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Pyridine
Kinds of Pyridine Terms modified by Pyridine Selected AbstractsDynamic Stereochemical Behaviour of Congested Ruthenium(II) Complexes Containing Asymmetric Thioether Ligands Based on Pyridine and PyrimidineEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 30 2008Giuseppe Tresoldi Abstract The asymmetric thioethers L [L = 2-pyridylmethyl 2,-pyrimidyl sulfide (pps) and 2-(4-methylpyrimidyl) 2,-pyridylmethyl sulfide (mps)] reacted with cis -[RuCl2(N,N -L,)2] [L, = di-2-pyridyl sulfide (dps); 2,2,-bis(4-methylpyridyl) sulfide (4mdps); 2,2,-bis(5-methylpyridyl) sulfide (5mdps)] to give the five-membered-ring chelate complexes [Ru(N,N -L,)2(Npyridine,S -L)]++ as the major products (92,95,%). Because the sulfur and ruthenium atoms are stereogenic centres, with (R) and (S) and , and , configurations, respectively, four isomers, including the enantiomers were obtained. At low temperature and in the methylene region of the 1H NMR spectra, two AB systems due to the enantiomer couples ,S ,R (a) and ,R ,S (b) were observed with abundances of 77,89 and 6,18,%, respectively. Furthermore, NMR spectroscopic investigations showed that the hybrid polydentate ligands L change their coordination mode. Thus, although a and b largely predominate, a mixture of species containing L and the Ru(N,N -L,)2 unit in the ratio 1:1 are present. The four-membered-ring chelate complexes [Ru(N,N -L,)2(Npyrimidine,S -L)]++ (c), as minor species (abundance 1,8,%), are always observed, whereas the dinuclear species [{Ru(N,N -L,)2}2(,-L)2]+4 (d, e) are observed when L, = dps or 5mdps. In these cases, four AB systems are assigned to dinuclear species d and e containing two bridging L that act as Npyridine,S- or Npyridine,Npyrimidine -donor ligands. The 1H NMR spectra are temperature dependent in that at low temperature the complexes undergo inversion of the chiral centre of the coordinated sulfur atom (a [rlhar2] b) and the dimer (d, e) and monomer (c) are in equilibrium; at higher temperatures the complexes undergo a structural dynamic rearrangement, which involves exchange between the coordinated and uncoordinated N atoms (b [rlhar2] c). One-dimensional band-shape analysis of the exchanging methylene and methyl proton signals showed that the energy barriers for inversion of the sulfur centre are in the 50,53 kJ,mol,1 range, whereas those for the higher-temperatures process are in the 62,68 kJ,mol,1 range. The possible mechanisms of the processes are discussed. NMR spectroscopic findings suggest that inversion at the sulfur centre occurs without any bond rupture, whereas the exchange, at higher temperatures (b [rlhar2] c), is a dissociative process involving the breaking of a Ru,Npyridine bond.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Benzylideneruthenium Complexes Bearing Pyridine-Based Ligands and Their Influence on the Formation of Mono- or Bis(pyridine) ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 34 2007Wen-Zhen Zhang Abstract Benzylideneruthenium complexes bearing the N-heterocyclic carbene (NHC) ligand 1,3-bis(2,6-dimethylphenyl)-4,5-dihydroimidazol-2-ylidene (H2IMe) and one or two pyridine-based ligands have been prepared by treating [RuCl2(=CHPh)(H2IMe)(PPh3)] with the corresponding pyridine derivative. X-ray crystallographic and mass spectrometric evidence is used to investigate the interconversion between mono- and bis(pyridine) complexes and the influence of the pyridine ligand on the formation of these complexes. The catalytic activity of these complexes has been tested in the ring-closing metathesis (RCM) reaction of diallylmalononitrile and the cross metathesis (CM) reaction of acrylonitrile with terminal olefins.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Pyridine Carboxylate Complexes of MoII as Active Catalysts in Homogeneous and Heterogeneous PolymerizationEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 18 2007Maria Vasconcellos-Dias Abstract New lamellar materials intercalated with molybdenum(II) complexes with potential catalytic properties were prepared by a stepwise procedure. The lamellar material was first calcined at 823 K for four hours to eliminate all the carbonate ions; the layered structure was reconstructed after treatment with a solution of either pycH (pyridine-2-carboxylic acid) or pydcH2 (pyridine-2,6-dicarboxylic acid) in a KOH solution of dmf at 343 K. Impregnation with a solution of the organometallic precursor [Mo(CO)3I2(NCCH3)2] led to substitution of the nitrile groups by two pyridine ligands. All the materials were characterized by powder X-ray diffraction, FTIR, and 13C CP MAS and 27Al MAS solid-state NMR spectroscopy. Similar MoII complexes were also prepared by using pycH or pydcH2 and characterized by elemental analysis as well as FTIR and 1H and 13C solution NMR spectroscopy. These new materials and the complexes of pyc or pydc ligands containing 4.54 wt.-% and 6.33 wt.-% of Mo respectively, catalyze the ring-opening-metathesis polymerization of norbornene and the polymerization of styrene at 333 K, their performance increasing upon the addition of methylalumoxane (MAO) as cocatalyst.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Hexaazamacrocycle Containing Pyridine and Its Dicopper Complex as Receptors for Dicarboxylate AnionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2005Feng Li Abstract The host,guest binding interactions of the hexaazamacrocycle [26]py2N4, in its tetraprotonated form H4[26]py2N44+ as well as in its dicopper(II) complex [Cu2([26]py2N4)(H2O)4]4+, with dicarboxylate anions of different stereoelectronicrequirements, such as oxalate (ox2,), malonate (mal2,), succinate (suc2,), fumarate (fu2,) and maleate (ma2,), were evaluated. The association constants were determined using potentiometric methods in aqueous solution, at 298.0 K and 0.10 mol·dm,3 KCl. These values for the tetraprotonated ditopic receptor with the dicarboxylate anions revealed that the main species in solution corresponds to the formation of {H4[26]py2N4(A)}2+ (pH , 4,9), A being the substrate anion. The values determined are not especially high, but the receptor exhibits selectivity for the malonate anion. The study of the cascade complexes revealed several species in solution, involving mononuclear and dinuclear complexes, mainly protonated and hydrolysed species, as well as the expected complexes [Cu2([26]py2N4)(A)(H2O)x]2+ or [Cu2([26]py2N4)(A)2(H2O)y]. Ox2, and mal2, form cascade complexes with only one anion, which will necessarily bridge the two copper atoms because of the symmetrical arrangement of the dinuclear complex. The two other studied anions, suc2, and ma2,, form species involving two substrate anions, although species with only one suc2, anion were also found. UV/Vis and EPR spectroscopy have shown that the dicopper complex can operate as a sensor to detect and quantitatively determine oxalate spectrophotometrically because of the red shift of the maximum of the visible band observed by addition of ox2, to an aqueous solution of the dinuclear copper complex. However the selectivity of [Cu2([26]py2N4)(H2O)4]4+ as a receptor for ox2, in the studied series is not sufficiently high to detect ox2, spectrophotometrically in the presence of the other anions. Molecular dynamics simulations indicated that the H4[26]py2N44+ receptor provides a large and flexible cavity to accommodate the studied anions. Molecular recognition is based in electrostatic interactions rather than in multiple hydrogen-bonding interactions acting cooperatively. By contrast, the [Cu2([26]py2N4)]4+ receptor has a well-shaped cavity with adequate size to uptake these anions as bridging ligands with formation of four Cu,O bonds. The ox2, anion is encapsulated within the cascade complex while the remaining anions are located above the N6 macrocyclic plane, suggesting a selective coordination behaviour of this receptor. In spite of our molecular simulation being carried out in gas phase, the modelling results are consistent with the solution studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Thermodynamic Study of the Binding of Methyltrioxorhenium with Pyridine and Its Derivatives in Benzene SolutionEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2005S. Masoud Nabavizadeh Abstract A spectrophotometric study of the interaction of methyltrioxorhenium (MTO) with pyridine and its derivatives in benzene solution has been carried out at various temperatures. The stability constants of the resulting 1:1 complexes were determined by analysis of spectrophotometric data and found to vary in the order 3,4-Me2Py > 4- tBuPy > 4-MePy > 3-MePy > 4-BenzylPy > Py > 3-PhPy > 3-C(O)OMePy > 3-ClPy. The enthalpy and entropy of adduct formation were determined from the temperature dependence of the stability constants. All complexes formed were enthalpy stabilized but entropy destabilized. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] 3,4-Ethylenedioxythiophene,Pyridine-Based Polymers: Redox or n-Type Electronic Conductivity?ADVANCED MATERIALS, Issue 24 2002C.J. DuBois A family of polymers based on alternating bi-EDOT and pyridine units is reported. Poly(BEDOT-PyrPyr-Ph2), with a bandgap of 1.2 eV, has four electrochemically accessible colors (dark gray, burgundy, lime green, and light gray) each corresponding to a distinct redox state. In-situ conductance measurements illustrate high n-type doping conductances only thirty times less than those of the p-type doping conductances. [source] Binding Properties of 2-Pentyl Pyridine to Soy Protein as Measured by Solid Phase MicroextractionJOURNAL OF FOOD SCIENCE, Issue 1 2002A. Zhou ABSTRACT: The binding properties of 2-pentyl pyridine (2-pp) were investigated for soybean protein isolates (SPI) and the beta-conglycinin and glycinin soy protein fractions. The glycinin fraction had the highest binding affinities for 2-pp, followed by beta-conglycinin fraction, and then SPI. More 2-pp was bound by SPI and beta-conglycinin or glycinin fractions under alkaline conditions than under neutral conditions, which exhibited more binding than acidic conditions. More 2-pp was also bound at high temperature (74 °C) than at 25 °C, but greater binding affinity of 2-pp was observed at 4 °C than at 25 °C. With increased NaCl concentrations, the binding affinity of 2-pp decreased. Exposure to UV light increased binding of 2-pp to all types of soy protein. [source] Synthesis of poly(methyl methacrylate) in a pyridine solution by atom transfer radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 19 2001José Luis de la Fuente Abstract Pyridine was used as a solvent for the atom transfer radical polymerization (ATRP) of methyl methacrylate. The homopolymerizations were carried out with methyl 2-halopropionate (MeXPr, where X was Cl or Br) as an initiator, copper halide (CuX) as a catalyst, and 2,2,-bipyridine as a ligand from 80 to 120 °C. The mixed halogen system methyl 2-bromopropionate/copper chloride was also used. For all the initiator systems used, the polymerization reaction showed linear first-order rate plots, a linear increase in the number-average molecular weight with conversion, and relatively low polydispersities. In addition, the dependence of the polymerization rate on the temperature is presented. These data are compared with those obtained in bulk, demonstrating the effectiveness of this solvent for this monomer in ATRP. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3443,3450, 2001 [source] Curing Behavior of Epoxy Resin Using Controllable Curing Agents Based on Nickel ComplexesMACROMOLECULAR MATERIALS & ENGINEERING, Issue 2 2006Abdollah Omrani Abstract Summary: The curing reaction kinetics and mechanism of the diglycidyl ether of bisphenol A (DGEBA) with three complexes of Ni(II) with diethylentriamine (Dien), Pyrazole (Pz) and Pyridine (Py) as ligands have been studied using differential scanning calorimetry (DSC). The curing reaction was characterized by high cure onset and peak maximum temperatures. The kinetics of the curing reaction were evaluated using the Ozawa method. The average values of activation energy for the three nickel complexes increased in the order: Dien-based curing agent,>,Pz-based curing agent,>,Py-based curing agent. Three main curing mechanisms (catalytic, complex cation and free ligand polymerization path) have been proposed depending on the cure temperature. It was also shown that the cure kinetics of DGEBA with Dien- and Py-based complexes could be described by the Sestak-Berggren equation. The water absorption, chemical resistance and thermal stability of the thermosets were also studied. The results showed that the thermoset obtained with the Py-based complex was more thermally stable than those obtained with the other two curing agents. Activation energy versus conversion plots for the epoxy systems studied. [source] ChemInform Abstract: A Convenient Synthesis of Pyridine and 2,2,-Bipyridine Derivatives.CHEMINFORM, Issue 23 2009Marta Altuna-Urquijo Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Palladium-Catalyzed Silylation of Electron-Deficient Aryl Iodides Using Triorganosilane in the Presence of Pyridine and LiCl.CHEMINFORM, Issue 26 2008Muneaki Iizuka Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: A Novel Pyridine-Based Three-Component Condensation Reaction: Synthesis of Highly Substituted Quinolizines.CHEMINFORM, Issue 24 2008Ahmad Shaabani Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Reactions with Dimethylformamide-Dimethylacetal: Synthesis and Reactions of Several New Pyridine and Pyrazolo[3,4-b]pyridine Derivatives.CHEMINFORM, Issue 38 2007Mohamed A. A. Elneairy Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Homocoupling of Aryl Bromides Catalyzed by Nickel Chloride in Pyridine.CHEMINFORM, Issue 47 2006Xiao-Chun Tao Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Identification of a Novel 3,5-Disubstituted Pyridine as a Potent, Selective, and Orally Active Inhibitor of Akt1 Kinase.CHEMINFORM, Issue 42 2006Sheela A. Thomas Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] A New Process for the Synthesis of Aurones by Using Mercury (II) Acetate in Pyridine and Cupric Bromide in Dimethyl Sulfoxide.CHEMINFORM, Issue 39 2006Nitin N. Agrawal Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Synthesis of Amides from Carboxylic Acids and Urea in the Presence of Pyridine under Microwave Irradiation.CHEMINFORM, Issue 17 2006M. Afzal Pasha Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Electrophilic Activation of Lactams with Tf2O and Pyridine: Expedient Synthesis of (.+-.)-Tetraponerine T4.CHEMINFORM, Issue 14 2006Andre B. Charette Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Synthesis and Reactions of Some New Substituted Pyridine and Pyrimidine Derivatives as Analgesic Anticonvulsant and Antiparkinsonian Agents.CHEMINFORM, Issue 2 2006Abd El-Galil E. Amr Abstract For Abstract see ChemInform Abstract in Full Text. [source] Synthesis of Some New Azole, Azepine, Pyridine, and Pyrimidine Derivatives Using 6-Hydroxy-4H-4-oxo[1]-benzopyran-3-carboxaldehyde as a Versatile Starting Material.CHEMINFORM, Issue 22 2005A. H. Abdel-Rahman No abstract is available for this article. [source] Molecular Complex 3-Methyl-2,4-dinitrothiophene 1,1-Dioxide,Pyridine in Reactions with Amines.CHEMINFORM, Issue 15 2005I. E. Efremova Abstract For Abstract see ChemInform Abstract in Full Text. [source] Heterocyclic Synthesis with Ethyl ,-(3-Carbamoyl-4,5,6,7-tetrahydrobenzo [b]thiophen-2-ylhydrazono)acetates: An Expeditious Synthetic Approach to Polyfunctionally Substituted Pyran, Pyridine, and Pyridazine Derivatives.CHEMINFORM, Issue 40 2004Rafat M. Mohareb Abstract For Abstract see ChemInform Abstract in Full Text. [source] (Pyridine)(tetrahydroborato)zinc Complex, [Zn(BH4)2(py)], as a New Stable, Efficient and Chemoselective Reducing Agent for Reduction of Carbonyl Compounds.CHEMINFORM, Issue 36 2003Behzad Zeynizadeh Abstract For Abstract see ChemInform Abstract in Full Text. [source] The Reactions of 2-(Chloroseleno)benzoyl Chloride with Pyridine and Related Azines.CHEMINFORM, Issue 42 2002M. Osajda Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Synthesis of Pyridine and Isoquinoline Derivatives by the Palladium-Catalyzed Cyclization of Olefinic Ketone O-PentafluorobenzoyloximesCHEMINFORM, Issue 44 2001Hironori Tsutsui Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Synthetic Studies on the Synthesis of Pyridine, ,-Pyran, ,-Thiopyran, and Thienothiopyranopyrrole Derivatives Using PTC Technique.CHEMINFORM, Issue 36 2001A. Khodairy Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Biaryls Made Easy: PEPPSI and the Kumada,Tamao,Corriu ReactionCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2007Michael G. Organ Prof. Abstract An easily employed, highly versatile Kumada,Tamao,Corriu (KTC) protocol utilizing the PEPPSI (Pyridine, Enhanced, Precatalyst, Preparation, Stabilization and Initiation) precatalysts 1 and 2 is detailed. The ease-of-use of these catalysts and the synthesis of a wide range of hindered biaryls, large coupling partners and drug-like heterocycles, in high yield, makes the PEPPSI-KTC protocol very attractive. The high reactivity of the PEPPSI system allowed a tetra- ortho -substituted heterocycle, 11 to be synthesized at room temperature for the first time using any protocol. The PEPPSI protocols also tolerated the Boc protecting group and phenols required no protection in modified conditions. A relatively large scale (10 g) reaction was also performed with no loss in performance. Furthermore, PEPPSI-IPr, 1, was compared to previously reported highly active phosphine ligands 42, 43, and 44 and was shown to result in significantly better yields under identical conditions. Finally, we demonstrated that the PEPPSI catalyst system is very adept at performing sequential KTC coupling reactions, analogous to multicomponent reactions, which allow complex polyaryl and polyheteroaryl architectures to be produced in one single operation. [source] NMR Parameters and Geometries of OHN and ODN Hydrogen Bonds of Pyridine,Acid ComplexesCHEMISTRY - A EUROPEAN JOURNAL, Issue 20 2004Hans-Heinrich Limbach Prof. Abstract In this paper, equations are proposed which relate various NMR parameters of OHN hydrogen-bonded pyridine,acid complexes to their bond valences which are in turn correlated with their hydrogen-bond geometries. As the valence bond model is strictly valid only for weak hydrogen bonds appropriate empirical correction factors are proposed which take into account anharmonic zero-point energy vibrations. The correction factors are different for OHN and ODN hydrogen bonds and depend on whether a double or a single well potential is realized in the strong hydrogen-bond regime. One correction factor was determined from the known experimental structure of a very strong OHN hydrogen bond between pentachlorophenol and 4-methylpyridine, determined by the neutron diffraction method. The remaining correction factors which allow one also to describe H/D isotope effects on the NMR parameters and geometries of OHN hydrogen bond were determined by analysing the NMR parameters of the series of protonated and deuterated pyridine- and collidine,acid complexes. The method may be used in the future to establish hydrogen-bond geometries in biologically relevant functional OHN hydrogen bonds. [source] Insights into CO/Styrene Copolymerization by Using PdII Catalysts Containing Modular Pyridine,Imidazoline LigandsCHEMISTRY - A EUROPEAN JOURNAL, Issue 15 2004Amaia Bastero Dr. Abstract Continuing our studies into the effect that NN, ligands have on CO/styrene copolymerization, we prepared new C1 -symmetrical pyridine,imidazoline ligands with 4,,5,- cis stereochemistry in the imidazoline ring (5) and 4,,5,- trans stereochemistry (6,10) and compared them with our previously reported ligands (1,4). Their coordination to neutral methylpalladium(II) (5,a,10,a) and cationic complexes (5,b,10,b), investigated in solution by NMR spectroscopy, indicates that both the electronic and steric properties of the imidazolines determine the stereochemistry of the palladium complexes. The crystal structures of two neutral palladium precursors [Pd(Me)2,nCln(NN,)] (n=1 for 8,a; n=2 for 9,a,) show that the PdN coordination distances and the geometrical distortions in the imidazoline ring depend on the electronic nature of the substituents in the imidazoline fragment. Density functional calculations performed on selected neutral and cationic palladium complexes compare well with NMR and X-ray data. The calculations also account for the formation of only one or two stereoisomers of the cationic complexes. The performance of the cationic complexes as catalyst precursors in CO/4- tert -butylstyrene copolymerization under mild pressures and temperatures was analyzed in terms of the productivity and degree of stereoregularity of the polyketones obtained. Insertion of CO into the PdMe bond, which was monitored by multinuclear NMR spectroscopy, shows that the N ligand influences the stereochemistry of the acyl species formed. [source] High-Level Ab Initio Study of Anion,, Interactions in Pyridine and Pyrazine Rings Coordinated to AgICHEMPHYSCHEM, Issue 3 2008David Quiñonero Dr. Enhanced binding: High-level ab initio calculations (RI,MP2(full)/aug-cc-pVQZ) demonstrate that the anion binding properties of pyridine and pyrazine are dramatically enhanced when it is coordinated to AgI, as shown in the picture. [source] | |||||||||||||||||||||||||||||||||||||