133699-10-2Relevant articles and documents
2,2'-Bipyridine lariat calixcrowns: A new class of encapsulating ligands forming highly luminescent Eu3+ and Tb 3+ complexes
Fischer, Claudia,Sarti, Gianluca,Casnati, Alessandro,Carrettoni, Barbara,Manet, Ilse,Schuurman, Ruud,Guardigli, Massimo,Sabbatini, Nanda,Ungaro, Rocco
, p. 1026 - 1034 (2007/10/03)
A new class of calix[4]arene crown ethers with one or two bipyridines appended to the polyether ring (lariat calixcrowns) have been designed and synthesized; the luminescence properties of their Eu3+ and Tb3+ complexes have been studied in acetonitrile. In this solvent, long lifetimes for the metal emitting states and high metal-luminescence intensities obtained upon ligand excitation have been observed in both Eu3+ and Tb3+ complexes. The association constants in methanol have been determined for some of the complexes studied.
Synthesis of novel dansyl appended cyclodextrins. Self-inclusion and sensor properties
Nelissen, Hubertus F. M.,Venema, Fokke,Uittenbogaard, Rene M.,Feiters, Martinus C.,Nolte, Roeland J. M.
, p. 2045 - 2053 (2007/10/03)
The synthesis of three dansyl appended cyclodextrin derivatives, differing in the spacer length between cyclodextrin and the dansyl moiety, is described. In compound 4 the fluorophore is directly attached to the cyclodextrin. Compound 5 contains an ethyl spacer and compound 6 a triethylene glycol spacer. These compounds are designed to detect neutral organic guest molecules like cyclohexanol and adamantanecarboxylic acid in water by fluorescence spectroscopy. At neutral pH none of the compounds is sensitive towards guest molecules. For compound 4 this is due to the fact that the dansyl group is located outside the cyclodextrin cavity. For compunds 5 and 6 the low sensitivity is the result of a strong self-inclusion of the dansyl group. Lowering the pH results in protonation of the dimethylamino group of the dansyl moiety, which makes the self-inclusion less favourable leading to a strongly increased response towards guests. This phenomenon allows the sensors to be switched on and off by lowering or increasing the pH of the solution. Compound 6 is able to detect adamantanecarboxylic acid at 5 × 10-7 mol-1 dm3 concentration at pH 1.
Recognition by New Symmetrically Substituted Chiral Diphenyl- and Di-tert-butylpyridino-18-crown-6 and Asymmetrically Substituted Chiral Dimethylpyridino-18-crown-6 Ligands of the Enantiomers of Various Organic Ammonium Perchlorates
Huszthy, Peter,Bradshaw, Jerald S.,Zhu, Cheng Y.,Izatt, Reed M.,Lifson, Shneior
, p. 3330 - 3336 (2007/10/02)
Three new chiral pyridino-18-crown-6 ligands have been prepared.These ligands contain either two phenyl, two tert-butyl, or two methyl substituents on chiral macroring carbon atoms.The chiral di-tert-butyl-substituted diester crown analogue was also prepared.The starting chiral di-tert-butyl-substituted tetraethylene glycol needed to prepare the two di-tert-butyl-substituted crowns was obtained from chiral tert-butyl-1,2-ethanediol, which was resolved from its bis(hydrogen phthalate) brucine salt.A high degree of chiral recognition in CD2Cl2 of the enantiomers of ammonium perchlorate (NapEt) was shown by the diphenyl- and di-tert-butyl-substituted crowns as measured by differences in the free energy of avtivation (ΔGc*) values determined by temperature dependent 1H NMR spectroscopy.The diphenyl- and di-tert-butyl-substituted crowns also exhibited high chiral recognition for the enantiomers of NapEt and other chiral organic ammonium salts in methanol and methanol-chloroform mixtures as shown by a large difference in the log K values determined by a direct 1H NMR technique.
