Application of ionic liquids in organic reactions

Room-temperature ionic liquids are good solvents for a wide of organic, inorganic and organometallic compounds. Typically consisting of nitrogen-containing organic cations and inorganic anions, they are easy to recycle, nonflammable, and have no detectable vapor pressure. More recently, ionic liquids have been found to be excellent solvents for a number of chemical reactions, e. g. hydrogenation, alkylation, epoxidation, Heck-vinylation, Suzuki cross-coupling reactions and enzyme catalyzed organic reactions. This paper focuses on the recent development of using ionic liquids as solvents for transition metal and enzyme catalyzed reactions.

Oxythiamine hexafluorophosphate monohydrate, a thiamine antagonist with the same conformation as thiamine

In the title compound, 3-[(3,4-dihydro-2-methyl-4-oxopyrimidin-5-yl)methyl]-5-(2-hydroxyethyl)-4-methylthiazolium hexafluorophosphate monohydrate, C12H16N3O2S+. PF6-.H2O, oxythiamine is a monovalent cation with a neutral oxopyrimidine ring. The molecule assumes the F conformation, which is a common form for thiamine but which is substantially different from the unusual V conformation found in the chloride and hydrochloride salts of oxythiamine. The anion-bridging interaction, C-H . . . anion . . . pyrimidine, is emphasized as being important for stabilization of the F conformation.

Electrocrystallized platinum nanoparticle on carbon substrate

Platinum nanoparticles were electrocrystallized on a 4-aminophenyl monolayer-grafted carbon substrate. These Pt-modified surfaces were characterized by scanning tunneling microscopy (STM). The characterization by STM revealed that the platinum nanoparticles obtained had good size monodispersity and were well separated from one another on HOPG surfaces. (C) 2000 Elsevier Science S.A. All rights reserved.

1,1 '-di(tert-butyl)metallocenium cations. The x-ray crystal structures of [M((C5H4Bu)-Bu-t)(2)]PF6 (M = Fe, Co) and [Co((C5H4Bu)-Bu-t)(2)](2)CoCl4

The hexafluorophosphate salts [Fe((C5H4Bu)-Bu-t)(2)]PF6 (1) and [Co((C5H4Bu)-Bu-t)(2)]PF6 (2) crystallize in isotypic structures with centrosymmetric cations which have a staggered (transoid) conformation of the exactly parallel ring Ligands (conformational angle tau = 180 degrees). The tetrachlorocobaltate salt, [CO((C5H4Bu)-Bu-t)(2)](2)CoCl4 (3), contains one almost eclipsed (tau = 140.4 degrees) and one almost staggered (tau = 101.4 degrees) cobaltocenium cation; in both cases, the cyclopentadienyl ring planes are slightly inclined (by alpha = 5.4 degrees and 4.1 degrees, respectively) to give more room to the tert-butyl substituents which are bent away from the metal in all three complexes 1 - 3.

Two new coordination polymers of Co(II) with 1,1 '-(1,4-butanediyl)bis(benzimidazole)

Two new compounds, [CoL2(H2O)(2)](NO3)(2). 8H(2)O (1) and [CoL(H2O)(2)(CH3CO2)(2)]. H2O (2), were obtained from self-assembly of the corresponding metal salts with 1,1'-(1,4-butanediyl)bis(benzimidazole) (L). In 1, each cobalt ion is coordinated to four nitrogen atoms from four molecules of L, and to two water molecules. Metal ions are bridged by L ligands to form infinite (4, 4) networks that contain 44-membered rings. The (4, 4) networks of 1 stack in a parallel fashion, resulting in the formation of large channels in the material. In 2, each cobalt ion is coordinated to two N atoms from two L molecules, two water molecules and two carboxylate O atoms from two acetate anions. Each L molecule is coordinated to two cobalt ions, acting as a bridging ligand as in 1. The bridged cobalt ions form an infinite zigzag chain structure.

Networks with hexagonal circuits in co-ordination polymers of metal ions (Zn-II, Cd-II) with 1,1 '-(1,4-butanediyl)bis(imidazole)

Three new compounds, [ZnL1.5(H2O)(SO4)]. 6H(2)O 1, [ZnL1.5(H2O)(2)][NO3](2). 2H(2)O 2 and [CdL1.5(H2O)(2)(SO4)]. 4H(2)O 3 were obtained from self-assembly of the corresponding metal salts with 1,1'-(1,4-butanediyl)bis(imidazole) (L). In both 1 and 2 zinc ion is five-co-ordinated, showing a less-common trigonal bipyramidal co-ordination polyhedron, while cadmium ion of 3 is six-co-ordinated with a common octahedral arrangement. The sulfate ions of 1 and 3 are co-ordinated, however the nitrate ions of 2 are not. Each of the three compounds is composed of a (6, 3) network with the hexagonal smallest circuit containing six metal ions and six L; each L is co-ordinated to two metal ions, acting as a bridging ligand. In 1 the 2-D sheet of (6, 3) networks is interpenetrated in an inclined mode by symmetry related, identical sheets to give an interlocked 3-D structure, while the (6, 3) networks of both 2 and 3 stack in a parallel fashion to construct frameworks having channels.

Mechanical relaxation time of comblike polymer electrolyte

Using poly(styrene-co-maleic anhydride) as the backbone and poly(ethylene glycol) methyl ether as side chains,three kinds of comblike polymers of different side chain length were synthesized. The Li-salt complexes and their firms were prepared. The dynamic mechanical properties were investigated. It was found that the main chain was rigid and the side chain was flexible in this comblike polymer system. Based on the time-temperature equivalence principle, a master curve was constructed. By selecting T-alpha as reference temperature, Arrhenius plots of shift factor and iso-free-volume plots were attained. The values of WLF parameters C-1 and C-2 increase with increasing salt concentration. By reference to T-0 = 50 degrees C, the relation between the average relaxation time 1g tau(c) and Li-salt concentration C is linear. The master curves are displaced progressively to higher frequencies as the M-w of side chains is increased. The relation between the average relaxation time 1g tau(n) and M-w of side chains is also linear. And the master curves are movable with the change of salts. It shows the effect of different kinds of salt on relaxation time.

Pentamethylcyclopentadienyl halfsandwich rhodium complexes containing 1,1 '-ferrocene dichalcogenido chelate ligands

The heterobimetallic complexes Cp * Rh(CN Bu-t)(EC5H4)(2)Fe [E = S(2),Se(3), Te(4)] have been synthesized by the reaction of halfsandwich rhodium complex Cp * Rh(CNtBu) Cl-2 with Fe(C5H4ELi)(2). 2THF. Oxidation of 2,3 by AgBF4 to give ferrocenium - type salts [Cp * Rh(CNtBu) (EC5H4)(2)Fe] (+) [BF4] (-) [E = S(5),Se(6)] also occurs readily. The new complexes have been characterized by MS IR, H-1 and C-13 NMR spectroscopy and elemental analysis.

A novel epitaxy of isotactic polypropylene (alpha phase) on PTFE and organic substrates

Isotactic polypropylene in its a modification (alpha iPP) crystallises epitaxially on polytetrafluoroethylene (PTFE) and several hemiacids or salts of substituted benzoic acids via a novel contact plane, namely (110): so far, the only known contact plane involved in alpha iPP homo- and hetero-epitaxies was (010). In spite of its complicated architecture (alternation of antichiral helices with different azimuthal settings), the (110)(alpha iPP) contact plane displays well defined, if not prominent, rows of methyl side chains parallel to the crystallographic (112) direction (at 57 degrees to the c-axis) and approximate to 5.5 Angstrom apart. The matching contact planes of the substrates display linear gratings made of rows of e.g. chlorine atoms or PTFE chains with similar approximate to 5.5 Angstrom inter-row or interchain distances. Various morphologies are observed in iPP thin films crystallised at different cooling rates in the presence of PTFE; they can be analysed in terms of a succession and interplay of successive epitaxies: initial alpha iPP/PTFE heteroepitaxy, followed by alpha iPP/alpha iPP and gamma iPP/alpha iPP homoepitaxies. (C) 1999 Published by Elsevier Science Ltd. All rights reserved.

Chlorohydrin water swellable rubber compatibilized by an amphiphilic craft copolymer. I. Synthesis and characterization of compatibilizer PVA-g-PBA

The graft copolymerization of butyl acrylate onto poly(vinyl alcohol) with eerie ammonium nitrate as redox initiator in a aqueous medium has been investigated. The formation of graft copolymer was confirmed by means of IR, scanning electron microscopy (SEM), and wide-angle X-ray diffraction (WAXD). The percentage of mononer conversion and percentage of grafting varied with concentrations of initiator, nitric acid, monomer, macromolecular backbone (X-n = 1750, M = 80 000), reaction temperature and reaction time. Some inorganic salts and organic solvents have a great influence upon grafting. The reaction mechanism has been explored, and rate equations for the reaction are established. (C) 2000 John Wiley & Sons, Inc.

Analysis of poly (arylene phosphonate) cyclic oligomer by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MAIDI-TOF-MS) was used for analysis of poly(arylene phosphonate) cyclic oligomers. A comparison was made by using 1,8,9-dithranol, 2,5-dihydroxybenzoic acid and retinoic acid as the matrix. The result showed that the retinoic acid produced the strongest ion signals under the conditions used. Different salts of metals were used as the cationization agents to examine the effect on the cyclic oligomers. It was found that the salts could produce metal-cyclic oligomer cation spectra and lithium was the stronger one than those of silver so, the suitable matrix and cationization agent for the new cyclic oligmer were obtained. They were very effective for the analysis of poly(arylene phosphonate) cyclic oligomer.

Use of nitrocellulose films for affinity-directed mass spectrometry for the analysis of antibody/antigen interactions

Combination of affinity extraction procedures with mass spectrometric analyses is termed affinity-directed mass spectrometry, a technique that has gained broad interest in immunology and is extended here with several improvements from methods used in previous studies. A monoclonal antibody was immobilized on a nitrocellulose (NC) membrane, allowing the corresponding antigen to be selectively captured from a complex solution for analysis by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). This method was also used to rapidly determine the approximate binding region responsible for the antibody/antigen interaction. The tryptic fragments of antigen protein in buffer were applied to the antibody immobilized on NC film and allowed to interact. The NC film was then washed to remove salts and other unbound components, and subjected to analysis by MALDI-TOFMS. Using interferon-alpha (2a) and anti-interferon-alpha (2a) monoclonal antibody IgG as a model system, we successfully extracted the antigen protein and determined the approximate binding region for the antigen/antibody interaction (i.e., the tryptic fragment responsible). Copyright (C) 2001 John Wiley & Sons, Ltd.

The effect of KSCN on the partition of proteins in polyethylene glycol/(NH4)(2)SO4 aqueous two-phase system

The effect of potassium thiocyanate on the partitioning of lysozyme and BSA in polyethylene glycol 2000/ammonium sulfate aqueous two-phase system has been investigated. As a result of the addition of potassium thiocyanate to the PEG/ammonium sulfate system, the PEG/mixed salts aqueous two-phase system was formed. It was found that the potassium thiocyanate could alter the pH difference between the two phases, and, thus, influence the partition coefficients of the differently charged proteins. The relationship between partition coefficient of the proteins and pH difference between two phases has been discussed. It was proposed that the pH difference between two phases could be employed as the measurement of electrostatic driving force for the partitioning of charged proteins in polyethylene glycol 2000/ammonium sulfate aqueous two-phase system.

Investigation of a series of synthetic cationic porphyrins using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) was used to study a series of synthetic cationic porphyrins as the perchlorate and bromide salts. This work presents the analytical results for the porphyrins obtained using 2,5-dihydroxybenzoic acid (DHB) and 1,8,9-anthratriol as matrices. The selective use of matrix affects ion formation from these porphyrins. By using DHB as the matrix, we not only observed [M - nCIO(4)](+) (n = 1-4) ions, but also obtained [2M - nCIO(4)](+) (n = 2-7) ions from the synthetic cationic porphyrins. The space volume of the side chains (R groups) and the nature of the anions (Br- or CIO4-) affected the relative importance of monomeric and dimeric ions of the porphyrin. The possible mechanisms of desorption and ionization of these cationic porphyrins were also considered in this study. MALDI-TOFMS proved to be a very useful method for obtaining structural information on these synthetic cationic porphyrins. Copyright (C) 1999 John Whey & Sons, Ltd.

Facile synthesis of phenyl-capped oligoanilines using pseudo-high dilution technique

Monodispersed phenyl-capped trianiline and tetraaniline were successfully synthesized by the reactions of diphenylamine with acetaldehyde-based Sckiff's bases of N-phenyl-1,4-phenylenediamine and 1,4-phenylenediamine, respectively, in the presence of ammonium persulfate and hydrochloric acid, subsequent deprotonation and reduction with phenylhydrazine. The reaction mechanism probably involves the slow hydrolysis of the Sckiff's bases and subsequent oxidative coupling reactions of the formed ammonium salts with diphenylamine at pseudo-high dilution condition of the salts.