Browsing by Author "Özbek, HA"

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    Synthesis, structure, and electrochemical properties of N,N′-bis(ferrocenylmethylene) ethylenediamine Schiff base and its metal complexes
    Kardas, TA; Özbek, HA; Akgül, Y; Demirhan, F
    The reaction of N,N '-bis(ferrocenylmethylene)ethylenediamine (FcNN) Schiff base with metal salts gave SnCl(4)FcNN (1), SnCl(2)FcNN(H2O)(2) (2), Sn-2(CH3)(4)Cl(4)FcNN (3), Ti(2)Cl(8)FcNN (4), CdFcNN(NO3)(2) (5), and CuFcNN(NO3)(2) (6). New complexes (1)-(6) were characterized by IR and elemental analysis techniques. IR spectra showed that the Schiff base was coordinated to the metal ions in a bidentate manner with N,N' donor sites. The H-1 NMR spectra of complexes (1), (2), and (4) show all the expected signals with a typical signal pattern of disubstituted ferrocenyl groups. The electrochemical properties of complexes were determined by cyclic voltammetry. Cyclic voltammetry results show that these complexes exhibit one irreversible oxidation peak.
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    ANTIMICROBIAL AND SOD-LIKE ACTIVITIES OF N,N'-BIS(FERROCENYLMETHYLENE)ETHYLENEDIAMINE SCHIFF BASE AND IT'S METAL COMPLEXES
    Özbek, HA; Çinar, S; Oskay, M; Aydemir, T; Demirhan, F
    The synthesized N,N'-bis(ferrocenylmethylene)ethylenediamine Schiff base and it's metal complexes were screened in vitro for antimicrobial activity against two Gram-positive (Staphylococcus aureus ATCC 25923, Bacillus cereus ATCC 7064), four Gram-negative (Escherichia coli ATCC 25922, Citrobacter koseri DBCC 01, Entorebacter aeruginosa ATCC 13048, Salmonella typhimurium DBCC 02) and antifungal activity against a Candida albicans. MIC values of the compounds ranged from 27 to 533 mu g/mL. Compound (5) showed very strong activity against S. aureus with the best MIC (27 mu g/mL). The lowest MIC for C. albicans was obtained 107 mu g/mL. The superoxide dismutase activity of Schiff base and it's metal complexes has been measured and discussed. SOD-like activities of bis ferrocenyl Schiff base ligand metal complexes were investigated using NBT. While only the Cu (II) complex showed SOD-like (40 mu m IC50) activity, the SOD-like activity value was not determined in the other complex and ligand.
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    Synthesis, characterization, and antibacterial properties of novel N-heterocyclic carbene (NHC) precursors and their silver complexes
    Atli, DD; Özbek, HA; Aksu, D
    In this work, a new compound, 1-(3,5-dimethoxybenzyl)-5,6-dimethylbenzimidazole, was prepared by N-alkylation of 5,6-dimethylbenzimidazole with potassium hydroxide and 3,5-dimethoxybenzyl bromide in ethanol. Three 5,6-dimethylbenzimidazolium salts were obtained by quaternisation of 1-(3,5-dimethoxybenzyl)-5,6-dimethylbenzimidazole with 4-cyanobenzyl bromide, 4-tert-butylbenzyl bromide, and bromoethane, respectively. Deprotonation of these with silver oxide afforded NHC silver complexes in good yields. The formation of the compounds was validated by nuclear magnetic resonance, Fourier transform infrared spectroscopy, elemental analysis, and LC-MS/MS (only for the silver complexes) methods. The complexes were found to be stable against air and light by H-1 NMR analysis of their solutions after one week. Experimental studies were carried out on the antibacterial properties of both benzimidazolium salts and NHC silver complexes against pathogenic strains of Staphylococcus aureus, Bacillus cereus, Escherichia coli, and Enterobacter cloacae. Inhibition zone and minimum inhibitory concentration values were determined. On the basis of these data, it was concluded that all the compounds studied were antibacterial against all the bacterial chains tested, particularly Gram-positive bacteria. The MIC values indicate that the coordination of the NHC ligands to the Ag(I) ion leads to an increase in their antibacterial activity. Bromo[1-(3,5-dimethoxybenzyl)-3-(4-tert-butylbenzyl)-5,6-dimethylbenzimidazolin-2-ylidene]silver showed better activity against S. aureus than the standard antibiotic gentamicin. [GRAPHICS] .
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    Synthesis, structure, and antimicrobial properties of mixed-metal organometallic polyoxometalates [Cp*2M5VO17]- (M = Mo, W)
    Özbek, HA; Kopar, EE; Demirhan, F
    A series of Lindqvist-type polyoxometalate (POM) compounds [Cat][Cp*2M5VO17] (M = Mo (1), W (2)) were obtained from Cp*2M2O5 and NaVO3 in a 1:10 molar ratio in an acidic aqueous-methanol medium ([Cat]: Bu4P+ (1a, 2a), Bu4N+ (1b, 2b), Ph4P+ (1c, 2c), and BuNC5H5+ (1d, 2d)). They have been structurally characterized by H-1 and P-31 NMR, FT-IR, TGA, ESI, and elemental analysis techniques which support the proposed structures. In antibacterial studies, Ph4P[Cp*2Mo5VO17] (1c) is the compound that shows the highest antimicrobial activity against both gram-positive and gram-negativebacteria.
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    Epoxidation of Cis-cyclooctene with Hydrogen Peroxide Catalyzed by Lindqvist Type Polyoxometalates
    Özbek, HA; Demirhan, F
    In our study, a method for the epoxidation of cis-cyclooctene was researched using a series of Lindqvist type POMs Cp*2MoxW6-xO17 (x=0, 2, 4, 6) and [Cp*MoxW6-xO18](-) (x=0, 1, 5, 6) as a catalyst in the presence of 30 % H2O2 as a green oxidant. This catalytic system containing polyoxometalates and H2O2 has applied the most succesful system in obtaining epoxide product with excellent yields for cis-cyclooctene in acetonitrile at 55 & DEG;C. Maximum epoxidation efficiency of 99 % was observed under optimized conditions for Ph4P[Cp*MoW5O18] (2c).
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    V-subtituted lindqvist-type polyoxometalates: preparation, structural characterization and antibacterial activity
    Özbek, HA
    A series of six V-substituted Lindqvist type polyoxometalate [M2V4O19](4-) (M = Mo, W) have been successfully prepared in good yields. Their structures were identified using elemental analysis, FT-IR, H-1 NMR, P-31 NMR, ICP-MS, and TGA. The antibacterial activity of these new series of V-substituted Lindqvist type polyoxometalates were carried out by disc diffusion method with gram-positive Staphylcoccus aureus ATCC 25923 and gram-negative Escherichia coli ATCC 25922 bacteria and some of the tested polyoxometalates have shown greater antibacterial activity than Ofloxacin (standard antibiotic). Moreover the MIC values of [Ph4P](4)[W2V4O19] (1b) and [Ph4P](4)[Mo2V4O19] (2b), against Staphylcoccus aureus bacterial strain are 1.22 and 9.76 mu g/ml respectively.
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    Synthesis and characterization of Anderson-Evans type polyoxometalates, antibacterial properties
    Özbek, HA
    Absract: In the present work, the new aluminium-substituted polyoxometalates of the Anderson-Evans type have been prepared and structurally defined by the reaction of aluminium (III) chloride hexahydrate and sodium tungstate dihydrate/sodium molybdate dihydrate in an aqueous basic medium. Elemental analysis, FT-IR, TGA, 1H NMR, and 31P NMR analysis revealed that these polyoxometalates had the following formula: [Ph4P]3[Al(OH)6Mo6O18]& BULL;4H2O 1, [Ph4P]3[Al(OH)6W6O18]& BULL;4H2O 2, [C7H10N]3[Al(OH)6Mo6O18]& BULL;4H2O 3, [C7H10N]3[Al(OH)6W6O18]& BULL;4H2O 4. The compounds 1 and 2 show promising antibacterial activity against gram-positive Staphylcoccus aureus ATCC 25923 and gram-negative Escherichia coli ATCC 25922 bacteria.
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    Synthesis, structure, electrochemical and antimicrobial properties of N,N′-bis(ferrocenylmethyl)imidazolinium salts
    Özbek, HA; Aktas, PS; Daran, JC; Oskay, M; Demirhan, F; Çetinkaya, B
    The N, N'-bis(ferrocenylmethyl)imidazolinium chloride (3) and bromide (4) were prepared by reaction of N,N'-bis(ferrocenylmethyl)ethylenediamine (2) with NH4X (X = Cl, Br). The N,N'-bis(ferrocenylmethyl)imidazolinium tetrafluoroborate (6) was obtained in two steps from compound (2). The first step involves the synthesis of N,N'-bis(ferrocenylmethyl)imidazolidine (5) by condensation of (2) with aqueous formaldehyde. Compound (5) was successfully converted to the N,N'-bis(ferrocenylmethyl)imidazolinium tetrafluoroborate (6) by treatment with tritylium tetrafluoroborate. The new compounds were characterized by H-1 and C-13 NMR, IR and elemental analysis techniques which support the proposed structures. The X-ray crystal structure of the N,N'-bis(ferrocenylmethyl)imidazolidine (5) shows two ferrocenyl moieties bridged by an imidazolidine ring. The electrochemical properties were determined by cyclic voltammetry for all compounds. The compounds were screened for their in vitro antimicrobial activities against the Gram-positive, Gram-negative bacteria and antifungal activity against a Candida albicans. (3), (4), (6) show significant antimicrobial activity and theirs MIC values ranged from 169 to 520 mu g/mL. (C) 2014 Elsevier B.V. All rights reserved.