Nurşen Sarı

Synthesis and biological activity of new cycloalkylthiophene-Schiff bases and their Cr(III) and Zn(II) complexes

A series of some novel Ethyl 2-((1-hydroxynaphthalen-2-yl)methyleneamino)-5,6-dihydro-4H-cyclopenta[b]thiopehene-3-carboxylate, Ethyl 2-((1-hydroxynaphthalen-2-yl)methyleneamino)-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate, Ethyl 2-((1-hydroxynaphtalen-2-yl)methyleneamino)-5,6,7,8-tetrahydro-4H-cyclohepta[b]thiophene-3-carboxylate and their Cr(III) and Zn(II) complexes have been synthesized. All of these substances have been examined for antibacterial activity against pathogenic strains Listeria monocytogenes 4b (ATCC-19115), Staphylococcus aureus (ATCC25923), Proteus OX2 Wrah (ETS.40-A-4), Escherichia coli (ATCC-1280), Salmonella typhi H (NCTC-901.8394), Pseudomonas putida sp., Brucella abortus (A.99, UK-1995) RSKK-03026. Sh. boydii type 11 (Pasteur51.6), Sh. boydii type 16 (cHe 67.11), Sh. boydii type 6 (RSKK-96043), and antifungal activity against Candida albicans (Y-1200-NIH, Tokyo). Some of the compounds exhibited activity comparable to ampicillin ofloxacin, nystatin, kanamycin, sulphamethoxazol, amoxycillin, and chloroamphenicol. Most of the studied compounds were found effective against bacteria studied and yeast.

Preparation of carbon paste electrodes including poly(styrene) attached glycine-Pt(IV) for amperometric detection of glucose.

In this study, a novel carbon paste electrode that is sensitive to glucose was prepared using the nanoparticles modified (4-Formyl-3-methoxyphenoxymethyl) with polystyren (FMPS) with L-Glycine-Pt(IV) complexes. Polymeric nanoparticles having Pt(IV) ion were prepared from (4-Formyl-3-methoxyphenoxymethyl) polystyren, glycine and PtCl4 by template method. Glucose oxidase enzyme was immobilized to a modified carbon paste electrode (MCPE) by cross-linking with glutaraldehyde. Determination of glucose was carried out by oxidation of enzymatically produced H2O2 at 0.5 V vs. Ag/AgCl. Effects of pH and temperature were investigated, and optimum parameters were found to be 8.0 and 55°C, respectively. Linear working range of the electrode was 5.0×10(-6)-1.0×10(-3) M, R(2)=0.997. Storage stability and operational stability of the enzyme electrode were also studied. Glucose biosensor gave perfect reproducible results after 10 measurements with 2.3% relative standard deviation. Also, it had good storage stability (gave 53.57% of the initial amperometric response at the end of 33th day).

Spectroscopic characterization of novel d-amino acid-Schiff bases and their Cr(III) and Ni(II) complexes as antimicrobial agents

The aim of this work was to investigate the antibacterial and antifungal activities of novel d-amino acid-Schiff bases including fluorine atom and their Cr(III) and Ni(II) complexes. All these substances have been examined for antibacterial activity against pathogenic strains Listeria monocytogenes 4b ATCC19115, Staphylococcus aureus ATCC25923, Escherichia coli ATCC1280, Salmonella typhi H NCTC 901.8394, Brucella abortus (A.99, UK-1995) RSKK03026, Staphylococcus epidermis sp., Micrococus luteus ATCC9341, and Shigella dysenteriatyp 10 NCTC 9351, and antifungal activity against Candida albicans Y-1200-NIH, Tokyo. The antimicrobial test results of these amino acid-Schiff base complexes exhibited better activity than some known antibiotics. In particular, diamagnetic Ni(II) complexes were more potent bactericides than all of the substances synthesized.

Synthesis, potentiometric and antimicrobial activity studies on DL-amino acids-Schiff bases and their complexes

A relationship between antimicrobial activities and the formation constants of amino acid-Schiff bases and their Cu(II) and Ni(II) complexes was studied. For this purpose, a series of Schiff bases were prepared from DL-amino acids (DL-glycine, DL-alanine) and halo aldehydes (5-chloro-2-hydroxybenzaldehyde, 5-bromo-2-hydroxybenzaldehyde). Schiff bases and their Cu(II) and Ni(II) complexes were characterized by the elemental analysis, spectral analysis, magnetic moment (at ca. 25°C), molar conductivity, and thermal analysis data. The complexes were found to have general compositions [ML(H2O)]. The protonation constants of the Schiff bases and stability constants of the complexes were determined potentiometrically in a dioxane-water (1: 1) solution at 25°C and 0.1 M KCl ionic strength. Antimicrobial activities of the Schiff bases and their complexes were estimated for six bacteria, such as Bacillus cereus RSKK 863, Staphylococcus aureus ATCC 259231, Micrococcus luteus NRLL B-4375, Escherichia coli ATCC 11230, Aeromonas hydrophila 106, Pseudomonas aeroginosa ATCC 29212, and the yeast Candida albicans ATCC 10239. The role of halogen substitution on the ligands, effect of the metal ion, and stabilities of the complexes are discussed on antimicrobial activities.

Synthesis, potentiometric and antimicrobial activity studies on 2-pyridinilidene-DL-amino acids and their complexes

To investigate the relationship between antimicrobial activities and the formation constants of CuII, NiII and CoII complexes with three Schiff bases, which were obtained by the condensation of 2-pyridinecarboxyaldehyde with DL-alanine, DL-valine and DL-phenylalanine, have been synthesized. Schiff bases and the complexes have been characterized on the basis of elemental analyses, magnetic moments (at ca. 25 °C), molar conductivity, thermal analyses and spectral (i.r., u.v., n.m.r.) studies. The i.r. spectra show that the ligands act in a monovalent bidentate fashion, depending on the metal salt used and the reaction pH = 9, 8 and 7 medium, for CuII, NiII and CoII, respectively. Square-planar, tetrahedral and octahedral structures are proposed for CuII, NiII and CoII, respectively. The protonation constants of the Schiff bases and stability constants of their ML-type complexes have been calculated potentiometrically in aqueous solution at 25 ± 0.1 °C and at 0.1 M KCl ionic strength. Antimicrobial activities of the Schiff bases and the complexes were evaluated for three bacteria (Bacillus subtillis, Staphylococcus aureus, and Escherichia coli) and a yeast (Candida albicans). The structure–activity correlation in Schiff bases and their metal(II) complexes are discussed, based on the effect of their stability contants.

SYNTHESIS, CHARACTERIZATION AND SELECTIVITY STUDIES OF POLY(ACRYLAMIDE) INCORPORATING SCHIFF BASES

Three novel polymers incorporating Schiff bases, derived from condensation reactions of poly(acrylamide) with 5-chloro-2-hydroxybenzaldehyde, 5-bromo-2-hydroxybenzaldehyde and 5-methyl-2-hydroxybenzaldehyde, have been synthesized, and their Cu(II) and Ni(II) complexes have been prepared. The 1H-NMR signals of the –CH=N– and –NH2 groups have been utilized to determine the relative abundances of Schiff base and acrylamide groups in the polymers containing Schiff bases. Poly(acrylamide) incorporating Schiff bases and metal complexes thereof have been characterized by molar conductance, magnetic susceptibility and electronic and IR spectral studies. The selectivity of poly(acrylamide) incorporating Schiff bases in forming Ni(II)-aldehyde and Cu(II)-aldehyde complexes has been studied. The Cu(II) and Ni(II) contents in the metal-bearing polymer complexes were determined by the ICP-MS technique.

Synthesis of Some Polymer‐Metal Complexes and Elucidation of their Structures

In this study, the nine coordination polymers of Fe(III), Co(II) and Ni(II) salts have been synthesized using polyacrylamide (PAA), polt(ethylene glycol) (PEG) and poly(vinyl alcohol) (PVA) and their structures were characterized by magnetic and conductivity measurements, ultraviolet‐visible (UV‐VIS), FTIR spectroscopy and thermogravimetric analysis (TGA). The structures of Fe(III) complexes in the all coordination polymers were found as tetrahedral. The structures of PAA‐Co(II) coordination polymer was determined as octahedral geometry whereas PEG‐Co(II) and PVA‐Co(II) complexes showed as tetrahedral structure. PAA‐Ni(II) and PEG‐Ni(II) complexes have octahedral geometry, whereas PVA‐Ni(II) has a square planar structure. Besides, the stress‐strain experiments of PVA‐metal coordination polymers obtained rubber‐like structure were carried out and the value of breaking‐strain of PVA‐Ni(II) complex was found to be about 17% of vulcanized natural rubber. The conductivities of the resulting polymer‐metal complexes were measured by four‐probe technique and were found in the range 10−5−10−6 Scm−1. Thus, it was suggested that they can be used in the field potential application of conducting polymers. TGA results revealed that among the complexes PEG‐Fe(III) and PVA‐Fe(III) complexes have the highest thermally stable.

Immobilization of β-galactosidase on Novel Polymers Having Schiff Bases

Abstract: We have developed a strategy to immobilize β-galactosidase as a model enzyme by using polymeric supports having Schiff bases, which were prepared from (aminomethyl)polystyrene and 2-phenlyindole-3-carboxaldehyde by condensation. β-galactosidase was immobilized onto the new polymer supports via covalent bonds. The influence of temperature, pH, reusability, and storage capacity on the free and immobilized β-galactosidase was investigated. Our results indicate that the (aminomethyl)polystyrene with Schiff bases is most suitable for the immobilization of β-galactosidase. These kinds of new supports can be used for the immobilization of β-galactosidase due to their strong storage capacity and reusability.

Tetradentate asymmetric Schiff bases and their Ni(II) and Fe(III) complexes

Three asymmetric Schiff-base tetradentate diimines H2L1, H2L2, and H2L3 [(2-OH)C6H4N=CHC6H42-N=CHC6H3(2-OH)(5-X), X = H, CH3, Cl respectively] have been synthesized by a two step process. The reaction of 2-hydroxy aniline with 2-nitro-benzaldehyde in EtOH gave the starting Schiff base, 2-hydroxy-N-(2-nitrobenzylidene)aniline (SB-NO2), which was reduced into the amino derivative (SB-NH2) in solution. Reacting SB-NH2 with 2-hydroxybenzaldehyde, 2-hydroxy-5-methylbenzaldehyde and 2-hydroxy-5-chlorobenzaldehyde gave the three new ligands H2L1, H2L2, and H2L3 respectively. Their dimeric, binuclear metal complexes with Ni(II) and Fe(III) have also been synthesized. The ligands and their complexes were characterized by elemental analyses, LC–MS, IR, electronic, 1H and 13C-NMR spectra, TGA, conductivity and magnetic measurements. All of the spectroscopic, analytical and other data indicate octahedral geometry M2L2(H2O)X2 (M: Ni,Co;X: Cl or H2O), except for NiL2 which is monomeric. Antimicrobial activities of the ligands and the complexes were evaluated against five bacteria. While the ligands and the Ni complexes are inactive towards Pseudomonas aeruginosa and Staphylococcus aureus, Fe complexes are active; only Fe complexes are inactive against Escherichia coli. All of the compounds have antimicrobial activities against Bacillus subtilis, and Yersinia enterecolitica.

Polystyrene Attached Pt(IV)–Azomethine, Synthesis and Immobilization of Glucose Oxidase Enzyme

Modified polystyrene with Pt(IV)–azomethine (APS–Sch–Pt) was synthesized by means of condensation and demonstrated to be a promising enzyme support by studying the enzymatic properties of glucose oxidase enzyme (GOx) immobilized on it. The characteristics of the immobilized glucose oxidase (APS–Sch–Pt–GOx) enzyme showed two optimum pH values that were pH = 4.0 and pH = 7. The insertion of stable Pt(IV)–azomethine spacers between the polystyrene backbone and the immobilized GOx, (APS–Sch–Pt–GOx), increases the enzymes’ activity and improves their affinity towards the substrate even at pH = 4. The influence of temperature, reusability and storage capacity on the free and immobilized glucose oxidase enzyme was investigated. The storage stability of the immobilized glucose oxidase was shown to be eleven months in dry conditions at +4 °C.