L. G. Klapshina

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.

Degenerate four-wave mixing measurements of the ?(3) non-linear optical properties of poly(arylene-ethynylenesilylene)s

The third-order optical non-linearity in solution of a series of poly(arylene-ethynylenesilylene)s containing a variety of backbone arylene groups and substituents at silicon has been studied by using the degenerate four-wave mixing technique at 1064 nm with a 6 ns pulse duration. Thermal grating effects may be neglected under the experimental set-ups employed. The results obtained are greater by more than two orders of magnitude than those previously measured for some of the polymers using the Z-scan technique at the same wavelength. The electronic contribution to the fast non-linearity is greater than the nuclear (orientational) contribution by a factor of at least 4. The presence of a single 8-(dimethylamino)naphthyl ligand at silicon affording pentacoordination has a beneficial effect on the X (3) properties. The high X (3) properties of the polymers (e.g. [Re(X (3) )]=9.5 × 10 -12 esu for [-C≡C-SiPh 2 -C≡C - (1,4-C 6 H 4 )-] n in chloroform [5 g] l -1 ]) confirm the presence of extensive through-Si conjugation along the backbone.

Some features of the anionic copolymerization of 1,3,5-triphenyl-1,3,5-trimethylcylotrisiloxane and octamethylcyclotetrasiloxane in the presence of a crown ether☆

Abstract The anionic copolymerization of 1,3,5-triphenyl-1,3,5-trimethylcyclotrisiloxane and octamethylcyclotetrasiloxane in the presence of 15-crown-5 has been investigated by the GPC and PMR methods. Data were obtained on the dynamics of change in the MWD parameters and in the copolymer composition and microstructure during copolymerization with and without addition of the crown-ether, keeping the initial ratio of siloxane monomers constant. It was found that at a definite stage in the reaction a far-reaching rearrangement of the siloxane macrochain takes place. The longer the retention of blocks of phenylmethylsiloxy units in the copolymer is maintained, the higher is the probability of gelation due to a side reaction of chain transfer to polymer as a result of elimination of the phenyl group from the Si atom.

New porphyrazine macrocycles with high viscosity-sensitive fluorescence parameters

New tetraaryltetracyanoporphyrazines have been obtained in the form of metal complexes and free bases via template assembly of a variety of aryltricyanoethylenes as structural units of the macrocycle, and photophysical properties of the products have been studied. The unique high sensitivity of the fluorescent properties to viscosity has been demonstrated. This property opens the possibility of application of the said compounds as sensors of local viscosity. The prepared macrocycles exhibit significant photocytotoxicity, and can be thus used as sensitizers of photodynamic therapy.

Synthesis of C-functionalized acetylacetone and its europium complex. Preparation and study of luminescence of europium-containing sol-gel films

New fuctionalized ligand 3-(3′-triethoxysilylpropylaminocarbonyl)pent-2-on-3-en-4-ol (EtO)3SiCH2·CH2CH2NHC(O)-C[C(O)CH3][=C(OH)CH3] (I) containing ketoenol and triethoxysilyl groups is synthesized from 3-triethoxysilylpropyl isocyanate (EtO)3SiCH2CH2CH2N=C=O and acetylacetone. The reaction is accompanied by the formation of 2-(3′-triethoxysilylpropylaminocarboxy)-pent-2-en-4-one (EtO)3SiCH2CH2·CH2NHC(O)-OC(CH3)=CH-C(O)CH3 (II), the product of addition of acetylacetone enol form to isocyanate group. The ratio of amide I and urethane II forms is 7:3. Europium(III) tris[3-(3′-triethoxysilylpropylaminocarbonyl) pent-2-on-3-en-4-olate] is prepared from I and Eu(i-OPr)3. An alternative pathway consists in the reaction of europium tris(acetylacetonate) with 3-triethoxysilylpropyl isocyanate. Conditions of formation of transparent europium-containing sol-gel films were developed. Thermal stability and photoluminescence of the films were investigated.

High-sensitivity methods of determining the cubic nonlinear-optical susceptibility of organometallic polymers

Using new, high-sensitivity methods to determine the cubic optical susceptibility in the femtosecond range of laser pulse widths, the presence of large coefficients of cubic nonlinearity of electronic type is revealed in new organometallic polymers. Measurement methods based on two-wave mixing of laser pulses in the sample are compared with respect to sensitivity and simplicity of the experimental implementation.

New promising porphyrazine-based agents for optical theranostics of cancer

New porphyrazine bases containing peripheral benzyloxyphenyl groups have been synthesized by the template method. The procedure includes condensation of aromatic aldehydes with malononitrile, transformation of arylmethylidenemalononitriles to arylethenetricarbonitriles, template assembly of porphyrazine macrocycle on bis(indenyl)ytterbium(II) complex, and removal of the central metal ion. Luminescence properties of the synthesized porphyrazines and their dependence on the viscosity of the medium were studied, and the light and dark toxicities of the porphyrazines have been estimated. The obtained results suggest the possibility of using these porphyrazines as optical theranostic agents of new generation.

Efficient Luminescent Solar Concentrators Based on Defectless Organic Glasses Containing Novel Ytterbium Cyanoporphyrazine Complex

A photocurable polymeric luminescent composition doped by a new ytterbium tetra(4-fluorophenyl)tetracyanoporphyrazine complex capable of efficiently absorbing and reemitting light in a wide spectral range is developed. Defect-free organic glasses obtained with the use of this composition were applied as waveguides in the creation of laboratory models of a luminescent solar concentrator. Tests results of the created models showed the possibility of creating a stationary solar energy concentrator for photovoltaic cells (PVCs) which is at least as efficient as the best kinds of similar devices previously found worldwide.

The light-emitting and optical properties of high-optical-quality organic glasses doped with europium tris(benzoyltrifluoroacetonate)

Two types of transparent high-optical-quality organic glasses (rigid and flexible, 40 × 40 × 2.2 mm in size) containing 0.6–3.2 mass % europium tris(benzoyltrifluoroacetonate) (0.1–0.6 mass % of Eu) were obtained from photopolymerizing compositions using the technique of layer-by-layer photopolymerization. The glasses are characterized by a high level of light transmission (nearly 90%) within the range of 500–1100 nm. The photoluminescence (PL) spectra of samples which are not Eu-doped exhibit weak spectral bands in the region 350–600 nm. Doped glasses show intensive europium(III) cation PL: 538 nm (5D1 → 7F1), 580 nm (5D0 → 7F0), 593 nm (5D0 → 7F1), 614 nm (5D0 → 7F2), 653 nm (5D0 → 7F3), and 703 nm (5D0 → 7F4); the transition (5D0 → 7F2) demonstrates the strongest emission. Glass properties were studied using atomic force microscopy (AFM), differential scanning calorimetry (DSC), and X-ray spectroscopy.

Reaction of Perylene-3,4,9,10-tetracarboxylic Acid Dianhydride with 3-Aminopropyltriethoxysilane and Hexamethyldisilazane

The reaction of perylene-3,4,9,10-tetracarboxylic acid dianhydride with 3-aminopropyltriethoxysilane and hexamethyldisilazane was investigated. A possibility of obtaining a new dye resistant to UV light and heating (up to 300°C), consisting of structural fragments of perylene-3,4,9,10-tetracarboxydiimede, diethoxysiloxane, and 3-aminopropylethoxysiloxane was demonstrated. A compound obtained in 43% yield by heating (7 h, 180–200°C) perylene-3,4,9,10-tetracarboxylic acid dianhydride with excess 3-aminopropyltriethoxysilane in the presence of catalytic amounts of zinc acetate is an oligomer appropriate for the solgel process, displays strong luminescence in the red spectral region (540–620 nm), and has good film-forming properties. The participation of hexamethyldisilazane consists in binding water molecules formed in the reaction of perylene-3,4,9,10-tetracarboxylic acid dianhydride with 3-aminopropyltriethoxysilane and in the formation of trimethylsilanol which replaces a part of the EtO groups at the silicon atoms by a more bulky Me3SiO groups, causing significant increase in the solubility of the dye in organic solvents and silicon sol-gel monomers. The hydrolysis of silicon-containing dye and subsequent dehydration of the resulting gel lead to the formation of insoluble xerogel.