- Self-assembly and characterization of three-dimensional silver(I) coordination polymers containing N,N,N′,N′-tetrakis(pyridin-4-yl) methanediamine
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Silver(I) coordination polymers, [Ag(tpmd)](NO3)·2CH3OH (1), [Ag(tpmd)](CF3SO3) (2), and [Ag(tpmd)] (CF3CO2)·0.5CH3OH (3), have been obtained by the self-assembly of AgX (X = NO3-, CF3SO3-, CF3CO2-) and N,N,N′,N′-tetrakis(pyridin-4-yl)methanediamine (tpmd) in MeOH/MeCN. The coordination geometries of silver(I) ions in 1 and 2 are distorted tetrahedral structures, while that of 3 is a distorted trigonal bipyramid. 1 and 2 feature three-dimensional coordination polymers formed by coordination of the silver(I) ions to the tpmd ligands. 3 shows two-dimensional network basically. However, the network of 3 can be considered three-dimensional structure by the weak axial bonding of the fourth pyridine group from another tpmd ligand. 1-3 display strong emissions at 331, 342, and 326 nm, respectively.
- Shin, Jong Won,Min, Kil Sik
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- 1,2,4-Triazolium-5-ylidene and 1,2,4-triazol-3,5-diylidene as new ligands for transition metals
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Ab initio calculations show the 1,2,4-triazolium-5-ylidene (3a) and 1,2,4-triazol-3,5-diylidene (4a) are true minima on the potential surface. As expected, 4a is much higher in energy than its triazole isomers 5a, 6a and 8a and the 1,2,4-triazol-3-ylidene (7a). Sodium methoxyde adds to the diquaternary salt of 1,2,4-triazoles (9b,c) to give the corresponding monocationic heterocycles 10b,c in 70 and 50% yield, respectively. One equivalent of silver(I) acetate reacts with 9b leading to the bis(1,2,4-triazolium-5-ylidene)silver(I) complex (11b) in 80% yield. Under the same experimental conditions, but using two equivalents of silver(I) acetate, solid-state one-dimensional polymers 12′b,c featuring the coplanar 1,2,4-triazol-3,5-diylidene ligands coordinated to silver(I) are obtained in 90% yield. 12′c has been fully characterized including a single-crystal X-ray diffraction study.
- Guerret, Olivier,Solé, Stéphane,Gornitzka, Heinz,Trinquier, Georges,Bertrand, Guy
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- Complex formations of silver(I) trifluoroacetate and trifluoromethanesulfonate with benzene and cyclohexene
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An apparatus for measurements of equilibrium ligand vapor pressure has been applied in order to determine the stoichiometry of benzene and cyclohexene complexes of silver(I) trifluoroacetate (AgCF3CO2) and silver(I) trifluoromethanes
- Yanagihara, Naohisa,Gotoh, Tomio,Ogura, Tetsuya
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- Strain-Induced Reactivity in the Dynamic Covalent Chemistry of Macrocyclic Imines
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The displacement of molecular structures from their thermodynamically most stable state by imposition of various types of electronic and conformational constraints generates highly strained entities that tend to release the accumulated strain energy by undergoing either structural changes or chemical reactions. The latter case amounts to strain-induced reactivity (SIR) that may enforce specific chemical transformations. A particular case concerns dynamic covalent chemistry which may present SIR, whereby reversible reactions are activated by coupling to a high-energy state. We herewith describe such a dynamic covalent chemical (DCC) system involving the reversible imine formation reaction. It is based on the formation of strained macrocyclic bis-imine metal complexes in which the macrocyclic ligand is in a high energy form enforced by the coordination of the metal cation. Subsequent demetallation generates a highly strained free macrocycle that releases its accumulated strain energy by hydrolysis and reassembly into a resting state. Specifically, the metal-templated condensation of a dialdehyde with a linear diamine leads to a bis-imine [1+1]-macrocyclic complex in which the macrocyclic ligand is in a coordination-enforced strained conformation. Removal of the metal cation by a competing ligand yields a highly reactive [1+1]-macrocycle, which then undergoes hydrolysis to transient non-cyclic aminoaldehyde species, which then recondense to a strain-free [2+2]-macrocyclic resting state. The process can be monitored by 1H NMR spectroscopy. Energy differences between different conformational states have been evaluated by Hartree-Fock (HF) computations. One may note that the stabilisation of high-energy molecular forms by metal ion coordination followed by removal of the latter, offers a general procedure for producing out-of-equilibrium molecular states, the fate of which may then be examined, in particular when coupled to dynamic covalent chemical processes.
- Ratjen, Lars,Vantomme, Ghislaine,Lehn, Jean-Marie
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supporting information
p. 10070 - 10081
(2015/07/07)
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- High current density electrodeposition of silver from silver-containing liquid metal salts with pyridine-N-oxide ligands
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New cationic silver-containing ionic liquids were synthesized and used as non-aqueous electrolytes for the electrodeposition of silver layers. In the liquid state of these ionic liquids, a silver (i) cation is coordinated by pyridine-N-oxide (py-O) ligands in a 1:3 metal-to-ligand ratio, although in some cases a different stoichiometry of the silver center crystallized out. As anions, bis(trifluoromethanesulfonyl)imide (Tf2N), trifluoromethanesulfonate (OTf), methanesulfonate (OMs) and nitrate were used, yielding compounds with the formulae [Ag(py-O)3][Tf2N], [Ag(py-O)3][OTf], [Ag(py-O)3][OMs] and [Ag(py-O) 3][NO3], respectively. The compounds were characterized by CHN analysis, FTIR, NMR, DSC, TGA and the electrodeposition of silver was investigated by cyclic voltammetry, linear potential scans, scanning electron microscopy (SEM) and energy-dispersive X-ray spectrometry (EDX). With the exception of [Ag(py-O)3][Tf2N], which melts at 108 °C, all the silver(i) compounds have a melting point below 80 °C and were tested as electrolytes for silver electrodeposition. Interestingly, very high current densities were observed at a potential of -0.5 V vs. Ag/Ag+ for the compounds with fluorine-free anions, i.e. [Ag(py-O)3][NO 3] (current density of -10 A dm-2) and [Ag(py-O) 3][OMs] (-6.5 A dm-2). The maximum current density of the compound with the fluorinated anion trifluoromethanesulfonate, [Ag(py-O) 3][OTf], was much lower: -2.5 A dm-2 at -0.5 V vs. Ag/Ag+. Addition of an excess of ligand to [Ag(py-O) 3][OTf] resulted in the formation of the room-temperature ionic liquid [Ag(py-O)6][OTf]. A current density of -5 A dm-2 was observed at -0.5 V vs. Ag/Ag+ for this low viscous silver salt. The crystal structures of several silver complexes could be determined by X-ray diffraction, and it was found that several of them had a stoichiometry different from the 1:3 metal-to-ligand ratio used in their synthesis. This indicates that the compounds form crystals with a composition different from that of the molten state. The electrochemical properties were measured in the liquid state, where the metal-to-ligand ratio was 1:3. Single crystal X-ray diffraction measurements showed that silver(i) is six coordinate in [Ag(py-O) 3][Tf2N] and [Ag(py-O)3][OTf], while it is five coordinate in the other complexes. In [Ag3(py-O)8][OTf] 3, there are two different coordination environments for silver ions: six coordinate central silver ions and five coordinate for the outer silver ions. In some of the silver(i) complexes, silver-silver interactions were observed in the solid state. The Royal Society of Chemistry.
- Sniekers, Jeroen,Brooks, Neil R.,Schaltin, Stijn,Van Meervelt, Luc,Fransaer, Jan,Binnemans, Koen
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p. 1589 - 1598
(2014/01/06)
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- Gibbs Free Energies of Transfer for Cations in Amide-Solvents
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Gibbs free energies of transfer for several cations have been calculated from electrochemical measurements in formamide, N-methylformamide and N,N-dimethylacetamide.The data are discussed together with values for N,N-dimethylformamide and N,N-diethylacetamide considering electrostatic models and Lewis type donor-acceptor concepts.The bis(biphenyl)chromium assumption has been employed to obtain Gibbs free energies of transfer.The electrochemical measurements that formed the basis for these calculations have been carried out by polarography and cyclic voltammetry in 0.1 mol dm-3 solutions of tetrabutylammonium perchlorate in formamide and N,N-dimethylacetamide.The polarographic and voltammetric behaviour of Cu(CF3SO3)2, Cd(CF3SO3)2, Pb(CF3SO3)2, TlClO4, bis(biphenyl)chromium(I) tetraphenylborate and ferrocene (bis(η-cyclopentadiene)-iron(II)) has been studied in formamide and of LiClO4, NaClO4, KClO4, RbClO4, CsClO4, TlClO4, Ba(ClO4)2, Mn(CF3SO3)2, Co(CF3SO3)2, Ni(ClO4)2*2H2O, Cu(CF3SO3)2, Zn(CF3SO3)2, Cd(CF3SO3)2, Pb(CF3SO3)2, ferrocene, perylene, bis(biphenyl)chromium(I) tetraphenylborate and oxygen in N,N-dimethylacetamide.All potential data have been recorded versus bis(biphenyl)chromium(I)/(0) as a reference redox system. - Keywords: Gibbs free energies of transfer / Polarography and voltammetry in formamide and N,N-dimethylacetamide / Solvents effects on redox potentials / Bisbiphenylchromium assumption / Formamide, N-methylformamide, N,N-dimethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide
- Gsaller, Guenther,Gritzner, Gerhard
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p. 137 - 156
(2007/10/02)
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- Cephalosporin compounds
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Novel 7-azido-3-cephem compounds are prepared via α-amino-phosphonoacetate esters. The cephem compounds are intermediates for the preparation of novel and known useful antibiotic cephalosporins.
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