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Corresponding Anion (corresponding + anion)
Selected AbstractsThe Variable Binding Modes of Phenylbis(pyrid-2-ylmethyl)phosphane and Bis(pyrid-2-ylmethyl) Phenylphosphonite with AgI and CuIEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 20 2009Fernando Hung-Low Abstract A series of new bridging phosphane and phosphonite structures forming three- and six-membered rings with the metal centers were synthesized and characterized. The resulting compounds of phenylbis(pyrid-2-ylmethyl)phosphane (1) with the silver(I) salts of trifluoroacetate (tfa,), tetrafluoroborate (BF4,), and trifluoromethanesulfonate (OTf,), and copper tetrakis(acetonitrile) hexafluorophosphate (PF6,) shows the flexibility of the ligand by displaying different coordination modes associated with the electronic and structural characteristics of the corresponding anion. Accordingly, ligand 1 in these complexes displays two different binding modes. With Agtfa and AgBF4 compounds 3 and 4 are obtained where the ligand chelates to two silver atoms that exhibit normalAg,Ag contacts in the range of 2.9 Å. When AgOTf or Cu(NCCH3)4PF6 are used, one molecule of 1 bridges the metal centers through a phosphorus atom while another is terminally bound. This induces short M,M distances of 2.6871 and 2.568 Å for 5 and 6, respectively. Similarly, the coordination behavior of the heterofunctional bis(pyrid-2-ylmethyl) phenylphosphonite ligand (2) is reported with Cu(NCCH3)4PF6 (7) and AgBF4 (8) to form two novel discrete molecules. In these complexes 2 coordinates through the P and N atoms, with the difference that in 7 the O atom of one of the carbinol arms is also bound to the Cu. Elemental analysis, variable-temperature multinuclear NMR spectroscopy, single-crystal X-ray diffraction, and low-temperature luminescence studies were carried out to fully characterize the compounds. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Electron-Transfer-Initiated Cascade Cyclizations of Terpenoid Polyalkenes in a Low-Polarity Solvent: One-Step Synthesis of Mono- and Polycylic Terpenoids with Various FunctionalitiesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 17 2004Mustafa E. Ozser Abstract A methodology for the one-step synthesis of cyclic polyalkene terpenoids in a low-polarity solvent (dichloromethane) by photoinduced electron transfer (PET) is described. For the efficiency of such processes in low-polarity solvents, the use of the cationic electron acceptor N -methylquinolinium hexafluorophosphate is vital. The first direct cyclizations of farnesol and geranylgeraniol to the corresponding all- trans -fused 6,6- and 6,6,6-cyclic products are also reported. The mechanism of the termination of the cyclizations is also discussed, isotope-labeling experiments having shown that it proceeds through reduction of the final radical to the corresponding anion, followed by protonation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Hydrogen-bonded supramolecular motifs in pyrimethaminium 4-methylbenzoate, pyrimethaminium 3-hydroxypicolinate and pyrimethaminium 2,4-dichlorobenzoateACTA CRYSTALLOGRAPHICA SECTION C, Issue 3 2010Kaliyaperumal Thanigaimani In 2,4-diamino-5-(4-chlorophenyl)-6-ethylpyrimidin-1-ium (pyrimethaminium, PMNH) 4-methylbenzoate, C12H14ClN4+·C8H7O2,, (I), pyrimethaminium 3-hydroxypicolinate, C12H14ClN4+·C6H4NO3,, (II), and pyrimethaminium 2,4-dichlorobenzoate, C12H14ClN4+·C7H3Cl2O2,, (III), the PMNH cations interact with the carboxylate groups of the corresponding anion via nearly parallel N,H...O hydrogen bonds, forming R22(8) ring motifs. A description of the observed arrays of quadruple hydrogen bonds in (I) and (II) in terms of hydrogen donors and acceptors (the DA model), their graph-set motifs and the resulting supramolecular ladder is given. In (III), supramolecular chains along the b axis and helical chains along the a axis are formed via N,H...O hydrogen bonds involving the 2-amino and 4-amino groups of the PMNH cation, respectively. Weak Cl...Cl interactions are also found in (III). [source] Hydrogen-bonded supramolecular motifs in 2-amino-4,6-dimethoxypyrimidinium 4-hydroxybenzoate monohydrate, 2-amino-4,6-dimethoxypyrimidinium 6-carboxypyridine-2-carboxylate monohydrate and 2-amino-4,6-dimethoxypyrimidinium hydrogen (2R,3R)-tartrate 2-amino-4,6-dimethoxypyrimidineACTA CRYSTALLOGRAPHICA SECTION C, Issue 5 2007Kaliyaperumal Thanigaimani In the crystal structures of the title compounds, C6H10N3O2+·C7H5O3,·H2O, (I), C6H10N3O2+·C7H4NO4,·H2O, (II), and C6H10N3O2+·C4H5O6,·C6H9N3O2, (III), the 2-amino-4,6-dimethoxypyrimidinium cation [abbreviated as (MeO)2 -Hampy+] interacts with the carboxylate group of the corresponding anion through a pair of nearly parallel N,H...O hydrogen bonds to form R22(8) ring motifs. In (I), the (MeO)2 -Hampy+ cation is centrosymmetrically paired through a pair of N,H...N hydrogen bonds involving the 2-amino group and a ring N atom forming an R22(8) motif. In (II), inversion-related R22(8) motifs (amino,pyrimidine,carboxylate motifs) are further bridged by N,H...O hydrogen bonds on either side forming a DDAA array of quadruple hydrogen bonds. This array is extended further on either side by Owater,H...Omethoxy hydrogen bonds, resulting in an array of six hydrogen bonds (ADDAAD). The water molecule plays a pivotal role, and five hydrogen-bonded fused rings are formed around the water molecule. In (III), the carboxy group of the tartrate anion interacts with the ring N atom and 2-amino group of the neutral (MeO)2 -ampy molecule through N,H...O and O,H...N hydrogen bonds. There is also an intramolecular O,H...O hydrogen bond in the tartrate anion. In all three crystal structures, C,H...O hydrogen bonds are observed. [source] Synthesis of 2-phosphinoxidomethyl- and 2-phosphonomethyl glutaric acid derivatives,HETEROATOM CHEMISTRY, Issue 7 2005Kálmán Harsányi Michael addition of the corresponding anions derived from diphenylphosphine oxide, dialkylphosphites, and a cyclic phosphite to ,-methylene-glutaric esters (1) afforded the title compounds (2,6). Double debenzylation of 2-phosphono glutaric esters 4b and 5a by catalytic hydrogenation under the appropriate conditions gave the correspon- ding diacides 8 and 9, respectively. © 2005 Wiley Periodicals, Inc. Heteroatom Chem 16:562,565, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20142 [source] Substituent effect on electron affinity, gas-phase basicity, and structure of monosubstituted propargyl radicals and their anions: a theoretical studyJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 2 2010Gab-Yong Lee Abstract The substituent effect of electron-withdrawing groups on electron affinity and gas-phase basicity has been investigated for substituted propargyl radicals and their corresponding anions. It is shown that when a hydrogen of the , -CH2 group or acetylenic CH in the propargyl system is substituted by an electron-withdrawing substituent, electron affinity increases, whereas gas-phase basicity decreases. The calculated electron affinities are 0.95,eV (CHCCH2,), 1.15,eV (CHCCHF,), 1.38,eV (CHCCHCl,), 1.48,eV (CHCCHBr,) for the isomers with terminal CH and 1.66,eV (CFCCH2,), 1.70,eV (CClCCH2,), 1.86,eV (CBrCCH2,) for the isomers with terminal CX at B3LYP level. The calculated gas-phase basicities for their anions are 378.4,kcal/mol (CHCCH2:,), 371.6,kcal/mol (CHCCHF:,), 365.1,kcal/mol (CHCCHCl:,), 363.5,kcal/mol (CHCCHBr:,) for the isomers with terminal CH and 362.6,kcal/mol (CFCCH2:,), 360.4,kcal/mol (CClCCH2:,), 356.3,kcal/mol (CBrCCH2:,) for the isomers with terminal CX at B3LYP level. It is concluded that the larger the magnitude of electron-withdrawing, the greater is the electron affinity of radical and the smaller is the gas-phase basicity of its anion. This tendency of the electron affinities and gas-phase bacisities is greater in isomers with the terminal CX than isomers with the terminal CH. Copyright © 2009 John Wiley & Sons, Ltd. [source] The relationship between changes in the cell wall, lipid peroxidation, proliferation, senescence and cell deathPHYSIOLOGIA PLANTARUM, Issue 1 2003Gerhard Spiteller Plants and mammals contain polyunsaturated fatty acids (PUFAs) in their membranes. PUFAs belong to the most oxygen sensitive molecules encountered in nature. It would seem that nature has selected this property of PUFAs for signalling purposes: PUFAs are stored in the surface of cells and organelles not in free form but conjugated to phospho- and galactolipids. Any change in membrane structure apparently activates membrane-bound phospholipases, which cleave the conjugates. The obtained free PUFAs are substrates for lipoxygenases (LOX). These transform PUFAs to lipidhydroperoxides (LOOHs). LOOHs are converted to a great variety of secondary products. These lipid-peroxidation (LPO) products and the resulting generated products thereof represent biological signals, which do not require a preceding activation of genes. They are produced as a non-specific response to a large variety of external or internal impacts, which therefore do not need interaction with specific receptors. When, due to an external impact, e.g. attack of a microorganism, or to a change in temperature, the amount of liberated free PUFAs exceeds a certain threshold, LOX commit suicide. Thus iron ions, located in the active centre of LOX, are liberated. Iron ions react with LOOHs in the close surroundings by generating alkoxy radicals (LO.). These induce a non-enzymatic LPO. A fraction of the LO. radicals generated from linoleic acid (LPO products derived from linoleic acid play a dominant role in signalling which was previously overlooked) is converted to 2,4-dienals which induce the programmed cell death (PCD) and the hypersensitive reaction (HR). While peroxyl radicals (LOO.) generated as intermediates in the course of an enzymatic LPO are transformed within the enzyme complex to corresponding anions (LOO,), and thus lose their reactivity, peroxyl radicals generated in non-enzymatic reactions are not deactivated. They not only react by abstraction of hydrogen atoms from activated X-H bonds of molecules in their close vicinity, but also by epoxidation of double bonds and oxidation of a variety of biological molecules, causing a dramatic change in molecular structure which finally leads to cell death. As long as reducing agents, like glutathione, or compounds with free phenolic groups are available, the amount of LOOHs is kept low. Cell death is induced in a defined way by apoptosis. But when the reducing agents have been consumed, PCD seems to switch to necrotic processes. Thus proliferation is induced by minor changes at the cell membrane, while slow changes at cell membranes are linked with apoptosis (e.g. response to attack of microorganisms or drought) and necrosis (severe wounding), depending only on the amount, but not on the type, of applied stimulus. [source] Charge-assisted hydrogen-bonded supramolecular networks in acetoguanaminium hydrogen phthalate, acetoguanaminium hydrogen maleate and acetoguanaminium 3-hydroxypicolinate monohydrateACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2010Kaliyaperumal Thanigaimani In 2,4-diamino-6-methyl-1,3,5-triazin-1-ium (acetoguanaminium) hydrogen phthalate, C4H8N5+·C8H5O4,, (I), acetoguanaminium hydrogen maleate, C4H8N5+·C4H3O4,, (II), and acetoguanaminium 3-hydroxypicolinate monohydrate, C4H8N5+·C6H4NO3,·H2O, (III), the acetoguanaminium cations interact with the carboxylate groups of the corresponding anions via a pair of nearly parallel N,H...O hydrogen bonds, forming R22(8) ring motifs. In (II) and (III), N,H...N base-pairing is observed, while there is none in (I). In (II), a series of fused R32(8), R22(8) and R32(8) hydrogen-bonded rings plus fused R22(8), R62(12) and R22(8) ring motifs occur alternately, aggregating into a supramolecular ladder-like arrangement. In (III), R22(8) motifs occur on either side of a further ring formed by pairs of N,H...O hydrogen bonds, forming an array of three fused hydrogen-bonded rings. In (I) and (II), the anions form a typical intramolecular O,H...O hydrogen bond with graph set S(7), whereas in (III) an intramolecular hydrogen bond with graph set S(6) is formed. [source] | ||||||||||