Cycloaddition of fluorinated oxazoles

Cycloaddition reactions of polyfluorinated 1,3-oxazoles with cyclic and acyclic alkenes were studied. The results of these reactions were interpreted using quantum chemical calculations. An unusual product, viz., fluorine-containing acylpyrrole, was studied by X-ray diffraction. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1630–1635, July, 2005.     

Synthesis of Naturally Occurring Pyrazine and Imidazole Alkaloids from Botryllus LeachiRID=”a”ID=”a”?Dedicated to Prof. G. M?rkl on the occasion of his 75th birthday

The synthesis of the naturally occurring and biologically active alkaloids 1 and 2, first isolated from the red ascidian Botryllus leachi by Duran et al. [1], is described and the structure proposed for Botryllazine B (1) is confirmed. The analytical data for 2-(p-hydroxybenzoyl)-4-(p-hydroxyphenyl)imidazole (2) are discussed and compared with the literature. With special emphasis of ¹H NMR data the tautomerism of aroylimidazolemethanones is described.     

Reaction of cyclopentadienyllutetium anthracenide with azobenzene. Synthesis and molecular and crystal structure of the binuclear complex [C5H5(THF)Lu(μ−η2:η2−PhN—NPh)]2(THF)2 and its dynamic behavior in solution

The reaction of the cyclopentadienyllutetium anthracenide, C₅H₅Lu(C₁₄H₁₀)²⁻(THF)₂ (1), with azobenzene yielded the [C₅H₅(THF)Lu(μ−η²:η²−PhN—NPh)]₂(THF)₂ (2) binuclear complex. The structure of the reaction product was established by X-ray structural analysis. The dynamic behavior of complex2 in a THF-d₈ solution was studied by¹H NMR spectroscopy in the temperature range of 265–330 K. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1667–1671, September, 1997.     

Fano resonances in semiconductor superlattices

We use semiconductor superlattices as a model system for the investigation of Fano resonances. In absorption the excitonic transitions of the Wannier–Stark ladder show the typical asymmetric line shape due to coupling to the continuum of lower-lying transitions. The unique feature of these Fano resonances is that they allow to continuously tune the key parameter – the coupling strength Γ between the discrete state and the degenerate continuum – by varying the bias voltage. Using this feature, we directly show that the Fano coupling leads to a fast polarization decay. We also investigate the dependence of the Fano parameters on the structure of the superlattice and compare with an extensive theoretical model of the resonances.     

The Electron-Hole plasma in CdS between 5 K and room temperature

We investigate and analyze the time-integrated nonlinear optical behaviour of an electronhole plasma in CdS as a function of the temperature and the exciting intensity. The competition between the temperature dependences of the absorption tail and of the manyparticle effects leads with increasing temperature around 160 K to a turn-over from a red- to a blue-shift of the absorption edge under excitation. The frequency dependence of the absorption for high plasma concentrations is in good agreement with theoretical calculations.     

ACID SODIUM SALT OF 1H-PYRAZOLE-3,4,5- TRICARBOXYLIC ACID: SYNTHESIS,CRYSTAL STRUCTURE AND FEATURES OF INTRAMOLECULAR BONDS

Journal of Structural Chemistry - The oxidation reaction of 3,3′,5,5′-tetramethyl-1H,1′H-4,4′-bipyrazole in the HNO3–Fe3+ system unexpectedly resulted in the formation...     

Synthesis of unsymmetrical 2-(2-vinyl-4H-chromen-4-ylidene)malononitrile dyes via Knoevenagel reaction

A series of new chromophores based on 4-(dicyanomethylene)-2-vinyl 4H-chromenes was synthesized and their physical properties (UV–Vis, NMR, mass spectrometry) were studied. The chromophores show moderate or good solubility in organic solvents. Solvatochromism was investigated for compounds in solvents of low (1.4-dioxane, chlorobenzene, methylene chloride) and high polarity (acetone, acetonitrile). The calculations of the first hyperpolarizability (β) was performed using M052X/6-31+G(d) approximation. Chromophore’s molecules are characterized by high calculated values of the first hyperpolarizability (β) that is only 15% lower than that of FTC analogs.