Synthesis and crystal structure of allyl 7-(diethylamino)-2-oxo-2H-chromene-3-carboxylate

The title compound, C17H19NO4, was synthesized by the reaction of 7-(diethylamino)-2-oxo-2H-chromene-3-carboxylic acid with allyl bromide and purified by flash column chromatography on silica gel. Crystals suitable for single-crystal X-ray diffraction were obtained by recrystallization from acetone. The aromatic core of the molecule is not planar with the diethylamino group and with the carboxyl group that are rotated out of the 2-oxo-2H-chromene plane by 6.7 (2)° and 11.4 (2)°. The NC2 unit of the diethylamino group is planar with an angle sum close to 360°. Intermolecular Car—H...Ocarbonyl interactions lead to the formation of chains parallel to the b axis. X-ray powder diffraction analysis proves that the title compound was obtained as a pure phase.

4,6-Di-tert-butyl-2-({[4-(diethylamino)phenyl]imino}methyl)phenol

The title compound, C25H36N2O, adopts anEconformation about the C=N bond. The dihedral angle between the aromatic rings is 35.6 (6)°. The molecular structure is stabilized by an O—H...N hydrogen bond, which forms anS(6) loop, and weak C—H...O contacts. Weak intermolecular C—H...π interactions are observed in the crystal packing. The diethylamino group has rotational disorder with site occupancies of 0.85 (2) and 0.15 (2) for the major and minor components, respectively. The structure was refined as a three-component twin.

4′-Cyanobiphenyl-4-yl 7-diethylamino-2-oxo-2H-chromene-3-carboxylate

In the title compound, C27H22N2O4, the dihedral angles between the central benzene ring and the cyanobenzene ring and the 2H-coumarin ring system (r.m.s. deviation = 0.014 Å) are 22.95 (11) and 75.59 (8)°, respectively. Both terminal C atoms of the pendant diethylamino group lie to the same side of the coumarin ring system [deviations = 1.366 (2) and 1.266 (2) Å]. In the crystal, molecules are linked by C—H...O and C—H...N hydrogen bonds and a C—H...π interaction, generating a three-dimensional network.

Highly selective deethylation of rhodamine B: Adsorption and photooxidation pathways of the dye on theTiO2/SiO2composite photocatalyst

The photocatalytic degradation of Rhodamine B (RhB) withTiO2andTiO2/SiO2in the aqueous dispersion was investigated under both the visible light (λ>480 nm) and UV irradiation. The detailed photocatalytic oxidative process of RhB under these different conditions was revealed by measurement of the isoelectric points of the catalysts, UV-VIS spectra, HPLC and LC-MS. RhB adsorbs on the surface ofTiO2/SiO2particles by the positively-charged diethylamino group while, in the case of netTiO2, it adsorbs through the negatively-charged carboxyl group under the experimental conditions (pH∼4.3). In the RhB-TiO2/SiO2system, RhB firstly underwent a highly selective stepwise deethylation process before the destruction of the chromophore structure under visible light irradiation. The average yield of the every deethylation step was higher than 86%. It is confirmed that visible light-induced photocatalytic degradation of dye proceeds on the surface of catalysts rather than in the bulk solution and active oxygen species preferentially attack the molecular portion that connects directly to the surface of catalysts. This work provides a possibility for the modification of the surface characteristics ofTiO2to adsorb effectively the special colored organic molecules in selective mode for selective modification or deeply extent photooxidation.