Kinetics and Optical Properties of the Strongly Driven Gas Medium of Interacting Atoms

This paper investigates stimulated emission and absorption near resonance for a driven system of interacting two-level atoms. Microscopic kinetic equations for the density matrix elements of N-atom states including atomic motion are built, taking into account atom-field and atom-atom interactions. Analytical solutions are given for the resulting macroscopic equations in different limits, for a system composed of a strong coherent “pump” field and a weak counter-propagating “probe” field. It was shown that the existence of a dipole-dipole (long-range) interaction between atoms separated by distance less than the pump wave-length can cause the formation of periodic polarization and population structures (gratings in time and space) in the pumped medium without a probe field. The magnitude of pump induced population grating can have a strong dependence on the relation between the pump field detuning and the polarization decay rate. The “interaction” between pump and probe induced polarization/population gratings through a dipole-dipole interaction mechanism causes the absorption line shape asymmetry. Under certain conditions, this asymmetry is revealed in increasing probe gain for the “red”-shifted (relative to pump) probe and suppressing the gain for the “blue”-shifted probe field when pump is “red”-shifted relative to the ensemble averaged resonant frequency. The theoretical results are consistent with experimental data for the probe gain or absorption as the function of frequency and the dependance of the gain on atomic density for sodium vapor when the pump laser is tuned near the D ₂ line. Here the dependance of gain on particle density was explained in the terms of the long-range interaction between the atoms.     

S,N‐Chelated organotin(IV) compounds containing 6‐phenylpyridazine‐3‐thiolate ligand—structural,antibacterial and antifungal study

A series of tri‐ and diorganotin(IV) compounds containing potentially chelating S,N‐ligand(s) (L^SN, where L^SN is 6‐phenylpyridazine‐3‐thiolate) were prepared and structurally characterized by multinuclear NMR spectroscopy. X‐ray diffraction techniques were used for determination of the structure of compounds containing one [(L^SN)Ph₂SnCl], two [(n‐Bu)₂Sn(L^SN)₂] and the combination of two L^SN and one L^CN [(L^CN)(n‐Bu)Sn(L^SN)₂] (where L^CN is {2‐[(CH₃)₂NCH₂]C₆H₄}‐) ligands. The coordination number of the tin atom varies from five to seven and is dependent on the number of chelating ligands present. The formation of the five‐membered azastanna heterocycle is favored over the formation of four‐membered azastannathia heterocycle in compounds containing both types of ligands. The di‐n‐butyl‐substituted compounds are the most efficient ones in inhibition of growth of yeasts, molds and G⁺ bacteria strains. Copyright © 2011 John Wiley & Sons, Ltd.     

Reaction of methyl 3-[(dimethylamino)methylidene]-6-fluoro-4-oxo −3,4-dihydrochroman-2-carboxylate with primary and secondary amines*

A method was developed for substitution of the dimethylamino group by bioisosteric fragments by the action of various primary and secondary amines on methyl 3-[(dimethylamino)methylidene]-6-fluoro-4-oxo-3,4-dihydrochroman-2-carboxylate.     

Merocyanines based on 1,3‐indanedione: electronic structure and solvatochromism

A series of merocyanines derived from 1,3‐indanedione and heterocycles of various electron‐donating properties was studied in detail. Their solvatochromic properties were explored in a wide range of solvent polarities to reveal the dependences of their chromacity and electronic structure on the key structural parameters – the properties of a donor heterocycle and the polymethine chain length. Also the dyes were studied by NMR spectroscopy and by quantum chemical calculations, both with the semiempirical AM1 and the non‐empirical density functional theory/B3LYP method. The solvatochromic properties of the explored dyes are rather close to those of merocyanines derived from malononitrile as acceptor group. Appreciable distinctions were observed only in protic ethanol; obviously, they are connected with the formation of solvent–solute H‐bonds in the case of 1,3‐indanedione derivatives. The electron‐acceptor properties of 1,3‐indanedione were found to be somewhat stronger in comparison with those of malononitrile even in aprotic solvents, contrary to the known literature data. Analysis of the merocyanines' molecular orbitals and simulation of their electronic spectra were carried out both in vacuum and in the solvent matrix, and the absorption electronic transitions were analyzed. Static nonlinear optical properties were calculated for both the new merocyanines and the corresponding cationic and anionic cyanine dyes. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis and properties of new functionalized 2-benzazepines

2-Aryl-4-hydroxy-2,3-dihydro-1H-2-benzazepine-5-carbonitriles were obtained by the cyclization of methyl esters of N-aryl-N-(2-cyanomethylbenzyl)aminoacetic acids by the action of sodium methylate. The keto—enol tautomerism of these compounds and their reactions with hydrazines were studied. Previous communication, see ref. [1]. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1026–1031, July, 2006.     

Gaps in the spectrum of the Neumann Laplacian generated by a system of periodically distributed traps

The article deals with a convergence of the spectrum of the Neumann Laplacian in a periodic unbounded domain Ω^ϵ depending on a small parameter ϵ > 0. The domain has the form , where S^ϵ is an -periodic family of trap-like screens. We prove that, for an arbitrarily large L, the spectrum has precisely one gap in [0,L] when ϵ is small enough; moreover, when ϵ → 0, this gap converges to some interval whose edges can be controlled by a suitable choice of geometry of the screens. An application to the theory of 2D photonic crystals is discussed. Copyright © 2014 John Wiley & Sons, Ltd.     

Catalysis by Lithium Perchlorate Enables Double-Conjugate Addition of Electron-Deficient Maleimides to 2-Aminopyridines and 2-Aminothiazoles

Lithium perchlorate has been found to catalyze the conjugate addition of maleimides with 2-aminopyridines and 2-aminothiazoles. The reaction proceeds under mild conditions leading to the corresponding double adducts in good yields. A plausible mechanism of this reaction has been proposed.

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