Dissociative Excitation Processes upon Collisions of Slow Electrons with MgBr2 Molecules

Dissociative excitation of MgI, MgII, and MgBr upon e–MgBr₂ collisions was experimentally studied. The excitation cross sections of the spectral lines of MgI and MgII, as well as two sets of bands of the MgBr molecule were measured at an incident electron energy of 100 eV. In the electron energy range from the excitation threshold to 100 eV, ten optical excitation functions with a complex structure were recorded. The principal pathways of dissociative excitation of MgI, MgII, and MgBr by slow electrons are discussed.     

DNA Effect on Cis–Trans Equilibrium and Fluorescent Properties of 3,3′-Diethyl-9-thiomethylthiacarbocyanine Iodide in Aqueous Solution

The influence of DNA on the cis–trans equilibrium and fluorescent properties of 3,3-diethyl-9-thiomethylthiacarbocyanine iodide (DTTC) in a phosphate buffer (pH 7) was studied by various photochemical techniques. The interaction of dye molecules with DNA leads to the formation of stable noncovalently bonded complexes. Data obtained from DTTC absorption and fluorescence spectra suggest that complexation proceeds primarily through the cis-form of the dye. Complexation with DNA leads to a substantial increase in the quantum yield of the triplet state of DTTC molecules. The rate constant for quenching the dye triplet state by oxygen turned out to be significantly lower than the diffusion-controlled value.     

Dependence of Fluorescence Properties of Compounds from Psoralen,Angelicin, and Carbazole Series on the Character of Their Terminal Substituents

Absorption, luminescence excitation and emission spectra of nine compounds from 4,8,4'-trimethylpsoralen, 4,4'-dimethylangelicin, and 1,2,3,4-tetrahydrocarbazole series with various terminal substituents were studied in water and 2-propanol. Proceeding from the data obtained in the present and also some previous studies we have formulated the main rules concerning a general mechanism of changes in the fluorescence characteristics of DNA-specific dyes depending on their chemical structure, substrate properties, and measurement medium.     

Solid-phase synthesis of pyrazolines and isoxazolines with sodium benzenesulfinate as a traceless linker

[reaction: see text] The preparation of pyrazoline and isoxazoline derivatives with traceless solid-phase sulfone linker strategy is described. Key steps involved in the solid-phase synthetic procedure include (i) sulfinate S-alkylation, (ii) sulfone anion alkylation, (iii) gamma-hydroxy sulfone --> gamma-ketosulfone oxidation, and (iv) traceless product release via elimination-cyclization. A library of 12 pyrazolines and isoxazolines was synthesized.     

Condensed systems based on 4-amino-3-mercapto-1,2,4-triazole

1,2,4-Triazolo[3,4-b]-1,3,4-thiadiazines, hydrazones, and -thio adducts were obtained by reactions of 4-amino-3-mercapto-1,2,4-triazole with -bromoacetophenones, aldehydes, and ,-unsaturated ketones. Conditions that promote the cyclocondensation of the -thio adducts to the previously undescribed 1,2,4-triazolo[3,4-b]-1,3,4-thiadiazepines were found. The chemical and spectral properties of the compounds obtained are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 267–272, February, 1992.     

Crystal and molecular structure of the sesquiterpene humulane ester juniferdin

The spatial structure of the sesquiterpene humulane ester juniferdin, isolated fromFerula juniperina, has been established by the x-ray structural method. An analysis is given of the 11-membered humulane ring in comparison with the conformation observed in fexerol and juniferol.Institute of Chemistry of Plant Substances, Academy of Sciences of the Uzbek SSR, Tashkent. Institute of Crystallography, Academy of Sciences of the USSR, Moscow. Translated from Khimiya Prirodnykh Soedinii, No. 4, pp. 494–499, July–August, 1991.     

Steroids of the spirostan and furostan series from Nolina microcarpa IV. Structures of nolinogenin,nolinospiroside B,and nolinofuroside B

A glycoside has been isolated from the plantNolina microcarpa S. Wats. (family Dracaenaceae) which has been called nolinofuroside B and has the structure of 6-methoxy-3,5-cyclo-(25S)-furostan-1,22,26-triol 1-O--D-fucopyranoside 26-O--D-glucopyranoside (I). Enzymatic hydrolysis of the bioside (I) yielded nolinospiroside B (III) and nolinogenin (IV). The latter is 6-methoxy-3,5-cyclo-(25S)-spirostan-6-ol, and glycoside (III) is its 1-O--D-fucopyranoside.M. V. Frunze Simferopol' State University. Institute of Chemistry of Plant Substances, Uzbekistan Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 218–224, March–April, 1992.     

Photo- and thermochromic mannich bases. 1. Mannich bases from 3,5-di-tert-butyl-4-hydroxybenzaldehyde and 2-naphthols

Mannich bases exhibiting photo- and thermochromic properties in solutions were synthesized from 3,5-di-tert-butyl-4-hydroxybenzaldehyde and 2-naphthols. An investigation of an acetyl derivative of methylenequinone, modeling a product of photo- and thermochromic transformations, proved that the color change of solutions of the Mannich bases is due to reversible dissociation into colored methylenequinones and morpholine. On the basis of data of x-ray diffraction analysis of one of the Mannich bases, characteristics of their molecular structure were determined, and reasons were stated for their effect on the dissociation mechanism.     

Reaction of 4-aminoimadazo[4.5-c]pyridin-2-ones with α-bromomethylketones

The reactions of 4-amino derivatives of imidazo[4.5-c]pyridin-2-ones with -bromomethylketones have been studied. Depending on the nature of the reagents and the reaction conditions, either 5-acylmethyl salts of the starting amine or 2-substituted imidazo[4.5-c]imidazo[1,2-a]pyridin-8-ones can be obtained. The latter compounds are also easily obtained by treatment of the 5-acylmethyl salts with alkali.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 227–232, February, 1986.     

Synthesis and structure of the new binuclear complex η5-C5H5(CO)2Fe-η1-C5H4(CO)2Fe-CH3

Conclusions The new binuclear complex ⁵-C₅H₅(CO)₂Fe-¹-C₅H₄(CO)₂Fe-CH₃ was synthesized. Its structure was established by x-ray crystallographic analysis.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 437–440, February, 1986.