Showing papers in "Russian Chemical Bulletin in 2008"

Polymeric cryogels as a new family of macroporous and supermacroporous materials for biotechnological purposes

Abstract: The review is devoted to a specific kind of polymeric gels formed as a result of non-deep freezing of solutions or colloidal sols of the corresponding precursors. These materials are termed as cryogels. They possess a series of unique properties, first of all, the specific character of porosity (macroporous cryogels with the pore cross-section from tenth fractions of μm to ∼10 μm and supermacroporous (gigaporous) cryogels with pores of tens and hundreds of μm) and are attractive from the viewpoint of biotechnological implementation. Approaches to the preparation of the so-called “smart” composites based on the cryogels are considered. The use of various cryogels as carriers of immobilized biocatalysts (enzymes, cells), matrices for wide-porous affinity sorbents and immunosorbents, and spongy scaffolds for 3D culturing of animal cells is discussed.

Bistable organic, organometallic, and coordination compounds for molecular electronics and spintronics

Abstract: The review is concerned with advances in molecular elecronics and spintronics as applied to the design of hardware components for molecular computers (molecular switches; optical, redox-based, and magnetic molecular memory; and conducting molecular materials).

Azolo[5,1- c ]-1,2,4-triazines as a new class of antiviral compounds

Abstract: Synthetic methods, reactivity, and the properties of a new class of antiviral compounds, pyrazolo-, imidazo-, 1,2,4-triazolo[5,1-c]-1,2,4-triazinones, tetrazolo[5,1-b]-1,2,4-triazinones, and azoloannulated amino-1,2,4-triazines having structural similarity with biogenic purines and capable of mimicking them in metabolic processes are considered.

Some aspects of the chemical behavior of icosahedral carboranes

Abstract: Important features of the chemical behavior of icosahedral carboranes are considered. The ways of introducing functional groups at the carbon and boron atoms of carboranes by conventional methods of organic chemistry and methods applicable only to carboranes are discussed. The latter methods include transformations of dicarbadodecaborate(14) dianions. Examples of the enantiomeric resolution of optically active carboranes, whose chirality is associated with the molecular asymmetry, are given. The diversity of chemical transformations of carboranes is exemplified by intramolecular nucleophilic rearrangements, cross-coupling reactions, and the formation of chelate metallacycles.

Zinc(II) complexes with Schiff bases derived from ethylenediamine and salicylaldehyde: the synthesis and photoluminescent properties

Abstract: The effect of the nature of organic ligands and complex formation on the photoluminescent characteristics (relative quantum yield, excited-state lifetime) and thermal stability of tetradentate Schiff bases (H2L), derivatives of salicylaldehyde (H2(SAL)1, H2(SAL)2), o-vanillin (H2(MO)1, H2(MO)2) with ethylenediamine and o-phenylenediamine, and their zinc(II) complexes was studied. Zinc(II) complexes were synthesized by the reaction of H2L with Zn(AcO)2·2H2O in MeOH at room temperature or under reflux. In the case of H2L = H2(SAL)2, H2(MO)1, H2(MO)2, complexes of the composition ZnL·H2O were isolated irrespective of the temperature. For H2L = H2(SAL)1, the reaction results in Zn(SAL)1·H2O at room temperature and in anhydrous dimeric complex [Zn(SAL)1]2 under reflux. Density functional calculations of H2L and ZnL confirmed that (1) luminescence of these compounds is due to the π-π* transition between orbitals of the organic ligand and (2) enhancement of conjugation of the chain and introduction of electron-donating substituents lead to a decrease of the energy gap and, there-fore, to a bathochromic shift of the emission maximum.

Chemical modification of nanocrystalline metal oxides: effect of the real structure and surface chemistry on the sensor properties

Abstract: The relationships between the composition, structure, chemistry of the surface, and sensor properties of nanocomposites SnO2-M n O m (M n O m = Fe2O3, MoO3, V2O5) obtained by chemical precipitation from solutions were analyzed. The relationships between the elemental and phase composition of the nanocomposites and the effect of the composition on the nanostructure and the acidic and oxidation properties of the nanocomposite surface were considered. The modification of the SnO2 surface by other oxides makes it possible to control the type and density of the acid sites and the oxidation properties of the surface and to enhance the selectivity of the materials in the detection of various gases.

Antioxidant properties of gold nanoparticles studied by ESR spectroscopy

Abstract: The Au-containing nanocomposites were synthesized by UV irradiation followed by the thermal treatment of chitosan oligomer solutions doped by HAuCl4. The size of the formed gold nanoparticles depends on the concentration of the dopant, which is proved by UV—Vis absorption spectroscopy and small-angle X-ray scattering (SAXS). The antioxidant activity of the gold nanoparticles with respect to hydroxy radicals significantly depends on the specific surface of the particles, which was found using the secondary radical spin-trapping technique. The change in the ·OH radical concentration was monitored by the intensity of the ESR signal of the adduct of the spin trap (α-phenyl-N-tert-butylnitrone) with the Me·radicals formed in the reaction of ·OH with DMSO.

New pyrrolidine and pyrroline derivatives of fullerenes: from the synthesis to the use in light-converting systems

Abstract: The results of the authors’ studies on the [2+3] cycloaddition of azomethine and nitrile ylides generated from picolylamine and benzylamine derivatives to fullerenes are systematized and new experimental data are considered. Catalysts and microwave radiation promoting the formation of ylides and their addition to fullerenes were successfully used for the first time. A large series of new pyrrolidine and pyrroline derivatives of fullerenes C60 and C70 were synthesized and characterized. The proposed procedures afford the reaction products in yields twice as high (80–85%) as those attained by the classical Prato reaction. The reactions proceed with virtually complete regio- (in the case of C70) and stereoselectivity to afford only cis-2′,5′-disubstituted and trans-1′,2′,5′-trisubstituted pyrrolidinofullerenes. Pyridyl-substituted pyrrolidinofullerenes react with metalloporphyrins and phthalocyanines to form self-ordered coordination complexes. The latter are analogs of natural photosynthetic antenna systems due to photoinduced charge separation that occurs in these complexes upon exposure to light.

Mechanochemical preparation and pharmacological activities of water-soluble intermolecular complexes of arabinogalactan with medicinal agents

Abstract: A possibility of mechanochemical preparation of water-soluble complexes of a plant polysaccharide arabinogalactan and poorly soluble medicinal agents (Sibazon(=Diazepam), Mezapam(=Medazepam), Indometacin, and Azaleptin(=Clozapine)) has been investigated. Their molecular dynamics (NMR relaxation method in solution) and some pharmacological properties have been studied in comparison with the original pharmaceutical drugs.

1,3-Dipolar addition reactions to fullerenes: the role of the local curvature of carbon surface

Abstract: Structural peculiarities of fullerenes C20, C24, C30, C36, C40, C60, C70, and C76 and their adducts with 1,3-dipolarophiles (ozone and diazomethane) were investigated by the DFT method with the PBE functional. A correlation between the heats of 1,3-dipolar addition reactions and the carbon surface curvatures at reaction sites in the original fullerene molecules was found.

Dissociation energies of O-H bonds in natural antioxidants

Abstract: The dissociation energies of O-H bonds in natural antioxidants were estimated from the kinetic data (rate constants of reactions of the antioxidants with the peroxy radicals). The calculations were performed using the method of intersecting parabolas. α-Tocopherol was used as a reference phenol with D O-H = 330 kJ mol−1. The following groups of antioxidants were chosen for the estimation: tocopherols, their sulfur- and selenium-containing analogs, flavones, flavanones, and gallates. The discrepancy in the D O-H values for the same phenol by measurements of k(RO2 · + ArOH) of different authors does not exceed 2 kJ mol−1. The D O-H values were calculated for 64 phenols.

New chiral Schiff bases derived from (+)- and (−)-α-pinenes in the metal complex catalyzed asymmetric oxidation of sulfides

Abstract: New chiral Schiff bases were derived from (+)- and (−)-α-pinenes for the first time. Coordinated to vanadium ions, they can be used as ligands in catalytic oxidation of sulfides into chiral sulfoxides. Conditions for the asymmetric oxidation of thioanisole to methyl phenyl sulfoxide in optical purity up to 32% were found. Variation of substituents in the ligand has a significant effect not only on enantioselectivity of the reaction, but also on absolute configuration of the sulfoxide formed.

Asymmetric aldol condensation in an ionic liquid-water system catalyzed by (S)-prolinamide derivatives.

Abstract: Asymmetric aldol reaction of unmodified aldehydes with ketones catalyzed by 1(R),2(R)-bis((S)-prolinamido)cyclohexane (1) or (Rax)-2,2′-bis((S)-prolinamido)-1,1′-binaphtyl (2) proceeds with high yield (68–99%) and diastereoselectivity (dr ≥ 75/25) in the system (1-butyl-3-methylimida-zolium) tetrafluoroborate ([bmim][BF4])-water. The dependence of ee of the dominating anti-diastereomer of aldol on the percentage of water has a maximum at 50 vol.%. Catalyst 1 can be recycled 5 times without losses in the aldol yield, dr and ee.

Molecular meccano for light-sensitive and light-emitting nanosized systems based on unsaturated and macrocyclic compounds

Abstract: The review presents the results of the development of an universal approach to the molecular design of light-sensitive and light-emitting nanosized systems with desired properties based on unsaturated and macrocyclic compounds. Within the same class of compounds, various nanosized systems were constructed using a limited number of structural fragments. These nanosized systems are susceptible to all main types of photoprocesses, such as fluorescence, photodissociation, photoisomerization, photocycloaddition, photoelectrocyclization, excimer formation, charge-transfer complex formation, the formation of the twisted intramolecular charge-transfer state (TICT state), and the electron transfer. The use of photostructural transformations for controlling the complexation and mechanical movements in molecular devices and machines is discussed. The prospects of application of the new strategy are exemplified by the design of the previously unknown types of molecular switches, materials for optical chemosensors, optical data recording and storage media, photoswitchable molecular devices, and photocontrolled molecular machines.

Modification of multiwalled carbon nanotubes by carboxy groups and determination of the degree of functionalization

Abstract: Multiwalled carbon nanotubes were modified by carboxy groups. Four independent methods for the determination of the degree of functionalization of the surface were proposed: 13C NMR spectroscopy, thermogravimetry, titrimetry, and fluorimetry. The first two methods show the total content of carboxy groups in the sample, and the latter two methods give information about the content of the surface groups only.

Fluoride optical nanoceramics

Abstract: The methods for preparation of highly transparent optical ceramics based on simple and complex fluoride compounds of elements of the first, second, and third Group in the Periodical system are considered. The use of precursors as nanopowders and processes of their self-assembling on heating results in maximally homogeneous, transparent, and mechanically strong ceramics. The resulting calcium fluoride ceramics possess optical losses of 10−2–10−3 cm−1 at 1.06 μm and shock resistance characterized by the fracture toughness K 1C = 4.7±0.3 MPa m1/2 (for comparison, for a calcium fluoride single crystal K 1C = 1.5±0.15 MPa m1/2). Regularities of the chemistry of fluoride nanopowders were considered in comparison with the oxide nanopowders: the fluorides are prone to hydrolysis, and powder nanoparticles precipitated from aqueous solutions have complex and heterogeneous (over the volume) chemical composition. The spectral luminescence properties of the ceramics activated by rare-earth metals (Ce3+, Nd3+, Er3+, Yb3+) or containing active color centers are presented. The generation properties of the lithium fluoride ceramics with the color centers and the ternary Ca-Sr-Yb fluoride during diode laser pumping are describe

Versatile three-component synthesis of 2′-amino-1,2-dihydrospiro[(3H)-indole-3,4′-(4′H)-pyran]-2-ones

Abstract: A versatile method for the synthesis of 2′-amino-1,2-dihydrospiro[(3H)-indole-3,4′-(4′H)-pyran]-2-ones has been suggested consisting in the three-component reaction of isatins, cyanoacetic acid derivatives, and α-methylenecarbonyl compounds (β-dicarbonyl compounds, activated phenols, and OH-substituted heterocycles) in ethanol in the presence of triethylamine as a catalyst. The reaction proceeds selectively to form spiro[(3H)-indole-3,4′-(4′H)-pyrans].

Complexation of N-alkyl(aryl)- and N,N-dialkylcarbamoylmethylphosphine oxides with the f-elements

Abstract: Complexation of N-alkyl(aryl)carbamoylmethylphosphine oxides (CMPO) and their N, N-dialkyl analogs in neutral media was studied. N-Alkyl derivatives react with praseodymium and europium nitrates both in solution and in the individual state to give 1: 2 and 1: 3 complexes, depending on the ratio of the starting reagents; for N-aryl amides, 1: 3 complexes were obtained only. With the uranyl cation, both N-alkyl and N,N-dialkyl derivatives of CMPO form various 1: 1 complexes.

First molecular octahedral rhenium cluster complexes with terminal As- and Sb-donor ligands

Abstract: Six new molecular octahedral cluster complexes with the general formulas trans-[{Re6(μ3-Q)8}(EPh3)4Br2] and fac-[{Re6(μ3-Q)7(μ3-Br)}(AsPh3)3Br3] (Q = S or Se and E = As or Sb) were synthesized by the reactions of the cesium salts of the [{Re6(μ3−S)8}Br6]4−, [{Re6(μ3-Se)8Br6]3−, and [{Re6(μ3-Q)7(μ3-Br)}Br6]3− anions with molten triphenylarsine (AsPh3) and triphenylantimony (SbPh3), respectively. The compositions and structures of the resulting complexes were established by single-crystal X-ray diffraction and confirmed by elemental analysis and vibrational spectroscopy. The compositions and structures of the complexes depend on the composition of the cluster core in the starting salts. The luminescence spectra were recorded for powdered samples of all these compounds and the earlier described complexes trans-[{Re6Q8}(PPh3)4Br2] and fac-[{Re6Q7Br}(PPh3)3Br3].

Effect of immobilization on the main dynamic characteristics of the enzymatic oxidation of methane to methanol by bacteria Methylosinus sporium B-2121

Abstract: The main dynamic characteristics of biochemical methanol formation by the oxidation of methane using a biocatalyst were studied. The biocatalyst is based on cells of bacteria Methylosinus sporium B-2121, both suspended in a medium and immobilized in the poly(vinyl alcohol) cryogel. The change in the methane concentration and the biocatalyst amount affects the productivity of the system, the maximal concentration of methanol in the cultural liquid, and the rate of methanol accumulation. The most part of the dynamic characteristics are described by extremal curves. The experimental conditions were optimized prior to experiments. The use of the immobilized biocatalyst makes it possible to enhance the productivity of the process more than fivefold compared to that of the free cells and to achieve the highest methanol concentration in the medium: 62±2 mg L−1.

Synthesis of macrocyclic systems from 4,4′-diamino-3,3′-bi-1,2,5-oxadiazole and 3(4)-amino-4(3)-(4-amino-1,2,5-oxadiazol-3-yl)-1,2,5-oxadiazole 2-oxides

Abstract: Oxidative cyclocondensation of 4,4′-diamino-3,3′-bi-1,2,5-oxadiazole and isomeric 3(4)-amino-4(3)-(4-amino-1,2,5-oxadiazol-3-yl)-1,2,5-oxadiazole 2-oxides under the action of dibro-moisocyanurate gave 12- and 18-membered macrocyclic systems containing two or three bifurazanyl or furazanylfuroxanyl moieties linked by azo bridges. The latter were oxidized into azoxy groups with Caro’s acid in 20% oleum.

Cetane numbers of hydrocarbons: calculations using optimal topological indices

Abstract: The QSPR problem for cetane numbers of hydrocarbons, a key property of oil fuels, was considered for the first time. Based on the approach developed, calculations have been carried out and relations derived for prediction of the cetane numbers of alkanes and cycloalkanes. Results of cetane number calculations for 180 unknown and non studied hydrocarbons are presented.

Thermodynamics of methane adsorption on the microporous carbon adsorbent ACC

Abstract: The behavior of the thermodynamic functions (differential molar isosteric heat of adsorption, entropy, enthalpy, and heat capacity) of the adsorption system methane—microporous carbon adsorbent ACC was analyzed at different adsorption equilibrium parameters in the temperature interval from 177.65 to 393 K and in the pressure range from 1 Pa to 6 MPa. The influence of the nonideal character of the gas phase and noninertness of the adsorbent were taken into account, which resulted in the appearance of the temperature dependence of the isosteric heat of adsorption, especially in the region of high pressures of the adsorptive. For the system studied, nonideality of the gas phase exerts the main effect on the thermodynamic functions of the adsorption system. In this interval of the parameters of the adsorption system, the correction to the noninertness of the adsorbent is not higher than 2.5%.

Spiropyrans and spirooxazines

Abstract: The Duff formylation of 5-bromo- or 5-chloro-8-hydroxyquinoline leads to the corresponding 7-formyl derivatives, condensation of which with 2-methyleneindolines or 3H-indolium halides in the presence of a base afforded new photochromic 6′-halo-substituted spiro[indoline-2,2′-2H- pyrano[3,2-h]quinolines]. Thermal and photo-induced isomerization of compounds obtained have been investigated by 1H NMR and UV spectroscopy.

Thermal arene exchange in the naphthalene complex [CpRu(η6-C10H8)]+

Abstract: Naphthalene in the [CpRu(6−C10H8)]+ complex (1) is substituted for other arenes under reflux in 1,2-dichloroethane to form the [CpRu(6-arene)]+ cations (arene = C6H6, 1,2-C6H4Me2, 1,2,4,5-C6H2Me4, or C6Me6) in 70–80% yields. The reaction is accelerated in the presence of a catalytic amount of acetonitrile. The structure of [1]PF6 was established by X-ray diffraction.

Behavior of [1,2,5]oxadiazolo[3,4- e ][1,2,3,4]tetrazine 4,6-dioxide in various media

Abstract: A behavior of [1,2,5]oxadiazolo[3,4-e][1,2,3,4]tetrazine 4,6-dioxide (1) in organic solvents and aqueous solutions of various acidity has been studied by UV spectrophotometry. Kinetic laws for the N,N′-dioxide 1 hydrolysis have been established and decomposition process constants at various temperatures in the media with pH 6.86 have been determined. A product of the reaction with water, viz., 5H-[1,2,3]triazolo[4,5-c][1,2,5]oxadiazole, has been isolated. 5-(tert-Butyl)-5H-[1,2,3]triazolo[4,5-c][1,2,5]oxadiazole has been synthesized as the model compound. Decomposition of N,N′-dioxide 1 occurs in basic media.

Synthesis of new lanthanide naphthalocyanine complexes based on 6,7-bis(phenoxy)-2,3-naphthalodinitrile and their spectral and electrochemical investigation

Abstract: A number of naphthalocyanine and dinaphthalocyanine complexes of the rare-earth elements based on 6,7-bis(phenoxy)-2,3-naphthalodinitrile obtained for the first time has been synthesized and their spectral properties have been investigated. Electrochemical behavior of lutetium [bis(octaphenoxy)naphthalocyanine] in the thin hydrophobic films has been studied.

Modes of coordination and stereochemistry of the NO3− anions in inorganic nitrates

Abstract: Stereochemical features of 950 nitrate groups in the structures of 365 inorganic nitrates were analyzed using TOPOS software. The types of coordination of nitrate groups are systematized by means of Voronoi-Dirichlet polyhedra and the method of intersecting spheres. Terminal coordination (53% of the total number of nitrate groups), most of all terminal bidentate coordination (47%) was found to prevail. Bridging nitrate groups occur less frequently (20%). A considerable number of nitrate groups are not incorporated in the coordination sphere of the complexing atom but form H-bonds or bonds of mainly ionic nature (27%). A number of metal cations show clear-cut tendency for a certain mode of coordination of the NO3 group. Criteria for classification of nitrate groups into four types (slightly distorted groups and groups with monodentate, bidentate and asymmetric type distortion) are proposed. Structural features of nitrate groups depending on the mode of coordination are considered. The geometry of mono- or bidentate nitrate groups can differ appreciably from the typical one because of participation of terminal oxygen atoms in ionic or hydrogen bonds.

Reaction of 3-(polyfluoroacyl)chromones with hydrazines: new regioselective synthesis of RF-containing pyrazoles

Abstract: Reactions of 3-(polyfluoroacyl)chromones with hydrazine, methyl-and phenylhydrazines proceed by the mechanism of nucleophilic 1,4-addition with subsequent pyrone ring opening and heterocyclization at the polyfluoroacyl group to 4-(2-hydroxyaroyl)-3-polyfluoro-alkylpyrazoles or at the aroyl group to 4-polyfluoroalkyl-2,4-dihydrochromeno[4,3-c]pyrazol-4-ols. Regiochemistry of the products was established based on the data of 2D-experiments HSQC, HMBC, and NOESY and X-ray diffraction study.

Endohedral gadolinium-containing metallofullerenes in the trifluoromethylation reaction

Abstract: An efficient method for the synthesis of trifluoromethyl derivatives of endohedral gadolinium-containing metallofullerenes was proposed. High-purity (98–99%) trifluoromethyl derivatives Gd@C82(CF3)5 (two isomers) and Gd2@C80(CF3) have been synthesized for the first time. They were isolated and characterized by HPLC, MALDI-TOF mass spectrometry, and UV-Vis spectroscopy.