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MeOH
Terms modified by MeOH Selected AbstractsCellulose dimethylphenylcarbamate-immobilized zirconia for chiral separation in reversed-phase CECELECTROPHORESIS, Issue 22 2009Jurim Gwon Abstract Cellulose dimethylphenylcarbamate (CDMPC)-immobilized zirconia (CDMPCZ) was used as a chiral stationary phase for enantioseparation of a set of nine racemic compounds in reversed-phase CEC. Influences of the type and composition of organic modifier and the applied voltage on enantioseparation were examined. Separation data on CDMPCZ were also compared with those on CDMPC-immobilized silica (CDMPCS). Enantiomers of the analytes investigated are well separated in ACN/phosphate buffer mobile phases. Better enantioselectivity and resolution were obtained with ACN than MeOH as the organic modifier. Retention was longer but better enantioselectivity and resolution were obtained on CDMPCZ than CDMPCS. [source] Determination of DNA methylation by COBRA: A comparative study of CGE with LIF detection and conventional gel electrophoresisELECTROPHORESIS, Issue 17 2009Simon Goedecke Abstract DNA methylation as an epigenetic modification of the human genome is under emphatic investigation. Several studies have demonstrated a role of DNA methylation in oncogenesis. In conjunction with histone modifications, DNA methylation may cause the formation of heterochromatin and thus mediate the inactivation of gene transcription. It is important to develop methods that allow for an accurate quantification of the amount of DNA methylation in particular DNA regions, to gain information concerning the threshold of methylation levels necessary for gene inactivation. In this article, a CGE method with on-column LIF detection using SYBR Green is compared with a conventional slab-gel electrophoresis. We thus investigate the validity to analyze DNA methylation in the samples of a combined bisulfite restriction analysis. It is demonstrated that CGE is superior to gel electrophoresis in means of linearity, precision, accuracy, automatization (high throughput), and sample consumption. However, gel electrophoresis is easier to perform (simple devices, no PC usage), and the running costs are comparatively low. A further advantage of CGE is the sparse use of toxic compounds (MeOH and SYBR Green), whereas gel electrophoresis is performed in polyacrylamide gels with ethidium bromide staining. [source] Two variable semi-empirical and artificial neural-network-based modeling of peptide mobilities in CZE: The effect of temperature and organic modifier concentrationELECTROPHORESIS, Issue 5 2009Stefan Mittermayr Abstract This work was focused on investigating the effects of two separation influencing parameters in CZE, namely temperature and organic additive concentration upon the electrophoretic migration properties of model tripeptides. Two variable semi-empirical (TVSE) models and back-propagation artificial neural networks (ANN) were applied to predict the electrophoretic mobilities of the tripeptides with non-polar, polar, positively charged, negatively charged and aromatic R group characteristics. Previously published work on the subject did not account for the effect of temperature and buffer organic modifier concentration on peptide mobility, in spite of the fact that both were considered to be influential factors in peptide analysis. In this work, a substantial data set was generated consisting of actual electrophoretic mobilities of the model tripeptides in 30,mM phosphate buffer at pH 7.5, at 20, 25, 30, 35 and 40°C and at four different organic additive containing running buffers (0, 5, 10 and 15% MeOH) applying two electric field strengths (12 and 16,kV) to assess our mobility predicting models. Based on the Arrhenius plots of natural logarithm of mobility versus reciprocal absolute temperature of the various experimental setups, the corresponding activation energy values were derived and evaluated. Calculated mobilities by TVSE and back-propagation ANN models were compared with each other and to the experimental data, respectively. Neural network approaches were able to model the complex impact of both temperature and organic additive concentrations and resulted in considerably higher predictive power over the TVSE models, justifying that the effect of these two factors should not be neglected. [source] Determination of flurbiprofen enantiomers in plasma using a single-isomer amino cyclodextrin derivative in nonaqueous capillary electrophoresis,ELECTROPHORESIS, Issue 17 2008Anne Rousseau Abstract A nonaqueous capillary electrophoresis (NACE) assay was developed for the separation and determination of flurbiprofen enantiomers in plasma samples using 6-monodeoxy-6-mono(3-hydroxy)propylamino-,-cyclodextrin as chiral selector. The nonaqueous background electrolyte was made up of 40,mM ammonium acetate in methanol (MeOH), and flufenamic acid was employed as internal standard. Solid-phase extraction was used for sample cleanup prior to the NACE separation. The NACE method reproducibility was optimized by evaluating different capillary washing sequences between runs. After having tested various conditions, trifluoroacetic acid (1,M) in MeOH was finally selected. Concerning the solid-phase extraction procedure, good and reproducible analyte recoveries were obtained using MeOH for protein denaturation and a polymeric phase combining hydrophobic interactions with anion exchange properties (Oasis® MAX) was selected as extraction sorbent. The method selectivity was not only demonstrated toward a blank plasma sample but also toward other non-steroidal anti-inflammatory drugs. The method was then successfully validated with respect to response function, trueness, precision, accuracy, linearity and limit of quantification. [source] Development of HPLC and NACE methods for the simultaneous determination of benzoic and sorbic acids in sour snap beans containing oilELECTROPHORESIS, Issue 22 2007Po Han Abstract The practical methods were developed for the simultaneous determination of benzoic acid (BA) and sorbic acid (SA) in sour snap bean samples containing oil. BA and SA in the samples were extracted by ultrasonication with water, followed by cleanup procedures with precipitation for removing the potential proteins and with petroleum ether liquid,liquid extraction for removing the edible oil contained in the samples. The HPLC method was developed using Supelco C18 (250,mm×4.6,mm id, 5,,m) as column, MeOH,20,mM NH4Ac (25:75 v/v) at 1.0,mL/min as the mobile phase and 230,nm as the detection wavelength. The optimal NACE method was established with a running buffer of 20.0,mM NH4Ac in 95% MeOH (pH*,10.6), and an applied voltage of ,30,kV over a capillary of 50,,m id×48.5,cm (40,cm to the detector window), which gave a baseline separation of BA and SA, and as well as of the blank matrix within ca. 10,min. Both HPLC and NACE methods gave the relatively lower limits of quantification at about 0.01,0.02 and 0.04,0.05,mg/kg, respectively, whereas the overall recoveries were larger than 85.0%. The proposed methods have been successfully applied to measure 15 real sour bean samples and the content profile of BA and SA in sour bean samples was obtained and evaluated. [source] Separation of Nile Blue-labelled fatty acids by CE with absorbance detection using a red light-emitting diodeELECTROPHORESIS, Issue 8 2007Michael C. Breadmore Dr. Abstract The separation of fatty acids derivatised with Nile Blue (NB) by CE with detection using a red light-emitting diode (LED) was examined. NB was selected as the derivatisation agent due to its high molar absorption coefficient of 76,000,M,1cm,1 at 633,nm, making it well suited for sensitive absorbance detection using a red 635,nm LED. NB-labelled fatty acids were separated by both MEKC using SDS micelles, i -PrOH and n -BuOH and by NACE in a number of solvents including MeOH, EtOH and ACN. The sensitivity of NACE was superior to MEKC, with detection limits of 5×10,7,7×10,7,M obtained for each acid, approximately 20 times lower than the MEKC method. The NACE detection limits are approximately 100 times lower than previous reports on the separation of fatty acids by CE using indirect absorbance detection, ten times lower than using indirect fluorescence detection and are inferior only to those obtained using precapillary derivatisation and direct fluorescence detection. The efficiency of the NACE method was also superior to MEKC and allowed the separation of unsaturated fatty acids to be examined, although it was not possible to baseline-resolve linoleic (C18:2) and linolenic (C18:3) acids in a reasonable time. The method was used to analyse the fatty acid profile of two edible oils, namely sunflower and sesame oils, after alkali hydrolysis, where it was possible to identify both the saturated and unsaturated fatty acids in each sample. [source] Application of polymeric surfactants in micellar electrokinetic chromatography-electrospray ionization mass spectrometry of benzodiazepines and benzoxazocine chiral drugsELECTROPHORESIS, Issue 5-6 2006Jingguo Hou Abstract Chiral micellar EKC (CMEKC) coupled to ESI-MS using polymeric surfactants as pseudostationary phases is investigated for simultaneous enantioseparation of two benzodiazepines, (±)-oxazepam ((±)-OXA) and (±)-lorazepam ((±)-LOR), and one benzoxazocine, (±)-nefopam ((±)-NEF). First, enantioselectivity and electrospray sensitivity of six chiral polymeric surfactants for all three chiral compounds are compared. Second, using poly(sodium N -undecenoyl- L -leucinate) as pseudostationary phase, the organic modifiers (methanol (MeOH), isopropanol, and ACN) are added into the running buffer to further improve chiral resolution (RS). Next, a CMEKC-ESI-MS method for the simultaneous enantioseparation of two benzodiazepines is further developed by using a dipeptide polymeric surfactant, poly(sodium N -undecenoxy carbonyl- L,L -leucyl-valinate) (poly- L,L -SUCLV). The CMEKC conditions including nebulizer pressure, capillary length, ammonium acetate concentration, pH, poly- L,L -SUCLV concentration, and capillary temperature were optimized to achieve maximum chiral RS and highest sensitivity of MS detection. The spray chamber parameters (drying gas temperature and drying gas flow rate) as well as sheath liquid conditions (MeOH content, pH, flow rate, and ionic strength) were found to significantly influence MS S/N of both (±)-OXA and (±)-LOR. Finally, a comparative study between simultaneous UV and MS detection showed high plate numbers, better chiral RS, and enhanced detectability with CMEKC-MS. However, speed of analysis was faster using CMEKC-UV. [source] Comparison of methanol and acetonitrile as solvents for the separation of sertindole and its major metabolites by capillary zone electrophoresisELECTROPHORESIS, Issue 17 2005Xavier Subirats Abstract Sertindole (1-[2-[4-[5-chloro-1-(4-fluorophenyl)-1H -indol-3-yl]-1-piperidinyl]ethyl]-2-imidazolidinone), an atypical antipsychotic drug, was separated by capillary electrophoresis from its two main metabolites norsertindole and dehydrosertindole. The low solubility of the analytes in water (octanol-water partition coefficient is about 105) is overcome by the use of methanol (MeOH) and acetonitrile (ACN) as solvents for the background electrolyte (BGE). Mobilities were measured in BGEs with defined pH in a broad range. It was found that in MeOH the mobility of the analytes is mainly governed by acid,base equilibria, whereas in ACN other reactions like ion pairing and homoconjugation play a pronounced role and lead to a complex pattern of the mobility as function of the pH. However, separation can be obtained in less than 10,min in both solvent systems. [source] Determination of enantiomeric purity of a novel COX-2 anti-inflammatory drug by capillary electrophoresis using single and dual cyclodextrin systemsELECTROPHORESIS, Issue 9 2003Carlos Pérez-Maseda Abstract E-6087 is the most advanced compound among the cyclooxygenase-2 (COX-2) inhibitor drugs developed in our company. Its activity is mainly associated with the S(,)-enantiomer (E-6232), whereas the R(,)-enantiomer (E-6231) becomes an impurity whose content should be determined. Five main impurities and degradation products of E-6232 have been found (E-6144, E-6024, E-6072, E-6397 and E-6132), and some of them co-elute with the distomer when using a chiral high-performance liquid chromatography (HPLC) method. Consequently, we have optimized the separation of all the impurities from the two enantiomers of E-6087 by capillary electrophoresis (CE), in order to use the method for the enantiomeric purity determination of E-6232. The effect of the methanol (MeOH) content in the background electrolyte (BGE), the sulfobutyl ether-,-cyclodextrin (SBE-,-CD) and heptakis-(2,6-di- O -methyl)-,-cyclodextrin (DM-,-CD) concentration, and the capillary temperature have been studied. Separation of all compounds could be achieved in different systems, either in a single CD-system (with SBE-,-CD) or in a dual CD-system (with DM-,-CD as a neutral CD). By using the dual CD system a limit of detection (LOD) and a limit of quantitation (LOQ) of 0.03% and 0.1% of distomer, respectively, were achieved*. [source] Slow desorption behavior of one highly resistant aromatic amine in Lake Macatawa, Michigan, USA, sedimentENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 12 2005Shihua Chen Abstract The desorption behavior of benzidine from Lake Macatawa (Holland, MI, USA) sediment was investigated in this study using batch solvent extraction method. Seven solvents were tested as the extracting reagents: Deionized water (DI), calcium chloride in DI (CaCl2), sodium hydroxide in DI (NaOH), acetonitrile (ACN), a mixture of acetonitrile and ammonium acetate in DI (ACNNH4OAc), methanol (MeOH), and hydrochloric acid in DI (HCl). These solvents are proposed to react with sediment-associated benzidine by different mechanisms (e.g., cation exchange, hydrophobic partitioning, and covalent binding). Three sets of sorption isotherm experiments were conducted separately in these seven solvents with a 7-d, three-week, and two-month contact time. The results demonstrated nonlinear isotherms with Freundlich 1/n values varying from 0.25 to 0.52. The desorption behavior of benzidine in the solvents was evaluated after the sorption of benzidine onto the sediment with same contact times of 7 d, three weeks, and two months. A two-stage model subsequently was applied to simulate the experimental data. The rapidly desorbing rate constants were on the order of one to two per day for ACN, ACN-NH4OAc, and NaOH solvents, and the slowly desorbing rate constants were on the order of 10,5 to 10,4/d. Sequential desorption experiment demonstrated low total extraction efficiency of less than 40%. Both the observed sorption and desorption phenomena suggested that hysteresis and/or mass-transfer limited diffusion may result in the slow desorption behavior observed in this study. [source] A Dynamically Entangled Coordination Polymer: Synthesis, Structure, Luminescence, Single-Crystal-to-Single-Crystal Reversible Guest Inclusion and Structural TransformationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 24 2010Arshad Aijaz Abstract A ZnII coordination polymer {[Zn2(cpa)2(bpy)]·3H2O}n (1) (cpa2, = 4-(methoxycarbonyl)benzoate and bpy = 4,4,-bipyridine) has been synthesized under solvothermal condition and structurally characterized. This coordination polymer has nanotubular threefold entangled (2D,3D) structure with embedded water molecules; the water molecules can be partially exchanged in reversible single-crystal-to-single-crystal (SC-SC) fashion by different solvent molecules like methanol, ethanol and acetone giving rise to {[Zn2(cpa)2(bpy)]·(0.5MeOH)·(2.5H2O)}n (2), {[Zn2(cpa)2(bpy)]·(0.5EtOH)·(0.5H2O)}n (3) and {[Zn2(cpa)2(bpy)]·(0.5Me2CO)·(H2O)}n (4). Inclusion of EtOH or MeOH leaves the size of the voids in the framework unaltered. Inclusion of acetone, however, is accompanied by shrinking of the voids in the framework. Heating of 1 at 100 °C under vacuum for 4 h affords the de-solvated compound, {Zn2(cpa)2(bpy)}n (1,). Single-crystal X-ray structure of 1, shows sliding of the individual nanotubular components expanding the overall framework. Thus, the coordination polymer exhibits dynamic motion of the molecular components in SC-SC fashion. All compounds were further characterized via IR spectroscopy, PXRD, elemental and TGA analysis. When 1 is placed in benzene at 100 °C for 2 days, compound {[Zn2(cpa)2(bpy)]·(2.5H2O)}n (5) is formed in a SC-SC fashion where coordination number of ZnII ion increases from four to five. Compound 1 also exhibits reversible guest-dependent photoluminescence properties. [source] Dehydrogenation of Hydridoirida-,-diketones in Methanol: The Selective Formation of Mono- and Dinuclear Acyl ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2010Roberto Ciganda Abstract The hydridoirida-,-diketone [IrH{(PPh2(o -C6H4CO))2H}Cl] (1) reacts with diimines (NN) or with pyridine (py) in refluxing methanol to undergo dehydrogenation. The reactions afford selectively the cis -acyl, trans -phosphane isomers of the cationic [Ir(PPh2(o -C6H4CO))2(NN)]+ {NN = 2,2,-bipyridine (2); R,N=C(CH3),C(CH3)=N,R, [R = R, = NH2 (3); R = R, = OH (4); R = OH, R, = NH2 (5)]} or neutral [IrCl(PPh2(o -C6H4CO))2(py)] (6) derivatives. The reactions are faster for ligands containing amino substituents. Refluxing 1 in MeOH affords the formation of an equimolar mixture of dimercationic species [Ir2(,-Cl)(,-PPh2(o -C6H4CO))2(PPh2(o -C6H4CO))2]+ (7a and 7b) containing two acyls and a chloride as bridging groups. The isomers could be separated by fractional precipitation. Compound [3]Cl, containing amino substituents in the imino functionalities, catalyses the hydrogen transfer from 2-propanol to cyclohexanone to afford cyclohexanol. All the complexes were fully characterised spectroscopically. Single crystal X-ray diffraction analysis was performed on complexes 6 and [7b]ClO4. [source] 1,3,5-Triazapentadiene Nickel(II) Complexes Derived from a Ketoxime-Mediated Single-Pot Transformation of NitrilesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2010Maximilian N. Kopylovich Abstract A series of cationic (2+) [Ni{HN=C(R)NHC(R)=NH}2](X)2 {R = 4-(Cl)C6H4 (1), 3-(NC)C6H4 (3), 4-(NC)C6H4 (4) and Me (7); X = Cl, (1, 3, 4) or MeCOO,·H2O (7)} and neutral [Ni{HN=C(R)NC(R)=NH}2](solvate) {R = 3-(Cl)-4-py (2), 3-py (5) and 4-py (6); solvate = MeOH and/or H2O; py = pyridyl} N,N -chelating bis(1,3,5-triazapentadiene/ato)nickel(II) [Ni(tap)2]2+/0 complexes has been easily generated by a ketoxime-mediated single-pot reaction of a nickel(II) salt [NiCl2·2H2O or Ni(MeCOO)2·4H2O] with 4-chlorobenzonitrile, isophthalonitrile, terephthalonitrile, acetonitrile, 2-chloro-4-cyanopyridine, 3-cyanopyridine or 4-cyanopyridine, respectively. The obtained compounds have been characterized by IR, 1H and 13C{1H} NMR spectroscopy, FAB-MS(+) or ESI-MS(+), elemental analyses and single-crystal X-ray diffraction [for 7 and solvated mono- {1a·(Me2CO)0.33·(MeOH)0.67} and bis-deprotonated (2b·2Me2CO, 4b·CHCl3, 5b·Me2CO and 6b·MeOH) products, formed upon recrystallization of 1, 2, 4, 5 and 6, respectively]. The crystal structures of all compounds bear similar monomeric Ni(tap)2 units with a nearly square-planar geometry. In addition, the structure of 7 features the formation of infinite 1D zig-zag water,acetate chains {[(H2O)2(MeCOO)2]2,}n, which multiply interact with the [Ni(tap)2]2+ cations to generate a 2D hydrogen-bonded supramolecular assembly. [source] Nucleophilic Addition of Water and Alcohols to Dicyanonitrosomethanide: Ligands with Diverse Bonding Modes in Magnetically Coupled d-Block ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 1 2010Anthony S. R. Chesman Abstract Ligands resulting from the transition-metal-promoted nucleophilic addition of water or an alcohol to dicyanonitrosomethanide ions (dcnm) have been utilised in the formation of a large series of polynuclear complexes. Addition of water to dcnm results in formation of carbamoylcyanonitrosomethanide (ccnm); deprotonation of this ligand gives amidocarbonyl(cyano)nitrosomethanide (acnm), which has been incorporated into the trinuclear complex [Cu3(acnm)2(dmae)2(H2O)2] [dmae = 2-(dimethylamino)ethoxide] (1) which shows strong antiferromagnetic coupling with an exchange coupling constant, J = ,500 cm,1. [Cu(acnm)(NH3)2], (2) marks the first instance of acnm facilitating the formation of a coordination polymer, namely a 1D chain with intramolecular hydrogen bonding. Attempts to synthesise 2 through different reaction conditions instead resulted in the mononuclear [Cu(acnm)(NH3)2(py)] (py = pyridine) (3). The addition of ethanol to dcnm results in cyano[imino(ethoxy)methyl]nitrosomethanide (cenm) which features in the mononuclear [Cu(cenm)2(H2O)2] (4) and polymeric {[Cu(cenm)2]2·H2O}, (5). The latter is the first example of the cenm ligand in a coordination polymer and has a highly unusual coordination mode through the nitrile groups and extremely weak antiferromagnetic coupling. {[Mn3(ccnm)2(EtOH)2(OAc)4]·2EtOH}, (6) and (Et4N)2[Cu(ccnm)4] (7) contain previously unobserved coordination modes of the ccnm ligand while the complex [Mn(cmnm)3Mn(bipy)(MeOH)](ClO4) (8) {cmnm = cyano[imino(methoxy)methyl]nitrosomethanide, bipy = 2,2,-bipyridine} displays weak antiferromagnetic coupling between manganese atoms with J = ,1.44 cm,1. A change in the solvent systems used in the synthesis of 7 results in the formation of the mononuclear complexes [Mn(bipy)2(dcnm)2] (9) or [Mn(bipy)2(H2O)(dcnm)](dcnm)·H2O (10) and [Mn(bipy)2(dcnm)(H2O)](dcnm) (11). The addition of ethlyene glycol monomethyl ether to dcnm gives cyano[imino(2-methoxyethoxy)methyl]nitrosomethanide (cgnm) and the formation of [Cu(cgnm)2(H2O)2] (12). [source] Two New Iron(II) Spin-Crossover Complexes with N4O2 Coordination Sphere and Spin Transition around Room TemperatureEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 36 2009Birgit Weber Abstract The reaction of iron(II) acetate with the tetradentate Schiff base like ligand H2L1 {[3,3,]-[4,5-dihydroxy-1,2-phenylenebis(iminomethylidyne)bis(2,4-pentanedion)]} leads to the formation of the complex [FeL1(MeOH)]. Reaction of this complex with pyridine (py) or N,N,-dimethylaminopyridine (dmap) leads to the two N4O2 -coordinated complexes [FeL1(py)2]·py (1) and [FeL1(dmap)2]·MeOH·0.5dmap (2). Both complexes are spin-crossover compounds that were characterised by using magnetic measurements, X-ray crystallography and temperature-dependent 1H NMR spectroscopy. Special attention was given to the role of the two hydroxy groups on the phenyl ring in the formation of a hydrogen-bonding network and the influence of this network on the spin-transition properties. Although only a gradual spin crossover was observed for both complexes, the transition temperature was shifted to higher temperatures relative to that of the complexes with no additional hydroxy groups at the Schiff base like ligand. The hydrogen-bonding network was responsible for this effect.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Azido, Cyanato, and Thiocyanato Coordination Induced Distortions in Pentacoordinated [CoIIA(bip)]2 (A = NCS,, N3,, or NCO,) ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 31 2009Mrinal Sarkar Abstract A new family of distorted pentacoordinate [Co2] complexes was prepared and structurally characterized. In [CoIIA(bip)]2·S (1,3) [A = NCS,, N3,, NCO,; S = dmf, MeOH, dcm; Hbip = 2,6-bis(phenylmethyliminomethyl)-4-methylphenol], the nonbonded Co···Co separations are in the 3.243 to 3.254 Å range, and the pseudohalide-coordinated CoII ions are asymmetrically doubly bridged by the phenolate oxygen atoms of the ligand. The complementary basal,apical (b,a) and apical,basal (a,b) coordination modes of the phenolate bridges of bip, offer one O and two N donors for metal-ion coordination. In the three dinuclear complexes, the h.s. CoII ions are coupled antiferromagnetically to yield a singlet ground state. The solid-state variable-temperature magnetic susceptibility measurement data on the complexes were fitted to an isotropic Heisenberg dimer model that allowed estimation of the antiferromagnetic interactions for 1,3. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Bis(terdentate) Pyrazole/Pyridine Ligands: Synthesis, Crystal Structures and Magnetic Properties of Bridged Binuclear and Tetranuclear Copper(II) ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2009Akhilesh Kumar Singh Abstract A new binucleating bis(terdentate) ligand, 3,5-[3-bis(2-pyridyl)pyrazole-1-ylmethyl]pyrazole (HL2), was synthesized. Reaction of the deprotonated ligand L2 with hydrated CuII salts gives (,-pyrazolato)(,-hydroxido)-bridged binuclear and tetranuclear complexes [L2Cu2(,-OH)(ClO4)(MeCN)](ClO4) (2), [L2Cu2(dmf)2(,3 -OH)]2(ClO4)4·4dmf (3·4dmf) and [L2L,Cu2](ClO4)2 [4; HL, = 3-(2-pyridyl)pyrazole]. In these complexes, both ,-OH and ,3 -OH bridges were observed. This contrasts the situation for a dicopper(II) complex of the related bis(terdentate) ligand 3,5-bis[6(2,2,-dipyridyl)]pyrazole (HL1), {L1Cu2(OMe)(MeOH)[,1 - O -(NO3)]}{[Cu2(NO3)2(,-OMe)2]}0.5·MeOH (1·MeOH), where the shorter and more rigid ligand side arms enforce a larger Cu···Cu separation and the formation of a MeO,HOMe moiety within the bimetallic pocket. Molecular structures of all complexes were elucidated by X-ray crystallography. Variable-temperature magnetic susceptibility measurements (295,2 K) for powdered samples of complexes 2,4 reveal strong antiferromagnetic coupling between two copper centres. The magnitude of the coupling is discussed in view of the structural features. During the preparation of complex 4, partial ligand hydrolysis was also observed, but this strongly depends on the reaction conditions.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Nickel Complexes with N2O Donor Ligands: Syntheses, Structures, Catalysis and Magnetic StudiesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 32 2007Jishnunil Chakraborty Abstract Two new terephthalato-bridged tetranuclear polymeric NiII complexes, namely [Ni4L41(,-tp-,4 -O)(H2O)2(,-tp-,2 -O)]·2C2H5OH·CH3OH·3H2O (1) and [Ni4L42(,-tp-,4 -O)(H2O)2(,-tp-,2 -O)]·3H2O (2) [L1 = N -(3-aminopropyl)-5-bromosalicylaldimine and L2 = N -(3-aminopropyl)salicylaldimine], are reported along with the syntheses and structures of the dicyanoargentate-bridged polymeric complexes [Ni(L1)(H2O){Ag(CN)2}], (3) and [Ni(L3)(MeOH){Ag(CN)2}], (4) [L3 = N -(3-amino-2,2-dimethylpropyl)-5-bromosalicylaldimine]. All four complexes are found to be effective heterogeneous catalysts for the epoxidation of alkenes such as styrene, ,-methylstyrene and cyclohexene in the presence of tert -butyl hydroperoxide. The variable-temperature magnetic susceptibility measurements (300,2 K) of complex 1 show a fair degree of antiferromagnetic coupling between the NiII centers.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Synthesis and Characterization of CuII Complexes with Amino Acid Substituted Di(2-pyridyl)amine LigandsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2007ko I. Kirin Abstract The two-step syntheses of the substituted di(2-pyridyl)amine ligands (dpa), dpa-CH2CO2H (1) and dpa-PhCO2H (2), are described. Ligands 1 and 2 are successfully coupled to the amino acid phenylalanine, yielding the derivatives 4 and 6, respectively. Four CuII(dpa)2 complexes, [Cu(dpa-CH2CO2tBu)2(NO3)2] (3Cu), [Cu(dpa-CH2CO-PheOMe)2(H2O)2](NO3)2·2MeOH (4Cu), [Cu(dpa-PhCO2Me)2 (MeOH)2](ClO4)2 (5Cu) and [Cu(dpa-PhCO-PheOMe)2(ClO4)2] (6Cu) have been prepared and characterized, including their single crystal X-ray structures. Fluorescence emission at UV (for 3 and 4) or blue (for 5 and 6) wavelengths of the free ligands is preserved in the corresponding Cu complexes, although with lower intensity. X-band EPR spectra of 4Cu and 6Cu both revealed one axial CuII signal with hyperfine and superhyperfine splittings. Complexes 4Cu and 6Cu are chiral inorganic complexes with amino acid bioconjugates that may serve as nucleoside analogs in modified peptide nucleic acids (PNA). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Pentadentate Ligands for the 1:1 Coordination of Lanthanide(III) Salts,EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2007Markus Albrecht Abstract Three hydrazone type ligands, namely 2 -H, 3, and 4, which were designed to form 1:1 complexes with lanthanoid(III) ions, are presented. Although the tetradentate ligand 2, leads to an interesting complex [(2)(2 -H)YCl2] with yttrium(III), a more general principle for the coordination of the metal ions by hydrazone-type ligands can be found with ligand 3, where 1:1 complexes are obtained with an effective coordination of the metal salts by the ligand. The stabledimer [{(3)Nd(CF3SO3)}2(,-CF3SO3)3]CF3SO3 was characterized by X-ray structure determination. Depending on the size of the metal ion, additional co-ligands can also be bound to the metal centers. This is observed in the molecular structures of [(3)Pr(NO3)2(MeOH)2](NO3), [(3)NdCl2(MeOH)(EtOH)]Cl, [(3)ErCl2(MeOH)]Cl, and [(3)LuCl2]Cl. The solid-state molecular structures of 4 and 4·HCl show the helicating ability of this ligand upon metal coordination. The corresponding lanthanide complexes of 4 are characterized by standard techniques such as NMR and CD spectroscopy and mass spectrometry.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Transition Metal-Assisted Hydrolysis of Pyrazole-Appended Organooxotin Carboxylates Accompanied by Ligand TransferEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2007Vadapalli Chandrasekhar Abstract The reaction of the potentially multi-site coordination ligands [{nBu2SnO2CL}2O]2 (1), [{nBu2SnO2CL,}2O]2 (2), [nBuSn(O)O2CL]6 (3), and [nBuSn(O)O2CL,]6 (4), (L = (Pz)2CH-); L, = (3,5-Me2Pz)2CH-; Pz = pyrazolyl) with hydrated metal salts leads to the hydrolysis of the organotin carboxylates accompanied by the formation of insoluble organotinoxide/hydroxides and metal complexes. The in situ generated LCOO and L,COO ligands bind to the metal ions. The complexes [Cu(LCOO)2(NO3)2(nBu2Sn((H2O)2)]n[Cu(LCOO)2] (5), [Mg(L,COO)2] (6), [Cu(LCOO)2] (7), and [{(Cu(L,COO)2(Cu(MeOH))3}{ClO4}2]n (8) were isolated and structurally characterized. The solid-state structure of 5 reveals that two discrete molecules are present in the same asymmetric unit; a heterobimetallic coordination polymer, [Cu(LCOO)2(NO3)2(nBu2Sn((H2O)2)]n and a discrete coordination complex, [Cu(LCOO)2]. The cationic portion of the heterobimetallic compound contains alternate six-coordinate SnIV and CuII centers bridged by the carboxylate oxygen atoms of the LCOO ligand.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Di-2-pyridyl Ketone Oxime in Zinc Chemistry: Inverse 12-Metallacrown-4 Complexes and Cationic Pentanuclear ClustersEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 10 2005Maria Alexiou Abstract The use of di-2-pyridyl ketone oxime (Hpko)/X, "blends" (X, = PhCO2,, N3,, NCO,, acac,, NCS,) in zinc chemistry yields neutral tetranuclear and cationic pentanuclear clusters. Various synthetic procedures have led to the synthesis of compounds [Zn4(OH)2(O2CPh)2(pko)4]·3MeCN (1·3MeCN), [Zn4(OH)2(N3)2(pko)4]·4DMF (2·4DMF), [Zn4(OH)2(NCO)2(pko)4]·3DMF·H2O (3·3DMF·H2O), [Zn4(OH)2(acac)2(pko)4]·4CH2Cl2 (4·4CH2Cl2), [Zn5Cl2(pko)6][ZnCl(NCS)3]·2.5H2O·1.5MeOH (5·2.5H2O·1.5MeOH) and [Zn5(NCS)2(pko)6(MeOH)][Zn(NCS)4]·2.5H2O·MeOH (6·2.5H2O·MeOH). The structures of the six complexes have been determined by single-crystal X-ray crystallography. The tetranuclear molecules of 1,4 lie on a crystallographic inversion centre and have an inverse 12-metallacrown-4 topology. Two triply bridging hydroxides are accommodated in the centre of the metallacrown ring. The pko, ligands form a propeller configuration that imposes absolute stereoisomerism with , and , chirality. Two metal ions are in distorted O2N4 octahedral environments, whereas the rest are in severely distorted tetrahedral or trigonal bipyramidal environments. The five Zn ions of the cations of 5 and 6 are held together by six pko, ligands which adopt three different coordination modes; the chloro (5) and isothiocyanato (6) ligands are terminal. The five Zn ions define two nearly equilateral triangles sharing a common apex, and the novel Zn5 topology can be described as two "collapsed" 9-metallacrown-3 structures sharing a common Zn apex. Besides the pentanuclear cations, the structures of 5 and 6 contain slightly distorted tetrahedral [ZnCl(NCS)3]2, and [Zn(NCS)4]2, ions, respectively, with the isothiocyanato ligands binding the metal ion in a virtually linear fashion. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Synthesis of (1,2,4-Oxadiazole)palladium(II) Complexes by [2 + 3] Cycloaddition of Nitrile Oxides to Organonitriles in the Presence of PdCl2EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2005Nadezhda A. Bokach Abstract The reaction between the nitrile oxides 2,4,6-R3C6H2CNO (R = Me, OMe) and trans -[PdCl2(RCN)2], or RCN (R = Me, Et, CH2CN, NMe2, Ph) in the presence of PdCl2, proceeded smoothly under mild conditions and allowed the isolation of the 1,2,4-oxadiazole complexes trans -[PdCl2{Na=C(R)-ON=Cb(C6H2R3)(Na,Cb)}2] (1,8) in 40,85,% yields. In CH2Cl2, the reaction between 2,4,6-R3C6H2CNO and [PdCl2(MeCN)2] furnishes [PdCl2(ONCC6H2R3)2] (9 and 10), which are the first representatives of metal compounds where nitrile oxides act as ligands. The 1,2,4-oxadiazole complexes 1,8 were characterized by elemental analysis, FAB mass spectrometry, and IR, 1H and 13C{1H} NMR spectroscopy, while 2, 3, 7, and 8 were additionally characterized by X-ray crystallography. The liberation of the heterocyclic species from 1,8 was successfully performed by substitution reaction either with 1,2-bis(diphenylphosphanyl)ethane or with an excess amount of Na2S·7H2O in MeOH; the liberated 1,2,4-oxadiazoles (11,18) were characterized by positive-ion FAB mass spectrometry and 1H and 13C{1H} NMR spectroscopy. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] New Access to Homodinuclear Half-Sandwich Vinylidenemanganese ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 5 2005Koushik Venkatesan Abstract The d6 low-spin MnI half-sandwich dinuclear complexes of the type [{Mn(MeC5H4)(R2PCH2CH2PR2)=C=C(SnMe3)}2{X}] (X = {,-1,4-C6H4}, R = Me, 2a; X = {,-1,4-C6H4}, R = Et, 2b; X = {,-1,3-C6H4}, R = Me, 3a; X = {,-1,3-C6H4}, R = Et, 3b; X = {,-4,4-C6H4 -C6H4}, R = Me, 4a; X = {,-4,4-C6H4 -C6H4}, R = Et, 4b; X = {,-1,4-C4H2S}, R = Me, 5a; X = {,-1,4-C4H2S}, R = Et, 5b) were obtained by the treatment of [Mn(C5H4Me)(,6 -cycloheptatriene)] with 0.5 equiv. of the corresponding acetylene Me3Sn,C,C,X,C,C,SnMe3 (X = {,-1,4-C6H4}, {,-1,3-C6H4}, {,-4,4-C6H4 -C6H4}, {,-1,4-C4H2S}) and R2PCH2CH2PR2 (R = Me, Et) at 50 °C for 12 h to yield the corresponding dinuclear complexes in very good yields. These dinuclear tin-substituted vinylidene complexes were further treated with an excess of MeOH to give the corresponding dinuclear parent vinylidene complexes of the type [{Mn(MeC5H4)(R2PCH2CH2PR2)=C=C(H)}2{X}] (X = {,-1,4-C6H4}, R = Me, 6a; X = {,-1,4-C6H4}, R = Et, 6b; X = {,-1,3-C6H4}, R = Me, 7a; X = {,-1,3-C6H4}, R = Et, 7b; X = {,-4,4-C6H4 -C6H4}, R = Me, 8a; X = {,-4,4-C6H4 -C6H4}, R = Et, 8b). All dinuclear compounds were characterised by NMR and IR spectroscopy and elemental analysis. X-ray diffraction studies were performed on complexes 2b, 3a, 4a and 6a. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] A New Trinuclear Linear Copper(II) Complex: Unusual Crystal Structure with Semi-Coordinated Thiophene Moieties and Weak Antiferromagnetic Coupling Through the Bridging Imidazolate RingsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2004Yufei F. Song Abstract A trinuclear copper(II) complex, [Cu3(imthio)2(NO3)4(MeOH)2] [where Himthio is 1,1-bis(imidazol-2-yl)-3-(thiophen-2-yl)-2-azapropane], has been synthesized by the reaction of Himthio with Cu(NO3)2·3H2O in MeOH. The structure of the copper complex is centrosymmetric and contains a linear trinuclear array of copper atoms. The central copper(II) ion, Cu1, which lies on an inversion centre, is equatorially coordinated by four nitrogen atoms from two anionic imthio ligands and axially by two semicoordinated thiophene sulfur atoms to give an octahedral environment (Cu1,S1 3.136 Å). The Himthio ligand bridges Cu1 and the terminal copper(II) ions through imidazole nitrogen atoms. The coordination around the external ions is completed by the oxygen atoms from two nitrate groups and by a methanol molecule in a distorted square-pyramidal geometry. The two terminal copper(II) complexes can be considered to be chelating ligands for the central CuII ion. The EPR spectrum of the complex in MeOH at 77 K shows two mononuclear species, as is fully confirmed by EPR simulation. Magnetic susceptibility of the complex shows weak antiferromagnetic behaviour (J = ,71.37 cm,1) caused by the overlapping of the magnetic orbitals of the copper atoms and the bridging imidazolate rings. (© Wiley-VCH Verlag GmbH & Co.. KGaA, 69451 Weinheim, Germany, 2004) [source] Synthesis of (Vinylidene)- and (Cyclopropenyl)ruthenium Complexes Containing a Tris(pyrazolyl)borato (Tp) LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 23 2004Yih-Hsing Lo Abstract A convenient high-yield route to [Ru(C,C,Ph)(Tp)(PPh3)2] [2; Tp = HB(pz)3, pz = pyrazolyl] has been found through the intermediacy of [RuCl2(Hpz)2(PPh3)2] (1). This complex is readily obtained on treatment of [RuCl2(PPh3)3] with 2 equiv. of pyrazole in boiling THF. The molecular structures of complexes 1 and 2 have been confirmed by single-crystal X-ray diffraction analysis. A number of new cationic vinylidene complexes [Ru{=C=C(Ph)CH2R}(Tp)(PPh3)2]+ [3a, R = CN; 3b, R = HC=CH2; 3c, R = CH=C(CH3)2; 3d, R = Ph; 3e, R = C(O)OMe] have been prepared by electrophilic addition of organic halides to complex 2. The deprotonation reaction of 3a yields the cyclopropenyl complex 4a. One phosphane ligand of 4a is remarkably labile, being replaced by donor ligands L to yield diastereomeric mixtures of the cyclopropenyl complexes 5a,5d mostly in an approximate 4:1 ratio. The cyclopropenyl rings in 4a and 5a are susceptible to ring opening by I2. In addition, treatment of 4a with nBuNC in the presence of MeOH results in substitution of a phosphane ligand by nBuNC followed by protonation of the three-membered ring by MeOH. This is then followed by addition of methoxide to give the vinyl ether complex [Ru{C(OMe)=C(Ph)CH2CN}(Tp)(PPh3)(nBuNC)] (8a). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Antioxidant properties of extracts and compounds from Psoralea morisianaEUROPEAN JOURNAL OF LIPID SCIENCE AND TECHNOLOGY, Issue 7-8 2005Antonella Rosa Abstract The antioxidant activity of various extracts (MeOH, petroleum ether, EtOAc) from the aerial parts of Psoralea morisiana, an endemic Sardinian plant, was evaluated during autoxidation and iron-mediated oxidation of linoleic acid at 37,°C and during cholesterol oxidation at 140,°C, in the absence of solvent. The activity of erybraedin,C, bitucarpin,A and plicatin,B, isolated from the extracts, was investigated under the same experimental conditions and compared to that of BHT and ,-tocopherol. All the extracts, erybraedin,C (major constituent of the extracts) and plicatin,B showed powerful antioxidant properties. None of the extracts and pure compounds showed any prooxidant activity. The cytotoxicity of the extracts, erybraedin,C, and plicatin,B was further evaluated in VERO cells, a line of fibroblasts derived from monkey kidney. Erybraedin,C, at non-cytotoxic concentrations, showed a strong inhibition of FeCl3 -induced oxidation in VERO cells. [source] DFT Study of Brønsted Acid Catalyzed Nitroso Aldol Reaction Between Achiral Enamines and Nitrosobenzene: The Reason for Regio- and EnantioselectivityEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 25 2008Matsujiro Akakura Abstract The regio- and enantioselectivity of the nitroso aldol reaction between achiral enamines and nitrosobenzene catalyzed by chiral Brønsted acid catalysts (TADDOL or 1-naphthylglycolic acid) were investigated in experimental and theoretical studies. The use of a model involving a simple organic acid (MeOH or AcOH) revealed that the reaction was catalyzed by two or more molecules of the organic acid and that the transition-state structure encompassed several hydrogen bonds. The role of hydrogen bonding in the regioselectivity was also examined carefully. The enantioselectivity in the reaction catalyzed by chiral organic acids (S,S)-TADDOL and (S)-1-naphthylglycolic acid was also confirmed through computational study.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] An Efficient N -Arylation of Heterocycles with Aryl-, Heteroaryl-, and Vinylboronic Acids Catalyzed by Copper FluorapatiteHELVETICA CHIMICA ACTA, Issue 5 2010Lakshmi Kantam, Mannepalli Abstract N -Arylation of N-containing heterocycles, such as pyrazoles, imidazoles, and benzimidazoles with aryl-, heteroaryl-, and vinylboronic acids was efficiently carried out by copper fluorapatite (CuFAP) catalyst in MeOH at room temperature under base-free conditions. The N- arylated heterocycles were isolated in good-to-excellent yields. [source] A Mild and Efficient Method for N -Arylnucleobase Synthesis via the Cross-Coupling Reactions of Nucleobases with Arylboronic Acids Catalyzed by Simple Copper SaltsHELVETICA CHIMICA ACTA, Issue 6 2008Lan Tao Abstract A simple and efficient copper-salt catalyzed N -arylation of nucleobases is reported. In a mixed solvent of MeOH and H2O, the coupling products were obtained in moderate to excellent yields at room temperature within a short time. A variety of substituted N -aryl nucleobases can be prepared through this procedure. [source] | ||||||||||||||||||||||||||||||||||