A polydentate ligand based on 2,2’-dipyridylamine unit linked benzo-15-crown-5; alkali and transition metal complexes; photoresponsive ligand; antimicrobial evaluation against pathogenic microorganisms

Transition Metal Chemistry - New double-armed benzo-15-crown-5 compound (L) was successfully synthesized from 4’,5’-bis(bromethyl)benzo-15-crown-5 with 2,2’-dipyridylamine. The...     

Fe3O4@SiO2@Bacillus pumilis: magnetised solid phase bio-extractor for preconcentration of Pb(II) and Cu(II) from water samples

ABSTRACT

In this study, preconcentration and separation of Cu(II) and Pb(II) ions by using Fe₃O₄@SiO₂@Bacillus pumilis before their determinations by flame atomic absorption spectrometry (FAAS) were investigated. The thermophilic Bacillus pumilis were isolated from Meyremderesi spring, ??rnak, Turkey. Effects of important parameters such as pH, adsorbent amount, eluent type, concentration and volume of eluent and sample volume on magnetic solid phase extraction (MSPE) were examined in details. The preconcentration factors for Cu(II) and Pb(II) ions were calculated as 30 and 40, respectively. The accuracy of the proposed extraction procedure was validated analysing certificated reference materials and addition – recovery tests. The concentration of copper and lead were determined in water samples from Turkey by Flame AAS after application developed preconcentration-separation method.     

Radiation-induced molecular imprinting of d-glucose onto poly(2-hydroxyethyl methacrylate) matrices using various crosslinking agents

Radiation-induced molecular imprinting of d-glucose onto poly(2-hydroxyethyl methacrylate) matrix was achieved to create three-dimensional cavities to recognize and bind d-glucose. The optimization of imprinting capability of matrices was achieved by investigating the effects of various parameters such as the type and amount of crosslinking agent, type of solvent, template to monomer ratio and total absorbed dose. Crosslinking agents with increasing chain lengths and different flexibilities were used in an attempt to elucidate the impact of relevant imprint parameters on the effectiveness of imprinting technique. The absorbed dose varied from 1 to 15 kGy. Cavity sizes of MIPs were measured by positron annihilation lifetime (PAL) experiments. Control matrices were synthesized with exactly the same composition in the absence of d-glucose. Separation of d-glucose has been shown to be successfully achieved in HPLC columns filled with MIPs whereas no separation was observed for non-imprint matrices.     

Differential pulse polarographic behaviour of thiazopyr herbicide and application to its determination in fruit juice and soil samples

A differential pulse polarographic method for the determination of the herbicide thiazopyr has been developed. The polarographic study of thiazopyr exhibited two well-defined cathodic peaks within the pH range of 1.0 to 8.0. The variation of pH and polarographic parameters indicated that the optimum conditions under which thiazopyr could be reduced were a pH 7.0 BR buffer solution, a reduction peak potential of ?1270 mV (vs. SCE), scan rate of 5 mV s^?1, pulse amplitude of 50 mV with pulse duration of 50 ms at an ambient temperature of 25 ± 3°C. The main reduction peak was characterised by cyclic voltammetry as being irreversible and diffusion-controlled. A linear relationship between the peak current and the concentration of thiazopyr was obtained in the range of 0.43–38.6 µg mL^?1, with a detection limit of 0.127 µg mL^?1. The proposed method was successfully applied to the determination of thiazopyr in spiked fruit juice and soil samples. The mean recoveries of the 19.8 µg g^?1 and 3.96 µg mL^?1 thiazopyr spiked to soil and orange juice were 20.2 ± 1.0 µg g^?1 and 3.84 ± 0.12 µg mL^?1, at 95% confidence level, respectively. The sufficiently good recoveries and low relative standard deviation (RSD) data confirm the high accuracy and precision of the proposed method. The interferences effects of several commonly used pesticides and inorganic species were also studied. Interfering effects were eliminated either by providing selectivity with pH, or using EDTA as complexing agent.     

Syntheses and spectroscopic characterization of double-armed benzo-15-crown-5 derivatives and their sodium and potassium complexes

A series of new benzo-15-crown-5 derivatives (1–6) containing formyl and imine groups were prepared. New formyl crown ethers (1 and 2) were prepared by reaction of 4′,5′-bis(bromomethyl)benzo-15-crown-5 with 2-hydroxy-3-methoxybenzaldehyde (o-vanillin) and 2-hydroxy-5-methoxybenzaldehyde in the presence of NaOH. New Schiff bases (3–6) were synthesized by the condensation of corresponding aldehydes with 1,3-diaminopropane and 1,4-diaminobutane. Sodium and potassium complexes (1a–6a and 1b–6b) of the crown compounds forming crystalline complexes of 1:1 (Na⁺:ligand) and 1:2 (K⁺:ligand) stoichiometries were also synthesized. The structures of the aldehydes 1 and 2, imines 3–6 and complexes (1a–3a and 1b–3b) were confirmed on the basis of elemental analyses, IR, ¹H- and ¹³C-NMR, and mass spectroscopy.     

Synthesis and Antimicrobial Activity of New Pyrimidine Derivatives Incorporating 1H‐Tetrazol‐5‐ylthio Moiety

In this study, some new 4,6‐dimethoxy pyrimidine derivatives were synthesized. 2‐Amino‐4,6‐dimethoxy‐5‐thiocyanatopyrimidine ( 2 ) was synthesized by a reaction of 2‐amino‐4,6‐dimethoxypyrimidine with KSCN and was converted into 2‐amino‐5‐(1H‐tetrazol‐5‐ylthio)‐4,6‐dimethoxypyrimidine ( 4 ) by treatment with NaN₃ in the presence of NH₄Cl in DMF. Then, 1,5‐disubstitute tetrazole compounds were obtained from 4 by the alkylation reaction. In addition, some 2‐chloro‐4,6‐dimethoxy‐5‐substitute‐pyrimidines were synthesized by the diazotization method. The structures of these compounds were established on the basis of IR, ¹H NMR, APT, and HRMS spectral data and were evaluated for antibacterial activities against various bacterial strains. The results showed that some of these compounds exhibited good antibacterial activity as that of standard antibiotics Penicillin, Ampicillin, and Erythromycin.     

Novel amino- and thio(substituted)-1,4-naphthoquinone (NQ) compounds: Synthesis and characterization

Abstract

Synthesis of new 1,4-naphthoquinone derivatives is important in terms of searching new biologically active substances. In particular, compounds with piperazine and thiol moiety in their structure, show a wide range of pharmacological activity such as anti-inflammatory, anticancer, anti-fungal, anti-bacterial, anti-allergic, apoptosis and radical scavenging activities. In this study, new amino- and thio(substituted) naphthoquinone derivatives were synthesized by the reaction of thiols and thioalcohols with four naphthoquinone compounds which were used as starting materials. The new compounds were purified by column chromatography. The structure of the compounds was confirmed by different spectroscopic techniques.     

New Benzo-15-Crown-5 Ethers Featuring Salicylic Schiff Base Substitutions – Synthesis, Complexes and Structural Study

Condensation reactions between 4'-formyl-5'-hydroxybenzo-15-crown-5and 2-aminopyridine, 2-amino-6-methylpyridine, 2-amino-4-methylpyridine or2-(aminomethyl)furan yielded the new laterally functionalized crown ethers1–4. The crown compounds 1–3 form crystalline 1:1 (Na⁺:ligand) complexes 1a–3a with sodium perchlorate. Ligands and complexes have been characterized by elemental analyses, IR, UV-Vis, ¹H-, ¹³C-NMR and mass spectra. The tautomeric equilibria (phenol-imine, O...H–N and keto-amine, O...H–N forms) have been systematically studied by using UV-Vis absorption spectra. The spectra of the ligands 1–4 and complexes 1a–3a were recorded in polar, non-polar, acidic, and basic media. In solutions of polar solvents, tautomeric interconversion of the Schiff base into the keto-amine form has been observed. A crystal structure [monoclinic, space group P2₁/c,a = 14.292(2), b = 9.449(6), c = 16.059(2) Å, = 114.20(1)°,V = 1978.4(13) ų, Z = 4 and D_x = 1.314 g cm^-3] shows that compound 4 is in the form of phenol-imine in solid state. There is a strong intramolecular [O–H...N 1.78(6), O...N 2.581(7), O–H 0.89(6) Å and N...H–O 148.4(5)°] hydrogen bond between the phenolic oxygen and imine nitrogen atoms. The C=N imine bond reveals a trans planar (1E) configuration. The molecules stack in columns parallel to the a/c plane of the unit cell.     

Vortex-assisted magnetic solid phase extraction of Cd(II), Cu(II) and Pb(II) on the Nitroso–R salt impregnated magnetic Ambersorb 563 for their separation,preconcentration and determination by FAAS

A novel vortex-assisted magnetic solid phase extraction method followed by flame atomic absorption spectrometry was improved to separate, preconcentrate and determine the lead, copper and cadmium ions by using 1-Nitro-2-naphthol-3, 6-disulfonic acid disodium salt (Nitroso-R salt) impregnated magnetic Ambersorb-563 resin. The adsorbent was characterised by Fourier transform infrared spectra, BET surface analyser and scanning electron microscopy. The influences of various analytical parameters, such as pH value, type and volume of the eluent, sample volume, were optimised and the effects of potentially interfering ions were investigated. The analyte ions were quantitatively recovered at pH 7.0 on magnetic adsorbent and desorbed with a 2.0 M HNO₃ in 10% acetone as eluent. The detection limits were 1.4, 5.8 and 1.5 ng mL^?1 for Cd(II), Cu(II) and Pb(II), respectively. The method has been validated with analytically by the analysis certified reference materials and standard additions prior to application to determine metal ions in water samples.