The role of dimeric molecules of metalloporphyrins in phototransfer of an electron through liposome membranes

Conclusions Charge separation in solutions of liposomes sensitized by MP at low temperatures and apparently also at 20°C takes place according to a mechanism of two-quantum photoionization of dimeric molecules of the metalloporphyrins.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 277–282, February, 1985.     

Stereochemistry of Seven-membered Heterocycles: XLIV. Spatial Structure of 4-R-3,5-Dioxabicyclo[5.1.0]octanes

4-R-3,5-Dioxabicyclo[5.1.0]octanes were prepared in good yields by reduction of the corresponding 8,8-dichloro derivatives in a system Li-t-BuOH. According to the data of dynamic ¹H and ¹³CNMR spectroscopy involving experiments in the NOESY mode the formal (R = H) at −93°C in (CD₃)₂CO exists in nearly equally occupied chair forms with endo- and exo-oriented three-membered ring. The like structure were found in the diastereomeric 4-Me(t-Bu)-analogs. The characteristic feature of ¹³C NMR spectra consists in considerable difference in the chemical shifts of the C⁸ atoms (Δδ∼16–17 ppm). The data on epimerization of diastereomers and calculations along AM1 procedure suggest for formal a three-component equilibrium including a twist-form.__________Translated from Zhurnal Organicheskoi Khimii, Vol. 41, No. 2, 2005, pp. 301–305.Original Russian Text Copyright © 2005 by Fedorenko, Baryshnikov, Khairutdinov, Vafina, Shtyrlin, Klochkov, Klimovitskii.     

Reactivities of heterocyclic compounds in nitration. 5. Kinetics of nitration of 5-substituted 2-picrylaminopyridines

The kinetics of nitration of 5-bromo-, 5-chloro-, and 5-nitro-2-picrylaminopyridines in 80–96% sulfuric acid were studied by a spectrophotometric method. The kinetic parameters of nitration were calculated. The UV spectra of the neutral and protonated forms in aqueous sulfuric acid solutions were identified. It was established that the indicated compounds are nitrated in the protonated form. The relative (as compared with benzene) rates of nitration were calculated.See [1] for communication 4.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1632–1636, December, 1980.     

Addition of thiols to (-)-carvone

Polyfunctional thioterpenoids were formed in the presence of a Lewis-acid catalyst by reaction of (-)-carvone with thiols that involved the endocyclic double bond and the carbonyl.Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 393–395, September–October, 2004.     

Cyclic transmembrane charge transport mediated by pyrylium and thiopyrylium ions

Transient spectroscopy revealed that 2,4,6-trimethylpyrylium, 2,4,6-triphenylpyrylium, and 2,4,6-triphenylthiopyrylium ions oxidatively quench excited triplet [5,10,15,20-tetrakis(4-sulfonatophenyl)porphinato]zinc(II) to form the corresponding neutral radicals and the zinc porphyrin pi-cation. The measured quenching rate constants were proportional to the pyrylium one-electron reduction potentials, that is, the reaction driving force. In the presence of anionic dihexadecyl phosphate vesicles, only the fraction of pyrylium not bound to the vesicle was capable of reacting with the photoexcited zinc porphyrin. Nonetheless, the pyrylium radicals mediated highly efficient transmembrane reduction of tris(2,2'-bipyridine)cobalt(III) contained within the inner aqueous core of the vesicles with apparent quantum yields that approached unity. Permeability coefficients (P) determined for the pyrylium radicals, pyrylium cations, and the proton were 10(-4)-2 x 10(-5) cm/s, 10(-10) cm/s, and < 5 x 10(-7) cm/s, respectively, so that only the neutral radicals are membrane-permeable on the time scale of the transmembrane redox reactions. However, each electron carrier was demonstrated to transport up to 200 electrons, at which point the internal pool of electron acceptors was exhausted. Since the cations are membrane-impermeable, a reaction cycle is proposed that includes hydrolysis of the pyrylium cations formed within the aqueous core to the corresponding 1,5-diketones which, as neutral molecules, can diffuse across the bilayer. According to this mechanism, while undergoing redox cycling the pyrylium ions function as cyclical antiporters of OH(-) and the electron, thereby maintaining electroneutrality in the reaction compartments.     

Photostimulated electron tunnel transfer in solid matrices

Tunnel recombination of photoseparated charges in frozen vitreous alcoholic solutions of zinc porphyrin (ZnP) and CCl₄ has been investigated. Considerable acceleration of the recombination in such systems when exposed to light in the ZnP⁺ or the CCl₄^? absorption band region is observed. Possible mechanisms which increase the charge recombination efficiency are considered in detail. The acceleration of the tunnel recombination of ZnP⁺ and CCl₄^? under irradiation in the porphyrin absorption band is shown to be due to energy transfer from an excited acceptor to a transferred electron. It is shown that data on the kinetics of photostimulated tunnel reactions can be used to determine the binding energy of a tunnelling electron.     

Supercritical Fluid Propane-Butane Extraction Treatment of Oil Sludge

The extraction process with propane: butane = 3: 1 (by mass) mixture in the liquid and supercritical fluid states was used to extract petroleum products containing 12.05 mass % of anhydrous oil sludge as solid particulates. The extraction was carried out at 85–160°С and 5–50 MPa. The desired oil product contains 2.8 mass % of sulfur, it has a density of 880 kg/m³ and a kinematic viscosity of 73.75 mm²/s at 20°С as well as start and end boiling point values of 43.6 and 325°С, respectively.