A study of the optical absorption induced in vacuum thermolysis of aluminum trihydroxide

The diffuse reflection spectroscopy technique was used to investigate the color centers (CC) in the products of thermolysis and photolysis of disperse Al(OH)₃ in a vacuum. The spectra were recorded in situ in the region of 2.5–6.0 eV and 4000–12,000 cm⁻¹. It was found that in thermolysis of Al(OH₃) production of Al is accompanied, by transformation of the IR spectra of the compound and overtone vibrations of OH groups and by the appearance of an absorption band (AB) at 4.0 eV with a shoulder at 4.4 eV. A similar AB is induced by UV irradiation of Al(OH)₃ in a vacuum. In the position of the maximum and shape, the AB at 4.0 eV in aluminum oxide produced by thermolysis of Al(OH)₃ coincides with the AB of CC responsible for light- and temperature-stimulated degradation of white anode oxide coatings on Al(Al-AOC). This suggests that in Al-AOC, CC are formed in decay of structural O_mH_n groups. In Al oxide and in Al-AOC, their nature is discussed with the use of data on optical absorption of radiation-induced defects in Al₂O₃. Research Institute of Physics at St. Petersburg State University, St. Petersburg 1, Ul’yanovskaya St., Petrodvorets St. Petersburg, 198904, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 400–404, May–June, 1998.     

Luminescence of NaL (T1) crystals with oxygen-containing impurities

Traces of NaOH, Na₂CO₃, and NaIO₃, reduce the light yield from-rays and in fluorescence; they produce a variety of defects.Read at the Fourth Conference on the Synthesis, Production, and Use of Scintillators, Khar'kov, May 1965.     

Synthesis and Study of Antimicrobial Activity of Water-Soluble Ammonium Acylhydrazones Based on New 1,ω-Alkylenebis(isatins)

Russian Journal of General Chemistry - Alkylation of isatin with 1,ω-dihaloalkanes afforded bis(heterocycles) connected by an oligomethylene linker. The reaction of the resulting bis(isatins)...     

Electrochemical properties of outer-sphere associates of bipyridyl and sepulchrate metal complexes with (thia)calix[4]arenes

The electrochemical one-electron reduction (oxidation) of bipyridyl metal complexes ([Co(bipy)₃]³⁺, [Cr(bipy)₃]³⁺, [Fe(bipy)₃]²⁺, [Ru(bipy)₃]²⁺ (as well as Co(III) sepulcrate)) with water-soluble (thia)calix[4]arenes has been studied by means of cyclic voltammetry. It has been shown that [M(bipy)₃]^3+/2+ bind to (thia)calix[4]arenes via sulfonate groups of the upper rim. Oxidized forms bind stronger than reduced ones leading to reduction (oxidation) of half-wave cathodic shift. The effect of predominant stabilization of oxidized forms of metal complexes for carboxylated calix[4]arene is stronger than for thiacalix[4]arene (ΔΔG₀?=???7.8?÷???12.5 and ??3.7 kJ/mol, respectively). The redox-switchable outer-sphere binding of Co(III) sepulchrate via lower rim of carboxylated calix[4]arene has been revealed using cyclic voltammetry. The binding constants of outer-sphere associates based on calix[4]arenes and unstable metal complexes ([Co(sep)]²⁺, [Ru(bipy)₃]³⁺, [Co(bipy)₃]²⁺) have been calculated for the first time using ¹H NMR titration and cyclic voltammetry data.

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Reactions of heteroaromatic chromophores with lanthanide complexes of p-sulfonatothiacalix[4]arene

The conditions for the formation of heteroleptic complexes of a lanthanide(iii) ion (Ln = La, Gd, and Tb) with p-sulfonatothiacalix[4]arene and a heteroaromatic chromophore in water were found using X-ray diffraction analysis, pH-metry, ¹H NMR and UV—Vis spectroscopy, and nuclear magnetic relaxation. In the resulting complexes, the heteroaromatic chromophore is in the calix[4]arene cavity and the lanthanide ion is coordinated by the electron-donating groups of the upper or lower calix[4]arene rim. Emission spectroscopic studies revealed changed emission properties of Tb^III ions in the terbium(iii)—p-sulfonatothiacalix[4]arene—bipy complex. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1871–1878, September, 2008.     

Nanosized reactors based on polyethyleneimines: from microheterogeneous systems to immobilized catalysts

Effective nanoreactors based on polyethyleneimines (PEIs) for the hydrolytic cleavage of O-alkyl O-p-nitrophenyl chloromethylphosphonates (alkyl = ethyl, hexyl) and di(p-nitrophenyl)phosphate were developed in conformity with the idea of modeling the polyfunctional catalytic mechanism of enzymes. A step-by-step modification of the single PEI solution by additives with their own catalytic activities (sodium dodecyl sulfate and lanthanum salt) gave rise to a marked improvement in the reaction efficiency. A 104-106-fold acceleration of the reaction compared to the aqueous basic hydrolysis of the substrates was achieved in the sodium dodecyl sulfate-polyethyleneimine-La(III) ternary system. This system can be considered to be metallomicelles immobilized on a hydrophilic polymer matrix. When the PEI immobilized on silica gel was used as a catalyst, the full completion of the reaction was achieved for 100 min under mild conditions, while the half-life of the reaction in a comparable homogeneous regime exceeds 100 h.     

Modification of Coal Humic Acids with Formaldehyde

Optimal conditions for condensation of coal humic acids with formaldehyde in alkaline medium were determined. The conversion of formaldehyde as influenced by temperature, reaction time, component ratio, and catalyst content was studied.     

Synthesis of diquinolinoanthracene and pyridonoanthraquinolines

New heterocyclic polycondensed systems — diquinolinoanthracene and pyridinoanthraquinoline — were synthesized by the action of polyphosphoric acid on 1,4-di(p-toluidino)anthraquinone and 6-arylaminoanthrapyridones. Dipyridonoanthraquinoline with an amino group in the pyridone ring was produced from N-[6-(p-toluidino)an-thrapyridonyl-1]-pyridinium chloride by cyclization and cleavage of the pyridinium group.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 962–964, July, 1984.     

Complexation and Self-Assembling of Sulfonatomethylated Calix[4]resorcinarene with Both Organic and Lanthanide Ions in Aqueous Media

The stoichiometry and binding constant of the paramagnetic lanthanide ion(Gd³⁺) with sulfonatomethylated calix[4]resorcinarene (H₈Xna₄) were evaluated from the NMR relaxation data. Both ¹H NMR spectroscopy and NMR relaxation data indicate that interaction of tetramethylammonium (TEMA) and N-methylpyridinium (MePy) cations with H₈Xna₄ in the presence of Ln³⁺ (Lu³⁺ or Gd³⁺) results in theformation of ternary complexes [Ln(G)H₈X] with lanthanide ions,coordinated via sulfonate groups and organic cation included intothe cavity of H₈Xna₄. The inclusion of long-chainedN-decyl-(DePy) and N-cetylpyridinium (CPy) ions into H₈Xna₄ cavity leads to self-assembling which can be revealed by NMR relaxation method with Gd³⁺ probe ions. The excess of alkylpyridinium or TEMA cations leads to disassembling of (Gd)_n(H₈X)_m(RPy)_maggregates.     

The effect of substituents (CH3 and NH2) in positions 4 and 6 on the acid-base properties of 2(1H)-pyrimidinethiones

The acid-base properties of 4,6-dimethyl- and 4,6-diamino-2(1H)-pyrimidinethiones (1 and2) were investigated by potentiometric titration. Dissosiation of1 and protonation of its anion occur in two steps, the first of which affords the deprotonated dimer [HA₂)^–. The relative stability of the dimer depends on the nature of the solvent. The effect of kinetic factors on the acid-base behavior of1 was elucidated by comparing the results of potentiometric titrations carried out under various kinetic conditions. It was concluded that the difference between the acid-base properties of1 and2 results from the electron-donating effect of the amino groups.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2145–2148, December, 1994.