Crown‐ether and azobenzene‐containing liquid crystalline polymers: An influence of macromolecular architecture on optical properties and photo‐orientation processes

A series of novel crown ether‐containing photochromic comb‐shaped liquid crystalline polyacrylates with different macromolecular structure of side groups were synthesized and investigated. Phase behavior, optical and photo‐optical properties of thin spin‐coated films of these polymers were studied. A special attention was paid to a comparative study of the photo‐orientation phenomena occurring in the polymer films under a polarized light action. It was shown that complex formation with the potassium ions results in the decrease in degree of the photoinduced order that can be used for the creation of new materials for sensor devices. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

1-Bromo-2-trifluoroacetylcyclobutenes as novel building blocks for the construction of trifluoromethyl substituted heterocycles. Part 2: Synthesis of trifluoromethyl substituted thiophenes, condensed with cyclobutene moieties

This paper describes a novel synthetic approach to 2-cyano-3-trifluoromethylthiophenes fused with cyclobutene rings with variable spiro conjunctions. The reaction of substituted 1-bromo-2-trifluoroacetylcyclobutenes with mercaptoacetonitrile results in the substitution of bromine with S-center to afford the corresponding nitriles in high yields, which form the target thiophenes by subsequent treatment of lithium 2,2,6,6-tetramethylpiperidide and acetic anhydride.     

Acylative kinetic resolution of racemic amines using N-phthaloyl-(S)-amino acyl chlorides

A comparative study of the kinetic resolution of racemic 2-methyl-1,2,3,4-tetrahydroquinoline and 2,3-dihydro-3-methyl-4H-1,4-benzoxazine using N-phthaloyl-(S)-amino acyl chlorides as chiral acylating agents is described. Temperature and solvent effects on the stereochemical features have been examined. It has been found that N-phthaloyl-(S)-phenylalanyl and N-phthaloyl-(S)-2-phenylglycyl chlorides bearing aromatic substituents close to the stereogenic centre are more stereoselective acylating agents than N-phthaloyl-(S)-alanyl chloride. For the preparative kinetic resolution of racemic amines N-phthaloyl-(S)-phenylalanyl chloride proved to be the most appropriate chiral acylating agent.     

Enhancement of electromagnetically induced transparency in room temperature alkali metal vapor

Electromagnetically induced transparency (EIT) has led to several quantum optics effects such as lasing without inversion or squeezed light generation. More recently quantum memories based on EIT have been experimentally implemented in different systems such as alkali metal atoms. In this system the excited state of the optical transition splits into several sublevels due to the hyperfine interaction. However, most of the theoretical models used to describe the experimental results are based on a Λ-system with only one excited state. In this article, we present a theoretical model for the Λ-type interaction of two light, fields and an atomic system with multiple excited state. In particular we show that if the control and probe fields are orthogonally circularly polarized the EIT effect in an alkali-metal vapor can almost disappears. We also identify the reasons of this reduction and propose a method to recover the transparency via velocity selective optical pumping.     

A new synthesis of 4′-trifluoromethyl-2,2′:6′,2″-terpyridine

1. Download : Download high-res image (44KB)
2. Download : Download full-size image

     

New 5-arylamino-4-(5-nitrofuran-2-yl)pyrimidines as promising antibacterial agents

A facile synthetic approach to 5-arylamino-4-(5-nitrofuran- 2-yl)pyrimidines by the Buchwald–Hartwig cross-coupling with various anilines has been developed. All synthesized compounds demonstrated a significant level of in vitro antibacterial activity against Neisseria gonorrhoeae, Streptococcus pyogene and Staphylococcus aureus, including their drug-resistant strains, which is much higher than that of the commercial drug Spectinomycin.     

A molecular dynamics simulation of the chemisorption of the optical isomers of propranolol on the graphitic electrode modified with melamine,cyanuric, and isocyanuric acids

To demonstrate the nature of the interaction of optical isomers of propranolol with the surface of the graphitic electrode modified with melamine, uracil, cyanuric, and isocyanuric acids, we have performed molecular dynamics simulations of the four‐component systems with variable modifier's molecules. We have considered the possible formation of complexes between the propranolol and modifier's molecules, covering the electrode approximated as the graphene surface. Our simulations demonstrate that the l ‐isomer in aqueous solutions is bonded to the electrode surface stronger than its d ‐counterpart; hence, the difference in analytical signals arises. Different strengths of bonding of the propranolol enantiomers to the surface modifiers are caused by the different intramolecular interactions taking place in the molecules of d ‐ and l ‐isomers. Thus, we have computationally shown that the modification of the graphite surface with melamine, uracil, cyanuric, and isocyanuric acids allows for increasing the sensitivity of the electrode toward the propranolol enantiomers and using the modified graphitic electrodes for the detection of its d ‐ and l ‐forms.     

Updating the Chemiluminescence Oxygen‐Aftereffect Method for Determining the Rate Constant of the Peroxy‐Radical Self‐Reaction: Oxidation of Cyclohexene

Updating the facile chemiluminescence oxygen‐aftereffect method, most suitable for determining the rate constant (k_t) of the peroxy‐radical self‐reaction (main chemiluminescence channel), pertained to considering the sensitivity of such a method toward a disturbing influence of the peroxy radicals of the initiator of the chain oxidation process. Such a disturbance may derive from the side chemiluminescent reaction, which involves peroxy radicals of both hydrocarbon and initiator. To examine the applicability and limitations of the chemiluminescence method under present scrutiny, cyclohexene was used as the model oxidizable hydrocarbon substrate. Computer simulations of the reaction and chemiluminescence kinetics have demonstrated the validity of the considered methodology at the value of the rate constant of the propagation of the overall chain process by peroxy radicals of the initiator higher than 1 m ^?1 s^?1. Despite that the chemiluminescence time profile and the stationary level of the total chemiluminescence intensity depend on the kinetics of the side chemiluminescence channel and on the ratio of the excited‐state generation yields in the mentioned reaction channel and in the main chemiluminescence process, the value of k_t assessed by the oxygen‐aftereffect method has been found independent of variation of these characteristics.     

Electrostatic fluctuations in nonequilibrium plasmas with particle collisions

We present a method for calculation of plasma fluctuations in a nonequilibrium plasma with stable particle distribution functions. The method takes into account particle collisions and collective particle interactions which affect the collision process. In contrast to the known approaches, our method makes no reference to a specific form of the collision integrals and distribution functions. Using the developed method, we calculate the high-frequency spectrum of the electric field fluctuations in a collisional plasma with arbitrary particle distribution functions.     

Quark–Diquark Structure and Masses of Doubly Charmed Baryons

finite size of a doubly heavy diquark yields a positive correction to baryon masses calculated in the local-diquark approximation. Upon evaluating this correction for the ground states of doubly charmed baryons, it became possible to obtain new predictions of importance for current searches of these baryons in LHCb experiments: \(m[\Xi _{cc}^{1/{2^{ + + }}}] \approx m[\Xi _{cc}^{1/{2^{ + + }}}]\) = 3615 ± 55 MeV and \(m[\Xi _{cc}^{3/{2^{ + + }}}] \approx m[\Xi _{cc}^{3/{2^{ + + }}}]\) 3747 ± 55 MeV