- Spectral and physicochemical characterization of dysprosium-based multifunctional ionic liquid crystals
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We report on the synthesis and characterization of multifunctional ionic liquid crystals (melting points below 100 °C) which possess chirality and fluorescent behavior as well as mesomorphic and magnetic properties. In this regard, (1R,2S)-(-)-N-methylephedrine ((-)MeEph), containing a chiral center, is linked with variable alkyl chain lengths (e.g., 14, 16, and 18 carbons) to yield liquid crystalline properties in the cations of these compounds. A complex counteranion consisting of trivalent dysprosium (Dy3+) and thiocyanate ligand (SCN-) is employed, where Dy3+ provides fluorescent and magnetic properties. Examination of differential scanning calorimetry (DSC) and hot-stage polarizing optical microscopy (POM) data confirmed liquid crystalline characteristics in these materials. We further report on phase transitions from solid to liquid crystal states, followed by isotropic liquid states with increasing temperature. These compounds exhibited two characteristic emission peaks in acetonitrile solution and the solid state when excited at ex = 366 nm, which are attributed to transitions from 4F9/2 to 6H15/2 and 4F9/2 to 6H13/2. The emission intensities of these compounds were found to be very sensitive to the phase.
- Lu, Chengfei,Das, Susmita,Siraj, Noureen,Magut, Paul K. S.,Li, Min,Warner, Isiah M.
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p. 4780 - 4786
(2015/06/02)
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- Chiral ammonium-capped rhodium(0) nanocatalysts: Synthesis, characterization, and advances in asymmetric hydrogenation in neat water
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Optically active amphiphilic compounds derived from N-methylephedrine, N-methylprolinol, or cinchona derivatives possessing bromide or chiral lactate counterions were efficiently used as protective agents for rhodium(0) nanoparticles. The full characterization of these surfactants and the obtained nanocatalysts was performed by means of different techniques. These spherical nanoparticles, with sizes between 0.8-2.5 nm depending on the stabilizer, were evaluated in the hydrogenation of model substrates in neat water as a green solvent. The rhodium catalysts showed relevant kinetic properties, but modest enantiomeric excess values of up to 13 % in the hydrogenation of ethyl pyruvate. They were also investigated in the hydrogenation of disubstituted arenes, such as m-methylanisole, providing interesting catalytic activities and a preferential cis selectivity of around 80 %; however, no asymmetric induction was observed. Green nanocatalysts: Optically active compounds derived from N-methylephedrine, N-methylprolinol, or cinchona derivatives with bromide or chiral lactate counterions are used as protective agents for rhodium(0) nanoparticles in asymmetric catalysis of the hydrogenation of ethyl pyruvate and m-methylanisole in water as a green solvent. Copyright
- Guyonnet Bilé, Elodie,Cortelazzo-Polisini, Elodie,Denicourt-Nowicki, Audrey,Sassine, Rita,Launay, Franck,Roucoux, Alain
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experimental part
p. 91 - 101
(2012/06/29)
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- Deracemization of bilirubin as the marker of the chirality of micellar aggregates
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The deracemization of bilirubin in micellar aggregates of structurally correlated chiral surfactants was studied by circular dichroism experiments and exploited as the marker of the expression of chirality of the aggregates. The obtained results suggest that the hydrophobic interactions control the transfer of chirality from the monomers to the aggregates, and that different regions of the same aggregate might feature opposite enantiorecognition capabilities.
- Sorrenti, Alessandro,Altieri, Barbara,Ceccacci, Francesca,Di Profio, Pietro,Germani, Raimondo,Giansanti, Luisa,Savelli, Gianfranco,Mancini, Giovanna
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experimental part
p. 78 - 85
(2012/03/26)
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- N-Methylephedrium salts as chiral surfactants for asymmetric hydrogenation in neat water with rhodium(0) nanocatalysts
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A new family of chiral surfactants derived from N-methylephedrine possessing different counter-ions (Br-, ${{{rm {rm HCO}}{{- hfill atop 3hfill}}}}$, (S)-(-)-lactate-) is easily prepared and used as efficient protective agents of rhodium(0) nanoparticles. The resulting, well-characterized materials prove to be active catalysts in the hydrogenation of ethylpyruvate in neat water, with modest enantiomeric excesses.
- Guyonnet-Bilé, Elodie,Denicourt-Nowicki, Audrey,Sassine, Rita,Beaunier, Patricia,Launay, Franck,Roucoux, Alain
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experimental part
p. 1276 - 1279
(2011/12/02)
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