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Back Cover: Large‐Scale Synthesis of Helicene‐Like Molecules for the Design of Enantiopure Thin Films with Strong Chiroptical Activity (Chem. Eur. J. 10/2016) 下载免费PDF全文
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Large‐Scale Synthesis of Helicene‐Like Molecules for the Design of Enantiopure Thin Films with Strong Chiroptical Activity 下载免费PDF全文
Dr. Amina Bensalah‐Ledoux Delphine Pitrat Thibault Reynaldo Dr. Monika Srebro‐Hooper Barry Moore II Prof. Jochen Autschbach Dr. Jeanne Crassous Prof. Stéphan Guy Dr. Laure Guy 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(10):3333-3346
Helicenes are fascinating molecules owing to their unusual properties and applications in many fields from catalysis to organic electronics. Herein, we report a straightforward pathway for the synthesis of helicene‐like molecules on a gram scale in an enantiopure form. Thin‐film materials with good propagating optical properties and very high chiroptical responses have been grown by using pulsed laser ablation without altering the structure or the enantiopurity of the molecules. Moreover, electronic and vibrational circular dichroism spectroscopies coupled with theoretical calculations enabled some dependences of the chiroptical properties with the structure to be highlighted, for example, effects of rigidification, aromatization, or the state of matter (liquid versus solid). 相似文献
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Nam T. Nguyen Edward Greenhalgh Mohd J. Kamaruddin Jaouad El harfi Kim Carmichael Georgios Dimitrakis Samuel W. Kingman John P. Robinson Derek J. Irvine 《Tetrahedron》2014
This paper reports the first detailed study focussed upon identifying the influence that microwave heating (MWH) has upon the mechanic steps involved in the tin catalysed ring-opening of lactones such as ?-caprolactone (CL). Direct comparison of conventional (CH) and microwave (MWH) heated kinetic studies showed that a key factor in the reduction of the polymerisation cycle time with MWH was the elimination of the induction period associated with in situ catalyst manufacture and initiation. NMR studies demonstrated that the most significant mechanistic change contributing to the observed induction time reduction/elimination was faster initiation (i.e., reaction of the initiatior/catalyst complex with the first monomer unit). Consequently, analysis of the dielectric properties of the reaction components predicted that this MWH induced change was related to the selective volumetric heating of both the catalyst and the monomer. Furthermore, this indication of the greater significance of the initiation step in defining the length of the induction period suggests that this is the rate determining step of the process, whether conducted by CH or MWH. Increasing the catalyst concentration was demonstrated to produce significant reductions in reaction heat-up time and to induce a significant (up to 30 °C) overshoot in reaction mixture bulk temperature in with MWH only. Thus supporting the conclusion that selective heating of the organometallic species in the system contributes directly to differences in the reaction conditions and which need to be taken into account when drawing comparisons with CH systems. Consequently, both effects were concluded to be thermally generated from selective volumetric heating. 相似文献
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Crenguta Dordea Frédéric Brisach Jaouad Haddaoui Françoise Arnaud-Neu Michael Bolte Alessandro Casnati 《Supramolecular chemistry》2013,25(6):347-357
Calix[4]arene derivatives fixed in the 1,3-alternate conformation and substituted at one side by four carbamoylmethylphosphine oxide (CMPO) residues were synthesised. Two CMPO groups are directly attached to the wide rim, while the second pair is bound to the narrow rim via a tri- or tetramethylene spacer. Similar compounds, in which two CMPO groups at the wide rim are combined with two picolinamide groups or two ionisable carboxylic groups at the narrow rim, were also prepared. Some of these calixarene derivatives were studied as extractants for lanthanides (La3+, Eu3+, Yb3+) and thorium (Th4+) from acidic solution into methylene chloride. For selected samples, stability constants in methanol were determined by spectrophotometric titrations. Three compounds (1b′, 13, 17) in the 1,3-alternate conformation and one intermediate in the cone conformation (18) were confirmed by a crystal structure. 相似文献
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G. Boulon Y. Guyot M. Ito A. Bensalah C. Goutaudier G. Panczer 《Molecular physics》2013,111(11-12):1119-1132
A spectroscopic characterization was carried out to identify crystal-field levels for magnetic-dipole transitions of Yb3+ ions located in the Y3+ dodecahedral S4 crystallographic site in YLiF4 (YLF) crystals which were grown either by the Czochralski technique or by the laser heated pedestal growth (LHPG) technique. The concentration dependence of the measured decay time of the 2F5/2 excited level of Yb3+ was analysed in order to understand relevant concentration quenching mechanisms. Under Yb3+ ion infrared pumping, self-trapping and up-conversion non-radiative energy transfer to trace rare-earth impurities (Er3+, Tm3+) has been observed over the visible region and interpreted by a limited-diffusion process within the Yb3+ doping ion subsystem to the impurities. The principal parameters useful for a theoretical approach for potential laser applications of Yb3+-doped YLiF4 crystals have also been given. 相似文献
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Bunker CE Novak KC Guliants EA Harruff BA Meziani MJ Lin Y Sun YP 《Langmuir : the ACS journal of surfaces and colloids》2007,23(20):10342-10347
The sonochemical reaction of iron pentacarbonyl is explored in water and in water with the protein BSA (bovine serum albumen). In water, the reaction is found to produce spherical nanoparticles of magnetite (Fe3O4) with a particle size distribution of <10 to approximately 60 nm. In water with BSA, the reaction produces either nanofibers or nanoneedles, depending on the concentration of BSA. The nanofiber and nanoneedle samples are found to be mixtures of goethite, lepidocrocite, and hematite (alpha-FeOOH, gamma-FeOOH, and alpha-Fe2O3, respectively). The sonochemical reaction of iron pentacarbonyl with BSA in water is thought to proceed through the thermal decomposition mechanism for iron pentacarbonyl with BSA acting as a templating agent. 相似文献
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H. Sato A. Bensalah N. Solovieva A. Beitlerova A. Vedda M. Martini M. Nikl T. Fukuda 《Radiation measurements》2004,38(4-6):463-466
Two-inch sized KMgF3,BaLiF3 and LiCaAlF6 (LiCAF) single crystals were grown by the Czochralski method under a CF4 atmosphere. X-ray irradiation was used to carry out a comparative study of induced optical absorption phenomena and colour centre creation in the ultra-violet and visible spectral regions. The integral of the induced absorption spectra is significantly lower in LiCAF with respect to the other studied materials. It is found that the amplitude of the F-absorption band is suppressed more than a factor of 3 by Mg-doping. For Mg-doped crystals, the optimum doping concentration is about 0.2 mol% of Mg2+. 相似文献
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Gordon D. Airey Jasmin Wilmot James R.A. Grenfell Derek J. Irvine Ian A. Barker Jaouad El Harfi 《European Polymer Journal》2011,47(6):1300-1314
Catalytic chain transfer polymerization has been successfully used to produce a range of methyl acrylate (MA) and butyl acrylate (BA) synthetic polymers of specific, targeted molecular weights, with polydispersity index values in the range of 2–4.5. The rheological properties of a subgroup of these synthetic binders consisting of four MA homo-polymers and one MA–BA co-polymer were then determined by means of oscillatory testing using a dynamic shear rheometer (DSR). The rheological tests consisted of a combination of stress/strain amplitude and frequency sweeps using a standard 8 mm diameter parallel plate testing geometry. The rheological parameters of phase angle and complex, storage and loss moduli were then shifted to form master curves at a reference temperature of 25 °C and isochronal plots at 0.1, 1 and 10 Hz. The rheological properties of the synthetic polymers were also compared to those of standard road pavement bitumens. The results show that it is possible to produce a range of synthetic polyacrylates with different rheological responses by altering the reactant type, reactant concentration and polymerization conditions to match the rheological properties of road bitumens. All the polyacrylate binders showed a similar rheological profile with a unique viscoelastic response as represented by the phase angle master curves together with an upper limiting stiffness and intermediate temperature/frequency ‘plateau’ region as shown in the complex modulus master curves. The results of the rheological examination of the binders showed that the key material property that influenced the performance of the polyacrylates in these specific application tests was glass transition temperature rather than molecular weight. Over this range of investigated molecular weights, it is the ratio between the two polymers which determines the glass transition and as such determines the material properties. These findings suggest that such sustainably sourced polyacrylate binders may allow for a move from petrochemical feed stocks to be made and allow for targeted road pavement design based on local climates, offering improved mechanical robustness. 相似文献