). Operational parameters effecting the extraction efficiency namely; the sample volume and pH, adsorption temperature and time, desorption temperature and time, stirring rate and salt amount were optimized. In order to reveal the major effects, these eight factors were selected and Plackett-Burman Design was constructed. The significant parameters detected; adsorption and temperature along with the stirring rate, were further investigated by Box-Behnken design. Under optimized conditions, calibration graphs were plotted and detection limits were calculated in the range of 0.002-0.667ng mL(-1). Relative standard deviations were no higher than 18%. Overall results have indicated that this novel PTh-IL-Mmt SPME surface developed by the aid of electrochemical deposition could offer a selective and sensitive head space analysis for the selected pesticide residues.

Synthesis and antimicrobial activities of hexahydroimidazo[1,5-a]pyridinium bromides with varying benzyl substituents

Variously substituted benzyl bromides were employed to quaternize hexahydrobenzylimidazo[1,5-a]pyridine (A) and the resulting bromides (1-11) were evaluated for their in vitro antimicrobial activity against 10 pathogenic microorganisms: Staphylococcus aureus, Staphylococcus epidermidis, Bacillus cereus, Micrococcus luteus, Proteus vulgaris, Escherichia coli, Salmonella typhimurium, Klebsiella pneumonia, Candida albicans and Candida krusei. Antimicrobial activities were surprisingly high (MIC: 0.78-400 μg/mL) and the sensitivity of the salts tested has been found to depend strongly both on the benzyl substituents and the microorganisms used. However, the correlation observed between antimicrobial activity and calculated partition coefficient (ClogP) was poor. Acute toxicity assessment of these salts showed LD(50) of 757-2000 mg/kg, after oral administration in mice in 24h.

Rhodium-catalyzed carbonylative arylation of alkynes with arylboronic acids: an efficient and straightforward method in the synthesis of 5-aryl-2(5H)-furanones

5-Aryl-2(5H)-furanones can be synthesized by the Rh-catalyzed reactions of arylboronic acids with internal alkynes under a CO atmosphere.

A spectrophotometric method for determination of molybdenum in water samples by using pyrogallol red and a water soluble ionic liquid

The present study describes a simple and sensitive spectrophotometric method for the determination of molybdenum in real water samples. The method is based on the hyperchromic and bathochromic effect of an ionic liquid namely, 1-methyl-3-octadecyl-imidazolium bromide (C18mimBr), on molybdenum ion (Mo(VI)) and pyrogallol red (PGR) complex. The ternary complex of Mo–PGR–C18mimBr displays a distinct absorption peak with excellent analytical characteristics and offers the advantages of simplicity for the determination of Mo(VI) ions, without any need for a solvent extraction step. The limit of detection (LOD) and limit of quantification (LOQ) of the method were calculated as 0.74 ng mL−1 and 2.47 ng mL−1 respectively. The method was validated and applied successfully to the determination of Mo(VI) ions in real water samples. The interference of ferric ions was shown to be removed from samples with less ionic content by using an ion exchange resin prior to the analysis, and the performance of the method was compared with that of ICP-MS.

Ionic liquid intercalated clay nanofillers for chromatographic applications

In this study, the preparation and characterization of ionic liquid (IL) intercalated montmorillonite (MMT) and their application as a micro-solid phase extraction material for the determination of Chlorpyrifos (CP) pesticide in water samples were reported. The ionic liquids bearing different chain lengths [1-methyl-3-octylimidazolium bromide (C8mimBr), 1-methyl-3-undecyl-imidazolium bromide (C12mimBr) and 1-methyl-3-octadecyl-imidazolium bromide (C18mimBr)] were intercalated in the galleries of MMT. The IL-intercalated MMTs were characterized by means of XRD and TG methods. The (C12mimBr)-intercalated MMT had the highest sorption efficiency for the CP, which was 32 times higher than the original MMT. We also optimized the parameters for extracting CP from the (C12mimBr)-intercalated MMT.

Ionic liquid modified carbon paste electrode and investigation of its electrocatalytic activity to hydrogen peroxide

Abstract. This paper reports on the preparation and advantages of novel amperometric biosensors in the presence of hydrophobic ionic liquid (IL), 1-methyl-3-butylimidazolium bromide ([MBIB]). Carbon paste biosensor has been constructed by entrapping horseradish peroxidase in graphite and IL mixed with paraffin oil as a binder. The resulting IL/graphite material brings new capabilities for electrochemical devices by combining the advantages of ILs composite electrodes. Amounts of H2O2 were amperometrically detected by monitoring current values at reduction potential (–0·15 V) of K3Fe(CN)6. Decrease in biosensor responses were linearly related to H2O2 concentrations between 10 and 100 μM with 2 s response time. Limit of detection of the biosensor were calculated to be 3·98 μM for H2O2. In the optimization studies of the biosensor some parameters such as optimum pH, optimum temperature, enzyme amount, interference effects of some substances on the biosensor response, reproducibility and storage stability were carried out. The promising results are ascribed to the use of an ionic liquid, which forms an excellent charge-transfer bridge and wide electrochemical windows in the bulk of carbon paste electrode.