Cinnamoyl pyrones in proton-donating media: electronic structure and spectral properties of protolytic forms

Spectral properties of cinnamoyl pyrone (CP) and its derivatives were studied in water-alcohol and water solutions within a wide pH/H(0) range. It was found that the most of CP may exist in neutral, anionic and cationic forms, except for alkylamino substituted CP, which can also form dications. The constants characterizing equilibria between all the protolytic forms were obtained. CP anions appears as a result of 4-hydroxy group dissociation. It was found that the acidity of CP decreases upon the excitation, that excepts the photodissociation or intramolecular proton transfer in the excited state. The formation of cations and dications occurs by means of protonation of alkylamino group or/and exocyclic carbonyl group. The theoretical analysis of electronic structure has shown that long-wavelength electronic transitions of neutral and anionic CP forms are of interfragmental charge-transfer (ICT) character. However, in the case of anions, ICT is hindered due to their nonplanar geometrical structure. The band maxima positions in experimental absorption spectra of neutral CP and in absorption and emission spectra of cations correlate linearly with theoretical estimations of charge transfer in CP molecules. The absence of the fluorescence, characteristic for the most of neutral CP, is due to the intersystem crossing, that is proved by the appearance of the phosphorescence of non-fluorescent CP at low temperatures.     

Selective synthesis of cyclic triperoxides from 1,1′-dihydroperoxydi(cycloalkyl)peroxides and acetals using SnCl4

Russian Chemical Bulletin - A method for the synthesis of 1,2,4,5,7,8-hexaoxonanes by the reaction of 1,1′-dihydroperoxydi(cycloalkyl)peroxides with acetals using SnCl4 has been developed....     

On the 1920 Å continuous spectrum of the supersonic argon jet excited by an electron beam

The T₀/?(T₀) dependences (T₀ is the intensity of the 1920 Å continuum at its maximum, ? is the concentration of argon atoms at the intersection of an electron beam and a jet, T₀ is the temperature of argon at the nozzle) for the 1920 Å continuum radiated by a supersonic argon jet excited by an electron beam were investigated at various pressures of argon at the entry to a nozzle. The experiments performed suggested a possible generation mechanism of the 1920 Å continuum emitted by an argon jet.     

Selective synthesis of cyclic peroxides from triketones and H2O2

A method for the assembly of tricyclic structures containing the peroxide, monoperoxyacetal, and acetal moieties was developed based on the acid-catalyzed reaction of β,δ-triketones with H(2)O(2). Tricyclic compounds are formed selectively in yields from 39% to 90% by the reactions with the use of large amounts of strong acids, such as H(2)SO(4), HClO(4), or HBF(4), which act both as the catalyst and as the co-solvent. The reaction is unusual in that, despite the diversity of possible peroxidation pathways giving cyclic compounds and oligomers, the reaction proceeds with high selectivity and produces tricyclic peroxides via the monoperoxidation of the carbonyl groups in the β-positions and the transformation of the δ-carbonyl group into the acetal one. The syntheses are scaled up to tens of grams, and the resulting peroxides can be easily isolated from the reaction mixture.     

Catalyst Development for the Synthesis of Ozonides and Tetraoxanes Under Heterogeneous Conditions: Disclosure of an Unprecedented Class of Fungicides for Agricultural Application

The catalyst H_3+xPMo_12−x⁺⁶Mo_x⁺⁵O₄₀ supported on SiO₂ was developed for peroxidation of 1,3- and 1,5-diketones with hydrogen peroxide with the formation of bridged 1,2,4,5-tetraoxanes and bridged 1,2,4-trioxolanes (ozonides) with high yield based on isolated products (up to 86 and 90 %, respectively) under heterogeneous conditions. Synthesis of peroxides under heterogeneous conditions is a rare process and represents a challenge for this field of chemistry, because peroxides tend to decompose on the surface of a catalyst . A new class of antifungal agents for crop protection, that is, cyclic peroxides: bridged 1,2,4,5-tetraoxanes and bridged ozonides, was discovered. Some ozonides and tetraoxanes exhibit a very high antifungal activity and are superior to commercial fungicides, such as Triadimefon and Kresoxim-methyl. It is important to note that none of the fungicides used in agricultural chemistry contains a peroxide fragment.     

Aziridinyl ketones and their heteroanalogs

5-Aryl-7-(4-nitrophenyl)-1,4-diazabicyclo[4.1.0]hepta-4-enes (I), which have photochromic properties, were synthesized. The structures of the compounds were confirmed by data from the IR, PMR, and mass spectra. The acidolysis of I was investigated, and it was assumed that the mechanism of the reaction includes diprotonation of the bases, while the primary process is the formation of immonium salts. The structures of the photocolored forms of the salts and bases are discussed.See [1] for communication 1.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 536–540, April, 1979.     

Aroyl[bis(4-hydroxycoumarin-3-yl)]methanes in reactions with 1,2-diaminobenzenes

The reaction of aroyl[bis(4-hydroxycoumarin-3-yl)]methanes with 1,2-phenylenediamines in PrⁱOH is accompanied by the recyclization to 8-R-or 7-R-4-(2-hydroxyphenyl)-1,5-benzodiazepin-2-ones, whereas the reaction with o-phenylenediamine and its 4-methyl-substituted derivatives in MeOH produces organic ionic salts of the bis-coumarin anion with monoprotonated o-phenylenediamine as the cation. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2200–2205, November, 2007.     

Scandium thin films-structure and electrical resistance (I). A study on films obtained in a vacuum of 10−5 up to 10−6 Torr

A structure as well as a specific electrical resistance of scandium films having a various thickness (300 up to 2800 Å) obtained at a condensation rate: w⋍ 1 up to 155 Å/s have been studied in the present work. Depending on condensation conditions in films a hydride ScH_x, h.c.p. — Sc, or ScH_x + Sc alternatively, is formed, a phase containing a distorted hexagonal lattice evolving into the ScH_x over a period of a few hours. The ScH_x and h.c.p-Sc change to Sc₂O₃ when annealed in a vacuum of 5 · 10⁻⁵ Torr at a T ≈ 800°C, while in a vacuum of 3 · 10⁻⁸ Torr a change to h.c.p.-Sc with negligible inclusions of oxidic Sc₂O₃ particles takes place. Formation of oxide is observed also when heating the films with an electron beam directly in a microscope under vacuum of ∼ 8 · 10⁻⁵ Torr. The specific electrical resistance ϱ of the film just after a condensation has taken place is approximatly by an order higher as against the ScH_x- and h.c.p.-Sc solid specimens. An irreversible gain in said resistance is observed while holding at a room temperature or annealing in a vacuum of 5 · 10⁻⁵ Torr, this being associated with absorption of H₂, O₂ and, possibly, of water steam, and then with formation of Sc₂O₃. Annealing in a vacuum of 5 · 10⁻⁸ up to 10⁻⁷ Torr involves a temperature relationship for ϱ of an intricated nature, this being accounted for by a structure transition as follows: A diode-effect diminishing with a temperature rise is observed in annealed films.