[Show abstract][Hide abstract] ABSTRACT: New crownophanes containing 2,7-dioxyfluorenone and 4,4′-azobiphenoxy moieties linked by di-, tri-, tetra-, and pentaethylene glycol residues were synthesized. Just in case of obtaining largest crownophane with pentaethyleneglycol linkers, the dimeric cyclization product was also isolated in low yield. Obtained crownophanes, according to 1H NMR spectral data exist in conformations with closed intramolecular cavity in solution. Photoinduced E–Z isomerization of crownophane containing triethylene glycol linkers were investigated. The azobenzene fragment inclusion into crownophane reduces the photoisomerization rate compared to model 4,4′-dimethoxyazobenzene. In all the obtained crownophanes according to NMR, UV–Vis and X-ray data 4,4′-azobiphenoxy fragment is in E-configuration in solution as well as in the solid state. Crystal packing of all crownophanes has distinct feature—stacking arrangement of fluorenone moieties probably due to electrostatic dipole–dipole interactions. The formation of pseudorotaxane-type host–guest complexes of these crownophanes with paraquat dication was detected by FABMS and 1H NMR spectroscopy. UV–Vis spectra show no significant changes upon complex formation.
Full-text · Article · Apr 2015 · Journal of inclusion phenomena and macrocyclic chemistry
[Show abstract][Hide abstract] ABSTRACT: A new facile synthetic route to benzils containing fragments of 12-crown-4, 15-crown-5, and 18-crown-6 by oxidation of corresponding stilbenes was developed. The first representative of a new family of fluorescent sensors was obtained by reaction of bis(15-crown-5)benzil with o-phenylenediamine. The latter exhibits great fluorescence enhancement upon association with K+ and Rb+ compared to Na+ and Cs+.
No preview · Article · Feb 2015 · Synthetic Communications
[Show abstract][Hide abstract] ABSTRACT: The interaction of new molecular clips containing diphenylglycoluril and benzocrown ethers moieties with alkali metals ions was studied. Stability constants were determined by spectrophotometric titrations with chloride salts in methanol. Complex stability and cation binding selectivity were shown to be dependent on the size of the crown ether moiety. The "sandwich-type" 1:1 (clip to cation) complexes and the "classical" 1:2 complexes were found. Their ratio varies depending on the molecular clips nature and on the cation type. It was found an unexpected selectivity of the molecular clip with benzo-15-crown-5 moieties toward K+ and Rb+ cations. The molecular structure of the clip complex with benzo-15-crown-5 fragments and sodium picrate was determined by X-ray crystallography. The crystal structure and solution-state structure were proven to be similar.
Preview · Article · Aug 2013 · Journal of inclusion phenomena and macrocyclic chemistry
[Show abstract][Hide abstract] ABSTRACT: Novel glycoluril-bridged bis(benzocrown ethers) have been synthesized. The appropriate bis(benzo-18-crown-6) was formed in a good yield by reaction of bis(cyclomethoxymethylene)diphenylglycoluril with benzo-18-crown-6 in polyphosphoric acid. The reaction with dibenzo-18-crown-6 under the same conditions leads only to polymeric products. The corresponding bis(dibenzo-18-crown-6) was prepared in moderate yield by the reaction of tetrakis(chloromethyl)diphenylglycoluril with the dibenzo-18-crown-6 in the presence of SnCl4 in dichloroethane. Extraction of alkali metal picrates from water into chloroform by bis(benzocrown ethers) was examined to estimate their complexation ability. The extraction capability of bis(benzocrown ethers) is much greater than of the corresponding monomeric crown ethers.
No preview · Article · Jan 2010 · Macroheterocycles
[Show abstract][Hide abstract] ABSTRACT: New fluorenocrownophanes containing fragments of 2,7-dioxyfluorene and hydroquinone or 4,4'-dioxybiphenyl linked by tri-and tetraethylene glycol residues were synthesized by palladium-catalyzed hydrogenation of the appropriate fluorenonocrownophanes. The formation of the pseudorotaxane type inclusion complexes of these ligands with paraquat was established by means of FAB mass spectrometry, 1H NMR and electronic spectroscopy. The crownophanes with larger ring formed the more stable complexes.
No preview · Article · Jan 2009 · Macroheterocycles
[Show abstract][Hide abstract] ABSTRACT: Two representatives of a novel class of crownophanes containing fragments of fluorenone and stilbene bridged by units of diethylene glycol and triethylene glycol, respectively, have been synthesized. The crystal structure and complexation behavior of these crownophanes were studied. They form much stronger complexes with dibenzylammonium hexafluorophosphate (logKa value in CH3CN is equal to 3.92±0.06 and 4.40±0.05, respectively) than benzocrown ethers. This makes them an attractive alternative for benzocrown ethers as components in supramolecular synthesis.
No preview · Article · Mar 2004 · Tetrahedron Letters
[Show abstract][Hide abstract] ABSTRACT: Convenient and effective procedures for the synthesis of benzo-12-crown-4, benzo-15-crown-5, benzo-18-crown-6, benzo-21-crown-7 and benzo-24-crown-8 under phase-transfer catalysis conditions have been developed.