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991.
Maria Carmen Florian Eric Condamine loïc Toupet Yvan Ramondenc Gérard Plé 《Supramolecular chemistry》2013,25(6):383-392
The synthesis and the structure of new macrocycles containing semiflexible dispiro-1,3-dioxane units is reported. The structural analysis of the compounds is performed by high field NMR spectra, mass spectrometry investigations (MALDI, ESI-MS) and the solid state molecular structure obtained for two compounds by single crystal X-ray diffractometry. The dynamics of the macrocycles promoted by the flipping of the middle cyclohexane ring of the dispirane units is investigated using low temperature NMR experiments. New macrocycles containing dispiro-1,3-dioxane units were investigated by NMR, X-ray diffractometry and mass spectrometry 相似文献
992.
Duc-Truc Pham Philip Clements Christopher J. Easton John Papageorgiou Bruce L. May 《Supramolecular chemistry》2013,25(6):510-519
This study shows that stereochemical factors largely determine the extent to which 6-(4′-t-butylphenylamino)-naphthalene-2-sulphonate, BNS? and its dimer, (BNS? )2, are complexed by β-cyclodextrin, βCD, and a range of linked βCD dimers. Fluorescence and 1H NMR studies, respectively, show that BNS? and (BNS? )2 form host–guest complexes with βCD of the stoichiometry βCD.BNS? (10? 4 K 1 = 4.67 dm3 mol? 1) and βCD.BNS2 2 ? (10? 2 K 2′ = 2.31 dm3 mol? 1), where the complexation constant K 1 = [βCD.BNS? ]/([βCD][BNS? ]) and K 2′ = [βCD. (BNS? )2]/([βCD.BNS? ][BNS? ]) in aqueous phosphate buffer at pH 7.0, I = 0.10 mol dm3 at 298.2 K. (The dimerisation of BNS? is characterised by 10? 2 K d = 2.65 dm3 mol? 1.) For N,N-bis((2AS,3AS)-3A-deoxy-3A-β-cyclodextrin)succinamide, 33βCD2su, N-((2AS,3AS)-3A-deoxy-3A-β-cyclodextrin)-N′-(6A-deoxy-6A-β-cyclodextrin)urea, 36βCD2su, N,N-bis(6A-deoxy-6A-β-cyclodextrin)succinamide, 66βCD2su, N-((2AS,3AS)-3A-deoxy-3A-β-cyclodextrin)-N′-(6A-deoxy-6A-β-cyclodextrin)urea, 36βCD2ur, and N,N-bis(6A-deoxy-6A-β-cyclodextrin)urea, 66βCD2ur, the analogous 10? 4 K 1 = 11.0, 101, 330, 29.6 and 435 dm3 mol? 1 and 10? 2 K 2′ = 2.56, 2.31, 2.59, 1.82 and 1.72 dm3 mol? 1, respectively. A similar variation occurs in K 1 derived by UV–vis methods. The factors causing the variations in K 1 and K 2 are discussed in conjunction with 1H ROESY NMR and molecular modelling studies. 相似文献
993.
994.
Nikolaos Mourtzis Kyriaki Eliadou Konstantina Yannakopoulou 《Supramolecular chemistry》2013,25(8):587-593
Methyl Orange (MO), an azo-dye molecule with an inherent dipole moment, has been used as a probe to explore the influence of anionic or cationic substituents of cyclodextrins (CDs) on the mode of insertion to form pseudorotaxanes, using NMR spectroscopy. MO is oriented in a single mode inside the βCD cavity, with the dimethylamino group localized at the secondary side. This orientation is completely reversed when MO enters the anionic sodium heptakis[6-deoxy-6-(3-thiopropionate)]-βCD (βpsp) cavity, whereas inside the cationic heptakis(6-deoxy-6-amino)-βCD hydrochloride, MO flips once more, to adopt the same orientation as in βCD. In the latter case the water solubility of MO is significantly lowered. The disposition of the guest in βCD and in each βCD derivative in a single mode was attributed principally to anti-parallel dipole-dipole stabilization. In the wider γCD, the availability of more cavity space leads to 1:2 and 2:2 host/guest stoichiometries and the effect of dipoles is of secondary significance. In the anionic sodium octakis[6-deoxy-6-(3-thiopropionate)]-γCD, MO is positioned as in βpsp, but a 1:2 adduct is also detected. Finally, MO does not dissolve in octakis(6-deoxy-6-amino)-γCD hydrochloride solution. 相似文献
995.
The synthesis of simple, chromogenic pyridine-2,6-dicarboxylic acid amides, derivatives of isomeric nitroanilines and aminonitrophenols, and their ion binding properties are described. The ligands' response to ionic species was examined by naked eye and was studied with the use of UV–vis spectroscopy in DMSO and its mixture with water. The effect of the localisation and the type of the substituents in aromatic rings were discussed. 1H NMR experiments were carried out to probe the mechanism of anion recognition, i.e. complexation via hydrogen bond formation versus ligand deprotonation. A selective response of N,N′-bis(2-hydroxy-4-nitrophenyl)pyridine-2,6-dicarboxamide (L5) towards dihydrogen phosphate was found in both DMSO and DMSO–water (95:5) solvent mixture. The structure of N,N′-bis(2-hydroxy-5-nitrophenyl)pyridine-2,6-dicarboxamide (L4) was confirmed by X-ray crystallography. 相似文献
996.
997.
998.
999.
Stephen E. Fosdick Kyle N. Knust Karen Scida Prof. Richard M. Crooks 《Angewandte Chemie (International ed. in English)》2013,52(40):10438-10456
A bipolar electrode (BPE) is an electrically conductive material that promotes electrochemical reactions at its extremities (poles) even in the absence of a direct ohmic contact. More specifically, when sufficient voltage is applied to an electrolyte solution in which a BPE is immersed, the potential difference between the BPE and the solution drives oxidation and reduction reactions. Because no direct electrical connection is required to activate redox reactions, large arrays of electrodes can be controlled with just a single DC power supply or even a battery. The wireless aspect of BPEs also makes it possible to electrosynthesize and screen novel materials for a wide variety of applications. Finally, bipolar electrochemistry enables mobile electrodes, dubbed microswimmers, that are able to move freely in solution. 相似文献
1000.
Alexandre Zagdoun Dr. Aaron J. Rossini Dr. Matthew P. Conley Wolfram R. Grüning Martin Schwarzwälder Dr. Moreno Lelli Dr. W. Trent Franks Prof. Dr. Hartmut Oschkinat Prof. Dr. Christophe Copéret Prof. Dr. Lyndon Emsley Dr. Anne Lesage 《Angewandte Chemie (International ed. in English)》2013,52(4):1222-1225