Photochemistry of quaternary salts of aromatic heterocycles and some of their mesoionic derivatives (Review)

The photochemical methods far the synthesis of quaternary salts of aromatic heterocycles, their photochemical reduction reactions, photoreactions with water, some photochemical transformations that proceed without a change in the charged heterocycle, and photoreactions involving valence isomerization and fragmentation of the mesoionic derivatives are examined.     

Reaction of indolizines with elemental sulfur

The fusion of 3,8-diphenyl-, 1,2-diphenyl-, and 6-methyl-2,7-diphenyl-indolizines with sulfur results in the formation of bis(indolizin-3-yl) disulfides with the respective substituents. Bis(2,8-diphenylindolizin-3-yl) disulfide is reduced to the original indolizine, and its treatment with nitric acid gives 2,8-diphenyl-1, 3-dinitroindolizine. Bis(dibenzo[b,g]indolizin-11-yl) disulfide is obtained from dibenzo[b,g]indolizine. The formation of the disulfides is apparently a general region of indolizines without substituents at C₃ or C₁ of the pyrrole ring. The structures of the disulfides obtained have been confirmed by data from x-ray diffraction analysis and NMR spectroscopy.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1371–1375, October, 1984.     

Photoionization of oriented molecules

A general expression for the angular distribution of photoelectrons with defined spin polarization ejected from oriented molecules is derived in the electric-dipole approximation in the limit of a weak radiation field. An analysis of its geometrical part permits to draw definite conclusions without calculating matrix elements. For linear molecules it is shown that in Hund's cases (a) and (b) photoelectrons may be polarized only parallel to the molecular axis, while in Hund's case (c) they may be polarized in any direction. Appearance of a circular dichroism for nonchiral oriented molecules of relatively low symmetry is predicted. Dependence of a circular dichroism in the angular distribution of photoelectrons on the symmetry of molecules is demonstrated. The results may serve as the framework for studying molecules oriented on surfaces, in liquid crystals, or by molecular beam techniques.     

Interaction between a Decahydro-closo-Decaborate(2–) Anion and Aliphatic Carboxylic Acids

Interaction between a closo-decaborate anion B₁₀H^2– ₁₀and carboxylic acids RCOOH (R = H, CH₃, C₂H₅, iso-C₃H₇, C₄H₉) is studied. The mono-, di- tri- and tetrasubstituted products B₁₀H_{10 – n} (OCOR)^2– _n are formed in sequence with the temperature growth. The reaction follows an essentially regioselective mechanism: only one of all possible isomers forms at every stage of the process. The respective hydroxy-closo-decaborates B₁₀H_{10 – n} (OH)^2– _n were prepared by alkaline hydrolysis in aqueous and nonaqueous solutions. All the compounds were identified by chemical analysis and ¹¹B NMR and IR spectroscopy. The crystal structure of [Pb(Bipy)(DMF)(B₁₀H₉OH)] · DMF was determined by X-ray diffraction.     

The Mechanism of Acid-Catalyzed Nucleophilic Substitution in Decahydro-closo-Decaborate(2–) Anions

The reactions of salts formed by the B₁₀H^2– ₁₀anion with carboxylic acids were studied. From the model systems Cat₂B₁₀H₁₀+ HCOOH (Cat = Et₄N⁺, Bu₄N⁺, Ph₄P⁺, Ph₄As⁺), several intermediates were isolated and characterized. A mechanism was proposed for the replacement of the exo-polyhedral hydrogen atoms in B₁₀H^2– ₁₀by carboxylate groups in the reactions of Cat₂B₁₀H₁₀with carboxylic acids.     

Self-organization of poly(methyl methacrylate) and polystyrene macromolecules functionalized by fullerene C60

Poly(methyl methacrylate) and polystyrene functionalized by fullerene C₆₀ tend to form micellar structures comprising a fullerene cluster as a core and a macromolecular shell. Films prepared from PMMA-C₆₀ and PS-C₆₀ micellar solutions are polymer matrices with fullerene-containing globular structures uniformly distributed in the polymer bulk.     

Substituted benzotriazoles as inhibitors of copper corrosion in borate buffer solutions

The adsorption of substituted 1,2,3-benzotriazoles (R-BTAs) onto copper is measured via ellipsometry in a pure borate buffer (pH 7.4) and satisfactorily described by Temkin’s isotherm. The adsorption free energy (?ΔG _a ⁰ ) values of these azoles are determined. The (?ΔG _a ⁰ ) values are found to rise as their hydrophobicity, characterized by the logarithm of the partition coefficient of a substituted BTA in a model octanol–water system (logP), grows. The minimum concentration sufficient for the spontaneous passivation of copper (C _min) and a shift in the potential of local copper depassivation with chlorides (E _pt) after an azole is added to the solution (i.e., ΔE = E _pt ⁱⁿ ? E _pt ^backgr characterizing the ability of its adsorption to stabilize passivation) are determined in the same solution containing a corrosion additive (0.01М NaCl) for each azole under study. Both criteria of the passivating properties of azoles (logC _min and ΔE) are shown to correlate linearly with logP, testifying to the role played by surface activity of this family of organic inhibitors in protecting copper in an aqueous solution.     

Electromagnetic Parameters of Composite Materials Based on Polyethylene and Multi-Walled Carbon Nanotubes Modified by Iron Oxide Nanoparticles

Russian Journal of Applied Chemistry - Specific features are revealed of how composite materials are formed on the basis of polyethylene and multi-walled carbon nanotubes modified with iron oxide...     

In situ Polymerization Technique for Obtaining Composite Materials Based on Polyethylene,Multi-walled Carbon Nanotubes and Cobalt Nanoparticles

Specific features of formation of composite materials based on polyethylene, multi-walled carbon nanotubes, and cobalt nanoparticles (MWCNT–PE and Co/MWCNT–PE) by in situ polymerization were revealed. The in situ polymerization technique is based on ethylene polymerization on a highly dispersed Ti-containing catalyst supported on the surface of MWCNT and Со/MWCNT. This method ensures uniform distribution of MWCNT and Co/MWCNT in the polyethylene matrix. The effect of MWCNT and Со/MWCNT on the final properties of the composite materials was determined. Introduction of MWCNT into the polyethylene matrix increases the specific electrical conductivity of the material. Such composite materials can be used for preparing concentrates with preset composition for the subsequent preparation of antistatic coatings. Introduction of the Со/MWCNT filler into the polyethylene matrix makes the material paramagnetic owing to Co nanoparticles and allows its use for preparing coatings that efficiently protect from electromagnetic radiation.