Abstract  This paper is aimed at providing an overview of our studies on the title compounds as spin trapping agents, and at emphasising the links between purely cognitive, academic research and industrial applications. Phosphoryl- and thiophosphoryl-dithioformates exhibit a comparable and interesting spin trapping ability, their efficiency being analogous to that of some aromatic thioketones. The spectral hyperfine structure may provide valuable information on the nature of the trapped radical but the phosphorus hfs constant cannot be used as an useful indicator. Thionformates are less efficient spin traps than the corresponding dithioformates, being inert towards stabilised radicals such as benzyl or relatively hindered radicals as tert-butoxyl. In no case could spin adducts to thiolformates be detected, this being an indication that their carbonyl group is significantly deactivated with respect to that of organic and organometallic ketones. Because of their ability in trapping either alkyl or alkoxy radicals both kind of dithioformates were exploited as stabilisers in the processing of such polymers as polypropylene, but their outstanding performance could not compensate for some organoleptic drawbacks that were intrinsic of the thiocarbonyl function. A much more promising application of dithioesters is instead their use as RAFT chain transfer agents in the controlled polymerisation of styrene. Preliminary experiments with benzyl diethoxyphosphoryldithioformate have afforded polystyrene with a polydispersity as low as 1.17, but further studies are needed to fully elucidate the RAFT-polymerisation mechanism and to optimise its outcome.

Abstract  We report a novel optimized nonlinear optical chromophore, 1-n-butoxyl-2,5-dimethyl-4-(4'-nitrophenyl-azo)benzene (BDMNPAB), that acts effectively as both electro-optic chromophore and plasticizer in a low glass-transition-temperature photorefractive polymeric composite. In the polymeric composite of BDMNPAB:poly(N-vinylcarbazole) (PVK):2,4,7-trinitro-9-fluorenone in a weight ratio of 44.55:1, the glass transition temperature was lowered to 43 degrees C. Two-beam coupling gain as high as 195 cm(-1) and an index grating amplitude of about 4.3 x 10(-3) were obtained. Furthermore, high solubility of the dye in PVK and high stability of the photorefractive composite were also exhibited.

Abstract  Kinetic solvent effects on hydrogen abstractions, namely, acceleration in nonpolar solvents, have been presumed to be restricted to O-H hydrogen donors. We demonstrate that also abstractions from C-H and even Sn-H bonds by cumyloxyl radicals and n,pi*-excited 2,3-diazabicyclo[2.2.2]oct-2-ene are fastest in the gas phase and nonpolar solvents but slowest in acetonitrile. Accordingly, solvent effects on hydrogen abstractions are more general, presumably due to stabilization of the reactive oxygen or nitrogen species in polar solvents.

Abstract  This paper reports the first example of the intramolecular three-center C-H center dot center dot center dot O hydrogen bonding. Nine 1,4-di(2-methoxy and/or i-butoxy)phenyl-1,2,3-triazole derivatives, that is, 1-9, are prepared. The X-ray diffraction studies reveal that 1, 2, and 4, which bear a methoxyl or i-butoxyl group on the N-1- or C-4-substituted benzene ring, form a six-membered C-H center dot center dot center dot O hydrogen bond between the C(5)-H of their triazole unit and the alkoxyl O, while 5-8, which bear two methoxyl and/or i-butoxyl groups on the similar benzene rings, form two three-center C-H center dot center dot center dot O hydrogen bonds. It is also found that in most cases the hydrogen bond oil the C-4 side is shorter than that oil the N-1 side and both of them can be stabilized by the aromatic stacking and other intermolecular interactions. The (NOESY) (1)H NMR experiments in CDCl(3) and CDCl(3)-DMSO-d(6) mixture (4: 1) support that both the six-membered and the three-center C-H center dot center dot center dot O hydrogen bonds also exist in solution.

Abstract  We report a strong electroabsorptive effect in a photorefractive polymeric composite of 1-n-butoxyl-2,5-dimethyl-4-(4'-nitrophenylazo)benzene:poly(N-vinylcarbazole):2,4,7-trinito-9-flourenone with a weight ratio of 44:55:1. An electroabsorption coefficient as large as 27 cm(-1) at 632.8 nm was measured with an applied field of 92.4 V/mu m and an incident angle of 60 degrees in air. This effect was found to depend strongly on the incident angle of the beam. With the quick translating technique, an orientationally enhanced electroabsorption grating was observed in the composite. Contributions to the electroabsorption grating were proved to be similar to 1/3 from the variation of the magnitude and 2/3 from the variation of the direction of the total electric field inside the sample film. (C) 1999 Optical Society of America [S0740-3224(99)01203-5]. OCIS codes: 160.5320, 160.5470, 050.2770, 250.2030.

Abstract  Effects of hydrolysis-rate-control-additives (carbonyl compounds such as ethylacetoacetate and acetylacetone) on the hydrolysis behavior of aluminium secondary butoxide and condition for the formation of monodispersed alumina particles were investigated. The reactive enol form of the carbonyl compounds substituted butoxyl group of aluminium secondary butoxide and chelated the aluminium atom. The chelating ligand would not be easily removed upon hydrolysis reaction because the aluminium-ligand bond was sufficiently strong. As a consequence, the rate of hydrolysis and polycondensation of modified precursor decreased. By hydrolyzing this modified stable precursor, the monodispersed alumina particles were prepared in the wide range of water concentration; about 8 times that of non-modified precursor when 0.006 mol/I ethylacetoacetate was added and about 4 times when 0.006 mol/l acetylacetone was added. The average particle size of obtained monodispersed particles and the geometrical standard deviation were 0.2-mu-m and 1.18, respectively. The morphology of particles changed with increasing water concentration as follows; agglomerates of coarse texture-->monodispersed particles-->agglomerates of fine texture.

Abstract  Theoretical and experimental investigations of the intensity- and field-dependent photorefractive response in polymeric composites were presented. Measurements of the decay time constant and the corresponding grating-amplitude were demonstrated in photorefractive composite consists of 1-n-butoxyl-2,5 -dimethyl-4-(4'-nitrophenylazo)benzene (BDMNPAB): poly(N-vinylcarbazole) (PVK):2,4,7-trinitro-9-fluorenone (TNF) with a weight ratio 44:55.1. Analysis suggested that two gratings exist simultaneously, one was caused by the photorefractive effect, and the other was caused by the photoisomerization process.

Abstract  For poly(9,9-di(6-(2-(3-oxetanyl)butoxyl)hexyl)-2,7-fluorene) (POBOHF), measurements on field induction-thermally stimulated current (FI-TSC) and electroluminescence (EL) under a wide temperature range demonstrate that electric field induction (FI) accompanied by side chain motion can lead to a formation of excimers, which contribute to a growth of a green component in the EL spectrum. This phenomenon also happens to poly(9,9-di-n-octyl-2,7-fluorene) (PFO), especially under long-term operations with higher electric fields (1 x 10(6) V/cm), copolymers of OBOHF and FO (PF-1/1 and PF-1/3), and even cross-linked POBOHF. The higher polarity of the side chain in the polyfluorenes (PFs) can cause a more pronounced FI effect. For POBOHF, the green component can even dominate after a few cycles of device operation. Lowering the content of cross-linkable commoner in the copolymers from 50 to 25 mol % only moderately suppresses the formation of FI excimers.

Abstract  Electron photodetachment from methylphosphide, cyclohexylphosphide, and phenylphosphide ions was carried out using an ion cyclotron resonance (ICR) spectrometer to generate, trap, and detect the ions. The electron affinities of the corresponding radicals inferred from the onsets were as follows: methylphosphinyl, 21.6 +/- 0.4 kcal/mol; cyclohexylphosphinyl, 23.8 +/- 0.4 kcal/mol; and phenylphosphinyl, 35.1 +/- 0.9 kcal/mol. The acidity of methylphosphine was determined by bracketing reactions to be DELTA-H-degrees(acid) between 371.5 and 366.4 kcal/mol, giving a P-H bond energy in methylphosphine between 74 and 79.5 kcal/mol.

Abstract  Emissions of volatile organic compounds (VOC) from different types of furniture coatings have been investigated by test chamber studies under dynamic conditions. A total of 150 VOCs could be identified in the chamber air. Compound groups occurring most often were aliphatic and aromatic aldehydes, ketones, aromatic hydrocarbons, glycols and esters. Special attention was paid to the detection of typical components of coating materials such as acrylic monomers, photo initiators and other additives. The TVOC-values, measured after a preconditioning period of 20 days, ranged from 4 "mu"g/m3 to 1288 "mu"g/m3 with an arithmetic mean of 173.9 "mu"g/m3 and a median 60.0 "mu"g/m3. The highest chamber concentrations of individual components were found for some solvent residues such as n-butylacetate, butylglycol, 1-butanol-3-methoxy-acetate and butyldiglycolacetate. The results have shown that furniture may contribute significantly to indoor air pollution. The calculated emission factors were comparable with data reported for other indoor materials.

Abstract  Abstract: The reactivity of two aminoalkyl radicals formed from ethyldimethylaminobenzoate (EDB) and a polymeric derivative (PoEDB) toward different additives such as oxygen, TEMPO, methylacrylate MA, phenols, an onium salt, CBr4 is investigated through Laser Flash Photolysis. The transient absorption spectra of the radicals are in a good agreement with the spectra calculated by using molecular orbitals calculations. The interaction rate constants with the different additives are measured. The reactivity of EDB and PoEDB radicals appears as quite similar. Quantum mechanical calculations support the experimental results. [Copyright 2009 Elsevier] Copyright of Chemical Physics Letters is the property of Elsevier Science Publishers B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts)

Abstract  Several processes by which astrocytes protect neurons during ischemia are now well established. However, less is known about how neurons themselves may influence these processes. Neurons release zinc (Zn2+)from presynaptic terminals during ischemia, seizure, head trauma, and hypoglycemia, and modulate postsynaptic neuronal function. Peak extracellular zinc may reach concentrations as high as 400 mu M. Excessive levels of free, ionic zinc can initiate DNA damage and the subsequent activation of poly(ADP-ribose) polymerase I (PARP-1), which in turn lead to NAD(+) and ATP depletion when DNA damage is extensive. In this study, cultured cortical astrocytes were used to explore the effects of zinc on astrocyte glutamate uptake, an energy-dependent process that is critical for neuron survival, Astrocytes incubated with 100 or 400 mu M of zinc for 30 min showed significant decreases in ATP levels and glutamate uptake capacity. These changes were prevented by the PARP inhibitors benzamide or DPQ (3,4-dihydro-5-(4-(1-piperidinyl)butoxyl)-1 (2H-isoquinolinone) or PARP-1 gene deletion (PARP-1 KO). These findings suggest that release of Zn2+ from neurons during brain insults could induce PARP-1 activation in astrocytes, leading to impaired glutamate uptake and exacerbation of neuronal injury.

Abstract  Inhibition of DNA repair and oxidative stress are 2 common mechanisms associated with arsenic-induced genotoxicity. The purpose of this study was to examine mechanisms of genotoxicity induced by environmentally relevant doses of arsenite (As(+3)) in mouse thymus cells. An increase in DNA damage and a decrease in poly(ADP-ribose) polymerase (PARP) activity were seen in vitro following exposure to 50 nM As(+3) in primary mouse thymus cells and a murine thymus pre-T cell line, D1. 3,4-Dihydro-5[4-(1-piperindinyl) butoxyl]-1(2H)-isoquinoline, a well-characterized PARP inhibitor, also produced DNA damage in D1 cells, confirming the correlation between PARP inhibition and DNA damage increase. As(+3) at 500 nM induced double strand breaks (DSBs) in DNA and oxidative stress at 4 h in D1 cells, which was reversed at 18 h. No apoptosis or decrease of viability was observed in these exposures. 4-Hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl, a widely-used antioxidant, was utilized to confirm that oxidative stress is partially responsible for the increase of strand breaks in 500 nM As(+3) exposure at 4 h. Expression of As(+3) exporters, Mdr1 and Mrp1, were found to be induced by 500 nM As(+3) in D1 cells, suggesting a possible mechanism for reversal of oxidative stress and DSBs at the 18-h timepoint. Finally, we showed that DNA damage and PARP inhibition by As(+3) were reversed by zinc (Zn(+2)) at approximate equimolar doses. Collectively, these results demonstrate that As(+3) at doses within the nanomolar range induce genotoxicity by inhibiting PARP, and produces oxidative stress at higher concentrations, which can be reversed by a Zn(+2) treatment.

Abstract  A time-resolved kinetic study on the hydrogen abstraction reactions from a series of primary and secondary amines by the cumyloxyl (CumO(•)) and benzyloxyl (BnO(•)) radicals was carried out. The results were compared with those obtained previously for the corresponding reactions with tertiary amines. Very different hydrogen abstraction rate constants (k(H)) and intermolecular selectivities were observed for the reactions of the two radicals. With CumO(•), k(H) was observed to decrease on going from the tertiary to the secondary and primary amines. The lowest k(H) values were measured for the reactions with 2,2,6,6-tetramethylpiperidine (TMP) and tert-octylamine (TOA), substrates that can only undergo N-H abstraction. The opposite behavior was observed for the reactions of BnO(•), where the k(H) values increased in the order tertiary < secondary < primary. The k(H) values for the reactions of BnO(•) were in all cases significantly higher than those measured for the corresponding reactions of CumO(•), and no significant difference in reactivity was observed between structurally related substrates that could undergo exclusive α-C-H and N-H abstraction. This different behavior is evidenced by the k(H)(BnO(•))/k(H)(CumO(•)) ratios that range from 55-85 and 267-673 for secondary and primary alkylamines up to 1182 and 3388 for TMP and TOA. The reactions of CumO(•) were described in all cases as direct hydrogen atom abstractions. With BnO(•) the results were interpreted in terms of the rate-determining formation of a hydrogen-bonded prereaction complex between the radical α-C-H and the amine lone pair wherein hydrogen abstraction occurs. Steric effects and amine HBA ability play a major role, whereas the strength of the substrate α-C-H and N-H bonds involved appears to be relatively unimportant. The implications of these different mechanistic pictures are discussed.

Abstract  S-Malic acid is the chiral induction agent widely used in organic synthesis. In order to investigate the stereoselective synthesis of beta-lactams, eight new 3-(3S-t-butoxyl) succinimidyl-beta-lactam derivatives 2a-2h were obtained by Staudinger reaction using S-malic acid as the chiral induction agent and their structures were confirmed by (1)H NMR, IR and elemental analysis. The stereochemistry of the reaction was also investigated by the (1)H NMR, 2D NMR and X-ray diffraction analyses methods. The results indicate that the reaction of 3-(3S-t-butoxyl) succinimidyl acetyl chloride with imines(under Et(3)N) showing very good cis/trans stereoselectivity, and the trans-beta-lactam is the only product. The diastereomeric selectivity Is also good, the d. e. is between 28%-70%.

Abstract  The reaction of phenyl radicals with 1,1-diphenylethylene (DPE), carbon tetrachloride, and cyclohexene has been examined over a range of temperatures using laser flash photolysis techniques. The activation energies are 0.71 +/- 0.04, 3.53 +/- 0.11 and 2.32 +/- 0.33 kcal/mol, and the preexponential factors, expressed as log (A/M(-1)s(-1)), are 9.19 +/- 0.03, 8.96 +/- 0.09, and 9.02 +/- 0.26, for DPE, CCl4, and c-C6H10, respectively. In particular the CCl4 data provide a much needed reference for competitive studies.

Abstract  2-Benzyl-7-butoxyl-9-isobutyl-1-methyl-beta-carboline bromide (H-2-65) was synthesized by the reaction of Harmine with 1-iodobutane via N-9-alkylation, demethyl and N-2-qua-ternarization to obtain the new compound. The results demonstrate that H-2-65 has more remarkable anticancer activities in vitro. The results of H-1 NMR, C-13 NMR, DEPT, gCOSY, gHSQC, gHMBC, MS, single-crystal X-ray diffraction and elemental analysis showed that the title compound crystallizes in the triclinic system, space group P1 with a = 9.545(5), b = 11.724(5), c = 11.839(6) angstrom, alpha = 77.530(6), beta = 87.169(6), gamma = 72.823(5)degrees, Z = 2, V = 1235.8(10) angstrom(3), D-c = 1.294 g.cm(-3), F(000) = 504, the final R = 0.0453, wR = 0.1262 and S = 1.044.

Abstract  The structures and stabilities of carboxymethylchitosan and its derivatives were studied by using quantum chemical ab initio method. The calculated results indicated that the structure of carboxymethylchitosan in which the 2 site amino group of chitose(see Fig. 2) was substituted by ethyloic was more stable than that in which 6 site hydroxyl group was substituted(see Fig. 3). Between two isomers of carboxymethylchitosan derivatives(i. e. (2-hydroxyl-3-butoxyl) propyl-carboxymethylchitosan, see Fig. 4), isomer 1 was more stable than isomer 2. By using the optimized geometries, the vibration spectra of isomer 1 was calculated. And it was in good agreement with recent experimental results.

Abstract  Spin-trapping of oxygen-centred radicals (tert-butoxyl and carboxyl) by substituted N-benzylidene-tert-butylamine N-oxides (X-PBN) has been studied and the rates have been measured by means of EPR experiments. The experimental results revealed a substituent effect [X-PBN with an electron-donating substituent favours spin trapping (rho < 0)] and are rationalized by an electron-transfer mechanism between the frontier orbitals of the reactants. The reaction pathway has been deduced from molecular-orbital and molecular-mechanics calculations.

Abstract  The electropolymerization of manganese(III)-5-[o-(1-imidazolyl) butoxyl] phenyl-10, 15, 20-triphenylporphrine chloride (o-ImBPTPPMn (III) Cl) produces stable and electrochemically active film from strong acidic aqueous solutions. Cyclic voltammetry was used to study the in situ growth of poly(o-ImBPTPP Mn (III) Cl) films. The electrode was also employed to study the electrocatalytic oxidation of ascorbic acid (AA) and dopamine (DA), using cyclic voltammery. It has been found that the oxidation of AA at the surface of poly(o-ImBPTPP Mn (III) CI) films modified glassy carbon electrode occurs at a potential of about 407 mV more negative than. that of an unmodified glassy carbon electrode. Differential pulse voltammograms (DPV) of simultaneous determination of AA and DA exhibit linear dynamic rang from 2.0 x 10(-6) to 1.0 x 10(-4) mol/L and a detection limit of 1.0 mu mol/L for AA, and corresponding linear dynamic rang from 6.5 x 10(-7) to 2.6 x 10(-5) mol/L and a detection limit of 0.39 mu mol/l, for DA. In DPV, the poly (o-ImBPFPP Mn (III) Cl) films modified glassy carbon electrode could separate completely the oxidation peak potentials of AA and DA for about 240 mV present in the same buffer solution of 0.1 mol/L phosphate, though at the unmodified glassy carbon electrode the peak potentials were indistinguishable. This modified electrode was quite effective not only to detect AA and DA individually, but also to determine simultaneously each component concentration in the mixture, and they will not affect each other.

Abstract  Crystal structure of 1, 4, 8, 11, 15, 18, 22, 25-octa-butoxyphthalocyaninatocopper (11) (1) was determined by X-ray diffraction methods. The crystal system is monoclinic, space group is P2(1)/c, Z = 4, a = 1.3741(1) nm, b = 2.6737(1) nm, c = 1.6690(1) mn, beta = 101.278(1)degrees. The steric congestion between the neighbouring butoxyl groups causes the distortion of the ring core of phthalocyanine (Pc) into a saddle shape conformation. In the crystal structure, molecules stack along a axis forming one-dimensional packing structure and there are two molecular overlap types which appear in turn with different distances between molecules, overlap area and angle.

Abstract  The solubilities of CO2 in 2-methoxyethyl acetate, 1-methoxy-2-propyl acetate, and 3-methoxybutyl acetate were measured by isothermal synthesis method under pressures up to 1.2 MPa and at temperatures ranging from (293.15 to 333.15) K. Henry's constant was calculated based on experimental data regression. The solubilities of CO2 were found to increase with decreased temperature and increased the methyl group to the molecular structure of the absorbent. Henry's constant and volumetric solubility of selected absorbents at T = 298.15 K were compared with those of commercial absorbents and common solvents. 3-Methoxybutyl acetate showed the best performance by mole fraction, and 2-methoxyethyl acetate behaved the best by volumetric fraction. Based on Henry's constant, thermodynamic properties such as Gibbs free energy of solution, enthalpy of solution, and absorption entropy of solution were determined. These properties are very essential for designing an absorption process. (C) 2014 Elsevier Ltd. All rights reserved.