Sample records for 2,4-pentanedione

  1. Infinite dilution partial molar volumes of platinum(II) 2,4-pentanedionate in supercritical carbon dioxide.


    Kong, Chang Yi; Siratori, Tomoya; Funazukuri, Toshitaka; Wang, Guosheng


    The effects of temperature and density on retention of platinum(II) 2,4-pentanedionate in supercritical fluid chromatography were investigated at temperatures of 308.15-343.15K and pressure range from 8 to 40MPa by the chromatographic impulse response method with curve fitting. The retention factors were utilized to derive the infinite dilution partial molar volumes of platinum(II) 2,4-pentanedionate in supercritical carbon dioxide. The determined partial molar volumes were small and positive at high pressures but exhibited very large and negative values in the highly compressible near critical region of carbon dioxide.

  2. Uptake and reaction kinetics of acetone, 2-butanone, 2,4-pentanedione, and acetaldehyde in sulfuric acid solutions.


    Esteve, Williams; Nozière, Barbara


    This work presents a study of the uptake of acetone, 2-butanone (methyl ethyl ketone), 2,4-pentanedione, and acetaldehyde by sulfuric acid solutions with an aim at understanding the reactivity of carbonyl compounds present in the atmosphere toward acidic aerosols. Experiments were performed in a rotating wetted-wall reactor coupled to a mass spectrometer at room temperature (298 +/- 3 K) with 0-96 wt % H(2)SO(4) solutions. For all compounds, a reactive uptake was observed at high acidity (>or=64 wt % H(2)SO(4)). The corresponding reactions were found to follow a second-order kinetics, and their rate constants, k (M(-1) s(-1)) were found to increase exponentially with acidity. These rate constants and their variations with acid concentration were in good agreement with the kinetic behavior of acid-catalyzed aldol condensation reported in the organic chemical literature, except for 2,4-pentanedione. The results of this work suggest that aldol condensation should be too slow to account for the enhanced organic aerosol mass observed in smog chamber studies and should have an even smaller contribution under atmospheric conditions. The rate constants of other compounds, such as large aldehydes, remain however to be measured. However, in order to contribute significantly to organic aerosol formation, a liquid phase reaction would have to result in an uptake coefficient of the order of 10(-2).

  3. Modification of Lys-237 on actin by 2,4-pentanedione. Alteration of the interaction of actin with tropomyosin.


    El-Saleh, S C; Thieret, R; Johnson, P; Potter, J D


    It has been possible to specifically label rabbit skeletal muscle actin at Lys-237 with 2,4-pentanedione, producing an enamine. This reaction can be reversed with hydroxylamine. The modification can be carried out with actin in either the G- or F-forms and does not affect polymerization-depolymerization. The modification does affect, however, the interaction of tropomyosin (Tm) with the modified F-actin. In the absence of Ca2+ and Mg2+ (mu = 0.12), Tm failed to bind to the modified F-actin whereas it did bind to unmodified F-actin (1 Tm:7 actins). Tm binding could be restored under these conditions by the addition of either troponin (Tn), Mg2+, or Mg2+ and Ca2+. Under certain conditions, Tm alone has been shown to inhibit actin-activated heavy meromyosin (HMM)-Mg2+-ATPase. This inhibition did not occur with the modified F-actin even though Tm was bound (approximately 1 Tm:7 actins). Even when Tn was added to this system (in the absence of Ca2+), no inhibition of ATPase could be observed. Thus, this modification appears to prevent F-actin X Tm from assuming the "blocking" inhibitory position (conformation). In addition, Tn appears to enhance the activation of heavy meromyosin-Mg2+-ATPase by the modified F-actin X Tm complex whether Ca2+ is present or not. This state may be analogous to the potentiated state (Murray, J. M., Knox, M. K., Trueblood, C. E., and Weber, A. (1982) Biochemistry 27, 906-915) seen with myosin subfragment 1-saturated actin at low ATP levels. Thus, using modified and unmodified F-actin, it is possible to produce three Tm X actin states: off (F-actin X Tm), on (modified F-actin X Tm), and "potentiated" (modified F-actin X Tm X Tn).

  4. Three-component reaction of tautomeric amidines with 3-ferrocenylmethylidene-2,4-pentanedione. Formation of polymeric coordination complexes of potassium ferrocenyl-(hexahydro)pyrimidoxides.


    Klimova, Elena I; Flores-Alamo, Marcos; Klimova, Tatiana; Maya, Sandra Cortez; Beletskaya, Irina P


    Acetamidine hydrochloride and p-aminobenzamidine dihydrochloride interact with 3-ferrocenylmethylidene-2,4-pentanedione at 80-82 °C in the presence of K2CO3 in the water-alcohol medium in two tautomeric forms (the amidoimine and enediamine ones) with formation of mixtures of pyrimidine and piperidone derivatives and polymeric coordination complexes of potassium ferrocenyl(hexahydro)pyrimidoxides. The structure of the resultant compounds is elucidated on the basis of IR, 1H- and 13C-NMR spectroscopy, mass spectrometry and elemental analysis data. The crystal structures of 6-ferrocenyl-4-hydroxy-4-methyl-2-piperidone, potassium 6-ferrocenyl-4-methyl-2-methylidene(hexahydro)pyrimidin-4-oxide and 2-(4-aminophenyl)-4-ferrocenyl-6-methyl-pyrimidine were determined by X-ray analysis of suitable single crystals.

  5. Optimization of photoluminescence of Y(2)O(3):Eu and Gd(2)O(3):Eu phosphors synthesized by thermolysis of 2,4-pentanedione complexes.


    Antic, B; Rogan, J; Kremenovic, A; Nikolic, A S; Vucinic-Vasic, M; Bozanic, D K; Goya, G F; Colomban, P H


    Spherical shaped nanoparticles of series Y(2 - x)Eu(x)O(3) (x = 0.06, 0.10, 0.20, and 2) and Gd(2 - x)Eu(x)O(3) (x = 0.06, 0.10) were prepared by thermolysis of 2,4-pentanedione complexes of Y, Gd, and Eu. The bixbyite phase of Gd(2 - x)Eu(x)O(3) samples was formed at 500 degrees C, whereas the thermal decomposition of Y and Eu complexes' mixtures occurred at higher temperatures. Linearity in the concentration dependence on lattice parameter confirmed the formation of solid solutions. The distribution of Eu(3+) in Gd(2 - x)Eu(x)O(3) was changed with thermal annealing: in the as-prepared sample (x = 0.10) the distribution was preferential at C(3i) sites while in the annealed samples, Eu(3+) were distributed at both C(2) and C(3i) sites. Rietveld refinement of site occupancies as well as emission spectra showed a random distribution of cations in Y(2 - x)Eu(x)O(3). The photoluminescence (PL) measurements of the sample showed red emission with the main peak at 614 nm ((5)D(0)-(7)F(2)). The PL intensity increased with increasing concentration of Eu(3+) in both series. Infrared excitation was required to obtain good Raman spectra. The linear dependence of the main Raman peak wavenumber offers a non-destructive method for monitoring the substitution level and its homogeneity at the micron scale.

  6. Induction of oxidative stress in Prototheca zopfii by indole-3-acetic acid/HRP or 2,4-pentanedione/HRP systems and their oxidation products.


    Cunha, L T; Pugine, S M P; Lins, P G; Brunetti, I L; De Melo, M P


    We investigated the toxic effects on Prototheca zopfii of indole-3-acetic acid (IAA) and 2,4-pentanedione (PD) combined with horseradish peroxidase (HRP) alongside the oxidation products of 3-methyl-2-oxindole (MOI) and indole-3-carbinol (I3C) from the IAA/HRP system and methylglyoxal (MGO) from the PD/HRP system. The microorganism was incubated in the absence (control) or presence of IAA, PD, IAA/HRP, PD/HRP, MOI, I3C and MGO and determined: (1) cytotoxicity by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium) assay; (2) growth inhibitory concentration by resazurin assay and (3) antioxidant enzymes activities of: catalase (CAT), glutathione reductase (GR) and superoxide dismutase (SOD). P. zopfii was more susceptible to IAA at 40 mM than PD at the same concentration, which seems to indicate that IAA was more effective at initiating cell death. These data corroborate results from the resazurin assay. Concentrations of 40 mM of IAA, IAA/HRP and PD/HRP, 20 mM of PD/HRP, 10 mM of MOI, 2 mM of I3C and 8 mM of MGO inhibited the growth of P. zopfii. With sub-inhibitory concentrations of IAA and IAA/HRP at 30 mM, MOI at 8 mM and I3C at 1 mM, the activities of CAT and GR increased, whereas no statistical difference was observed for CAT activity with IAA/HRP. Thus, PD at 30 mM and MGO at 6 mM increased the activities of CAT and GR, whereas PD/HRP system at 15 mM decreased CAT activity and PD/HRP and MGO showed no statistical difference for SOD activity. In conclusion, IAA/HRP or PD/HRP systems and their oxidation products exert cytotoxic effects on P. zopffi; however, I3C and MGO appear to exert greater microbicidal effect on P. zopfii.

  7. Effects of Eu3+ concentration on structural, optical and vibrational properties of multifunctional Ce(1-x)Eu(x)O2-delta) nanoparticles synthesized by thermolysis of 2,4-pentanedione complexes.


    Kremenovic, A; Bozanic, D K; Welsch, A M; Jancar, B; Nikolic, A S; Boskovic, M; Colomban, Ph; Fabian, Martin; Antic, B


    The 5-10 nm Ce(1-x)Eu(x)O(2-delta) (0 < or = x < or = 0.30) nanoparticles with fluorite structure were synthesized by thermal decomposition of Eu- and Ce-2,4-pentanedione complexes mixtures. X-ray line broadening analysis of mixed samples Ce(1-x)Eu(x)O(2-delta) (0.05 < or = x < or = 0.30) showed that the crystallite size was lower and root mean square strain higher than in pure ceria. However, within mixed samples Ce(1-x)Eu(x)O(2-delta) (0.05 < or = x < or = 0.30) crystallite size and root mean square strain were independent of Eu3+ concentration. Raman spectroscopy results indicated that europium ions yield disorder by breaking the phonon propagation and therefore making the non-centre Brillouin zone modes Raman active. The absorption bands in the spectra of mixed oxides were blue-shifted in comparison to pure CeO(2-delta) nanopowder. The samples show red emission typical for Eu ions. The biggest photoluminescent intensity was observed for the highest Eu3+ concentration (x = 0.30) and further enhanced with the increase in crystallinity.

  8. Active layer solution-processed NIR-OLEDs based on ternary erbium(III) complexes with 1,1,1-trifluoro-2,4-pentanedione and different N,N-donors.


    Martín-Ramos, P; Coya, C; Lavín, V; Martín, I R; Silva, M Ramos; Silva, P S Pereira; García-Vélez, M; Alvarez, A L; Martín-Gil, J


    Using a fluorinated 1,1,1-trifluoro-2,4-pentanedione (Htfac) ligand and either 2,2'-bipyridine (bipy), bathophenanthroline (bath) or 5-nitro-1,10-phenanthroline (5NO2phen) as an ancillary ligand, three new ternary erbium(iii) octacoordinated complexes have been synthesized. The single crystal structures of the new complexes (namely [Er(tfac)3(bipy)], [Er(tfac)3(bath)] and [Er(tfac)3(5NO2phen)]) have been determined and their properties have been investigated by Fourier transform infrared (FTIR) spectroscopy, Raman spectroscopy and thermodynamic analysis. After ligand-mediated excitation of these complexes in the UV, they all show the characteristic near-infrared (NIR) luminescence of the corresponding Er(3+) ion at 1532 nm. The same emission in the C-band transmission window can also be obtained from the solution-processed organic light-emitting diodes (OLEDs) with structure: glass/ITO/PEDOT:PSS/[Er(tfac)3(N,N-donor)]/Ca/Al. In spite of the fact that the photoluminescence intensity of [Er(tfac)3(5NO2phen)] is stronger than those of [Er(tfac)3(bipy)] and [Er(tfac)3(bath)], the best electroluminescence results correspond to the OLED based on the [Er(tfac)3(bath)] complex, as a consequence of the superior electron transport capabilities of bathophenanthroline.

  9. 3-(3,4,5-Trimethoxybenzylidene)-2,4-pentanedione: Design of a novel photostabilizer with in vivo SPF boosting properties and its use in developing broad-spectrum sunscreen formulations.


    Chaudhuri, R K; Ollengo, M A; Singh, P; Martincigh, B S


    The study concerned the synthesis of a novel photostabilizer based on benzylidenepentanedione chemistry and the evaluation of its potential in developing a broad-spectrum sunscreen formulation containing avobenzone. 3-(3,4,5-Trimethoxybenzylidene)-2-4-pentanedione (TMBP) was synthesized through a condensation reaction and incorporated into a sunscreen formulation containing, inter alia, avobenzone. The SPF, critical wavelength and in vitro photostability of the product were measured. The photostability was compared with that afforded by current avobenzone photostabilizers, namely octocrylene, ethylhexylmethoxycrylene and diethylhexylsyringylidenemalonate. The photostability of TMBP either alone or in the presence of avobenzone in a methanolic solution was also evaluated by UV spectrophotometric and HPLC analyses. The optical properties of TMBP were estimated experimentally and supported by time-dependent density functional theory (TD-DFT) calculations. The ability of TMBP to stabilize avobenzone under ultraviolet (UV) light exposure was shown both in formulated products and in solution. A comparative stability study incorporating various combinations of avobenzone, TMBP (vs. three commercial photostabilizers) and UVB sunscreens clearly showed TMBP to be a very effective stabilizer. The photostabilizing effect of TMBP arises from triplet-state energy transfer from avobenzone to TMBP and through light-induced reactions that preserve the main chromophores. Interestingly, a 50% in vivo SPF boosting was observed when TMBP was used with organic and inorganic sunscreens when alone it has no contribution to SPF. TMBP-containing sunscreen formulations clearly showed a critical wavelength of well over 370 nm and can thus be categorized as broad-spectrum sunscreens. We were able to design a very effective photostabilizer, trimethoxybenzylidene pentanedione (INCI name), based on benzylidenepentanedione chemistry. TMBP is very efficient in stabilizing avobenzone in formulated

  10. Substituent Effects on Keto-Enol Equilibria Using NMR Spectroscopy

    ERIC Educational Resources Information Center

    Manbeck, Kimberly A.; Boaz, Nicholas C.; Bair, Nathaniel C.; Sanders, Allix M. S.; Marsh, Anderson L.


    In this extension to a classic physical chemistry experiment, students record the proton nuclear magnetic resonance spectra of the [beta]-diketones 2,4-pentanedione, 3-methyl-2,4-pentanedione, and 3-chloro-2,4-pentanedione to investigate the effect of substituents on keto-enol tautomerization equilibria. From the integrated intensities of keto and…

  11. Substituent Effects on Keto-Enol Equilibria Using NMR Spectroscopy

    ERIC Educational Resources Information Center

    Manbeck, Kimberly A.; Boaz, Nicholas C.; Bair, Nathaniel C.; Sanders, Allix M. S.; Marsh, Anderson L.


    In this extension to a classic physical chemistry experiment, students record the proton nuclear magnetic resonance spectra of the [beta]-diketones 2,4-pentanedione, 3-methyl-2,4-pentanedione, and 3-chloro-2,4-pentanedione to investigate the effect of substituents on keto-enol tautomerization equilibria. From the integrated intensities of keto and…

  12. The role of intramolecular hydrogen bonds in nucleophilic addition reactions of ketenaminals

    NASA Astrophysics Data System (ADS)

    Isaev, A. N.


    Quantum-chemical calculations of the geometries and electronic structures of molecules of ketenaminals 3-(diaminomethylene)-2,4-pentanedione and dimethyl-2-(diaminomethylene)-malonate and calculations of the structures of intermediates in the reaction of the nucleophilic addition of the ketenaminals to the acetonitrile molecule are performed by B3LYP/6-31+G** method. Two possible scenarios of the process are shown, depending on the mutual orientation of reacting molecules. The nucleophilic addition proceeds in two stages. It is found that the rate-limiting stage of the process is the transfer of the proton of the intramolecular hydrogen bond in a ketenaminal molecule. The experimentally observed faster reaction of pyrimidine formation for the 3-(diaminomethylene)-2,4-pentanedione molecule relative to that for dimethyl-2-(diaminomethylene)-malonate is explained by the hydrogen bond being stronger and the barrier of proton transfer from the aminogroup to the ketogroup oxygen falling upon nucleophilic attack in the former molecule.

  13. Bridged Bicyclic Systems and Pretreatment Drugs as Acetylcholinesterase Reactivators

    DTIC Science & Technology


    hydroxy(tosyloxy)iodojbenzene (Koser Reagent) in CH3CN followed by thiourea and sodium bicarbonate solution, yielded 2-amino-4-phenyt-5-acetyl...acelyloximino Hydroiodide,(.37) Treatment of 2.4-pentanedio~e with (hydroxy(tosyloxy)iodolbenzene (Koser Reagent) in CH3CN, followed by thiourea and sodium ...Hydrochloide (391 2,4-Pentanedione, on treatment with {hydroxy(tosyloxy)iodo]benzene in CH 3CN followed by thiourea and sodium bicarbonate solution

  14. Studies on Some New Ru(III) Complexes Using aryl-azo Pentane- 2,4-dione and 2,6-bis (2'-Benzimidazolyl) Pyridine as Ligands: Synthesis, Spectroscopic, Luminescent, Electrochemical and Biological Activities

    PubMed Central

    Yadaw, Ajay K.; Phadke, Ratna S.; Choi, Chang S.; Araki, Koji


    Some ruthenium(III) complexes with aryl-azo 2,4-pentanedione as co-ligands (L1H - L3H2) have been synthesized and characterized spectroscopically IR, 1H NMR, UV/Vis, ESR, conductimetric) along with elemental analysis and FAB-mass data. Their luminescent and redox properties have been studied. The antibacterial, anti-HIV and antitmnour activities have also been reported. PMID:18475977

  15. Synthesis and structure of new mononuclear octahedral cobalt(III) dioximates derived from isonicotinic hydrazide

    NASA Astrophysics Data System (ADS)

    Cocu, Maria; Bulhac, Ion; Coropceanu, Eduard; Melnic, Elena; Shova, Sergiu; Ciobanica, Olga; Gutium, Victoria; Bourosh, Paulina


    New organic ligand L (1) resulting from isonicotinic hydrazide and 2,4-pentanedione has been prepared and investigated by physicochemical methods, including elemental analysis, 1H and 13C NMR, IR spectroscopy and X-ray studies. The X-ray investigation revealed that the condensation of 2,4-pentanedione with isonicotinic hydrazide is accompanied by the formation of a five-membered ring including three carbon atoms of 2,4-pentanedione and two nitrogen atoms of the isonicotinic hydrazide fragment. The reaction between [Co(DfgH)2Br(H2O)] (DfgH2 = diphenylglyoxime) and L resulted in the formation of the mononuclear octahedral complex [Co(DfgH)2BrL] (2) with the substitution of the water molecule in the apical position by the ligand L. The reaction starting from [Co(DmgH)2Cl(H2O)] (DmgH = dimethylglyoxime) and L resulted in the mononuclear octahedral Co(III) complex with the composition [Co(DmgH)2ClL‧] (3), where L‧ unexpectedly represents a dehydrated derivative of L. The two coordination compounds are characterized by X-ray diffraction method. The IR, 1H NMR spectral studies of new compounds are also reported.

  16. Horseradish peroxidase mediated free radical polymerization of methyl methacrylate.


    Kalra, B; Gross, R A


    This paper reports the free radical polymerization of methyl methacrylate (MMA) catalyzed by horseradish peroxidase (HRP). A novel method was developed whereby MMA polymerization can be carried out at ambient temperatures in the presence of low concentrations of hydrogen peroxide and 2,4-pentanedione in a mixture of water and a water-miscible solvent. Polymers of MMA formed were highly stereoregular with predominantly syndiotactic sequences (syn-dyad fractions from 0.82 to 0.87). Analyses of the chloroform-soluble fraction of syndio-PMMA products by GPC showed that they have number-average molecular weights, Mn, that range from 7500 to 75,000. By using 25% v/v of the cosolvents dioxane, tetrahydrofuran, acetone, and dimethylformamide, 85, 45, 7 and 2% product yields, respectively, resulted after 24 h. Increasing the proportion of dioxane to water from 1:3 to 1:1 and 3:1 resulted in a decrease in polymer yield from 45 to 38 and 7%, respectively. Increase in the enzyme concentration from 70 to 80 and 90 mg/mL resulted in increased reaction kinetics. By adjustment of the molar ratio of 2,4-pentanedione to hydrogen peroxide between 1.30:1.0 and 1.45:1.0, the product yields and Mn values were increased. On the basis of the catalytic properties of HRP and studies herein, we believe that the keto-enoxy radicals from 2,4-pentanedione are the first radical species generated. Then, initiation may take place through this radical or by the radical transfer to another molecule.

  17. Diagnostic and Therapeutic Radiopharmaceutical Agents for Selective Discrimination of Prostate Cancer

    DTIC Science & Technology


    pyridine did not yield the formation of complex 3 in water. Technetium -99m (t1/2 ) 6.02 h; γ ) 140 keV) is the radionuclide of choice in hospitals...comprising 90% of all nuclear medicine imaging scans.1 Development of organo- metallic technetium complexes, such as fac- [99mTc(OH2)3(CO)3]+, has provided...substitution of the technetium (I) center.10 Interest in developing new modes of complex formation has led us to investigate 2,4-pentanedione or

  18. Chemical solution deposition (CSD) of CeO2 and La2Zr2O7 buffer layers on cube textured NiW substrates

    NASA Astrophysics Data System (ADS)

    Kotzyba, G.; Obst, B.; Nast, R.; Goldacker, W.; Holzapfel, B.


    We present results of crack free layers of CeO2 and La2Zr2O7 deposited by means of CSD on cube textured Ni-4 at.% W substrates. EBSD-data show histograms with very good inplane- and out-of-plane textures and were used to simulate the critical current density in the YBCO layer. The surface roughness, a sensitive feature for good deposition results, was analyzed with a profilometer. In the CSD process we applied, the 2, 4-pentanedionates of the metal cations in glacial acetic acid and methanol served as starting substances.

  19. Catalyzed dehalogenation of Delor 103 by sodium hydridoaluminate.


    Hetflejs, J; Czakóová, M; Rericha, R; Vcelák, J


    The complete dechlorination of PCB liquid Delor 103 (42.6% Cl) to biphenyl has been effected in toluene with sodium dihydridobis(2-methoxyethoxo)aluminate (SDMA) in the presence of catalytic amounts of Ni(II) and Co(II) 2,4-pentanedionates at elevated temperatures. Changes in PCB congeners distribution during dechlorination were monitored by GC(ECD) and GC/MS, and the scheme of their transformation was proposed on the basis of site selectivity observed. A kinetic analysis of the reaction is presented.

  20. Aldol Condensation of Volatile Carbonyl Compounds in Acidic Aerosols

    NASA Astrophysics Data System (ADS)

    Noziere, B.; Esteve, W.


    Reactions of volatile organic compounds in acidic aerosols have been shown recently to be potentially important for organic aerosol formation and growth. Aldol condensation, the acid-catalyzed polymerization of carbonyl compounds, is a likely candidate to enhance the flux of organic matter from the gas phase to the condensed phase in the atmosphere. Until now these reactions have only been characterized for conditions relevant to synthesis (high acidities and liquid phase systems) and remote from atmospheric ones. In this work, the uptake of gas-phase acetone and 2,4\\-pentanedione by sulfuric acid solutions has been measured at room temperature using a Rotated Wetted Wall Reactor coupled to a Mass Spectrometer. The aldol condensation rate constants for 2,4\\-pentanedione measured so far for sulfuric acid solutions between 96 and 70 % wt. display a variation with acidity in agreement with what predicted in the organic chemical literature. The values of these constants, however, are much lower than expected for this compound, and comparable to the ones of acetone. Experiments are underway to complete this study to lower acidities and understand the discrepancies with the predicted reactivity.

  1. Formation and stability of lanthanide complexes and their encapsulation into polymeric microspheres

    SciTech Connect

    Mumper, R.J.; Jay, M.


    The complexation of lanthanides (Ln) with dicarbonyl compounds (acetylacetone, acac; ethyl acetoacetate; 3-ethyl-2,4-pentanedione; 2,4-hexanedione; 3-methyl-2,4-pentanedione; and diethyl malonate) was investigated using a potentiometric titration technique. The ability of a dicarbonyl compound to complex with the lanthanide elements was greatly dependent on its pK{sub a} and on the pH of the titrated solution. Selected lanthanide complexes (Ln complexes) were incorporated into spherical poly(L-lactic acid)(PLA) matrices and irradiated in a nuclear reactor with neutrons to produce short-lived high-energy {Beta}-particle-emitting radioisotopes. The lanthanides investigated (Ho, Dy, Sm, and La) were chosen on the basis of their physical and nuclear properties. A transition element (Re) was also studied. The small decrease in the ionic radii of the lanthanides with increasing atomic number led to (a) greater ability to extract and complex from an aqueous solution with complexing agents, (b) larger formation and stability constants for the Ln complexes, (c) increased solubility of the Ln complexes in chloroform, and (d) increase in the maximum percent incorporation of the stable lanthanides in PLA spheres. Ho(aca) was found to be the most promising candidate of the complexes studied on the basis of the above observations and due to the favorable physical properties of {sup 165}Ho and nuclear properties of {sup 166}Ho. 21 refs., 5 figs., 4 tabs.

  2. Asymmetric Synthesis of the Aminocyclitol Pactamycin, a Universal Translocation Inhibitor

    PubMed Central

    Sharpe, Robert J.; Malinowski, Justin T.; Johnson, Jeffrey S.


    An asymmetric total synthesis of the aminocyclopentitol pactamycin is described, which delivers the title compound in 15 steps from 2,4-pentanedione. Critical to this approach was the exploitation of a complex symmetry-breaking reduction strategy to assemble the C1, C2, and C7 relative stereochemistry within the first four steps of the synthesis. Multiple iterations of this reduction strategy are described, and a thorough analysis of stereochemical outcomes is detailed. In the final case, an asymmetric Mannich reaction was developed to install a protected amine directly at the C2 position. Symmetry-breaking reduction of this material gave way to a remarkable series of stereochemical outcomes leading to the title compound without recourse to non-strategic downstream manipulations. This synthesis is immediately accommodating to the facile preparation of structural analogs. PMID:24245656

  3. Synthesis, Spectroscopic, ac Conductivity and Thermal Studies on Co(III) Acetylacetonate-Iodine Complex

    NASA Astrophysics Data System (ADS)

    Hashem, H. A.; Refat, M. S.

    A spectrophotometric study of 1:1 donor-acceptor complex, cobalt (III) acetylacetonate (donor) and iodine (σ-acceptor) has been preformed. The equilibrium constants, (K) and the absorpitivity (ɛ) for the formation of the iodine complex have been calculated. The predicted structure of the solid triiodide charge-transfer complex reported in this study is further supported by thermal, far and mid infrared spectroscopic measurements. Electron transfer from Co (acac = 2, 4-pentanedionate)3 to iodine leads to the formation of an organic semiconductor with the formula of [Co(acac)3]_2 I+. I3-. The kinetic parameters (nonisothermal method) for their decomposition have been evaluated by graphical methods using the equations of Freeman-Carroll (FC), Horowitz-Metzger (HM) and Coats-Redfern (CR). The ac conductivity and dielectric properties of [Co(acac)3]_2 I+. I3- have been measured over the frequency 50-106 Hz at temperature 298 K.

  4. Walphos versus Biferrocene-Based Walphos Analogues in the Asymmetric Hydrogenation of Alkenes and Ketones

    PubMed Central


    Two representative Walphos analogues with an achiral 2,2″-biferrocenediyl backbone were synthesized. These diphosphine ligands were tested in the rhodium-catalyzed asymmetric hydrogenation of several alkenes and in the ruthenium-catalyzed hydrogenation of two ketones. The results were compared with those previously obtained on using biferrocene ligands with a C2-symmetric 2,2″-biferrocenediyl backbone as well as with those obtained with Walphos ligands. The application of one newly synthesized ligand in the hydrogenation of 2-methylcinnamic acid gave (R)-2-methyl-3-phenylpropanoic acid with full conversion and with 92% ee. The same ligand was used to transform 2,4-pentanedione quantitatively and diastereoselectively into (S,S)-2,4-pentanediol with 98% ee. PMID:24795493

  5. High performance of inverted polymer solar cells with cobalt oxide as hole-transporting layer

    NASA Astrophysics Data System (ADS)

    Wang, Xiangdong; Peng, Qing; Zhu, Weiguo; Lei, Gangtie


    Cobalt oxide (II, III) (CoOx) was inserted as efficient hole-transporting interlayer between the active layer and top electrode in inverted polymer solar cells (PSCs) with titanium (diisopropoxide) bis(2, 4-pentanedionate) (TIPD) as an electron selective layer. The work function of CoOx was measured by Kelvin probe and the device performances with different thicknesses of cobalt oxide were studied. The device with CoOx exhibited a remarkable improvement in power conversion efficiency compared with that without CoOx, which indicated that CoOx efficiently prevented the recombination of charge carriers at the organic/top electrode interface. The performance improvement was attributed to the fact that the CoOx thin film can module the Schottky barrier and form an ohmic contact at the organic/metal interface, which makes it a promising hole-transporting layer.

  6. Bifunctional Molecular Photoswitches Based on Overcrowded Alkenes for Dynamic Control of Catalytic Activity in Michael Addition Reactions.


    Pizzolato, Stefano F; Collins, Beatrice S L; van Leeuwen, Thomas; Feringa, Ben L


    The emerging field of artificial photoswitchable catalysis has recently shown striking examples of functional light-responsive systems allowing for dynamic control of activity and selectivity in organocatalysis and metal-catalysed transformations. While our group has already disclosed systems featuring first generation molecular motors as the switchable central core, a design based on second generation molecular motors is lacking. Here, the syntheses of two bifunctionalised molecular switches based on a photoresponsive tetrasubstituted alkene core are reported. They feature a thiourea substituent as hydrogen-donor moiety in the upper half and a basic dimethylamine group in the lower half. This combination of functional groups offers the possibility for application of these molecules in photoswitchable catalytic processes. The light-responsive central cores were synthesized by a Barton-Kellogg coupling of the prefunctionalized upper and lower halves. Derivatization using Buchwald-Hartwig amination and subsequent introduction of the thiourea substituent afforded the target compounds. Control of catalytic activity in the Michael addition reaction between (E)-3-bromo-β-nitrostyrene and 2,4-pentanedione is achieved upon irradiation of stable-(E) and stable-(Z) isomers of the bifunctional catalyst 1. Both isomers display a decrease in catalytic activity upon irradiation to the metastable state, providing systems with the potential to be applied as ON/OFF catalytic photoswitches.

  7. Selected spectroscopic and magnetic properties of lanthanide complexes in polyimide XU-218

    NASA Technical Reports Server (NTRS)

    Stoakley, D. M.; Shillady, D. D.; Vallarino, L. M.; Gootee, W. A.; Smailes, D. L.


    Polyimide XU-218 films containing approximately 5 wt pct of Eu(III), Gd(III), Tb(III), and Er(III) were prepared, and the effects of complexing each of the metals with the following four ligands were investigated: N-phenylphthalamate (NPPA), 2,4-pentanedionate (AcAc), 1,3-diphenyl 1,3-propanedionate (DBM), and a new hexa-aza-macrocyclic (MAC) ligand. The tris-chelated complexes of the mononegative ligands NPPA, AcAc, and DBM produced transparent, flexible films, which had magnetic and spectral properties very similar to those of the parent lanthanide complexes, while complexes of MAC showed problems due to the presence of lattice water and yielded dark brittle films. AcAc caused little or no effect on the glass transition temperature (Tg), while NPPA and DBM complexes lowered Tg to 269-290 C, and MAC indicated moisture by inflexion at 95-100 C with a true Tg at 320 C. All lanthanide-containing films were paramagnetic.

  8. Effect of thermal annealing treatment with titanium chelate on buffer layer in inverted polymer solar cells

    NASA Astrophysics Data System (ADS)

    Liu, Zhiyong; Wang, Ning; Fu, Yan


    The solution processable electron extraction layer (EEL) is crucial for polymer solar cells (PSCs). Here, we investigated titanium (diisopropoxide) bis(2,4-pentanedionate) (TIPD) as an EEL and fabricated inverted PSCs with a blend of poly(3-hexylthiophene) (P3HT) and indene-C60 bisadduct (ICBA) acting as the photoactive layer, with a structure of ITO/TIPD/P3HT:ICBA/MoO3/Ag. After thermal annealing treatment at 150 °C for 15 min, the PSC performances increased from 3.85% to 6.84% and they achieve stable power conversion efficiency (PCE), with a similar PCE compared with TiO2 as an EEL by the vacuum evaporated method. Fourier transform infrared spectroscopy (FTIR) and ultraviolet photoelectron spectroscopy (UPS) confirmed that the TIPD decomposed and formed the Tidbnd O bond, and the energy level of the lowest unoccupied molecular orbital and the highest occupied molecular orbital increased. The space charge limited current (SCLC) measurements further confirmed the improvement in electron collection and the transport ability using TIPD as the EEL and thermal annealing.

  9. The very covalent diammino(o-benzoquinonediimine) dichlororuthenium(II). An example of very strong pi-back-donation.


    Rusanova, Julia; Rusanov, Eduard; Gorelsky, S I; Christendat, Dharamdat; Popescu, Raluca; Farah, Abdiaziz A; Beaulac, Rémi; Reber, Christian; Lever, A B P


    The syntheses and X-ray structures of the complexes Ru(S-dmso)Cl2(opda) (1) and Ru(NH3)2Cl2(bqdi) (2) are described (opda= o-phenylenediamine, bqdi= o-benzoquinonediimine). Optical absorption and emission, vibrational (resonance Raman), and electrochemical data are discussed. We explore the nature of the ruthenium benzoquinone electronic interaction in species 2 primarily within the framework of density functional theory (DFT) but also using INDO/S to extract Coulombic and exchange integrals. The resonance Raman and emission data were understood in terms of a common set of coupled vibrations localized primarily within the ruthenium metallacycle ring. Experimental and computational data were also compared among a select group of ruthenium bqdi species with other spectator ligands, specifically ammonia, 2,2'-bipyridine, and 2,4-pentanedione. The changes in the electrochemistry, optical spectroscopy, and vibrational spectra with changing spectator ligand donicity were explained within a common theoretical (DFT) model which further provided a detailed analysis of the variation in the molecular orbital descriptions. With the application of an extended charge decomposition analysis (ECDA), a detailed picture emerged of the bonding between the bqdi ligand and the metal atom, illustrating the coupling between the orbitals of each fragment as a function of orbital symmetry and charge transfer between the fragments of the complex. Metal-to-bqdi pi-back-donation is seen to be very important.

  10. Transport of metal sulfides in supercritical carbon dioxide

    SciTech Connect

    Propp, W.A.; Carleson, T.E.; Wai, C.M.; Huang, S.


    This report presents the results of studies of supercritical fluid extraction of selected organics and of transition metal sulfides using carbon dioxide with and without modifiers. For the metal sulfides, the modifiers water, aqueous EDTA, methanol, and methanolic 2,4-pentanedione (acetyl acetone) were added in amounts ranging from 1 to 10 wt% depending on the specific modifier used. Extraction efficiency was studied as a function of fluid composition and extraction temperature and pressure. The objective of the work was to investigate the scientific feasibility of using this type of extraction process for metallurgical or environmental applications. Theoretical modeling studies were performed in an attempt to develop predictive capabilities for both solubility calculations and extraction simulation. The experimental studies have established the scientific feasibility of extraction and transport of selected cations by these fluids. Depending on the metal and conditions, transport of up to 12% of the starting material has been observed; however, the observed extraction efficiencies for inorganics do not approach those typical for organics under similar conditions.

  11. Calcium copper-titanate thin film growth: tailoring of the operational conditions through nanocharacterization and substrate nature effects.


    Lo Nigro, Raffaella; Toro, Roberta G; Malandrino, Graziella; Fragalà, Ignazio L; Losurdo, Maria; Giangregorio, Michelaria M; Bruno, Giovanni; Raineri, Vito; Fiorenza, Patrick


    A novel approach based on a molten multicomponent precursor source has been applied for the MOCVD fabrication of high-quality CaCu(3)Ti(4)O(12) (CCTO) thin films on various substrates. The adopted in situ strategy involves a molten mixture consisting of Ca(hfa)(2).tetraglyme, Ti(tmhd)(2)(O-iPr)(2), and Cu(tmhd)(2) [Hhfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; tetraglyme = 2,5,8,11,14-pentaoxapentadecane; Htmhd = 2,2,6,6-tetramethyl-3,5-heptandione; O-iPr = isopropoxide] precursors. Film structural and morphological characterizations have been carried out by several techniques [X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM)], and in particular the energy filtered TEM mapping and X-ray energy dispersive (EDX) analysis in TEM mode provided a suitable correlation between nanostructural properties of CCTO films and deposition conditions and/or the substrate nature. Correlation between the nanostructure and optical/dielectric properties has been investigated exploiting spectroscopic ellipsometry.

  12. A nanoporous Ag-Fe mixed-metal-organic framework exhibiting single-crystal-to-single-crystal transformations upon guest exchange.


    Zhang, Yixun; Chen, Banglin; Fronczek, Frank R; Maverick, Andrew W


    The reaction of solutions of Fe(Pyac)3 [PyacH=3-(4-pyridyl)-2,4-pentanedione] and AgNO3 produces two types of porous mixed-metal-organic frameworks (M'MOFs). With lower AgNO3 concentrations, the product (M'MOF1) has a 2D honeycomb structure with Ag:Fe=1:1 and pores of ca. 12x16 A. When a higher concentration of AgNO3 is employed, however, the product (M'MOF2) has Ag:Fe=3:2 and a porous 1D ladder structure. A variety of nonpolar solvents serve as guests in M'MOF2: with 1,2-C6H4Cl2, [AgNO3]3[Fe(Pyac)3]2(1,2-C6H4Cl2)5.5 (M'MOF2a); with C6H5Br, [AgNO3]3[Fe(Pyac)3]2(C6H5Br)6 (M'MOF2b). M'MOFs 2a and 2b can be interconverted by treatment with the appropriate solvent, in single-crystal-to-single-crystal transformations.

  13. Preparation of an isocyano-beta-diketone via its metal complexes, by use of metal ions as protecting groups.


    Zhang, Yixun; Maverick, Andrew W


    A ligand containing isocyanide and beta-diketone functional groups, 3-(4-isocyanophenyl)-2,4-pentanedione (HacphNC), and several of its metal complexes have been prepared. The free isocyano-beta-diketone could not be prepared by dehydration of the analogous formamide, HacphNHCHO, because of the reactivity of its beta-diketone moiety. Instead, the metal complexes Al(acphNC)(3), Fe(acphNC)(3), Cu(acphNC)(2), and Zn(acphNC)(2) were synthesized by dehydration of the formamido-beta-diketonate complexes Al(acphNHCHO)(3), Fe(acphNHCHO)(3), Cu(acphNHCHO)(2), and Zn(acphNHCHO)(2). The free isocyano-beta-diketone, HacphNC, can be liberated from its Al and Fe complexes by treatment with oxalate (C(2)O(4)(2-)) and HC(2)O(4)(-). In addition to these O-bound complexes, C(N)-bound complexes can be prepared by the reaction of either Al(acphNC)(3) or HacphNC with Au(I). X-ray analyses of HacphNC, Al(acphNC)(3), (HacphNC)AuCl, Cu(acphNHCHO)(2), trans-Zn(acphNHCHO)(2)(H(2)O)(2), and two other intermediates are also reported.

  14. An iron(II) diketonate-diamine complex as precursor for thin film fabrication by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Bratvold, Jon E.; Carraro, Giorgio; Barreca, Davide; Nilsen, Ola


    A new divalent Fe precursor has been explored for deposition of iron-containing thin films by atomic layer deposition and molecular layer deposition (ALD/MLD). The Fe(II) β-diketonate-diamine complex, Fe(hfa)2TMEDA, (hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate, TMEDA = N,N,N‧,N‧-tetramethylethylenediamine) can be handled in air, and sublimation at 60 °C ensures a satisfactory vaporization rate. The reactivity of the precursor does not allow for direct reaction with water as co-reactant. Nevertheless, it reacts with carboxylic acids, resulting in organic-inorganic hybrid materials, and with ozone, yielding α-Fe2O3. The divalent oxidation state of iron was maintained during deposition when oxalic acid was used as co-reactant, demonstrating the first preservation of Fe(II) from precursor to film during an MLD process. A self-saturating growth mode was proven by in situ quartz crystal microbalance (QCM) measurements, and the films were further characterized by grazing incidence X-ray diffraction (GIXRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS).

  15. Composition-dependent electrocatalytic activity of palladium-iridium binary alloy nanoparticles supported on the multiwalled carbon nanotubes for the electro-oxidation of formic acid.


    Bao, Jianming; Dou, Meiling; Liu, Haijing; Wang, Feng; Liu, Jingjun; Li, Zhilin; Ji, Jing


    Surface-functionalized multiwalled carbon nanotubes (MWCNTs) supported Pd100-xIrx binary alloy nanoparticles (Pd100-xIrx/MWCNT) with tunable Pd/Ir atomic ratios were synthesized by a thermolytic process at varied ratios of bis(acetylacetonate) palladium(II) and iridium(III) 2,4-pentanedionate precursors and then applied as the electrocatalyst for the formic acid electro-oxidation. The X-ray diffraction pattern (XRD) and transmission electron microscope (TEM) analysis showed that the Pd100-xIrx alloy nanoparticles with the average size of 6.2 nm were uniformly dispersed on the MWCNTs and exhibited a single solid solution phase with a face-centered cubic structure. The electrocatalytic properties were evaluated through the cyclic voltammetry and chronoamperometry tests, and the results indicated that both the activity and stability of Pd100-xIrx/MWCNT were strongly dependent on the Pd/Ir atomic ratios: the best electrocatalytic performance in terms of onset potential, current density, and stability against CO poisoning was obtained for the Pd79Ir21/MWCNT. Moreover, compared with pure Pd nanoparticles supported on MWCNTs (Pd/MWCNT), the Pd79Ir21/MWCNT exhibited enhanced steady-state current density and higher stability, as well as maintained excellent electrocatalytic activity in high concentrated formic acid solution, which was attributed to the bifunctional effect through alloying Pd with transition metal.

  16. Lanthanide(III)-polyimide nanocomposites: Enhancement of dimensional stability

    SciTech Connect

    Southward, R.E.; Thompson, D.S.; Thornton, T.A.


    The addition of lanthanide(RI) acetate and tris(2,4-pentanedionato)lanthanum(III) complexes to the soluble, low dielectric, colorless polyimides formed from 2,2-bis(3,4-dicarboxyphenyl)hexa-fluoropropanedianhydride/1,3-bis-(aminophenoxy)benzene, (6FDA/APB), and 6FDA/2,2-bis[4-4-aminophenoxy]hexa-fluoropropane, 6FDA/BDAF, was investigated with the expectation that thermal treatment of doped resin films would lead to an isotropic reduction in the linear coefficient of thermal expansion (CTE) while maintaining the essential properties of the parent polyimide. To realize visually clear metal-doped films the inorganic phase particle size, after thermal treatment, must be less than ca. 200 nm. This can only be accomplished by using Ln complexes which are soluble in the curing polymer matrix. Ln acetates gave homogeneous, visually clear films with manometer size inorganic clusters and slightly lowered CTE`s. The Ln-2,4-pentanedionates gave films with large CTE lowerings while maintaining visual clarity and acceptable mechanical and thermal properties. RI measurements indicate that the films are isotropic. TEM data are consistent with particle sizes for the lanthanide ion containing species which are in the manometer range. Dielectric constants (8-12 GHz) remain low.

  17. The Origin of the electrostatic Perturbation in Acetoacetate Decarboxylase

    SciTech Connect

    Ho, M.; Menetret, J; Tsuruta, H; Allen, K


    Acetoacetate decarboxylase (AADase) has long been cited as the prototypical example of the marked shifts in the pKa values of ionizable groups that can occur in an enzyme active site. In 1966, it was hypothesized that in AADase the origin of the large pKa perturbation (-4.5 log units) observed in the nucleophilic Lys 115 results from the proximity of Lys 116, marking the first proposal of microenvironment effects in enzymology. The electrostatic perturbation hypothesis has been demonstrated in a number of enzymes, but never for the enzyme that inspired its conception, owing to the lack of a three-dimensional structure. Here we present the X-ray crystal structures of AADase and of the enamine adduct with the substrate analogue 2,4-pentanedione. Surprisingly, the shift of the pKa of Lys 115 is not due to the proximity of Lys 116, the side chain of which is oriented away from the active site. Instead, Lys 116 participates in the structural anchoring of Lys 115 in a long, hydrophobic funnel provided by the novel fold of the enzyme. Thus, AADase perturbs the pKa of the nucleophile by means of a desolvation effect by placement of the side chain into the protein core while enforcing the proximity of polar residues, which facilitate decarboxylation through electrostatic and steric effects.

  18. Study of DT-diaphorase in pigment-producing cells.


    Smit, N P; Hoogduijn, M J; Riley, P A; Pavel, S


    DT-diaphorase is an FAD-containing enzyme capable of a two-electron reduction of ortho- and paraquinones. Nicotinamide coenzymes (NADH + H+ and NADPH + H+) serve as hydrogen sources in these reactions. The role of DT-diaphorase has been thoroughly investigated in situations when the enzyme is able to reduce exogenous and endogenous quinones, hence protecting the cells against these reactive intermediates. The enzyme has also been studied in connection with its ability to activate some quinoid cytostatics. It is surprising that DT-diaphorase has never been investigated in pigment-producing cells that are known to generate considerable amounts of ortho-quinones. Using a spectrophotometric method we could readily measure the activity of DT-diaphorase in epidermis and various cultured pigment cells. The melanocytes isolated from dark skin showed generally higher DT-diaphorase activity than those from fair skin samples. Also, darkly pigmented congenital naevus cells exhibited higher activity of this enzyme. The most striking was the high DT-diaphorase activity in melanoma cell cultures. In these cells DT-diaphorase activity could be induced by incubation of the cells with 4-hydroxyanisole. A similar effect was seen when a catechol-O-methyltransferase (COMT) inhibitor (3-(3,4-dihydroxy-5-nitrobenzylidene)-2,4-pentanedione (OR-462) was utilised. The induction was inhibited by cyclohexidine.

  19. Assessment of accidental intakes of uranyl acetylacetonate (UAA)

    SciTech Connect

    Fisher, D.R.; Briant, J.K.


    Uranyl acetylacetonate (UAA) is an organic complex of uranium used for military applications as a chemical catalyst in high explosives. It is prepared from depleted uranium metal (in lots of 5 kg to 7 kg) by dissolution in nitric acid, neutralization, and complexation with 2,4-pentanedione; the precipitate is dissolved in benzene and recrystallized, dried, ground, and packaged. About six workers at a small chemical company were exposed over a period of time to UAA powders during routine preparation and packaging of the uranium catalyst. The dissolution characteristics of the inhaled material were unknown and could not be determined from the published scientific literature. A 1.05-g sample of UAA powder was obtained from the responsible regulatory authority for further study to determine its chemical composition, and for dissolution in simulated lung fluid. We found the solubility of UAA to be equivalent to a mixture of 52% ICRP class D and 48% ICRP class W material. The annual limit on intake and the derived air concentration for radiological protection were estimated from this result for airborne exposure to UAA. A recycling biokinetic model was used to estimate both material-specific variations in urinary excretion rates and lung retention with time after accidental intakes. This study provides new information for evaluating future exposures to UAA.

  20. Reactivity of niobium(v) and tantalum(v) halides with carbonyl compounds: synthesis of simple coordination adducts, C-H bond activation, C=O protonation, and halide transfer.


    Marchetti, Fabio; Pampaloni, Guido; Zacchini, Stefano


    The metal halides of Group 5 MX(5) (M = Nb, Ta; X = F, Cl, Br) react with ketones and acetylacetones affording the octahedral complexes [MX(5)(ketone)] () and [TaX(4){kappa(2)(O)-OC(Me)C(R)C(Me)O}] (R = H, Me, ), respectively. The adducts [MX(5)(acetone)] are still reactive towards acetone, acetophenone or benzophenone, giving the aldolate species [MX(4){kappa(2)(O)-OC(Me)CH(2)C(R)(R')O}] (). The syntheses of (M = Ta, X = F, R = R' = Ph) and (M = Ta, X = Cl, R = Me, R' = Ph) take place with concomitant formation of [(Ph(2)CO)(2)-H][TaF(6)], and [(MePhCO)(2)-H][TaCl(6)], respectively. The compounds [acacH(2)][TaF(6)], and [TaF{OC(Me)C(Me)C(Me)O}(3)][TaF(6)], have been isolated as by-products in the reactions of TaF(5) with acacH and 3-methyl-2,4-pentanedione, respectively. The molecular structures of, and have been ascertained by single crystal X-ray diffraction studies.

  1. Poly(methyl methacrylate)-titania hybrid materials by sol-gel processing

    SciTech Connect

    Zhang, J.; Luo, S.; Gui, L.; Tang, Y.


    Sol-gel derived Poly(methyl methacrylate)-titania hybrid materials were synthesized by using acrylic acid or allyl acetylacetone (3-allyl-2,4-pentanedione) as coupling agents. Titanium butoxide modified with acrylic acid (or titanium isopropoxide modified with allyl acetylacetone) was hydrolyzed to produce a titania network, and then poly (methyl methacrylate) (PMMA) chains formed in situ through a radical polymerization were chemically bonded to the forming titania network to synthesize a hybrid material. Transparent hybrid materials with different contents of titania were achieved. With the increase of the titania content, the colors of the products changed form yellow to dark red. The synthesis process was investigated step by step by using FTIR spectroscopy, and the experimental results demonstrated that acrylate or acetylacetonato groups bound to titanium remain in the final hybrid materials. The thermal stability of the hybrid materials was considerably improved relative to pure PMMA. Field emission scanning electron microscopy (FE-SEM) analyses showed the hybrid materials are porous and pore diameters vary from 10nm to 100nm. The hybrid materials using allyl acetylacetone as the coupling agent exhibited thermochromic effects that both pure PMMA and titania do not have.

  2. Densification and crystallization of zirconia thin films prepared by sol-gel processing

    SciTech Connect

    Schwartz, R.W.; Voigt, J.A.; Buchheit, C.D.; Boyle, T.J.


    We have investigated the effects of precursor nature and heat treatment schedule on the densification and crystallization behavior of sol-gel derived zirconia thin films. Precursor solutions were prepared from n-propanol, zirconium (IV) n-propoxide, and either acetic acid, or 2,4-pentanedione (acac) and water additions. By controlling the ligand type and ligand-to-metal ratio, we were able to prepare films which displayed significant differences in densification behavior. We attribute the dissimilarity in densification to variations in the nature of the as-deposited films, as influenced by ligand type and concentration. While the acac- derived film was a physical gel, (i.e., a physical aggregation of the oligomeric species), the acetic acid-derived film, which exhibited less consolidation, was a chemical gel that could not be redissolved in the parent solvent. Films prepared with large acac/metal ratios and small water additions exhibited minimal crosslinking at 25{degree}C, displayed the greatest consolidation ({approximately}86% shrinkage) and the highest refractive index (n = 2.071) when heat treated. These results indicate the importance that M-O-M bonds (crosslinks) formed at low temperature can have on densification behavior. We also report on the effects of heat-treatment schedules and ramp rates on densification behavior. All of the films of the present study crystallized into the cubic phase, at temperatures ranging from {approximately}400{degree}C to greater than 700{degree}C, depending on the heating rate.

  3. Neurophysiological studies on the relation between the structural properties and neurotoxicity of aliphatic hydrocarbon compounds in rats.

    PubMed Central

    Misumi, J; Nagano, M


    In order to determine the specific structural properties responsible for neurotoxic activity, the comparative neurotoxicity of n-hexane, methyl n-butyl ketone, 2,5-hexanedione, and their relatives was investigated in the peripheral nerves of rats. The maximum conduction velocity of motor and sensory fibres and the motor distal latency of the tail nerves of rats were periodically examined in animals receiving repeated subcutaneous injections of 11 aliphatic monoketone or diketone compounds and their relatives for prolonged periods. A study of the comparative neurotoxicity of n-hexane, methyl n-butyl ketone, and their metabolites showed that 2,5-hexanedione was the most actively neurotoxic. Furthermore, a study of other symmetrical diketones with different carbon numbers showed that 2,4-pentanedione, which is structurally similar to 2,5-hexanedione, possessed a different type of neurotoxic activity than 2,5-hexanedione. Regarding aliphatic monoketone compounds, acetone, 2-pentanone, 2-heptanone, and 2-octanone were confirmed non-neurotoxic for the peripheral nervous system. Evidence from some previous reports, however, suggested that 3-heptanone, 4-octanone, and 5-nonanone might produce neuropathies by being converted to 2,5-diketones under specific conditions. PMID:6093852

  4. Efficient perovskite/fullerene planar heterojunction solar cells with enhanced charge extraction and suppressed charge recombination

    NASA Astrophysics Data System (ADS)

    Li, Cong; Wang, Fuzhi; Xu, Jia; Yao, Jianxi; Zhang, Bing; Zhang, Chunfeng; Xiao, Min; Dai, Songyuan; Li, Yongfang; Tan, Zhan'ao


    Alcohol soluble titanium chelate TIPD (titanium (diisopropoxide) bis(2,4-pentanedionate)) was used as an electron transporting layer to form an ohmic contact with the negative electrode, aiming to enhance the charge extraction and suppress the charge recombination for high performance CH3NH3PbI3/PCBM-based PHJ perovskite solar cells. The TIPD layer shows excellent suitability to CH3NH3PbI3 perovskite synthesized by different methods. For one-step synthesized CH3NH3PbI3, the power conversion efficiency (PCE) of the device with the TIPD buffer reaches 8.75%, with a nearly 33% increase in comparison with the device without the buffer layer (6.58%). For two-step synthesized CH3NH3PbI3, an open-circuit voltage (Voc) of 0.89 V, a short-circuit current density (Jsc) of 22.57 mA cm-2, and a fill factor (FF) of 64.5%, corresponding to a PCE of 12.95% for the device with a TIPD buffer layer were achieved, which is among the best performances reported in the literature for CH3NH3PbI3/PCBM-based PHJ perovskite solar cells.Alcohol soluble titanium chelate TIPD (titanium (diisopropoxide) bis(2,4-pentanedionate)) was used as an electron transporting layer to form an ohmic contact with the negative electrode, aiming to enhance the charge extraction and suppress the charge recombination for high performance CH3NH3PbI3/PCBM-based PHJ perovskite solar cells. The TIPD layer shows excellent suitability to CH3NH3PbI3 perovskite synthesized by different methods. For one-step synthesized CH3NH3PbI3, the power conversion efficiency (PCE) of the device with the TIPD buffer reaches 8.75%, with a nearly 33% increase in comparison with the device without the buffer layer (6.58%). For two-step synthesized CH3NH3PbI3, an open-circuit voltage (Voc) of 0.89 V, a short-circuit current density (Jsc) of 22.57 mA cm-2, and a fill factor (FF) of 64.5%, corresponding to a PCE of 12.95% for the device with a TIPD buffer layer were achieved, which is among the best performances reported in the literature

  5. Harvard--MIT research program in short-lived radiopharmaceuticals

    SciTech Connect

    Not Available


    This report describes progress on five projects. The first project showed a 1000 fold concentration of the cationic complex {sup 99m}Tc (MIBI) in heart cell mitochondria vs heart cell cytoplasm, as determined by high resolution electron probe microanalysis. Additional technetium-99m based complexes are being developed and tested. The second project involves evaluating technetium acetylacteonates as potential indicators of cerebral blood flow. An intermediate in the synthesis of a technetium porphyrin complex has been synthesized; an oxotechnetium(V)-2,4-pentanedione complex has been prepared and is currently being characterized. The third project involves using radio labelled antibodies for diagnosis and treatment of cancer. An early discovery was that chloramine-T based iodination protocols resulted in a reversal of the charge on mouse lgGs. Immunoperoxidase-labelled monoclonal antibody MOv 18 was shown to bind specifically to the most frequent ovarian aderon carcinomas, and not to healthy tissue, making this antibody a good candidate for immunotherapy or immunodetection. Work on a specific immunotherapy protocol suffered a setback when one reagent, a {sup 125}I-biotin complex, proved to be unstable in vivo. The fourth project involves labelling antibodies with positron emitting radionuclides. Radiofluorination was accomplished through reductive alkylation of {sup 18}F-aldehyde, or pentafluorophenyl esters. Radioiodination was accomplished using alkyl-tin derivation exchange. The fifth project examined antibody modification for use in radioimmune imaging. Technetium-99m-labelled lgG was shown to be biologically equivalent to Indium-III-labelled lgG for imaging focal sites of inflamation. Also, Indium III labelling of small bioactive peptides was examined as a means of imaging important physiological processes. 44 refs., 2 figs.

  6. A new route for the synthesis of titanium silicalite-1

    SciTech Connect

    Vasile, Aurelia; Busuioc-Tomoiaga, Alina Maria


    Graphical abstract: Well-prepared TS-1 was synthesized by an innovative procedure using inexpensive reagents such as fumed silica and TPABr as structure-directing agent. This is the first time when highly crystalline TS-1 is obtained in basic medium, using sodium hydroxide as HO{sup -} ion source required for the crystallization process. Hydrolysis of titanium source has been prevented by titanium complexation with acetylacetone before structuring gel. Highlights: Black-Right-Pointing-Pointer TS-1 was obtained using cheap reagents as fumed silica and tetrapropylammonium bromide. Black-Right-Pointing-Pointer First time NaOH was used as source of OH{sup -} ions required for crystallization process. Black-Right-Pointing-Pointer The hydrolysis Ti alkoxides was controlled by Ti complexation with 2,4-pentanedione. -- Abstract: A new and efficient route using inexpensive reagents such as fumed silica and tetrapropylammonium bromide is proposed for the synthesis of titanium silicalite-1. High crystalline titanium silicalite-1 was obtained in alkaline medium, using sodium hydroxide as HO{sup -} ion source required for the crystallization process. Hydrolysis of titanium source with formation of insoluble oxide species was prevented by titanium complexation with before structuring gel. The final solids were fully characterized by powder X-ray diffraction, scanning electron microscopy, Fourier transform infrared, ultraviolet-visible diffuse reflectance, Raman and atomic absorption spectroscopies, as well as nitrogen sorption analysis. It was found that a molar ratio Ti:Si of about 0.04 in the initial reaction mixture is the upper limit to which well formed titanium silicalite-1 with channels free of crystalline or amorphous material can be obtained. Above this value, solids with MFI type structure containing both Ti isomorphously substituted in the network and extralattice anatase nanoparticles inside of channels is formed.

  7. X-ray Emission Spectroscopy to Study Ligand Valence Orbitals in Mn Coordination Complexes

    SciTech Connect

    Smolentsev, Grigory; Soldatov, Alexander V; Messinger, Johannes; Merz, Kathrin; Weyhermuller, Thomas; Bergmann, Uwe; Pushkar, Yulia; Yano, Junko; Yachandra, Vittal K.; Glatzel, Pieter


    We discuss a spectroscopic method to determine the character of chemical bonding and for the identification of metal ligands in coordination and bioinorganic chemistry. It is based on the analysis of satellite lines in X-ray emission spectra that arise from transitions between valence orbitals and the metal ion 1s level (valence-to-core XES). The spectra, in connection with calculations based on density functional theory (DFT), provide information that is complementary to other spectroscopic techniques, in particular X-ray absorption (XANES and EXAFS). The spectral shape is sensitive to protonation of ligands and allows ligands, which differ only slightly in atomic number (e.g., C, N, O...), to be distinguished. A theoretical discussion of the main spectral features is presented in terms of molecular orbitals for a series of Mn model systems: [Mn(H2O)6]2+, [Mn(H2O)5OH]+, [Mn(H2O)5NH2]+, and [Mn(H2O)5NH3]2+. An application of the method, with comparison between theory and experiment, is presented for the solvated Mn2+ ion in water and three Mn coordination complexes, namely [LMn(acac)N3]BPh4, [LMn(B2O3Ph2)(ClO4)], and [LMn(acac)N]BPh4, where L represents 1,4,7-trimethyl-1,4,7-triazacyclononane, acac stands for the 2,4-pentanedionate anion, and B2O3Ph2 represents the 1,3-diphenyl-1,3-dibora-2-oxapropane-1,3-diolato dianion.

  8. Simple determination of hydrazine in waste water by headspace solid-phase micro extraction and gas chromatography-tandem mass spectrometry after derivatization with trifluoro pentanedione.


    Oh, Jin-Aa; Shin, Ho-Sang


    A headspace solid-phase micro extraction (HS-SPME) and gas chromatography-tandem mass spectrometric (GC-MS/MS) method is described to detect hydrazine after derivatization with 1,1,1-trifluoro-2,4-pentanedione (1,1,1-TFPD) to 3-methyl-5-(trifluoromethyl) pyrazole in industrial waste water. The following optimal HS-SPME conditions were used: 85 μm-carboxen-polydimethylsiloxane fibre, 100 mg L(-1) TFPD, saturated NaCl, an extraction/derivatization temperature of 80 °C, a heating time of 40 min, and a pH of 9.5. Under the established conditions, the detection and quantification limits were 0.002 μg L(-1) and 0.007 μg L(-1) by using 5 mL of waste water and the intra- and inter-day relative standard deviations were less than 10.2% at concentrations of 0.02 and 0.1 μg L(-1). The calibration curve showed good linearity, with r(2) = 0.998; the accuracy was in the range of 98.0-103%; and the precision of the assay was less than 10.2% in industrial waste water. Hydrazine was detected over a concentration range of 0.011-0.074 μg L(-1) in 5 of 20 waste water samples. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. Synthesis of Ir(III) complexes with Tp(Me2) and acac ligands and their reactivity with electrophiles.


    Morales-Cerón, Judith P; Salazar-Pereda, Verónica; Mendoza-Espinosa, Daniel; Alvarado-Rodríguez, José G; Cruz-Borbolla, Julián; Andrade-López, Noemí; Vásquez-Pérez, José M


    The reaction of the bis(ethylene) complex [Tp(Me2)Ir(C2H4)2] () (Tp(Me2) = hydrotris(3,5-dimethylpyrazolyl)borate) with an excess of 2,4-pentanedione (acetylacetone, Hacac) at 70 °C produced a mixture of the Ir(iii) complex [Tp(Me2)Ir(acac)(C2H5)] () as a major product (67% yield) and two other side complexes [Tp(Me2)Ir(acac)(H)] () and [Tp(Me2)Ir(C9H14O2)] () in 20 and 13% yields, respectively. According to the proposed reaction mechanism and DFT calculations, complexes and are generated from an 18e(-) intermediate [Tp(Me2)Ir(C2H4)(acac)(C2H3)] () which undergoes either hydrogen insertion or β-hydride elimination followed by the subsequent loss of a molecule of ethylene. The lowest yielding complex which features a 2-iridafuran is presumably generated from an unusual thermal coupling between one vinylic and one acac moiety. The availability of the acidic α-proton of the acac ligand was tested by the treatment of complex with Br2 and Cu(NO3)2 rendering the substitution complexes [Tp(3-Br,Me2)Ir(3-Br-acac)Br] () and [Tp(Me2)Ir(3-NO2-acac)(C2H5)] () in good yields. The series of heteroleptic iridium(iii) compounds display air and moisture stability and have been characterized by NMR, IR, and elemental analyses, and, in the case of , and , by single-crystal X-ray diffraction analyses.

  10. Reaction coordinate analysis for beta-diketone cleavage by the non-heme Fe2+-dependent dioxygenase Dke1.


    Straganz, Grit D; Nidetzky, Bernd


    Acetylacetone dioxygenase from Acinetobacter johnsonii (Dke1) utilizes a non-heme Fe2+ cofactor to promote dioxygen-dependent conversion of 2,4-pentanedione (PD) into methylglyoxal and acetate. An oxidative carbon-carbon bond cleavage by Dke1 is triggered from a C-3 peroxidate intermediate that performs an intramolecular nucleophilic attack on the adjacent carbonyl group. But how does Dke1 bring about the initial reduction of dioxygen? To answer this question, we report here a reaction coordinate analysis for the part of the Dke1 catalytic cycle that involves O2 chemistry. A weak visible absorption band (epsilon approximately 0.2 mM(-1) cm(-1)) that is characteristic of an enzyme-bound Fe2+-beta-keto-enolate complex served as spectroscopic probe of substrate binding and internal catalytic steps. Transient and steady-state kinetic studies reveal that O2-dependent conversion of the chromogenic binary complex is rate-limiting for the overall reaction. Linear free-energy relationship analysis, in which apparent turnover numbers (k(app) cat) for enzymatic bond cleavage of a series of substituted beta-dicarbonyl substrates were correlated with calculated energies for the highest occupied molecular orbitals of the corresponding beta-keto-enolate structures, demonstrates unambiguously that k(app) cat is governed by the electron-donating ability of the substrate. The case of 2'-hydroxyacetophenone (2'HAP), a completely inactive beta-dicarbonyl analogue that has the enol double bond delocalized into the aromatic ring, indicates that dioxygen reduction and C-O bond formation cannot be decoupled and therefore take place in one single kinetic step.

  11. Structure and NIR-luminescence of ytterbium(III) beta-diketonate complexes with 5-nitro-1,10-phenanthroline ancillary ligand: assessment of chain length and fluorination impact.


    Martín-Ramos, Pablo; Pereira da Silva, Pedro S; Lavín, Victor; Martín, Inocencio R; Lahoz, Fernando; Chamorro-Posada, Pedro; Silva, Manuela Ramos; Martín-Gil, Jesús


    Seven new tris(β-diketonear-nate)ytterbium(III) complexes with the general formula [Yb(β-diketonate)3(5NO2phen)] (where the β-diketone is either 4,4,4-trifluoro-1-(2-naphthyl)-1,3-butanedione, 4,4,4-trifluoro-1-(2-furyl)-1,3-butanedione, 1,1,1-trifluoro-2,4-pentanedione, 1,1,1-trifluoro-5,5-dimethyl-2,4-hexanedione, 1,1,1,5,5,6,6,7,7,7-decafluoro-2,4-heptanedione, 2,4-hexanedione or 2,6-dimethyl-3,5-heptanedione, and 5NO2phen = 5-nitro-1,10-phenanthroline) were synthesized and characterized by elemental analysis, attenuated total reflectance Fourier transform infrared spectroscopy and photoluminescence spectroscopy. Single crystal X-ray structures have been determined for three fluorinated complexes and ground state geometries of the other four complexes have been predicted using the Sparkle/PM6 model. These experimental structures and those designed by semi-empirical models reveal octacoordination around the Yb(3+) ion. Photoluminescence studies and lifetime measurements show that the increase in the fluorinated β-diketonate chain length is associated with a decrease in Yb(3+) luminescence intensity of the (2)F5/2→(2)F7/2 transition at around 980 nm and the (2)F5/2 excited state lifetime, while the ligand lifetime value remains almost unaffected. Finally, fluorination of the ligands is only advised when the complexes are to be used for co-doping with isostructural Er(3+) complexes for optical amplifiers, since it leads to a slight decrease in luminescence intensity for the same β-diketonate chain length.

  12. Atmospheric behavior of urban diesel soot tagged with an iridium tracer

    SciTech Connect

    Suarez, A.E.; Caffrey, P.F.; Borgoul, P.V.; Ondov, J.M.


    An important source of polynuclear aromatic hydrocarbons depositing to the Chesapeake Bay is diesel emissions, including, those from the heavily-industrial City of Baltimore which lies < 5 km to the west. To investigate the influence of Baltimore`s urban soot plum, approximately 38 g of Ir (100 g of Ir-III 2,4-pentanedionate dissolved in 8 L toluene) were used to tag 268 m{sup 3} of diesel fuel burned by the City of Baltimore`s sanitation truck fleet for a 20-day period in August, 1995. Size-segregated aerosol was collected daily using 80-L min{sup {minus}1} dichotomous samplers at four land-bas3ed sites and aboard ship at two locations on the Chesapeake Bay. Shipboard samples were collected on the EPA`s Research Vessel Anderson, either east or southeast of Baltimore, off Annapolis. Three of the land sites, i.e., those at Catonsville, MD, the Eastern Avenue Fire Station (14 km from the Bay), and the Coast Guard Station at Still pond (30 km northeast of Baltimore) were chosen to be aligned with prevailing westerly winds. The fourth site was located on Hart Miller Island, about 14 km southeast of the Fire Station to take advantage of drainage flow along the Patapsco River. In addition, 10-stage Micro-Orifice Impactors were operated daily aboard ship and at all but the Catonsville site. Deposition plates were exposed aboard ship and at two of the land sites. Finally, several samples of tagged diesel emissions were collected with an MOI mounted on one of the sanitation trucks. Iridium and {le} 40 other elements were determined by neutron activation analysis or X-ray fluorescence; graphitic carbon by light transmission, and aerosol mass by gravimetry.

  13. Application of an Ir tracer to determine soot exposure to students commuting to school on Baltimore public buses

    NASA Astrophysics Data System (ADS)

    Wu, Charles C.; Suarez, Ana E.; Lin, Zhibo; Kidwell, Christopher B.; Borgoul, Polina V.; Caffrey, Peter F.; Ondov, John M.; Sattler, Barbara

    An important component of urban aerosol, diesel soot is a known respiratory irritant and contains mutagenic and carcinogenic organic compounds. To estimate student exposures to soot emitted from public diesel buses during commutes to city high schools, a portion of the Baltimore municipal fuel supply was tagged with an iridium tracer and exposure was monitored during commutes with personal aerosol monitors as a part of an Environmental Justice Project. A total of 68.2 g of Ir as iridium(III)-2,4-pentanedionate were used to induce a concentration of 48.5 μg Ir ℓ -1 of fuel. Twenty samples were collected over 10 days while four students commuted on regularly scheduled buses and a fifth student commuted by private car. Individual samples integrated from 1 to 4 round trips. Iridium analyses were performed instrumentally after neutron activation with a detection limit (DL) of about 500 fg. For students commuting by bus and following protocols, Ir tracer concentrations ranged from 53±38 to >1980±49 fg m -3. Concentrations up to 3530±220 fg m -3 were observed for student #5, who sampled only when boarding and disembarking. Exposure were greatest for students commuting through the heavily trafficked central business district. Corresponding estimates of exposures to soot emitted from municipal buses ranged from ⩽3 to 82 ng soot m -3 (⩽145 ng m -3 for student #5), i.e. well below the exposure level of 2-10 μg m -3 total C from all sources, including the more than 30,000 diesel trucks which pass through the city's major toll facilities each day. Ir was undetectable in samples collected by the student commuting by car when its windows were closed, but comparable to those of the other students when commutes were made with windows open. The Ir tracer DL corresponds to about 21 ng soot, about half of which is carbon. This is far below the 230 ng reported for analysis by a highly sensitive thermal-optical technique.

  14. Chemical modification of the bifunctional human serum pseudocholinesterase. Effect on the pseudocholinesterase and aryl acylamidase activities.


    Boopathy, R; Balasubramanian, A S


    The effect of chemical modification on the pseudocholinesterase and aryl acylamidase activities of purified human serum pseudocholinesterase was examined in the absence and presence of butyrylcholine iodide, the substrate of pseudocholinesterase. Modification by 2-hydroxy-5-nitrobenzyl bromide, N-bromosuccinimide, diethylpyrocarbonate and trinitrobenzenesulfonic acid caused a parallel inactivation of both pseudocholinesterase and aryl acylamidase activities that could be prevented by butyrylcholine iodide. With phenylglyoxal and 2,4-pentanedione as modifiers there was a selective activation of pseudocholinesterase alone with no effect on aryl acylamidase. This activation could be prevented by butyrylcholine iodide. N-Ethylmaleimide and p-hydroxy-mercuribenzoate when used for modification did not have any effect on the enzyme activities. The results suggested essential tryptophan, lysine and histidine residues at a common catalytic site for pseudocholinesterase and aryl acylamidase and an arginine residue (or residues) exclusively for pseudocholinesterase. The use of N-acetylimidazole, tetranitromethane and acetic anhydride as modifiers indicated a biphasic change in both pseudocholinesterase and aryl acylamidase activities. At low concentrations of the modifiers a stimulation in activities and at high concentrations an inactivation was observed. Butyrylcholine iodide or propionylcholine chloride selectively protected the inactivation phase without affecting the activation phase. Protection by the substrates at the inactivation phase resulted in not only a reversal of the enzyme inactivation but also an activation. Spectral studies and hydroxylamine treatment showed that tyrosine residues were modified during the activation phase. The results suggested that the modified tyrosine residues responsible for the activation were not involved in the active site of pseudocholinesterase or aryl acylamidase and that they were more amenable for modification in comparison to

  15. Syntheses, X-ray crystal structures, and ligand substitution kinetics of the carbon-bonded chromium(III) complexes trans-(CrR(acac)/sub 2/(L)) (R = CH/sub 2/Cl, CHCl/sub 2/; L = H/sub 2/O, CH/sub 3/OH, pyridine)

    SciTech Connect

    Ogino, H.; Shoji, M.; Abe, Y.; Shimura, M.; Shimoi, M.


    The alkylchromium(III) complexes trans-(CrR(acac)/sub 2/(H/sub 2/O)) (a) (R = CHCl/sub 2/, CH/sub 2/Cl; Hacac = 2,4-pentanedione) were prepared by the reaction of (CrR(H/sub 2/O)/sub 5/)/sup 2 +/ with Hacac and triethylamine. Synthetic methods reported previously for (CrR(H/sub 2/O)/sub 5/)/sup 2 +/ (R = CHCl/sub 2/, CH/sub 2/Cl) were improved to give approximately quantitative yields. The complexes trans-(CrR(acac)/sub 2/L) (L = CH/sub 3/OH, pyridine) were derived by replacing a coordinated water molecule in a with L. The X-ray crystal structure analyses of trans-(CrR(acac)/sub 2/(py)) (R = CHCl/sub 2/, CH/sub 2/Cl) have been performed. The carbon-bonded ligands CHCl/sub 2/ and CH/sub 2/Cl lengthen specifically the Cr-N bond trans to the Cr-C bond in trans-(Cr(CHCl/sub 2/)(acac)/sub 2/(py)) (b; Cr-N = 2.154 (7) A) as well as in trans-(Cr-(CH/sub 2/Cl)(acac)/sub 2/(py)) (c; Cr-N = 2.201(4) A). The elongation of the Cr-N bonds in b and c is reflected in substantial labilization of the ligand substitution reactions at the position trans to R: trans-(CrR(acac)/sub 2/(CH/sub 3/OH)) + L reversible trans-(CrR(acac)/sub 2/L) + CH/sub 3/OH. The rate constants (M/sup -1/ s/sup -1/) at 25 /sup 0/C in methanol for the formation of trans-(CrR(acac)/sub 2/L) are 85 +/- 2 (R = CHCl/sub 2/, L = py), 98 +/- 1 (R = CHCl/sub 2/, L = 4-methylpyridine), 57 +/- 1 (R = CHCl/sub 2/, L = isonicotinamide), and (1.2 +/- 0.5) x 10/sup 3/ (R = CH/sub 2/Cl, L = py), and the rate constants (s/sup -1/) for the backward reaction at 25 /sup 0/C are 15 +/- 1 (R = CHCl/sub 2/, L = py), 11 +/- 1 (R = CHCl/sub 2/, L = 4-methylpyridine), 33 +/- 1 (R = CHCl/sub 2/, L = isonicotinamide), and (5 +/- 2) x 10/sup 2/ (R = CH/sub 2/Cl, L = py).

  16. Surface modified carbon nanoparticle papers and applications on polymer composites

    NASA Astrophysics Data System (ADS)

    Ouyang, Xilian

    a tensile strength of 360 MPa and an electrical conductivity of 4.45x104 S/m, much better than any similar materials reported in the literature. However, they didn't show good gas barrier properties. Since the GO paper presented zero gas permeability for both CO2 and H2, a hybrid paper fabrication approach was proposed to combine the advantages of individual GP and GO papers. This was done by filtering GP and GO layer by layer with GO sandwiched in between two layers of GP. The resulting hybrid papers showed high mechanical tensile strength and EMI shielding effectiveness that are close to GP nanopapers, and excellent gas barrier properties that comparable to GO nanopapers. The GP, GO and GP-Go-GP hybrid nanopapers have been successfully coated onto the thermoplastic surface by thermal lamination and injection molding. In the third part, the effect of PANI-CNF nanopapers and a chelating agent, 2, 4- Pentanedione (2, 4-P) on kinetics of an in-mold coating (IMC) resin was investigated. The results showed that the presence of amine functionalized carbon nanoparticles tended to retard the resin reaction, while 2, 4-P was capable of promoting the redox based free radical polymerization by forming a complex with the cobalt promoter in the initiation step. In order to understand the chemical and physical changes during the resin curing process, kinetics study on two major resin components, i.e. hexanediol diacrylate (HDDA) and styrene (St), were carried out using an integrated analysis design: differential scanning calorimetry (DSC) for overall reaction, Fourier transform infrared spectroscopy (FTIR) for individual component reactions, and rheometry for liquid-solid transition during the reaction. The gel point of this radical polymerization resin system was found to be <2% which implied that most curing was conducted in the solid phase. The results showed that the double bonds in acrylates and St followed an azeotropic polymerization pattern.

  17. Volatile organic compounds in the marine troposphere and surface oceans: methods, measurements and biogeochemical implications

    NASA Astrophysics Data System (ADS)

    Hudson, Edward


    first optimized for acetone and subsequently for a suite of 23 C1 -- C9 carbonyl compounds. The buffering capacity of seawater necessitated the use of artificial seawater for standard preparation, and acidification of seawater samples to achieve the method's optimum pH of 3.7. Sparging with UHP argon, and C-18 solid phase extraction of the dissolved PFBHA, were found to be the most effective methods for reducing the high process blanks observed for C1-C3 carbonyl compounds. Using this technique, the first acetone measurements for North Atlantic and Arctic waters (5.5 --9.6 nM acetone), the first surface water measurements of carbonyl compounds from the St. Lawrence Estuary (including glyoxal, methylglyoxal and 2,4-pentanedione), and concentrations of 11 C1 - C9 carbonyl compounds in surface seawaters from the Labrador Sea and from the Scotian Shelf were reported. This represents the first survey of these compounds in seawaters outside of the tropics. The results suggest that the North Atlantic is a sink for glyoxal and formaldehyde. Fluxes of several C4 - C9 aldehydes from the ocean to the atmosphere were estimated to be -13 to +14 mumol/m2/day.