B. A. Bushuk

Europium, terbium, and ytterbium 3-(3′-triethoxysilylpropyl)pentane-2,4-dionates. Synthesis and the formation of luminescent sol-gel films

Abstract3-(3′-Triethoxysilylpropyl)pentane-2,4-dione, (EtO)3SiCH2CH2CH2C[-C(O)CH3]2 (I), was synthesized from 3-allylpentane-2,4-dione, CH2 = CH-CH2-C[-C(O)CH3]2, and triethoxysilane, (EtO)3SiH, in the presence of Speier’s catalyst. The silylation occurred mainly at the terminal C atom of the allyl group. The corresponding europium(III), terbium(III), and ytterbium(III) β-diketonates were synthesized from compound I and appropriate metal isopropoxides and used to obtain transparent sol-gel films containing Eu3+, Tb3+, and Yb3+ cations. The film formation was studied by IR spectroscopy. It was found that moisture causes not only the hydrolysis and condensation of triethoxysilyl groups but also the hydration of the cation of the rare-earth metal. When the terbium complex was excited at the wavelength of one of the two peaks (230 and 308 nm) in the excitation spectrum, the cation fluoresced intensely at 491, 547, 585, and 623 nm due to the transitions 5D4 → 7F6, 5D4 → 7F5, 5D4 → 7F4, and 5D4 → 7F3, respectively. All these bands were narrow, the band at 547 nm being most intense. No emission from the organosilicon matrix at 440 nm was observed. The emission spectra of Eu3+-containing films showed, along with the bands at 593, 618, 667, and 700 nm due to the emission from the cation (5D0 → 7F1, 5D0 → 7F2, 5D0 → 7F3, and 5D0 → 7F4 transitions, respectively), an intense band at 491 nm due to the emission from the matrix.

Some features of formation of an inclusion complex ofβ-cyclodextrin with rhodamine 6G

Results of an investigation of the influence of the process of complex formation on the spectral and luminescence characteristics of aqueous solutions of inclusion complexes of β-cyclodextrin with rhodamine 6G are reported. It is shown that complex formation of rhodamine 6G proceeds mainly in the outer sphere of β-cyclodextrin.

Self-association of the molecules of alcohols in a condensed phase at different temperatures

Using a probability approach, we investigate the process of self-association of the molecules of alcohols in a condensed phase. We obtained data on the nature of association, in particular, on the association degree distribution of molecules and concerning the dependence of the form of this distribution on temperature.

Novel tetraaryltetracyanoporphyrazine vanadyl complexes with enhanced electron-withdrawing properties

Porphyrazines are the closest chemical analogues of porphyrins in which the meso carbon atoms are replaced by nitrogen atoms, and they exhibit all of the most typical and practically valuable physicochemical properties of macroheterocyclic compounds. For example, these are exceptionally high light absorption coefficients, which are often combined with lumines cence properties over a broad range of wavelengths including the spectral window of relative transparency of the biological tissue. Among specific features of porphyrazines, one can consider their enhanced sta bility against oxidation as compared with porphyrins. Therefore, porphyrazines with electron withdrawing properties can be used as oxidation catalysts, as well as for the design of photovoltaic devices [5, 6]. Note that one of the causes for the insufficiently wide practical application of porphyrazines as compared with their structural analogs, porphyrins and phthalocyanines, is the absence of convenient methods for synthesis. Pre viously, we proposed a new synthetic approach to the macroheterocyclic structure by the reaction of sand wich vanadium and ytterbium complexes with tetracy anoethylene and tricyanovinylbenzene; octacyanopo rphyrazine vanadyl and ytterbium complexes were thus prepared for the first time [7, 8]. The template assembly of the porphyrazine structure from tetracya noethylene molecules as structural units was per formed in high yields under mild conditions on vanadyl and ytterbium cations.

Transparent luminescent sol-gel films containing europium(III) and terbium(III) cations

The I : II product ratio calculated from the GLC and 1 H NMR data is 84 : 16. The IR spectrum of compound I exhibits absorption bands for stretching (2974, 2933, 2888 cm –1 ) and bending (1441, 1391, 1355, 1295 cm –1 ) C–H vibrations. The intense doublet at 1613 and 1583 cm –1 and the band at 1517 cm –1 refer to imino enol (HOC=CH–C=N) vibrations, while the triethoxysilyl group is responsible for a series of strong absorption bands at 1168, 1097, 961, Transparent Luminescent Sol–Gel Films Containing Europium(III) and Terbium(III) Cations

Kinetics of the formation of a hydrogen bond between photoexcited dye molecules and a solvent at different temperatures

Using probability-type velocity equations as a base, the kinetics of the formation of molecular complexes of an excited molecule with alcohol associates is investigated. Particular emphasis is placed on the temperature dependence of the kinetics of complexation. Theoretical deductions are compared with the results of an experiment.