Self-Sorting Supramolecular Polymerization: Helical and Lamellar Aggregates of Tetra-Bay-Acyloxy Perylene Bisimide

A new perylene bisimide (PBI), with a fluorescence quantum yield up to unity, self-assembles into two polymorphic supramolecular polymers. This PBI bears four solubilizing acyloxy substituents at the bay positions and is unsubstituted at the imide position, thereby allowing hydrogen-bond-directed self-assembly in nonpolar solvents. The formation of the polymorphs is controlled by the cooling rate of hot monomer solutions. They show distinctive absorption profiles and morphologies and can be isolated in different polymorphic liquid-crystalline states. The interchromophoric arrangement causing the spectral features was elucidated, revealing the formation of columnar and lamellar phases, which are formed by either homo- or heterochiral self-assembly, respectively, of the atropoenantiomeric PBIs. Kinetic studies reveal a narcissistic self-sorting process upon fast cooling, and that the transformation into the heterochiral (racemic) sheetlike self-assemblies proceeds by dissociation via the monomeric state.     

Stability,electronic, and optical properties of two-dimensional phosphoborane

The structure and properties of two-dimensional phosphoborane sheets were computationally investigated using Density Functional Theory calculations. The calculated phonon spectrum and band structure point to dynamic stability and allowed characterization of the predicted two-dimensional material as a direct-gap semiconductor with a band gap of ~1.5 eV. The calculation of the optical properties showed that the two-dimensional material has a relatively small absorptivity coefficient. The parameters of the mechanical properties characterize the two-dimensional phosphoborane as a relatively soft material, similar to the monolayer of MoS₂. Assessment of thermal stability by the method of molecular dynamics indicates sufficient stability of the predicted material, which makes it possible to observe it experimentally.     

Synthesis of Supported Heterogeneous Catalysts by Laser Ablation of Metallic Palladium in Supercritical Carbon Dioxide Medium

To obtain a supported heterogeneous catalyst, laser ablation of metallic palladium in supercritical carbon dioxide was performed in the presence of a carrier, microparticles of γ-alumina. The influence of the ablation process conditions—including supercritical fluid density, ablation, mixing time of the mixture, and laser wavelength—on the completeness and efficiency of the deposition of palladium particles on the surface of the carrier was studied. The obtained composites were investigated by scanning and transmission electron microscopy using energy dispersive spectroscopy. We found that palladium particles were nanosized and had a narrow size distribution (2–8 nm). The synthesized composites revealed high activity as catalysts in the liquid-phase hydrogenation of diphenylacetylene.     

The Interaction of Maleic Anhydride,N -Vinylpyrrolidone,and Their Mixture with 2,2-Diphenyl-1-picrylhydrazyl

Spectrophotometry studies have shown that N-vinylpyrrolidone and/or maleic anhydride interact with 2,2-diphenyl-1-picrylhydrazyl radical in a solution. Thermochemical parameters of the most probable reactions involving these compounds have been estimated by means of the PM6 and B3LYP/6-31+G(d) (gas phase) density functional theory methods. It has been suggested that the stable radical is attached to the monomer molecule, the resulting radical being involved in the chain growth reactions. Termination via the oligomeric radicals recombination is the most probable.     

A class of Steiner 4-wise balanced designs derived from preparata codes

The minimum weight codewords in the Preparata code of length n = 4^m are utilized for the construction of an infinite family of Steiner S(4, {5, 6}, 4^m + 1) designs for any m ≥ 2. © 1996 John Wiley & Sons, Inc.     

Polymer ultrathin films with immobilized photosynthetic reaction center proteins

Properties of mixed monolayers of lipid-photosynthetic reaction center proteins (RC) were studied and the optimum conditions for stable films fabrication were determined. The following synthetic: N-acryloylphosphatidylethanolamine (ACPE), tetracosa-11, 13-diinoic acid (TDA), pentacosa-10, 12-diinoic acid (PDA), dioctadecyldienoylphosphatidylcholine (DODL) and natural lipids: L-α-phosphatidylethanolamine (PE), L-α-phosphatidylcholine (PC) were used. The rate of polymerization of the mixed ACPE-RC and TDA-RC monolayers is lower in comparison with corresponding values for pure lipid-like monomers on air/water interface. The optical and photoelectrical measurements provide evidence for an orientation of RCs on interface. Hydrophilic H-subunit in monomeric and polymeric ACPE-RCs, and monomeric DODL-RCs monolayers is preferentially oriented towards water as in the pure RC monolayers. Opposite orientation was found with TDA-RCs and PDA-RCs films. No preferential orientation for lipid-RCs from C. aurantiacus monolayers was found because of the RCs having low assymmetry of hydrophobic subunits (M and L).     

Self-assembly phenomena in multicomponent systems composed of polyelectrolytes and ionic surfactants

The ability of anionic surfactants to expel fluorescencetagged poly(methacrylate) polyanion ( PMA ^*) from nonstoichiometric water-soluble interpolyelectrolyte complex ( NIPEC ) formed by PMA^* and polycation-quencher poly(N-alkyl-4-vinylpyridinium) ( PAlkVP ) and to form polyelectrolyte-surfactant complex ( PESC ): NIPEC(PMA^*-PAlkVP)+surfactant ⇔ PESC(PAlkVP-surfactant)+PMA^* was revealed and studied by fluorescence quenching technique and high-speed sedimentation. It was found that the transfer of poly(N-ethyl-4-vinylpyridinium) from NIPEC to PESC proceeded up to complete conversion providing a self-assembly of both PESC and NIPEC particles in the course of the reaction. The concentration of the surfactant and the “tail” length of the surfactant molecule, as well as the structure of Alk groups, temperature, pH, ionic strength, and the nature of added low-molecular-weight electrolyte proved to be the factors of the reaction equilibrium control.     

Selenium Dihalides Click Chemistry: Highly Efficient Stereoselective Addition to Alkynes and Evaluation of Glutathione Peroxidase-Like Activity of Bis(E-2-halovinyl) Selenides

Highly efficient stereoselective syntheses of novel bis(E-2-chlorovinyl) selenides and bis(E-2-bromovinyl) selenides in quantitative yields by reactions of selenium dichloride and dibromide with alkynes were developed. The reactions proceeded at room temperature as anti-addition giving products exclusively with (E)-stereochemistry. The glutathione peroxidase-like activity of the obtained products was estimated and compounds with high activity were found. The influence of substituents in the products on their glutathione peroxidase-like activity was discussed.