Browsing by Author "Demirhan, F"
Now showing 1 - 20 of 22
Results Per Page
Sort Options
Item ANTIMICROBIAL AND SOD-LIKE ACTIVITIES OF N,N'-BIS(FERROCENYLMETHYLENE)ETHYLENEDIAMINE SCHIFF BASE AND IT'S METAL COMPLEXESÖzbek, HA; Çinar, S; Oskay, M; Aydemir, T; Demirhan, FThe 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.Item Reduction of [CP2*Mo2O5] by thioglycolic acid in an aqueous mediumDemirhan, F; Taban, G; Baya, M; Dinoi, C; Daran, JC; Poli, RCompound [CP*2Mo2O5] reacts with thioglycolic acid, HSCH2COOH, in an acidic (CF3COOH) mixed water-methanol solvent, to yield compound [{Cp*Mo(mu-SCH2CO2)}(2)(mu-S)]. During this reaction, the thioglycolic acid acts as a reducing agent, as a ligand, and provides a sulfide ion for the Mo-S-Mo bridge. The molecular structure of the product can be described as containing two four-legged piano stools that share three legs. The Mo-Mo distance of 2.792(7) angstrom indicates metal-metal bonding, in agreement with the compound diamagnetism. (c) 2005 Elsevier B.V. All rights reserved.Item Reduction of [Cp*2Mo2O5] in aqueous medium: Structure and properties of a triangular mixed oxo-hydroxo-bridged product, [Cp*3Mo3(μ-O)2(μ-OH)4](X)2 (X =CF3CO2 or CF3SO3)Demirhan, F; Çagatay, B; Demir, D; Baya, M; Daran, JC; Poli, RThe reduction of [CP*2MO2O5] with Zn in a MeOH/H2O solotion acidified with either CF3COOH or CF3SO3H leads to the formation of the [CP*3MO3(mu-O)(2)(mu-OH)(4)](2+) ion as its trifluoroacetate or trifluoromethanesulfonate salt. The structure of the compound was confirmed by X-ray analyses. The anions establish hydrogen-bonding interactions with all four bridging OH groups. Density functional calculations afford bonding parameters in close agreement with the observed structure and indicate that the cluster is best described as a valence-delocalized Mo-3(13+) species. The five metal electrons are distributed among an a-type (z(2)) orbital, which accounts for most of the metal-metal attraction, and two essentially metal-metal nonbonding e-type (xy) orbitals with a slight Mo(mu-O) pi*-type contribution. Because of the C-2 symmetry, the latter orbitals are not degenerate. The calculations show that the unpaired electron is located in a molecular orbital with equal contribution from two Mo atoms, in agreement with the experimental observation of coupling of the unpaired electron to two Mo atoms in the isotropic EPR spectrum. (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Gerniany, 2006.Item Synthesis and spectroscopic characterization of new [Cu(tBusalpphen)]2, [MoCl2(salpphen)]2 complexes and Sn2Cl8 (tBu salpphen).2HNEt3 adductSözen, P; Akgül, Y; Demirhan, FTetradentate Schiff abase ligands, which were derived from the condensation of phenylenediamine with salicylaldehyde [salpphenH(2): N, N'-p-phenylene-bis(salicyclideneimine)] or 3,5-di-tert-butyl-2-hydroxybenzaldehyde [(tBu)salpphenH(2): N, N'-p-phenylene-bis(3,5-di-tert-butylsalicylidene)] and their complexes of Cu(II), Mo(IV) and adduct of Su(IV) were synthesized and characterized by H-1-NMR, C-13-NMR, and IR spectroscopic methods, mp, elemental analysis, and magnetic susceptibility. According to these data probable structures were assigned to these complexes and adduct. These are of the formula [Cu((tBu)salpphen)](2) and [MoCl2(salpphen)](2), and Sn2Cl8((tBu)salpphen).2HNEt(3). {Cu((tBu)salphhen)](2) was prepared by the reaction of the metal salt with the (tBu)salpphenH(2) Schiff base ligand in EtOH. [MoCl2(salpphen)](2) was synthesized by reactions of [MoCl4(CH3CN)(2)] with the salpphenH(2) Schiff base ligand in THF. The Schiff base adduct Sn2Cl8((tBu)salpphen).2HNEt(3) was synthesized by the reaction of SnCl4 with the (tBu)SalpphenH(2) Schiff base ligand in the presence of NEt3 in toluene.Item Synthesis, structure, and antimicrobial properties of mixed-metal organometallic polyoxometalates [Cp*2M5VO17]- (M = Mo, W)Özbek, HA; Kopar, EE; Demirhan, FA 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.Item Cyclopentadienylmolybdenum(VI) and molybdenum(V) oxo chemistry: New synthetic and structural featuresSaurenz, D; Demirhan, F; Richard, P; Poli, R; Sitzmann, HConvenient syntheses for Cp, Cp*, and related cyclopentadienyl derivatives (Cp-4 = C(5)HiPr(4); CP' = C(5)H(2)tBu(3)-1,2,4) of formula [(Ring)(2)MO2O5] are described. Compound [CP2MO2O5] was produced in good yields by the rapid oxidation of red [CPMoO2](4) with PhIO in CH2Cl2. [CP*2Mo2O5] was obtained by CH3COOH acidification of aqueous solutions of [CP*MoO3]-Na+, the latter being generated in a single step from [CP*MoCl4] and more than 5 equiv. of aqueous NaOH in air. Minor quantities of [CP*MoO2](2) were also isolated from this reaction, although the formation of this by-product may be reduced by using a two-step basic hydrolysis procedure. Extension of the latter strategy also allowed the preparation of [(CP2Mo2O5)-C-4], [CP'2Mo2O5], and [(CpMoO2Cl)-Cp-4] in good yields, in addition to the by-product [CP' MoO2](2). X-ray structures are reported for compounds [(CP2Mo2O5)-C-4], [CP'2Mo2O5], [Cp*MoO2](2), [Cp'MoO2](2), and [(CpMoO2Cl)-Cp-4]. (C) Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002.Item N-Heterocyclic carbene complexes of palladium(II) and rhodium(I) with pendant ferrocenylmethyl groupsDemirhan, F; Yildirim, Ö; Çetinkaya, B1-Ferrocenylmethyl-3-benzylimidazolidinium iodide and 1-ferrocenylmethyl-3-( 2,4,6-trimethylbenzyl) imidazolidinium iodide were prepared in good yields by boiling, under reflux, a solution of (ferrocenylmethyl)trimethylammonium iodide and the appropriate N-alkyl-2-imidazoline in MeCN. From the 1-ferrocenylmethyl-3-ben-zylimidazolidinium iodide salt, N-heterocylic carbene complexes of Pd-II and Rh-I were synthesized by in situ deprotonation and subsequent trapping. The new compounds were characterized by C, H, N analyses, H-1- n. m. r., C-13-n.m.r. and by cyclic voltammetry. The n. m. r. properties of the complexes are compared with those of nonferrocenylated carbene derivatives. The c. v.'s of these compounds show a number of resolved redox processes, indicating that CH(2)Fc substituents are electronically isolated from the remaining molecular framework.Item High oxidation state aqueous organometallics.: Formation and structure of an oxo-centred Cp* MoV trinuclear cation by chemical reduction of Cp*2Mo2O5Demirhan, F; Gun, J; Lev, O; Modestov, A; Poli, R; Richard, PReduction of Cp*2Mo2O5 by zinc/CF3CO2H in MeOH-H2O yields a salt which is composed of [Cp*3Mo3O4 (O2CCF3)(3)](+) and [Zn-2(O2CCF3)(6)](2-) ions after crystallisation from THF-Et2O.Item Epoxidation of Cis-cyclooctene with Hydrogen Peroxide Catalyzed by Lindqvist Type PolyoxometalatesÖzbek, HA; Demirhan, FIn 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).Item Heck coupling reactions of aryl halides catalyzed by saturated ferrocenylmethylimidazolinium salts/palladiumMusaoglu, D; Ozbek, HA; Demirhan, FIn situ prepared Pd(OAc)(2)/N,N '-bis(ferrocenyl methyl) imidazolinium salt catalyst systems were successfully applied to Heck reactions of various aryl halides (bromides, iodides) with olefins (styrene, ethyl acrylate). Catalytic studies showed that N,N '-bis(ferrocenylmethyl)imidazolinium chloride containing a saturated imidazole ring as an auxiliary catalyst in the presence of Pd(OAc)(2) was highly efficient in Heck coupling reaction of aryl halides in DMF.Item Rational, Facile Synthesis and Characterization of the Neutral Mixed-Metal Organometallic Oxides Cp2*MoxW6-xO17 (Cp* = C5Me5, x=0, 2, 4, 6)Taban-Çaliskan, G; Agustin, D; Demirhan, F; Vendier, L; Poli, RThe reaction of the bis(pentamethylcyclopentadienyl)pentaoxidodimetal complexes Cp*2M2O5 with four equivalents of Na2M'O-4 (M, M' = Mo, W) in acidic aqueous medium constitutes a soft and selective entry into neutral Lindqvist-type organometallic mixed-metal oxides Cp*2MoxW6-xO17 [x = 6 (1), 4 (2), 2 (3), 0 (4)]. The identity of the complexes is demonstrated by elemental analyses, thermogravimetric analyses and infrared spectroscopy. Thermal degradation of 1-4 up to above 500 degrees C leads to Mox/6W1-X/6O3. The molecular identity and geometry of compound 2 is further confirmed by a fit of the powder X-ray diffraction pattern with a model obtained from previously reported single-crystal X-ray structures of I and 4, with which 2 is isomorphous. DFT calculations on models obtained by replacing Cp* with Cp (I-IV) validate the structural assignments and assist in the assignment of the M,M'-O vibrations. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)Item Reduction of [CP*2Mo2O5] by mercaptopropionic acid in an aqueous medium. Isolation and characterization of a dinuclear oxo- and 3-sulfido-proprionato(2-)-bridged molybdenum(IV) compoundDinoi, C; Prikhodchenko, P; Demirhan, F; Gun, J; Lev, O; Daran, JC; Poli, RReaction of Cp-2*Mo2O5 with HSCH2CH2COOH in acidic (by CF3COOH) 50:50 MeOH-H2O solvent at room temperature yields compound Cp-2*Mo-2(mu-O)(mu-SCH2CH2CO2)(2), a dinuclear diamagnetic Mo-IV compound with a two-leg-sharing bis(four-legged piano stool) structure and a Mo-Mo distance of 2.6833(6) angstrom. A reaction monitoring by ESI MS shows the formation of an intermediate 18 mass units heavier, interpreted as a dihydroxo analogue. Electrochemistry shows a reversible, pH independent oxidation process and an irreversible, pH-dependent reduction process. Contrary to a recently published analogous reaction with the closely related HSCH2COOH substrate, this process does not lead to C-S bond cleavage. (c) 2007 Elsevier B.V. All rights reserved.Item Rational Synthesis and Characterization of the Mixed-Metal Organometallic Polyoxometalates [Cp*MoxW6-xO18]- (x=0, 1, 5, 6)Taban-Çaliskan, G; Fernandes, DM; Daran, JC; Agustin, D; Demirhan, F; Poli, RThe reaction between the oxometallic complexes Cp*2M2O5 and Na2M'O-4 (M, M' = Mo, W) in a 1:10 molar ratio in an acidic aqueous medium constitutes a mild and selective entry into the anionic Lindqvist-type hexametallic organometallic mixed oxides [Cp*MoxW6-xO18](-) [x = 6 (1), 5 (2), 1 (3), 0 (4)]. All of these compounds have been isolated as salts of nBu(4)N(+) (a), nBu(4)P(+) (b), and Ph4P+ (c) cations and two of them (1 and 3) also with the n-butylpyridinium (nBuPyr(+), d) cation. The compounds have been characterized by elemental analyses, thermogravimetric analyses, electrospray mass spectrometry, and IR spectroscopy. The molecular identity and geometry of compounds 1c, 2a, and 2c have been confirmed by single-crystal X-ray diffraction. Density functional theory calculations on models obtained by replacing Cp* with Cp (I-IV) have provided information on the assignment of the terminal M=O and bridging M-O-M vibrations.Item Speciation of [Cp*2M2O5] in Polar and Donor SolventsSözen-Aktas, P; Del Rosal, I; Manoury, E; Demirhan, F; Lledós, A; Poli, RThe speciation of compounds [Cp*2M2O5] (M=Mo, W; Cp*=pentamethylcyclopentadienyl) in different protic and aprotic polar solvents (methanol, dimethyl sulfoxide, acetone, acetonitrile), in the presence of variable amounts of water or acid/base, has been investigated by 1HNMR spectrometry and electrical conductivity. Specific hypotheses suggested by the experimental results have been further probed by DFT calculations. The solvent (S)-assisted ionic dissociation to generate [Cp*MO2(S)]+ and [Cp*MO3] takes place extensively for both metals only in water/methanol mixtures. Equilibrium amounts of the neutral hydroxido species [Cp*MO2(OH)] are generated in the presence of water, with the relative amount increasing in the order MeCN approximate to acetoneItem Investigation of the reaction of [Cp*2M2O5](M = Mo, W) with hydrogen peroxide and tert-butylhydroperoxide in MeCN; implications for olefin epoxidation catalyzed by organomolybdenum and organotungsten compoundsBhaumik, C; Manoury, E; Daran, JC; Sözen-Aktas, P; Demirhan, F; Poli, RCompounds [Cp*2M2O5] (M Mo, W) react with stoichiometric amounts of H2O2 (as a 30% w/w solution in water) and (BuOOH)-Bu-t (TBHP, as a 70% w/w solution in decane) in MeCN solution to yield a variety of products as shown by the H-1 NMR monitoring of the Cp* resonance. The reaction rate increases in the order W < Mo and TBHP < H2O2. While the total Cp* intensity remains constant when using stoichiometric amounts of oxidant, use of excess oxidant results in the ultimate total Cp* loss. From the decomposed solutions, crystals of [Cp*2Mo6O17] (1), (C5Me5O)[Cp*M6O18] (M Mo, 2a; W, 2b), and (C5Me(5)O)(2)[Mo6O19] (3) were recovered and analyzed by X-ray diffraction. Catalytic cyclooctene epoxidation experiments with ((Bu4N)-Bu-n)(2)[M6O19] (M Mo, W) in a 3: 1 MeCN/toluene mixture at 55 degrees C using either aqueous H2O2 or TBHP/decane as oxidant revealed that these are not the active forms of the catalyst which is generated under the same conditions from [Cp*2M2O5], as reported in previous contributions from our group (Chem. Eur. J., 2010, 16, 9572e9584; Eur. J. Inorg. Chem., 2013, 2728e2735). Further catalytic studies using aged [Cp*2Mo2O5]/TBHP and [Cp*2W2O5]/H2O2 solutions show a small loss of activity (< 50% in one week) attesting the robustness of the non-organometallic catalytically active species that is generated from the decomposition of [Cp*2M2O5]. These results cast doubts on the role of cyclopentadienyl as a supporting ligand for stable olefin epoxidation catalysts. (C) 2013 Elsevier B. V. All rights reserved.Item 1-Ferrocenylmethyl-3-(2,4,6-trimethylbenzyl)-1H-imidazolidin-3-ium iodide and trans-bis(3-benzyl-1-ferrocenylmethyl-1H-imidazolidin-2-ylidene)diiodidopalladium(II)Daran, JC; Demirhan, F; Yildirim, Ö; Çetinkaya, BOwing to increasing interest in the use of N-heterocyclic carbenes (NHCs) based on imidazolidinium ions as ligands in the design of highly efficient transition-metal-based homogeneous catalysts, the characterizations of the 1-ferrocenylmethyl-3-(2,4,6-trimethylbenzyl)imidazolidin-3-ium iodide salt, [Fe(C5H5)(C19H24N2)]I, (I), and the palladium complex trans-bis(3-benzyl-1-ferrocenylmethyl-1H-imidazolidin-2-ylidene)diiodidopalladium(II), [Fe2Pd(C5H5)(2)(C16H17N2)(2)I-2], (II), are reported. Compound (I) has two iodide anions and two imidazolidinium cations within the asymmetric unit (Z' = 2). The two cations have distinctly different conformations, with the ferrocene groups orientated exo and endo with respect to the N-heterocyclic carbene. Weak C-H donor hydrogen bonds to both the iodide anions and the pi system of the mesitylene group combine to form two-dimensional layers perpendicular to the crystallographic c direction. Only one of the formally charged imidazolidinium rings forms a near-linear hydrogen bond with an iodide anion. Complex (II) shows square-planar coordination around the Pd-II metal, which is located on an inversion centre (Z' = 0.5). The ferrocene and benzyl substituents are in a trans-anti arrangement. The Pd-C bond distance between the N-heterocyclic carbene ligands and the metal atom is 2.036 (7) angstrom. A survey of related structures shows that the lengthening of the N-C bonds and the closure of the N-C-N angle seen here on metal complexation is typical of similar NHCs and their complexes.Item Reaction of [Cp*2W2O5] with mercaptocarboxylic acids: Addition rather than reduction. Isolation and characterization of Cp*WO2(SCH2CH2COOH)Sözen, P; Daran, JC; Manoury, E; Demirhan, F; Poli, RThe reaction of Cp*2W2O5 with HS(CH2) nCOOH (n - 1, 2) in MeOH or in CH2Cl2 solutions at room temperature proceeds in slightly different ways depending on the value of n. For n = 2, it selectively yields compound Cp*WO2(SCH2CH2CO2H), which has been isolated and characterized by elemental analysis, NMR and single crystal X-ray diffraction. The reaction is equilibrated, being shifted to the product by absorption of water by anhydrous Na2SO4 in CH2Cl2, and to the reactants by addition of water. Contrary to the Mo analogue, no products resulting from metal reduction are obtained. The corresponding reaction for n = 1 occurs similarly at low substrate/W ratios (< 0.5), but proceeds further to several uncharacterized products for greater substrate amounts. The primary product could not be isolated, but its H-1 NMR spectrum suggests a different, asymmetric structure. (C) 2010 Elsevier B.V. All rights reserved.Item Aqueous reduction of [Cp*2W2O51]: Characterization of the triangular clusters [Cp*3W3O4(OH)2]2+ and [Cp*3W3O6]+ - Comparison with molybdenumDinoi, C; Sözen, P; Taban, G; Dernir, D; Demirhan, F; Prikhodchenko, P; Gun, J; Lev, O; Daran, JC; Poli, RZinc reduction Of CP * 2W2O5 in an acidified water-methanol medium affords the green 3-electron trinuclear cluster [CP*3W3O4(OH)(2)](+2), isolated and crystallographically characterized as the triflate salt, 1. Upon exposure to air, this complex is oxidized to a related 2-electron cluster, [Cp * 3W3O6], which was crystallized and characterized in three different salts, 2-4. The 3-electron cluster exhibits a near-tetragonal frozen-glass EPR spectrum, and it shows evidence of coupling of the unpaired electron to only one of the three W atoms. The two-electron cluster is diamagnetic. An electro-spray ionization MS' study revealed a stepwise expulsion of neutral [CP*WO2] units as the main fragmentation process. DFT calculations unveiled the intimate details of the electronic structures of these complexes and fully rationalized the structural and spectroscopic properties.Item Molybdenum versus Tungsten for the Epoxidation of Cyclooctene Catalyzed by [Cp*2M2O5]Sözen-Aktas, P; Manoury, E; Demirhan, F; Poli, RThe catalytic activity of [Cp*2M2O5] (M = Mo, W; Cp* = pentamethylcyclopentadienyl) for the homogeneous epoxidation of a solution of cyclooctene in MeCN/toluene follows the order Mo >> W when using tert-butyl hydroperoxide (TBHP)/decane as oxidant, in contrast to the inverse order (W >> Mo) when using aqueous H2O2 as oxidant. The catalytic activity for the Mo system strongly depends on the solvent used to deliver the oxidant (TBHP/decane >> TBHP/H2O). The low activity of the W system is also decreased when using TBHP/water in place of TBHP/decane. For both metals, H2O2/H2O is a better oxidant than TBHP/H2O. However, whereas the Mo-based catalyst is much more active for the TBHP/decane epoxidation in spite of the lower TBHP oxidizing power (TBHP/decane > H2O2/H2O > TBHP/H2O), the W-based system is much more active for the H2O2/H2O epoxidation in spite of the negative effect of water (H2O2/H2O > TBHP/decane > TBHP/H2O). The kinetic profile of the TBHP/decane epoxidation process is affected by product inhibition. Initial rate measurements show that the rate law is first order with respect to substrate and has saturation behavior with respect to the oxidant.Item Synthesis, structure, electrochemical and antimicrobial properties of N,N′-bis(ferrocenylmethyl)imidazolinium saltsÖzbek, HA; Aktas, PS; Daran, JC; Oskay, M; Demirhan, F; Çetinkaya, BThe 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.