Showing papers in "Russian Chemical Bulletin in 2007"

Ionic fullerene compounds containing negatively charged dimers and coordinatively bound anions

Abstract: The review summarizes the results of investigations of ionic fullerene compounds containing negatively charged dimers and fullerene anions coordinated to metalloporphyrins. Fullerene radical anions were found to form diamagnetic singly bonded (C60 −)2 and (C70 −)2 dimers. Dimerization is reversible and leads to paramagnetic—diamagnetic phase transitions or a decrease in the magnetic moment of the complexes. The temperature, at which dissociation of the (C60 −)2 dimers begins, varies from 140 to 320 K; the corresponding temperature for the (C70 −)2 dimers varies from 260 to 360 K and higher. We prepared the first doubly bonded (C60 −)2 dimer. At 300 K, this dimer exists as a biradical. The fullerene radical anions form Co—C coordination bonds with cobalt(II) porphyrinates. The resulting anions are diamagnetic. In some cases, Co—C coordination bonds undergo reversible dissociation, resulting in magnetic transitions from the diamagnetic to the paramagnetic state.

Functionalization of sterically hindered o-benzoquinones: amino-substituted 3,6-di(tert-butyl)-o-benzoquinones

Abstract: New sterically hindered functionalized o-quinones were synthesized by the 1,4-nucleophilic addition of secondary cyclic amines to 3,6-di(tert-butyl)-o-benzoquinone. The ability of these o-quinones to form o-semiquinone complexes with transition and main-group metals was studied by ESR spectroscopy in solution.

Ligands of the colchicine site of tubulin: A common pharmacophore and new structural classes

Abstract: Structure-activity relationships for ligands of the colchicine site of tubulin were analyzed based on their common pharmacophore. The role of the elucidation of the three-dimensional structure of the colchicine site of tubulin on the development of studies aimed at the search for the ligands of this site is analyzed.

Selective mono-and diamination of polyfluorinated benzenes and pyridines with liquid ammonia

Abstract: Amination of pentafluoropyridine, 2,3,5,6-tetrafluoropyridine, 4-chlorotetrafluoropyridine, 3,5-dichlorotrifluoropyridine, octafluorotoluene, α,α,α,2,3,5,6-heptafluorotoluene, decafluoro-m-xylene, decafluorobiphenyl, hexafluorobenzene, and pentafluorobenzene with liquid ammonia was investigated. Bis-aminodefluorination temperatures for the majority of substrates were shown to exceed significantly the corresponding temperatures of monoaminodefluorination. The optimal conditions for selective preparation of mono-and diaminopolyfluoro(het)arenes were elucidated. An efficient method for isolation of particular polyfluorophenylenediamines from product mixtures formed in nonselective reactions of pentafluorobenzene and hexafluorobenzene with aqueous ammonia based on complexation with a crown ether is proposed.

Biological studies of organotin( IV ) complexes with 2-mercaptopyrimidine

Abstract: The known organotin(IV) complexes with 2-mercaptopyrimidine (L) [Me2SnL2] (1), [Bun 2SnL2] (2), [Ph2SnL2] (3), and [Ph3SnL] (4) were synthesized using a new approach. The effect of the synthesized compounds on peroxidation of fatty acids (oleic and linoleic) was studied. Complexes 1–4 promote the peroxidation of oleic acid. Their effect on the enzymatic peroxidation of linoleic acid with lipoxygenase was compared with that of cisplatin and in vitro cytoxicity against sarcoma cancer cells was determined. The antiproliferative effect of complexes 2–4 was demonstrated.

Styryl dyes. Synthesis and study of the solid-state [2+2] autophotocycloaddition by NMR spectroscopy and X-ray diffraction

Abstract: New styryl dyes of the pyridine and benzothiazole series were synthesized with the aim of investigating the solid-state [2+2] autophotocycloaddition (PCA) reaction. The 1H NMR spectroscopy showed that for most of the compounds under study, the visible light irradiation of thin polycrystalline films of the dyes affords cyclobutane derivatives. The rate of the photoreaction depends on the structure of the dye and is higher for compounds, which contain a short N-substituent in the heterocyclic moiety and have strong absorption in the visible region. Dyes bearing electron-releasing substituents in the benzene ring undergo the stereospecific PCA in the syn-head-to-tail dimeric pair to give the only rctt isomer of cyclobutane derivatives. Electron-withdrawing and bulky substituents in the benzene fragment of styryl dyes extend the range of the mutual orientations of the molecules in the dimeric pairs, resulting in the formation of two or even four isomeric cyclobutanes in the PCA reactions. The structures of some dyes were established by X-ray diffraction. In the overwhelming majority of the structures, one of two packing modes, either syn-head-to-tail or syn-head-to-head, with extensive stacking interactions is observed. A rare example of the anti-head-to-head stacking mode was found for the dicationic dye containing the bulky N+(Et)Me2 substituent in the benzene ring. The syn-head-to-tail and anti-head-to-head stacking modes can facilitate the PCA reaction due to the close spatial proximity of the ethylenic bonds and their parallel orientation in the dimeric pairs of the dye molecules.

Cage complexes of transition metals in biochemistry and medicine

Abstract: The review presents the following main trends and the perspectives of application of the transition metal clathrochelates in medicine and biochemistry: encapsulation of radioactive metal ion for diagnostics and therapy; imaging agents for MRI; antidotes and prolonged pharmaceuticals; pharmaceuticals for boron neutron capture therapy; antihelminthic and antiparasitic detergents; antioxidants; membrane transport of the metal ions; interaction of the cage metal complexes with nucleic acids and the potential of their self-assembling reactions in immunology and molecular biology (recognition of antibodies, antigens and DNA sites); design of HIV inhibitors for the therapy.

Polyalkoxybenzenes from plant raw materials 1. Isolation of polyalkoxybenzenes from CO2 extracts of Umbelliferae plant seeds

Abstract: For the search for a domestic natural source of allylpolyalkoxybenzenes and development of an effective process for their isolation, CO2 extracts of several varieties of parsley, dill, celery, caraway, and nutmeg were analyzed systematically for the first time by GC/MS and GLC techniques. The varieties with high contents of myristicin, elemicin, allyltetramethoxybenzene, apiol, and dillapiol were identified. The conditions of CO2 extraction for obtaining concentrates with minimum contents of the distillation residues were selected. Using high performance fractional distillation, polyalkoxyallylbenzenes with 98–99% purity were isolated from the concentrates on a pilot unit. By isomerization of some allylbenzenes followed by ozonolysis under specially selected conditions, apiol-and dillapiolaldehydes were obtained in 75–80% yields.

cis -Tetra[(organo)(trimethylsiloxy)]cyclotetrasiloxanes: Synthesis and mesomorphic properties

Abstract: Hydrolytic condensation of organotrialkoxysilanes RSi(OR′)3 (R = Me, Et, Pr, CH=CH2; R′ = OMe, OEt) in the presence of sodium and/or potassium hydroxide gave new alkali organosiloxanolates {(M+)4[RSi(O)O−]4}·nL (R = Me, Et, Pr, CH=CH2; M = Na, K; L = R′OH, H2O) in which the main structural fragment is the cyclotetrasiloxanolate fragment cis-[RSi(O)O−]4. Based on these organosiloxanolates, a series of cis-tetra[(organo)(trimethylsiloxy)]cyclotetrasiloxanes was synthesized. For new cyclotetrasiloxanes, the thermotropic transitions and mesomorphic orderings were determined by differential scanning calorimetry, X-ray diffraction analysis, and polarization microscopy. In addition, new mesomorphic compounds were revealed. The character of thermotropic and time evolution of the phase state was found for a mixture of cis-tetra[ethyl(trimethylsiloxy)]-and cis-tetra[phenyl(trimethylsiloxy)]cyclotetrasiloxanes.

Guanidinate borohydride derivatives of lanthanides: synthesis and molecular structures of the [(Me3Si)2NC(NCy)2]Gd(BH4)2DME and [{(Me3Si)2NC(NPri)2}2Sm(BH4)2]−[Li(DME)3]+ complexes. Catalytic activity of the [(Me3Si)2NC(NCy)2]2Ln(BH4)2Li(THF)2 complexes (Ln = Nd, Sm, or Yb) in methyl methacrylate polymerization

Abstract: The reaction of Gd(BH4)3(THF)2 with two equivalents of sodium N,N′-dicyclohexyl-N″-bis(trimethylsilyl)guanidinate in THF followed by the treatment of the reaction product with 1,2-dimethoxyethane produced the monoguanidinate bis(borohydride) complex [(Me3Si)2NC(NCy)2]Gd(BH4)2DME (1) (Cy is cyclohexyl). The treatment of the heterobimetallic samarium complex {(Me3Si)2NC(NPri)2}2Sm(BH4)2Li(THF)2, in which the lanthanide and lithium atoms are linked by two bridging borohydride groups, with 1,2-dimethoxyethane afforded the ionic complex [{(Me3Si)2NC(NPri)2}2Sm(BH4)2]−[Li(DME)3]+ (2). The structures of complexes 1 and 2 were established by X-ray diffraction. The [(Me3Si)2NC(NCy)2]2Ln(BH4)2Li(THF)2 complexes (Ln = Nd (3), Sm (4), or Yb (5)) were found to catalyze methyl methacrylate polymerization.

Complexes of ZrIV and HfIV with monolacunary Keggin-and Dawson-type anions

Abstract: The reactions of the tetranuclear hydroxo complexes [M4(µ2-OH)8(H2O)16]8+ (M = Zr or Hf) with the lacunary Keggin-type ([α-PW11O39]7−) and Dawson-type ([α 2-P2W17O61]10−) phosphotungstates in aqueous solutions produce the sandwich polyoxometalate complexes [M(α-PW11O39)2]10− (M = Zr (1) or Hf (2)) and [M(α 2-P2W17O61)2]16− (M = Zr (3) and Hf (4)). The complexes were isolated and structurally characterized as salts with potassium and dimethylammonium cations. The zirconium and hafnium atoms have a square antiprismatic coordination environment (coordination number is 8). In all complexes, the mutual arrangement of the ligands corresponds to the syn isomer. Hafnium complexes 2 and 4 are the first structurally characterized polyoxometalate complexes of this metal. The structures of the resulting compounds were confirmed also by 31P NMR spectroscopy in solution.

Spinazarin and ethylspinazarin, pigments of the sea urchin Scaphechinus mirabilis

Abstract: 2,3,5,8-Tetrahydroxy-1,4-naphthoquinone (spinazarin) and 6-ethyl-2,3,5,8-tetrahydroxy-1,4-naphthoquinone (ethylspinazarin) were first isolated from the sea urchin Scaphechinus mirabilis. The structures of spinazarins were established based on analysis of spectroscopic data. A preparative synthetic route to ethylspinazarin was proposed.

A relation between energies of the short-lived negative ion states and energies of unfilled molecular orbitals for a series of bromoalkanes

Abstract: A series of bromoalkanes was investigated by means of electron transmission spectroscopy in the gas phase. Experimental values of vertical electron affinities associated with occupation of the LUMO by an incoming electron were assigned using ab initio quantum chemical calculations. The predicted vertical electron affinity values differ from measured ones by at most ±0.2 eV.

Kinetics and mechanism of reactions of photoexcited kynurenine with molecules of some natural compounds

Abstract: Photochemical reactions involving kynurenines, viz., molecules present in the eye lens, can result in modifications of the lens proteins and cause a development of a cataract. The rate constants of the reactions of photoexcited kynurenine with several amino acids and antioxidants contained in the lens were measured. The most efficient quenchers of triplet kynurenine are amino acids tryptophan and tyrosine, as well as antioxidant ascorbate. In all cases, the quenching reaction proceeds by the electron transfer mechanism, except for the reaction with oxygen where transfer of the triplet energy to the oxygen molecule occurs.

Synthesis of salicylaldehydes bearing bulky substituents in the positions 3 and 5

Abstract: Reaction of 2,4-disubstituted phenols with paraformaldehyde in the presence of SnCl4 and 2,6-lutidine afforded a number of new salicylaldehydes, containing bulky substituents (tert-butyl, 1-phenylethyl, 1-(4-tert-butylphenyl)ethyl, α-cumyl, and trityl) in the positions 3 and 5.

Reductive debenzylation of hexabenzylhexaazaisowurtzitane — the key step of the synthesis of polycyclic nitramine hexanitrohexaazaisowurtzitane

Abstract: Main features of the reductive debenzylation of 2,4,6,8,10,12-hexabenzyl-2,4,6,8,10,12-hexaazaisowurtzitane were studied. This process is the key step of the synthesis of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo[5.5.0.03,11.05,9]dodecane (hexanitrohexaazaisowurtzitane, CL-20), a compound with unique energetic and explosive characteristics. The use of the latter is restricted so far by the high cost of the two-step process of debenzylation during which the compound is rapidly deactivated. The expensive Pd/C catalyst is deactivated in the first step of the process, which limits the use of this polycyclic nitramine. The influence of the solvent nature; loadings of the reactants, catalyst, and cocatalyst; the hydrogen pressure and reaction temperature on the general features of the process and the yield of the target precursor of CL-20 was studied.

Macrocyclization of the semiclathrochelate o-carboranylboronate and n-butylboronate iron(II) oximehydrazonates: synthesis and structure of clathrochelate products and unexpected allosteric effect of the apical substituent

Abstract: The template condensation of diacetylmonooxime hydrazone (HDXO) with n-butylboronic acid and dimethyl ester of o-carboranyldiboronic acid on the iron(II) ion matrix afforded the [Fe(DXO)3(BBu)](BF4) and [Fe(DXO)3(Bo-carb)](BF4) semiclathrochelates. The H+-ion-catalyzed macrocyclization of these precursors with an excess of formaldehyde and triethyl orthoformate (TOF) resulted in the corresponding macrobicyclic complexes. In the case of o-carboranylboronate semiclathrochelate, the macrocyclization with TOF gave the clathrochelate with the previously unknown syn,syn,anti-orientation of the ethoxy substituents relative to the 1,3,5-triazacyclohexane capping fragment. The complexes obtained were characterized using elemental analysis, IR, UV-Vis, MALDI-TOF mass, 1H, 11B, and 13C NMR, and 57Fe Mossbauer spectroscopies and X-ray crystallography.

Supramolecular approach to crystallization of polynuclear chromium(III) aqua hydroxo complexes: synthesis and crystal structures of complexes [Cr2(OH)2(H2O)8]4+ and [Cr4(OH)6(H2O)12]6+ with cucurbit[n]uril (n = 7, 8)

Abstract: Supramolecular compounds of the compositions {[Cr2(OH)2(H2O)8](C42H42N28O14)2}-(NO3)4·18.75H2O (1) and {[Cr4(OH)6(H2O)12](C48H48N32O16)3(NO3)6·55H2O (2) were synthesized from aqueous solutions of chromium(III) nitrate and the macrocyclic cavitand cucurbit[n]uril (C6n H6n N4n O2n , where n = 7 or 8, respectively). According to the X-ray diffraction study, the polynuclear chromium aqua complexes are disposed in cavities formed by the cucurbit[n]uril molecules and are linked to these molecules through hydrogen bonds between the hydroxo and aqua ligands of the polycations and the portal oxygen atoms of the macrocycles. Compound 1 is the first example of supramolecular compounds of cucurbit[7]uril with metal aqua complexes. The isolation of the supramolecular adduct with cucurbit[8]uril 2 in the single-crystalline state allows the determination of the structure of the tetranuclear chromium aqua complex having an adamantane-like structure, [Cr4(μ2-OH)6(H2O)12]6+, which has been previously unknown in the solid state.

Synthesis of alkyl-substituted phosphorus phthalocyanines and triazatetrabenzocorroles

Abstract: New alkyl-substituted phosphorus phthalocyanines and triazatetrabenzocorroles were synthesized. The structures of these complexes were confirmed by 1H, 13C, and 31P NMR spectroscopy, mass spectrometry, and electronic absorption spectroscopy.

Electrocatalytic reduction of aryldichlorophosphines with the (2,2′-bipyridine)nickel complexes

Abstract: The reduction of aryldichlorophosphines in organic solvents was studied by cyclic voltammetry, preparative electrolysis, and chemical reduction. The reaction of the electrochemically generated (2,2′-bipyridine)nickel(0) complexes with aryldichlorophosphines PhPCl2 and tippPCl2 (tipp is 2,4,6-triisopropylphenyl) proceeds through the formation of highly reactive organophosphorus intermediates, whose reactions with diphenylacetylene and hex-1-ene afford phosphirene and phosphirane heterocycles, respectively.

Photochemistry of PtBr62− in aqueous solution

Abstract: Photochemistry of the PtBr62− complex in aqueous solution was studied by steady-state and laser flash photolysis (308 nm). The multistep photoaquation of the complex occurs in the nano-and microsecond time intervals without the formation of intermediate platinum(III) complexes.

Four new chamigrane sesquiterpenoids from the opistobranch mollusk Aplysia dactylomela

Abstract: Four new chamigrane sesquiterpenoids, (6S,10S)-10-bromo-3,11,11-trimethyl-7-methylidenespiro[5.5]undec-2-ene-4-one, (4S,6S,10S)-10-bromo-3,11,11-trimethyl-7-methylidenespiro[5.5]undec-2-ene-4-ol, (3R,4S,6S,10R)-10-bromo-3,11,11-trimethyl-7-methylidenespiro[5.5]undecane-3,4-diol, and (6S,7S,11R)-2-chloro-3,7,11-trimethyl-10-methylidenespiro[5.5]undec-2-ene-7-ol, were isolated from the sea hare Aplysia dactylomela. The chemical structures of new compounds were established by NMR spectroscopy and mass spectrometry. The cytotoxic activity of some of the obtained compounds against promyelocytic HL-60 and monocytic THP-1 leukemia cells was demonstrated.

Reactions of organotin chlorides R2SnCl2 (R = Et, But, or Ph) with lithium 4,6-di(tert-butyl)-N-(2,6-diisopropylphenyl)-o-amidophenolate. Synthesis and structures of tin(IV) o-iminoquinone complexes

Abstract: The exchange reactions of tin diorganohalides R2SnCl2 (R = Et, But, or Ph) with lithium amidophenolate APLi2 (AP is the 4,6-di(tert-butyl)-N-(2,6-diisopropylphenyl)-o-iminobenzo-quinone dianion) in tetrahydrofuran produced the new five-coordinate (Et2SnAP(THF) (3)) and four-coordinate (R2SnAP (R = But, Ph)) tin(IV) complexes. The reaction of Ph2SnCl2 with APLi2 in a nonpolar solvent (hexane or toluene) is accompanied by the additional redox process giving rise to the paramagnetic complex Ph2Sn(ImSQ)Cl (6) (ImSQ is the 4,6-di(tert-butyl)-N-(2,6-diisopropylphenyl)-o-iminobenzoquinone radical anion). The molecular structures of complexes 3 and 6 were established by X-ray diffraction.

Kinetics and mechanism of photolysis of the iron( III ) complex with tartaric acid

Abstract: The formation of MV•+ radical cations was observed upon the laser flash photolysis of the iron(III) tartrate complex [FeIIITart]+ (1) in the presence of methyl viologen (MV2+). The rate constants of the reactions involving MV•+ were measured. The intramolecular electron trans-fer to form FeII and escape of the organic radical to the solvent bulk upon the photolysis of 1 were proposed.

Thermodynamic properties of carbosilane dendrimers of the seventh and ninth generations with terminal butyl groups in the temperature range from T → 0 to 600 K

Abstract: Temperature dependences of the heat capacity of carbosilane dendrimers with butyl terminal groups of the seventh and ninth generations were determined in the temperature range from 6 to 600 K by precision adiabatic vacuum calorimetry and differential scanning (dynamic) calorimetry. The physical transitions were revealed and their thermodynamic characteristics were analyzed. The experimental data obtained were used to calculate the standard thermodynamic functions C p (T), H°(T) − H°(0), S°(T), and G°(T) − H°(0) for the temperature range from T → 0 to 600 K. The thermodynamic function-molar weight isotherms for the dendrimers of the third–ninth generations with terminal butyl groups in the glassy and highly elastic state are linear.

Synthesis and antioxidant properties of sodium S-[3-(hydroxyaryl)propyl] thiosulfates and [3-(hydroxyaryl)propane]-1-sulfonates

Abstract: Sodium S-[3-(hydroxyaryl)propyl] thiosulfates and [3-(hydroxyaryl)propane]-1-sulfonates with various spatial hindrance of their phenolic OH groups were synthesized from dialkylphenols via a number of intermediate products. On a model reaction of oxidation of methyl oleate in aqueous sodium dodecyl sulfate, the rate constants of the interaction of the synthesized compounds with lipoperoxide radicals were determined.

Hybrid macromolecular antioxidants based on hydrophilic polymers and sterically hindered phenols

Abstract: A novel class of biologically active substances was created. These are hybrid macromolecular antioxidants (HMAO) based on hydrophilic polymers with chemically grafted sterically hindered phenols with different structural parameters. The antiradical activities of HMAO were assessed in reactions with 2,2-diphenyl-1-picrylhydrazyl and the corresponding sodium sulfonate in various solvents. The mechanism that explains the substantially enhanced activities of HMAO in water was proposed. The state of HMAO in solutions was studied by viscosimetry and photon correlation spectroscopy. HMAO were assayed in biological models.

New type of 2-alkyl-substituted 1,8-naphthyridine systems containing a phosphoryl group in the side chain

Abstract: First organophosphorus derivatives of 2-alkyl-and 2,3-alkylene-substituted 1,8-naphthyridines were synthesized by the Friedlander reaction starting from 2-aminonicotinaldehyde and diphenylphosphoryl(cyclo)alkanones, respectively.

The sulfonation of pyrrole: Choice of relevant computational procedure for quantum chemical analysis of positional orientation

Abstract: The influence of the solvent effect, zero-point energy correction, and electron correlation on conclusions about positional orientation of pyrrole sulfonation was studied by the B3LYP, HF, and MP2 methods with the 6-31G(d) and 6-31+G(d) basis sets. The most important role is played by the solvation effects. Basis set extension effects and the inclusion of zero-point energy correction contribute insignificantly. According to calculations using all the methods listed above, the formation of β-pyrrolesulfonic acid in polar solvent is thermodynamically more favorable and less kinetically hindered. B3LYP calculations seem to be more appropriate, because the method allows experimental data on positional orientation of the sulfonation of pyrroles to be interpreted in a simpler and more reliable fashion.

Synthesis, complexation, and E—Z photoisomerization of azadithiacrown-containing styryl dyes as new optical sensors for mercury cations

Abstract: New styryl dyes containing azadithia-15-crown-5 fragments were synthesized. The complexation of these compounds with Ag+, Pb2+, Cu2+, Hg2+, and H+ cations was studied by 1H NMR spectroscopy, steady-state, and time-resolved spectroscopy. The stability constants of the complexes were calculated from the spectrophotometric titration data. The photophysical properties and E—Z photoisomerization of styryl dyes and their complexes with mercury and copper(II) cations in acetonitrile were examined.