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201.
AnneSophie Droz Ulf Neidlein Sally Anderson Paul Seiler Franois Diederich 《Helvetica chimica acta》2001,84(8):2243-2289
A new family of optically active cyclophane receptors for the complexation of mono‐ and disaccharides in competitive protic solvent mixtures is described. Macrocycles (−)‐(R,R,R,R)‐ 1 – 4 feature preorganized binding cavities formed by four 1,1′‐binaphthalene‐2,2′‐diyl phosphate moieties bridged in the 3,3′‐positions by acetylenic or phenylacetylenic spacers. The four phosphodiester groups converge towards the binding cavity and provide efficient bidentate ionic H‐bond acceptor sites (Fig. 2). Benzyloxy groups in the 7,7′‐positions of the 1,1′‐binaphthalene moieties ensure solubility of the nanometer‐sized receptors and prevent undesirable aggregation. The construction of the macrocyclic framework of the four cyclophanes takes advantage of Pd0‐catalyzed aryl—acetylene cross‐coupling by the Sonogashira protocol, and oxidative acetylenic homo‐coupling methodology (Schemes 2 and 8 – 10). Several cleft‐type receptors featuring one 1,1′‐binaphthalene‐2,2′‐diyl phosphate moiety were also prepared (Schemes 1, 6, and 7). An undesired side reaction encountered during the synthesis of the target compounds was the formation of naptho[b]furan rings from 3‐ethynylnaphthalene‐2‐ol derivatives, proceeding via 5‐endo‐dig cyclization (Schemes 3 – 5). Computer‐assisted molecular modeling indicated that the macrocycles prefer nonplanar puckered, cyclobutane‐type conformations (Figs. 7 and 8). According to these calculations, receptor (−)‐(R,R,R,R)‐ 1 has, on average, a square binding site, which is complementary in size to one monosaccharide. The three other cyclophanes (−)‐(R,R,R,R)‐ 2 – 4 feature, on average, wider rectangular cavities, providing a good fit to one disaccharide, while being too large for the complexation of one monosaccharide. This substrate selectivity was fully confirmed in 1H‐NMR binding titrations. The chiroptical properties of the cyclophanes and their nonmacrocyclic precursors were investigated by circular dichroism (CD) spectroscopy. The CD spectra of the acyclic precursors showed a large dependence from the number of 1,1′‐binaphthalene moieties (Fig. 9), and those of the cyclophanes were remarkably influenced by the nature of the functional groups lining the macrocyclic cavity (Fig. 11). Profound differences were also observed between the CD spectra of linear and macrocyclic tetrakis(1,1′‐binaphthalene) scaffolds, which feature very different molecular shapes (Fig. 10). In 1H‐NMR binding titrations with mono‐ and disaccharides (Fig. 13), concentration ranges were chosen to favor 1 : 1 host−guest binding. This stoichiometry was experimentally established by the curve‐fitting analysis of the titration data and by Job plots. The titration data demonstrate conclusively that the strength of carbohydrate recognition is enhanced with an increasing number of bidentate ionic host−guest H‐bonds (Table 1) in the complex formed. As a result of the formation of these highly stable H‐bonds, carbohydrate complexation in competitive protic solvent mixtures becomes more favorable. Thus, cleft‐type receptors (−)‐(R)‐ 7 and (−)‐(R)‐ 38 with one phosphodiester moiety form weak 1 : 1 complexes only in CD3CN. In contrast, macrocycle (−)‐(R,R,R,R)‐ 1 with four phosphodiester groups undergoes stable inclusion complexation with monosaccharides in CD3CN containing 2% CD3OD. With their larger number of H‐bonding sites, disaccharide substrates bind even more strongly to the four phosphodiester groups lining the cavity of (−)‐(R,R,R,R)‐ 2 and complexation becomes efficient in CD3CN containing 12% CD3OD. Finally, the introduction of two additional methyl ester residues further enhances the receptor capacity of (−)‐(R,R,R,R)‐ 3 , and efficient disaccharide complexation occurs already in CD3CN containing 20% CD3OD. 相似文献
202.
203.
Sophie Laurent Luce VanderElst Sylvain Houz Nathalie Gurit RobertN. Muller 《Helvetica chimica acta》2000,83(2):394-406
Four derivatives of diethylenetriaminepentaacetic acid (=3,6,9‐tris(carboxymethyl)‐3,6,9‐triazaundecanedioic acid (H5dtpa)), potential contrast agents for magnetic resonance imaging (MRI), carrying benzyl groups at various positions of the parent structure were synthesized and characterized by a thorough multinuclear NMR study, i.e., the (S)‐ and (R)‐stereoisomers 1a and 1b of 4‐benzyl‐3,6,9‐tris(carboxymethyl)‐3,6,9‐triazaundecanedioic acid (H5[(S)‐(4‐Bz)dtpa] and H5[(R)‐(4‐Bz)dtpa], the diamide derivative N,N″‐bis[(benzylcarbamoyl)methyl]diethylenetriamine‐N,N′,N″‐triacetic acid (=3,9‐bis[2‐(benzylamino)‐2‐oxoethyl]‐6‐(carboxymethyl)‐3,6,9‐triazaundecanedioic acid; H3[dtpa(BzA)2]; 2 ), and the diester derivative N,N″‐bis{[(benzyloxy)carbonyl]methyl}diethylenetriamine‐N,N′,N″‐triacetic acid (=3,9‐bis[2‐(benzyloxy)‐2‐oxoethyl]‐6‐(carboxymethyl)‐3,6,9‐triazaundecanedioic acid; H3[dtpa(BzE)2]; 3 ). From the 17O‐NMR chemical shift of H2O induced by their dysprosium complexes with ligands 1 – 3 , it was concluded that only one H2O molecule is contained in the first coordination sphere of these lanthanide complexes. The rotational correlation times (τR) of the complexes were estimated from the 2H‐NMR longitudinal relaxation rate of the deuterated diamagnetic lanthanum complexes. The exchange time of the coordinated H2O molecule (τM) was studied through the temperature dependence of the 17O‐NMR transverse relaxation rate. As compared to [Gd(dtpa)]2−, the H2O‐exchange rate is faster for [Gd{(S)‐(4‐Bz)dtpa}]2− and [Gd{(R)‐(4‐Bz)dtpa}]2−‐, slower for [Gd{dtpa(BzA)2}], and almost identical for [Gd{dtpa(BzE)2}]. The analysis of the 1H‐relaxivity of the gadolinium complexes recorded from 0.02 to 300 MHz established that i) the relaxivity of [Gd{dtpa(BzE)2}] is similar to that of [Gd(dtpa)]2−, ii) the slightly slower molecular rotation of [Gd{dtpa(BzA)2}] induces a mild enhancement of its relaxivity, and iii) the marked increase of relaxivity of [Gd{(S)‐(4‐Bz)dtpa}]2− and [Gd{(R)‐(4‐Bz)dtpa}]2− mainly results from an apparently shorter distance between the gadolinium ion and the H2O protons of the coordinated H2O molecule. 相似文献
204.
Andrew J. Taylor Dr. Robert Hein Sophie C. Patrick Prof. Jason J. Davis Prof. Paul D. Beer 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2024,136(6):e202315959
Anion sensing via either optical or electrochemical readouts has separately received enormous attention, however, a judicious combination of the advantages of both modalities remains unexplored. Toward this goal, we herein disclose a series of novel, redox-active, fluorescent, halogen bonding (XB) and hydrogen bonding (HB) BODIPY-based anion sensors, wherein the introduction of a ferrocene motif induces remarkable changes in the fluorescence response. Extensive fluorescence anion titration, lifetime and electrochemical studies reveal anion binding-induced emission modulation through intramolecular photoinduced electron transfer (PET), the magnitude of which is dependent on the nature of both the XB/HB donor and anion. Impressively, the XB sensor outperformed its HB congener in terms of anion binding strength and fluorescence switching magnitude, displaying significant fluorescence turn-OFF upon anion binding. In contrast, redox-inactive control receptors display a turn-ON response, highlighting the pronounced impact of the introduction of the redox-active ferrocene on the optical sensing performance. Additionally, the redox-active ferrocene motif also serves as an electrochemical reporter group, enabling voltammetric anion sensing in competitive solvents. The combined advantages of both sensing modalities were further exploited in a novel, proof-of-principle, fluorescence spectroelectrochemical anion sensing approach, enabling simultaneous and sensitive read out of optical and electrochemical responses in multiple oxidation states and at very low receptor concentration. 相似文献
205.
Anja Bhr AnneSophie Droz Martin Püntener Ulf Neidlein Sally Anderson Paul Seiler Franois Diederich 《Helvetica chimica acta》1998,81(11):1931-1963
The synthesis and carbohydrate-recognition properties of a new family of optically active cyclophane receptors, 1 – 3 , in which three 1,1′-binaphthalene-2,2′-diol spacers are interconnected by three buta-1,3-diynediyl linkers, are described. The macrocycles all contain highly preorganized cavities lined with six convergent OH groups for H-bonding and complementary in size and shape to monosaccharides. Compounds 1 – 3 differ by the functionality attached to the major groove of the 1,1′-binaphthalene-2,2′-diol spacers. The major grooves of the spacers in 2 are unsubstituted, whereas those in 1 bear benzyloxy (BnO) groups in the 7,7′-positions and those in 3 2-phenylethyl groups in the 6,6′-positions. The preparation of the more planar, D3-symmetrical receptors (R,R,R)- 1 (Schemes 1 and 2), (S,S,S)- 1 (Scheme 4), (S,S,S)- 2 (Scheme 5), and (S,S,S)- 3 (Scheme 8) involved as key step the Glaser-Hay cyclotrimerization of the corresponding OH-protected 3,3′-diethynyl-1,1′-binaphthalene-2,2′-diol precursors, which yielded tetrameric and pentameric macrocycles in addition to the desired trimeric compounds. The synthesis of the less planar, C2-symmetrical receptors (R,R,S)- 2 (Scheme 6) and (S,S,R)- 3 (Scheme 9) proceeded via two Glaser-Hay coupling steps. First, two monomeric precursors of identical configuration were oxidatively coupled to give a dimeric intermediate which was then subjected to macrocyclization with a third monomeric 1,1′-binaphthalene precursor of opposite configuration. The 3,3′-dialkynylation of the OH-protected 1,1′-binaphthalene-2,2′-diol precursors for the macrocyclizations was either performed by Stille (Scheme 1) or by Sonogashira (Schemes 4, 5, and 8) cross-coupling reactions. The flat D3-symmetrical receptors (R,R,R)- 1 and (S,S,S)- 1 formed 1 : 1 cavity inclusion complexes with octyl 1-O-pyranosides in CDCl3 (300 K) with moderate stability (ΔG0 ca. −3 kcal mol−1) as well as moderate diastereo- (Δ(ΔG0) up to 0.7 kcal mol−1) and enantioselectivity (Δ(ΔG0)=0.4 kcal mol−1) (Table 1). Stoichiometric 1 : 1 complexation by (S,S,S)- 2 and (S,S,S)- 3 could not be investigated by 1H-NMR binding titrations, due to very strong signal broadening. This broadening of the 1H-NMR resonances is presumably indicative of higher-order associations, in which the planar macrocycles sandwich the carbohydrate guests. The less planar C2-symmetrical receptor (S,S,R)- 3 formed stable 1 : 1 complexes with binding free enthalpies of up to ΔG0=−5.0 kcal mol−1 (Table 2). With diastereoselectivities up to Δ(ΔG0)=1.3 kcal mol−1 and enantioselectivities of Δ(ΔG0)=0.9 kcal mol−1, (S,S,R)- 3 is among the most selective artificial carbohydrate receptors known. 相似文献
206.
207.
208.
209.
Olivier Colin Martin Ritter Corine Lacour Karine Truffin Sophie Mouriaux Sergey Stepanyan Bertrand Lecordier Pierre Vervisch 《Proceedings of the Combustion Institute》2019,37(4):4875-4883
The cycle to cycle combustion variability which is observed in spark-ignition engines is often caused by fluctuations of the early flame development. LES can be exploited for a better understanding and mastering of their origins. For that purpose appropriate models taking into account energy deposition, mixture ignition and transition to propagation are necessary requirements. This paper presents first DNS and LES of spark ignition with a real automotive coil and simplified pin-pin electrodes. The electrical circuit characteristics are provided by ISSIM while the energy deposition is modelled by Lagrangian particles. The ignition model is first evaluated in terms of initial spark radius on a pin-pin ignition experiment in pure air performed at CORIA and EM2C laboratories, showing that it pilots the radius of the torus formed by the initial shock wave. DNS of a quiescent lean propane/air mixture are then performed with this ignition system and a two-step mechanism. The impact of the modelled transferred energy during glow phase as well as the initial arc radius on the minimum ignition energy (MIE) are examined and compared to experimental values. Replacing the two-step chemistry by an analytically reduced mechanism leads to similar MIE but shows a different ignition kernel shape. Finally, LES of turbulent ignition using a Lagrangian arc model show a realistic prediction of the arc shape and its important role on the energy transfer location and thus on the flame kernel shape. 相似文献
210.
Olivier Horner Sophie Neveu Sophie de Montredon Jean-Michel Siaugue Valérie Cabuil 《Journal of nanoparticle research》2009,11(5):1247-1250
Maghemite nanoparticles with sizes in the range 10–110 nm and good monodispersity have been synthesized by co precipitation
at room temperature from Fe2+ and Fe3+ ions by a (N(CH3)4OH) solution, followed by an hydrothermal treatment at 200 °C and an oxidation step with Fe(NO3)3. The influence of the incubation time (at 200 °C) and of the pH of the autoclaved solution on the particles size has been
studied. It was found that the pH value allows to tune the size of the maghemite particles.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献