[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.
Journal of inclusion phenomena and macrocyclic chemistry 04/2015; 81(3-4). DOI:10.1007/s10847-015-0484-0 · 1.43 Impact Factor
[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+.
[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.
Journal of inclusion phenomena and macrocyclic chemistry 08/2013; 79(3-4):343-348. DOI:10.1007/s10847-013-0357-3 · 1.43 Impact Factor
[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.