Structural changes in block copolymer micelles induced by cosolvent mixtures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kelley, Elizabeth G.; Smart, Thomas P.; Jackson, Andrew J.

2012-11-26

We investigated the influence of tetrahydrofuran (THF) addition on the structure of poly(1,2-butadiene-b-ethylene oxide) [PB-PEO] micelles in aqueous solution. Our studies showed that while the micelles remained starlike, the micelle core-corona interfacial tension and micelle size decreased upon THF addition. The detailed effects of the reduction in interfacial tension were probed using contrast variations in small angle neutron scattering (SANS) experiments. At low THF contents (high interfacial tensions), the SANS data were fit to a micelle form factor that incorporated a radial density distribution of corona chains to account for the starlike micelle profile. However, at higher THF contents (lowmore » interfacial tensions), the presence of free chains in solution affected the scattering at high q and required the implementation of a linear combination of micelle and Gaussian coil form factors. These SANS data fits indicated that the reduction in interfacial tension led to broadening of the core-corona interface, which increased the PB chain solvent accessibility at intermediate THF solvent fractions. We also noted that the micelle cores swelled with increasing THF addition, suggesting that previous assumptions of the micelle core solvent content in cosolvent mixtures may not be accurate. Control over the size, corona thickness, and extent of solvent accessible PB in these micelles can be a powerful tool in the development of targeting delivery vehicles.« less

IRIS Toxicological Review of Tetrahydrofuran (THF) (External ...

EPA Pesticide Factsheets

EPA is conducting a peer review and public comment of the scientific basis supporting the human health hazard and dose-response assessment of tetrahydrofuran (THF) that when finalized will appear on the Integrated Risk Information System (IRIS) database. EPA is undertaking an Integrated Risk Information System (IRIS) health assessment for tetrahydrofuran. IRIS is an EPA database containing Agency scientific positions on potential adverse human health effects that may result from chronic (or lifetime) exposure to chemicals in the environment. IRIS contains chemical-specific summaries of qualitative and quantitative health information in support of two steps of the risk assessment paradigm, i.e., hazard identification and dose-response evaluation. IRIS assessments are used in combination with specific situational exposure assessment information to evaluate potential public health risk associated with environmental contaminants.

Pervaporation study for the dehydration of tetrahydrofuran-water mixtures by polymeric and ceramic membranes.

PubMed

McGinness, Colleen A; Slater, C Stewart; Savelski, Mariano J

2008-12-01

Pervaporation technology can effectively separate a tetrahydrofuran (THF) solvent-water waste stream at an azeotropic concentration. The performance of a Sulzer 2210 polyvinyl alcohol (PVA) membrane and a Pervatech BV silica membrane were studied, as the operating variables feed temperature and permeate pressure, were varied. The silica membrane was found to exhibit a flux of almost double that of the PVA membrane, but both membranes had comparable separation ability in purifying the solvent-water mixture. At benchmark feed conditions of 96 wt% THF and 4 wt% water, 50 degrees C and 10 torr permeate pressure, the silica membrane flux was 0.276 kg/m(2)hr and selectivity was 365. For both membranes, flux was found to increase at an exponential rate as the feed temperature increased from 20 to 60 degrees C. The flux through the silica membrane increases at a 6% faster rate than the PVA membrane. Flux decreased as permeate pressure was increased from 5 to 25 torr for both membranes. The amount of water in the permeate decreased exponentially as the permeate pressure was increased, but increased linearly with increasing temperature. Optimum conditions for flux and selectivity are at low permeate pressure and high feed temperature. When a small amount of salt is added to the feed solution, an increase in flux is observed. Overall models for flux and permeate concentration were created from the experimental data. The models were used to predict scale-up performance in separating an azeotropic feed waste to produce dehydrated THF solvent for reuse and a permeate stream with a dilute THF concentration.

IRIS Toxicological Review of Tetrahydrofuran (THF) (Interagency Science Discussion Draft)

EPA Science Inventory

EPA is releasing the draft report, Toxicological Review of Tetrahydrofuran, that was distributed to Federal agencies and White House Offices for comment during the Science Discussion step of the IRIS Assessment Development Proc...

Aggregation of nitroaniline in tetrahydrofuran through intriguing H-bond formation by sodium borohydride.

PubMed

Ganguly, Mainak; Mondal, Chanchal; Pal, Anjali; Pratik, Saied Md; Pal, Jaya; Pal, Tarasankar

2014-07-07

The participation of sodium borohydride (NaBH4) in hydrogen bonding interactions and transient anion radical formation has been proved. Thus, the properties of NaBH4 are extended beyond the purview of its normal reducing capability and nucleophilic property. It is reported that ortho- and para-nitroanilines (NAs) form stable aggregates only in tetrahydrofuran (THF) in the presence of NaBH4 and unprecedented orange/red colorations are observed. The same recipe with nitrobenzene instead of nitroanilines (NAs) in the presence of NaBH4 evolves a transient rose red solution due to the formation of a highly fluorescent anion radical. Spectroscopic studies (UV-vis, fluorescence, RLS, Raman, NMR etc.) as well as theoretical calculations supplement the J-aggregate formation of NAs due to extensive hydrogen bonding. This is the first report where BH4(-) in THF has been shown to support such an aggregation process through H-bonding. It is further confirmed that stable intermolecular hydrogen bond-induced aggregation requires a geometrical match in both the nitro- and amino-functionalities attached to the phenyl ring with proper geometry. On the contrary, meta-nitroaniline remains as the odd man out and does not take part in such aggregation. Surprisingly, Au nanoparticles dismantle the J-aggregates of NA in THF. Explicit hydrogen bond formation in NA has been confirmed experimentally considering its promising applications in different fields including non-linear optics.

Quantitative determination of 1,4-dioxane and tetrahydrofuran in groundwater by solid phase extraction GC/MS/MS.

PubMed

Isaacson, Carl; Mohr, Thomas K G; Field, Jennifer A

2006-12-01

Groundwater contamination by cyclic ethers, 1,4-dioxane (dioxane), a probable human carcinogen, and tetrahydrofuran (THF), a co-contaminant at many chlorinated solvent release sites, are a growing concern. Cyclic ethers are readily transported in groundwater, yet little is known about their fate in environmental systems. High water solubility coupled with low Henry's law constants and octanol-water partition coefficients make their removal from groundwater problematic for both remedial and analytical purposes. A solid-phase extraction (SPE) method based on activated carbon disks was developed for the quantitative determination of dioxane and THF. The method requires 80 mL samples and a total of 1.2 mL of solvent (acetone). The number of steps is minimized due to the "in-vial" elution of the disks. Average recoveries for dioxane and THF were 98% and 95%, respectively, with precision, as indicated by the relative standard deviation of <2% to 6%. The method quantitation limits are 0.31 microg/L for dioxane and 3.1 microg/L for THF. The method was demonstrated by analyzing groundwater samples for dioxane and THF collected during a single sampling campaign at a TCA-impacted site. Dioxane concentrations and areal extent of dioxane in groundwater were greater than those of either TCA or THF.

Observations related to tetrahydrofuran and methane hydrates for laboratory studies of hydrate-bearing sediments

USGS Publications Warehouse

Lee, J.Y.; Yun, T.S.; Santamarina, J.C.; Ruppel, C.

2007-01-01

The interaction among water molecules, guest gas molecules, salts, and mineral particles determines the nucleation and growth behavior of gas hydrates in natural sediments. Hydrate of tetrahydrofuran (THF) has long been used for laboratory studies of gas hydrate-bearing sediments to provide close control on hydrate concentrations and to overcome the long formation history of methane hydrate from aqueous phase methane in sediments. Yet differences in the polarizability of THF (polar molecule) compared to methane (nonpolar molecule) raise questions about the suitability of THF as a proxy for methane in the study of hydrate-bearing sediments. From existing data and simple macroscale experiments, we show that despite its polar nature, THF's large molecular size results in low permittivity, prevents it from dissolving precipitated salts, and hinders the solvation of ions on dry mineral surfaces. In addition, the interfacial tension between water and THF hydrate is similar to that between water and methane hydrate. The processes that researchers choose for forming hydrate in sediments in laboratory settings (e.g., from gas, liquid, or ice) and the pore-scale distribution of the hydrate that is produced by each of these processes likely have a more pronounced effect on the measured macroscale properties of hydrate-bearing sediments than do differences between THF and methane hydrates themselves.

A high selective cataluminescence sensor for the determination of tetrahydrofuran vapor

NASA Astrophysics Data System (ADS)

Cao, Xiaoan; Dai, Huimei; Chen, Suilin; Zeng, Jiayi; Zhang, Keke; Sun, Yan

2013-02-01

A novel tetrahydrofuran (THF) vapor sensor was designed based on the cataluminescence (CTL) of THF on nanosized γ-Al2O3/MgO (mol ratio = 1.5:1). SEM and XRD were applied for its characterization. We found that the CTL was strongly produced when THF vapor flowed through a nanosized Al-Mg mixed-metal oxide surface, while the CTL was weakly generated when THF vapor flowed through a single nanosized γ-Al2O3 or MgO surface. Quantitative analysis was performed at an optimal temperature of 279 °C, a wavelength of 460 nm and a flow rate of 360 mL min-1. The linear range of the CTL intensity versus concentrations of THF vapor was 1.0-3000 mL m-3 with a detection limit of 0.67 mL m-3. No (or only very low) interference was observed by formaldehyde, methanol, ethanol, benzene, toluene, ethyl acetate, ammonia, cyclohexane, chloroform, glycol armour ether, glycol ether, isopropyl ether and n-butyl ether or acetic acid. Since the response of the sensor was rapid and the system was easy to handle, we believe that the sensor has great potential for real-world use.

Analytical validation applied to simultaneous determination of solvents dichloromethane (DCM), methyl isobutyl ketone (MIBK), tetrahydrofuran (THF) and toluene (TOL) in urine by headspace extraction and injection on chromatographic system with a flame ionization detector

NASA Astrophysics Data System (ADS)

Muna, E. D. M.; Pereira, R. P.

2016-07-01

The determination of the volatile organic solvents dichloromethane (DCM), methyl isobutyl ketone (MIBK), tetrahydrofuran (THF) and toluene (TOL) is applied on toxicological monitoring of employees in various industrial activities. The gas chromatography technique with flame ionization detector and headspace injection system has been applied. The analytical procedure developed allows the simultaneous determination of the above-mentioned solvents and the accuracy of the method was tested following the INMETRO guidelines through the DOQ-CGRE 008 Rev.04-July/2011.

Computer simulation of the linear and nonlinear optical susceptibilities of p-nitroaniline in cyclohexane, 1,4-dioxane, and tetrahydrofuran in quadrupolar approximation. II. Local field effects and optical susceptibilitities.

PubMed

Reis, H; Papadopoulos, M G; Grzybowski, A

2006-09-21

This is the second part of a study to elucidate the local field effects on the nonlinear optical properties of p-nitroaniline (pNA) in three solvents of different multipolar character, that is, cyclohexane (CH), 1,4-dioxane (DI), and tetrahydrofuran (THF), employing a discrete description of the solutions. By the use of liquid structure information from molecular dynamics simulations and molecular properties computed by high-level ab initio methods, the local field and local field gradients on p-nitroaniline and the solvent molecules are computed in quadrupolar approximation. To validate the simulations and the induction model, static and dynamic (non)linear properties of the pure solvents are also computed. With the exception of the static dielectric constant of pure THF, a good agreement between computed and experimental refractive indices, dielectric constants, and third harmonic generation signals is obtained for the solvents. For the solutions, it is found that multipole moments up to two orders higher than quadrupole have a negligible influence on the local fields on pNA, if a simple distribution model is employed for the electric properties of pNA. Quadrupole effects are found to be nonnegligible in all three solvents but are especially pronounced in the 1,4-dioxane solvent, in which the local fields are similar to those in THF, although the dielectric constant of DI is 2.2 and that of the simulated THF is 5.4. The electric-field-induced second harmonic generation (EFISH) signal and the hyper-Rayleigh scattering signal of pNA in the solutions computed with the local field are in good to fair agreement with available experimental results. This confirms the effect of the "dioxane anomaly" also on nonlinear optical properties. Predictions based on an ellipsoidal Onsager model as applied by experimentalists are in very good agreement with the discrete model predictions. This is in contrast to a recent discrete reaction field calculation of pNA in 1,4-dioxane, which found that the predicted first hyperpolarizability of pNA deviated strongly from the predictions obtained using Onsager-Lorentz local field factors.

Absolute vibrational cross sections for 1-19 eV electron scattering from condensed tetrahydrofuran (THF).

PubMed

Lemelin, V; Bass, A D; Cloutier, P; Sanche, L

2016-02-21

Absolute cross sections (CSs) for vibrational excitation by 1-19 eV electrons impacting on condensed tetrahydrofuran (THF) were measured with a high-resolution electron energy loss spectrometer. Experiments were performed under ultra-high vacuum (3 × 10(-11) Torr) at a temperature of about 20 K. The magnitudes of the vibrational CSs lie within the 10(-17) cm(2) range. Features observed near 4.5, 9.5, and 12.5 eV in the incident energy dependence of the CSs were compared to the results of theoretical calculations and other experiments on gas and solid-phase THF. These three resonances are attributed to the formation of shape or core-excited shape resonances. Another maximum observed around 2.5 eV is not found in the calculations but has been observed in gas-phase studies; it is attributed to the formation of a shape resonance.

Kinetic-energy release distributions of fragment anions from collisions of potassium atoms with D-Ribose and tetrahydrofuran*

NASA Astrophysics Data System (ADS)

Rebelo, André; Cunha, Tiago; Mendes, Mónica; da Silva, Filipe Ferreira; García, Gustavo; Limão-Vieira, Paulo

2016-06-01

Kinetic-energy release distributions have been obtained from the width and shapes of the time-of-flight (TOF) negative ion mass peaks formed in collisions of fast potassium atoms with D-Ribose (DR) and tetrahydrofuran (THF) molecules. Recent dissociative ion-pair formation experiments yielding anion formation have shown that the dominant fragment from D-Ribose is OH- [D. Almeida, F. Ferreira da Silva, G. García, P. Limão-Vieira, J. Chem. Phys. 139, 114304 (2013)] whereas in the case of THF is O- [D. Almeida, F. Ferreira da Silva, S. Eden, G. García, P. Limão-Vieira, J. Phys. Chem. A 118, 690 (2014)]. The results for DR and THF show an energy distribution profile reminiscent of statistical degradation via vibrational excitation and partly due to direct transformation of the excess energy in translational energy.

Polyethylene Glycol-Poly(2-Methyl-5-Vinyl Tetrazole) Polymer Blend (A desensitizing Binder for Propellants and Explosives)

DTIC Science & Technology

1989-03-01

PVA, CTBN , PBAA, PMMA, etc. As a test of this predictability, we dissolved a vinyl acetate polymer in THF, and then added PMVT, and did succeed in...Polyvinyl acetate CTBN Carboxy terminated butadiene acrylonitrile PBAA Polybutadiene acrylic acid PMMA Polymethyl. methacrylate THF Tetrahydrofuran NMR

The mechanism of epoxide carbonylation by [Lewis Acid]+[Co(CO)4]- catalysts.

PubMed

Church, Tamara L; Getzler, Yutan D Y L; Coates, Geoffrey W

2006-08-09

A detailed mechanistic investigation of epoxide carbonylation by the catalyst [(salph)Al(THF)2]+ [Co(CO)4]- (1, salph = N,N'-o-phenylenebis(3,5-di-tert-butylsalicylideneimine), THF = tetrahydrofuran) is reported. When the carbonylation of 1,2-epoxybutane (EB) to beta-valerolactone is performed in 1,2-dimethoxyethane solution, the reaction rate is independent of the epoxide concentration and the carbon monoxide pressure but first order in 1. The rate of lactone formation varies considerably in different solvents and depends primarily on the coordinating ability of the solvent. In mixtures of THF and cis/trans-2,5-dimethyltetrahydrofuran, the reaction is first order in THF. From spectroscopic and kinetic data, the catalyst resting state was assigned to be the neutral (beta-aluminoxy)acylcobalt species (salph)AlOCH(Et)CH2COCo(CO)4 (3a), which was successfully trapped with isocyanates. As the formation of 3a from EB, CO, and 1 is rapid, lactone ring closing is rate-determining. The favorable impact of donating solvents was attributed to the necessity of stabilizing the aluminum cation formed upon generation of the lactone.

Effect of clathrate hydrate formation and decomposition on NMR parameters in THF-D2O solution.

PubMed

Rousina-Webb, Alexander; Leek, Donald M; Ripmeester, John

2012-06-28

The NMR spin-lattice relaxation time (T(1)), spin-spin relaxation time (T(2)) and the diffusion coefficient D were measured for (1)H in a 1:17 mol % solution of tetrahydrofuran (THF) in D(2)O. The aim of the work was to clarify some earlier points raised regarding the utility of these measurements to convey structural information on hydrate formation and reformation. A number of irregularities in T(1) and T(2) measurements during hydrate processes reported earlier are explained in terms of the presence of interfaces and possible temperature gradients. We observe that T(1) and T(2) in solution are exactly the same before and after hydrate formation, thus confirming that the solution is isotropic. This is inconsistent with the presence of memory effects, at least those that may affect the dynamics to which T(1) and T(2) are sensitive. The measurement of the diffusion coefficient for a number of hours in the subcooled solution before nucleation proved invariant with time, again suggesting that the solution remains isotropic without affecting the guest dynamics and diffusion.

Dynamics of tetrahydrofuran as minority component in a mixture with poly(2-(dimethylamino)ethyl methacrylate): A neutron scattering and dielectric spectroscopy investigation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goracci, G., E-mail: sckgorag@ehu.es; Arbe, A.; Alegría, A.

2015-09-07

We have investigated a mixture of poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) and tetrahydrofuran (THF) (70 wt. % PDMAEMA/30 wt. % THF) by combining dielectric spectroscopy and quasielastic neutron scattering (QENS) on a labelled sample, focusing on the dynamics of the THF molecules. Two independent processes have been identified. The “fast” one has been qualified as due to an internal motion of the THF ring leading to hydrogen displacements of about 3 Å with rather broadly distributed activation energies. The “slow” process is characterized by an Arrhenius-like temperature dependence of the characteristic time which persists over more than 9 orders of magnitude in time. Themore » QENS results evidence the confined nature of this process, determining a size of about 8 Å for the volume within which THF hydrogens’ motions are restricted. In a complementary way, we have also investigated the structural features of the sample. This study suggests that THF molecules are well dispersed among side-groups nano-domains in the polymer matrix, ruling out a significant presence of clusters of solvent. Such a good dispersion, together with a rich mobility of the local environment, would prevent cooperativity effects to develop for the structural relaxation of solvent molecules, frustrating thereby the emergence of Vogel-Fulcher-like behavior, at least in the whole temperature interval investigated.« less

Routes to ultra-pure alkyls of indium and gallium and their adducts with ethers, phosphines and amines

NASA Astrophysics Data System (ADS)

Jones, Anthony C.; Holliday, A. Kenneth; Cole-Hamilton, David J.; Ahmad, M. Munir; Gerrard, Neil D.

1984-09-01

Electrolysis of tetrahydrofuran (thf) solutions of dimethylmagnesium containing tetraethylammonium percholrate using a gallium anode gives [Me 3Ga·thf], but higher yields of both [Me 3Ga·thf] and [Me 3In·thf] are obtained on electrolysis of thf solutions of Grignard reagents with sacrificial metal anodes in the absence of a carrying electrolyte. The thf adducts can be converted into adducts with other Lewis bases, [ Me3M· L], M = Ga or In, L = PMe 3, PEt 3, NEt 3, by simple base exchange reactions. Base-free trimethylgallium can be prepared from: (i) reaction of methyl iodide with the intermetallic compound [Mg 5Ga 2] in a high boiling ether; (ii) electrolysis of Grignard reagents in high boiling ethers using sacrificial gallium anodes; (iii) reactions of GaCl 3 with Grignard reagents in high boiling ethers or (iv) ether exchange reaction between [Me 3Ga·OEt 2] and high boiling ethers. All of these reactions lead to adducts between trimethylgallium and the high boiling ether which, on heating, decompose to give base-free trimethylgallium. [Me 3Ga·OEt 2] can be prepared from reaction of Grignard reagents with gallium trichloride in diethylether or from electrolysis of Grignard reagents in diethyl ether using a sacrificial gallium anode. Similar reactions using an indium anode lead to [Me 3In·OEt 2] from which base-free trimethylindium can be liberated using known chemistry. The use of alkyls prepared in this way for vapour phase epitaxy as well as the purity of the alkyls are discussed.

Ultrafast charge-transfer-to-solvent dynamics of iodide in tetrahydrofuran. 2. Photoinduced electron transfer to counterions in solution.

PubMed

Bragg, Arthur E; Schwartz, Benjamin J

2008-04-24

The excited states of atomic anions in liquids are bound only by the polarization of the surrounding solvent. Thus, the electron-detachment process following excitation to one of these solvent-bound states, known as charge-transfer-to-solvent (CTTS) states, provides a useful probe of solvent structure and dynamics. These transitions and subsequent relaxation dynamics also are influenced by other factors that alter the solution environment local to the CTTS anion, including the presence of cosolutes, cosolvents, and other ions. In this paper, we examine the ultrafast CTTS dynamics of iodide in liquid tetrahydrofuran (THF) with a particular focus on how the solvent dynamics and the CTTS electron-ejection process are altered in the presence of various counterions. In weakly polar solvents such as THF, iodide salts can be strongly ion-paired in solution; the steady-state UV-visible absorption spectroscopy of various iodide salts in liquid THF indicates that the degree of ion-pairing changes from strong to weak to none as the counterion is switched from Na+ to tetrabutylammonium (t-BA+) to crown-ether-complexed Na+, respectively. In our ultrafast experiments, we have excited the I- CTTS transition of these various iodide salts at 263 nm and probed the dynamics of the CTTS-detached electrons throughout the visible and near-IR. In the previous paper of this series (Bragg, A. E.; Schwartz, B. J. J. Phys. Chem. B 2008, 112, 483-494), we found that for "counterion-free" I- (obtained by complexing Na+ with a crown ether) the CTTS electrons were ejected approximately 6 nm from their partner iodine atoms, the result of significant nonadiabatic coupling between the CTTS excited state and extended electronic states supported by the naturally existing solvent cavities in liquid THF, which also serve as pre-existing electron traps. In contrast, for the highly ion-paired NaI/THF system, we find that approximately 90% of the CTTS electrons are "captured" by a nearby Na+ to form (Na+, e-)THF "tight-contact pairs" (TCPs), which are chemically and spectroscopically distinct from both solvated neutral sodium atoms and free solvated electrons. A simple kinetic model is able to reproduce the details of the electron capture process, with 63% of the electrons captured quickly in approximately 2.3 ps, 26% captured diffusively in approximately 63 ps, and the remaining 11% escaping out into the solution on subnanosecond time scales. We also find that the majority of the CTTS electrons are ejected to within 1 or 2 nm of the Na+. This demonstrates that the presence of the nearby cation biases the relocalization of CTTS-generated electrons from I- in THF, changing the nonadiabatic coupling to the extended, cavity-supported electronic states in THF to produce a much tighter distribution of electron-ejection distances. In the case of the more loosely ion-paired t-BA+-I-/THF system, we find that only 10-15% of the CTTS-ejected electrons associate with t-BA+ to form "loose-contact pairs" (LCPs), which are characterized by a much weaker interaction between the electron and cation than occurs in TCPs. The formation of (t-BA+, e-)THF LCPs is characterized by a Coulombically induced blue shift of the free eTHF- spectrum on a approximately 5-ps time scale. We argue that the weaker interaction between t-BA+ and the parent I- results in little change to the CTTS-ejection process, so that only those electrons that happen to localize in the vicinity of t-BA+ are captured to form LCPs. Finally, we interpret the correlation between electron capture yield and counterion-induced perturbation of the I- CTTS transition as arising from changes in the distribution of ion-pair separations with cation identity, and we discuss our results in the context of relevant solution conductivity measurements.

Templated Synthesis of Aluminum Nanoparticles - A New Route to Stable Energetic Materials

DTIC Science & Technology

2009-11-05

aluminum hydride (LiAlH4), anhydrous aluminum chloride (AlCl3), titanium (IV) isopropoxide , and 1-methylpyrrolidine were supplied by Sigma-Aldrich. The...film containing the titanium salt was immersed in a tetrahydrofuran (THF) solution of 1-methylpyrrolidine alane (0.5 or 1 M) with stirring for 12 h...and a small amount of titanium from the catalyst. However, there was only a negligible amount of oxygen in the specimen despite the fact that the EDX

Structure and Conductivity of Semiconducting Polymer Hydrogels.

PubMed

Huber, Rachel C; Ferreira, Amy S; Aguirre, Jordan C; Kilbride, Daniel; Toso, Daniel B; Mayoral, Kenny; Zhou, Z Hong; Kopidakis, Nikos; Rubin, Yves; Schwartz, Benjamin J; Mason, Thomas G; Tolbert, Sarah H

2016-07-07

Poly(fluorene-alt-thiophene) (PFT) is a conjugated polyelectrolyte that self-assembles into rod-like micelles in water, with the conjugated polymer backbone running along the length of the micelle. At modest concentrations (∼10 mg/mL in aqueous solutions), PFT forms hydrogels, and this work focuses on understanding the structure and intermolecular interactions in those gel networks. The network structure can be directly visualized using cryo electron microscopy. Oscillatory rheology studies further tell us about connectivity within the gel network, and the data are consistent with a picture where polymer chains bridge between micelles to hold the network together. Addition of tetrahydrofuran (THF) to the gels breaks those connections, but once the THF is removed, the gel becomes stronger than it was before, presumably due to the creation of a more interconnected nanoscale architecture. Small polymer oligomers can also passivate the bridging polymer chains, breaking connections between micelles and dramatically weakening the hydrogel network. Fits to solution-phase small-angle X-ray scattering data using a Dammin bead model support the hypothesis of a bridging connection between PFT micelles, even in dilute aqueous solutions. Finally, time-resolved microwave conductivity measurements on dried samples show an increase in carrier mobility after THF annealing of the PFT gel, likely due to increased connectivity within the polymer network.

Monte Carlo simulations of liquid tetrahydrofuran including pseudorotationa)

NASA Astrophysics Data System (ADS)

Chandrasekhar, Jayaraman; Jorgensen, William L.

1982-11-01

Monte Carlo statistical mechanics simulations have been carried out for liquid tetrahydrofuran (THF) with and without pseudorotation at 1 atm and 25 °C. The intermolecular potential functions consisted of Lennard-Jones and Coulomb terms in the TIPS format reported previously for ethers. Pseudorotation of the ring was described using the generalized coordinates defined by Cremer and Pople, viz., the puckering amplitude and the phase angle of the ring. The corresponding intramolecular potential function was derived from molecular mechanics (MM2) calculations. Compared to the gas phase, the rings tend to be more flat and the population of the C2 twist geometry is slightly higher in liquid THF. However, pseudorotation has negligible effect on the calculated intermolecular structure and thermodynamic properties. The computed density, heat of vaporization, and heat capacity are in good agreement with experiment. The results are also compared with those from previous simulations of acyclic ethers. The present study provides the foundation for investigations of the solvating ability of THF.

Cosolvent pretreatment in cellulosic biofuel production: Effect of tetrahydrofuran-water on lignin structure and dynamics

DOE PAGES

Smith, Micholas Dean; Mostofian, Barmak; Cheng, Xiaolin; ...

2015-10-05

The deconstruction of cellulose is an essential step in the production of ethanol from lignocellulosic biomass. However, the presence of lignin hinders this process. Recently, a novel cosolvent based biomass pretreatment method called CELF (Cosolvent Enhanced Lignocellulosic Fractionation) which employs tetrahydrofuran (THF) in a single phase mixture with water, was found to be highly effective at solubilizing and extracting lignin from lignocellulosic biomass and achieving high yields of fermentable sugars. Here, using all-atom molecular-dynamics simulation, we find that THF preferentially solvates lignin, and in doing so, shifts the equilibrium configurational distribution of the biopolymer from a crumpled globule to coil,more » independent of temperature. Whereas pure water is a bad solvent for lignin, the THF : water cosolvent acts as a "theta" solvent, in which solvent : lignin and lignin : lignin interactions are approximately equivalent in strength. Furthermore, under these conditions, polymers do not aggregate, thus providing a mechanism for the observed lignin solubilization that facilitates unfettered access of celluloytic enzymes to cellulose.« less

Structure and component dynamics in binary mixtures of poly(2-(dimethylamino)ethyl methacrylate) with water and tetrahydrofuran: A diffraction, calorimetric, and dielectric spectroscopy study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Goracci, G., E-mail: sckgorag@ehu.es; Arbe, A.; Alegría, A.

2016-04-21

We have combined X-ray diffraction, neutron diffraction with polarization analysis, small angle neutron scattering, differential scanning calorimetry, and broad band dielectric spectroscopy to investigate the structure and dynamics of binary mixtures of poly (2-(dimethylamino)ethyl methacrylate) with either water or tetrahydrofuran (THF) at different concentrations. Aqueous mixtures are characterized by a highly heterogeneous structure where water clusters coexist with an underlying nano-segregation of main chains and side groups of the polymeric matrix. THF molecules are homogeneously distributed among the polymeric nano-domains for concentrations of one THF molecule/monomer or lower. A more heterogeneous situation is found for higher THF amounts, but withoutmore » evidences for solvent clusters. In THF-mixtures, we observe a remarkable reduction of the glass-transition temperature which is enhanced with increasing amount of solvent but seems to reach saturation at high THF concentrations. Adding THF markedly reduces the activation energy of the polymer β-relaxation. The presence of THF molecules seemingly hinders a slow component of this process which is active in the dry state. The aqueous mixtures present a strikingly broad glass-transition feature, revealing a highly heterogeneous behavior in agreement with the structural study. Regarding the solvent dynamics, deep in the glassy state all data can be described by an Arrhenius temperature dependence with a rather similar activation energy. However, the values of the characteristic times are about three orders of magnitude smaller for THF than for water. Water dynamics display a crossover toward increasingly higher apparent activation energies in the region of the onset of the glass transition, supporting its interpretation as a consequence of the freezing of the structural relaxation of the surrounding matrix. The absence of such a crossover (at least in the wide dynamic window here accessed) in THF is attributed to the lack of cooperativity effects in the relaxation of these molecules within the polymeric matrix.« less

Investigation on the effect of THF on Nitrogen Hydrate formation under isobaric condition

NASA Astrophysics Data System (ADS)

Jamil, N.; Husin, H.; Aman, Z.; Hassan, Z.

2018-03-01

In this paper, we studied nitrogen (N2) hydrate formation in the presence of tetrahydrofuran (THF) under 3 different conditions; different concentration of THF (0, 3 and 30 %(v/v), different temperature setting (room temperature and induced temperature) and different water content (15, 35 and 55 mL) in an isobaric condition. We found that in the presence of THF which acting as an enhancer, hydrate formation kinetic is highly influenced by these parameters. We observed a striking contrast in hydrate formation behaviour observed at room temperature (RT) and induced temperature (IT) with and without the presence of THF under similar operating conditions. At the presence of 30 %(v/v) of THF in 15 mL water, it can be seen that, hydrate tend to form faster than other samples. Visual observation of N2hydrates are also conducted at 30 %(v/v) of THF in 15 mL water.

Pore shape of honeycomb-patterned films: modulation and interfacial behavior.

PubMed

Wan, Ling-Shu; Ke, Bei-Bei; Zhang, Jing; Xu, Zhi-Kang

2012-01-12

The control of the pore size of honeycomb-patterned films has been more or less involved in most work on the topic of breath figures. Modulation of the pore shape was largely ignored, although it is important to applications in replica molding, filtration, particle assembly, and cell culture. This article reports a tunable pore shape for patterned films prepared from commercially available polystyrene (PS). We investigated the effects of solvents including tetrahydrofuran (THF) and chloroform (CF) and hydrophilic additives including poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA), poly(ethylene glycol) (PEG), and poly(N-vinyl pyrrolidone) (PVP). Water droplets on/in the polymer solutions were observed and analyzed for simulating the formation and stabilization of breath figures. Interfacial tensions of the studied systems were measured and considered as a main factor to modulate the pore shape. Results indicate that the pores gradually change from near-spherical to ellipsoidal with the increase of additive content when using CF as the solvent; however, only ellipsoidal pores are formed from the THF solution. It is demonstrated that the aggregation of the additives at the water/polymer solution interface is more efficient in the THF solution than that in the CF solution. This aggregation decreases the interfacial tension, stabilizes the condensed water droplets, and shapes the pores of the films. The results may facilitate our understanding of the dynamic breath figure process and provide a new pathway to prepare patterned films with different pore structures.

Ultra-high-stability, pH-resistant sol-gel titania poly(tetrahydrofuran) coating for capillary microextraction on-line coupled to high-performance liquid chromatography.

PubMed

Segro, Scott S; Cabezas, Yaniel; Malik, Abdul

2009-05-15

A sol-gel titania poly(tetrahydrofuran) (poly-THF) coating was developed for capillary microextraction hyphenated on-line with high-performance liquid chromatography (HPLC). Poly-THF was covalently bonded to the sol-gel titania network which, in turn, became chemically anchored to the inner surface of a 0.25mm I.D. fused silica capillary. For sample preconcentration, a 38-cm segment of the sol-gel titania poly-THF coated capillary was installed on an HPLC injection port as a sampling loop. Aqueous samples containing a variety of analytes were passed through the capillary and, during this process, the analytes were extracted by the sol-gel titania poly-THF coating on the inner surface of the capillary. Using isocratic and gradient elution with acetonitrile/water mobile phases, the extracted analytes were desorbed into the on-line coupled HPLC column for separation and UV detection. The sol-gel titania poly-THF coating was especially efficient in extracting polar analytes, such as underivatized phenols, alcohols, amines, and aromatic carboxylic acids. In addition, this coating was capable of extracting moderately polar and nonpolar analytes, such as ketones and polycyclic aromatic hydrocarbons. The sol-gel titania poly-THF coated capillary was also able to extract polypeptides at pH values near their respective isoelectric points. Extraction of these compounds can be important for environmental and biomedical applications. The observed extraction behavior can be attributed to the polar and nonpolar moieties in the poly-THF structure. This coating was found to be stable under extremely low and high pH conditions-even after 18h of exposure to 1M HCl (pH approximately 0.0) and 1M NaOH (pH approximately 14.0).

Wet air co-oxidation of decabromodiphenyl ether (BDE209) and tetrahydrofuran.

PubMed

Zhao, Hongxia; Zhang, Feifang; Qu, Baocheng; Xue, Xingya; Liang, Xinmiao

2009-09-30

The wet air co-oxidation (WACO) of a major commercial polybrominated diphenyl ether flame retardant congener, decabromodiphenyl ether (BDE209), was investigated using tetrahydrofuran (THF) as an initiator in a stainless autoclave at temperature range of 120-170 degrees C and 0.5MPa oxygen pressure. Compared to the single oxidation of BDE209 under the same conditions, the addition of THF in the reaction system greatly improved the removal efficiency of BDE209. The effect of temperature on the reaction was studied. The removals of BDE209 and Br increased with increasing temperature. In addition, the effect of NaNO(2) as the catalyst on the WACO was also investigated and the results showed that the addition of NaNO(2) could improve the Br removal efficiency.

Production of all trans-beta-carotene by using impinging flow of supercritical carbon dioxide anti-solvent pulverization.

PubMed

Shen, Yi-Chen; Chng, Lee-Muei; Wang, Yuan-Chuen; Shieh, Chwen-Jen; Lin, Kuo-Li; Hsu, Shih-Lan; Chou, Hong-Nong; Chang, Chieh-Ming J

2012-12-28

This work investigated column elution chromatography coupled with supercritical anti-solvent precipitation to produce carotenoid rich microsized particulates from microalgal Dunaliella salina species. The extract contained carotenoids ranging from 61.3 mg/g(salina) to 72.5 mg/g(salina) using ultrasonic stirred ethyl ether or tetrahydrofuran (THF) extraction. When 10 L of ethyl alcohol was employed to elute the THF extract, purity of trans-β-carotene is 823.6 mg/g with a recovery of 86.2%. It was found that the supercritical anti-solvent of THF solution at 160 bar and 318 K produced powdered particulates with a purity of carotenoids above 90%. Subsequently, a central composite response surface design method was used to design supercritical anti-solvent precipitation of carotenoid-rich THF solution. This was accomplished by increasing the pressure from 140 bar to 180 bar and the time from 40 min to 60 min at a feed flow rate of 0.2 mL/min. A CO(2) flow rate of 15 L/min and a temperature of 318 K were also used to determine the effects on purity and recovery of trans-β-carotene. The combined process produced micronized precipitates with a mean particle size ranging from 3.5 μm to 19 μm and the purity of trans-β-carotene attained was 926.8 mg/g with a recovery of 54%. Copyright © 2012 Elsevier B.V. All rights reserved.

Enhanced sampling simulation analysis of the structure of lignin in the THF–water miscibility gap

DOE PAGES

Smith, Micholas Dean; Petridis, Loukas; Cheng, Xiaolin; ...

2016-01-26

Using temperature replica-exchange molecular dynamics, we characterize a globule-to-coil transition for a softwood-like lignin biopolymer in a tetrahydrofuran (THF)-water cosolvent system at temperatures at which the cosolvent undergoes a de-mixing transition. The lignin is found to be in a coil state, similar to that in the high-temperature miscible region. Analysis of the transition kinetics indicates that THF acts in a surfactant-like fashion. In conclusion, the present study thus suggests that THF-water based pretreatments may efficiently remove lignin from biomass even at relatively low (non-water boiling) temperatures.

An Unsymmetric Ligand Framework for Noncoupled Homo- and Heterobimetallic Complexes.

PubMed

Haas, Ruth M; Hern, Zachary; Sproules, Stephen; Hess, Corinna R

2017-12-18

We introduce a new unsymmetric ligand, PDIpCy (PDI = pyridyldiimine; Cy = cyclam), that offers two distinct, noncoupled coordination sites. A series of homo- and heterobimetallic complexes, [Zn 2 (PDIpCy)(THF)(OTf) 4 ] (1; THF = tetrahydrofuran and OTf = triflate), [Ni 2 (PDIpCy)(THF)(OTf) 2 ](OTf) 2 (2), and [NiZn(PDIpCy)(THF)(OTf) 4 ] (3), are described. The one-electron-reduced compounds, [Zn 2 (PDIpCy)(OTF) 3 ] (4), [Ni 2 (PDIpCy)(OTf)](OTf) 2 (5), and [NiZn(PDIpCy)(OTf) 3 ] (6), were isolated, and their electronic structures were characterized. The reduced compounds are charge-separated species, with electron storage at either the PDI ligand (4) or at the PDI-bound metal ion (5 and 6).

Temperature-dependent phase behaviour of tetrahydrofuran–water alters solubilization of xylan to improve co-production of furfurals from lignocellulosic biomass

DOE PAGES

Smith, Micholas Dean; Cai, Charles M.; Cheng, Xiaolin; ...

2018-03-06

Xylose, Xylan, Hemicellulose, CELF, THF, Co-solvent, Pretreatment, Biomass ABSTRACT: Xylan is an important polysaccharide found in the hemicellulose fraction of lignocellulosic biomass that can be hydrolysed to xylose and further dehydrated to the furfural, an important renewable platform fuel precursor. Here, pairing molecular simulation and experimental evidences, we reveal how the unique temperature-dependent phase behaviour of water-tetrahydrofuran (THF) co-solvent can delay xylan solubilization to synergistically improve catalytic co-processing of biomass to furfural and 5-HMF. Our results indicate, based on polymer correlations between polymer conformational behaviour and solvent quality, that both co-solvent and aqueous environments serve as ‘good’ solvents for xylan.more » Interestingly, the simulations also revealed that unlike other cell-wall components (i.e., lignin and cellulose), the make-up of the solvation shell of xylan in THF-water is dependent on the temperature-phase behaviour. At temperatures between 333K and 418K, THF and water become immiscible, and THF is evacuated from the solvation shell of xylan, while above and below this temperature range, THF and water are both present in the polysaccharide’s solvation shell. This suggested that the solubilization of xylan in THF-water may be similar to aqueous-only solutions at temperatures between 333K and 418K and different outside this range. Experimental reactions on beachwood xylan corroborate this hypothesis by demonstrating 2-fold reduction of xylan solubilization in THF-water within a miscible temperature regime (445K) and unchanged solubilization within an immiscible regime (400K). Translating this phase-dependent behaviour to processing of maple wood chips, we demonstrate how the weaker xylan solvation in THF-water under miscible conditions can delay furfural production from xylose, allowing 5-HMF production from cellulose to “catch-up” such that their high yield production from biomass can be synergized in a single pot reaction.« less

Temperature-dependent phase behaviour of tetrahydrofuran–water alters solubilization of xylan to improve co-production of furfurals from lignocellulosic biomass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Micholas Dean; Cai, Charles M.; Cheng, Xiaolin

Xylose, Xylan, Hemicellulose, CELF, THF, Co-solvent, Pretreatment, Biomass ABSTRACT: Xylan is an important polysaccharide found in the hemicellulose fraction of lignocellulosic biomass that can be hydrolysed to xylose and further dehydrated to the furfural, an important renewable platform fuel precursor. Here, pairing molecular simulation and experimental evidences, we reveal how the unique temperature-dependent phase behaviour of water-tetrahydrofuran (THF) co-solvent can delay xylan solubilization to synergistically improve catalytic co-processing of biomass to furfural and 5-HMF. Our results indicate, based on polymer correlations between polymer conformational behaviour and solvent quality, that both co-solvent and aqueous environments serve as ‘good’ solvents for xylan.more » Interestingly, the simulations also revealed that unlike other cell-wall components (i.e., lignin and cellulose), the make-up of the solvation shell of xylan in THF-water is dependent on the temperature-phase behaviour. At temperatures between 333K and 418K, THF and water become immiscible, and THF is evacuated from the solvation shell of xylan, while above and below this temperature range, THF and water are both present in the polysaccharide’s solvation shell. This suggested that the solubilization of xylan in THF-water may be similar to aqueous-only solutions at temperatures between 333K and 418K and different outside this range. Experimental reactions on beachwood xylan corroborate this hypothesis by demonstrating 2-fold reduction of xylan solubilization in THF-water within a miscible temperature regime (445K) and unchanged solubilization within an immiscible regime (400K). Translating this phase-dependent behaviour to processing of maple wood chips, we demonstrate how the weaker xylan solvation in THF-water under miscible conditions can delay furfural production from xylose, allowing 5-HMF production from cellulose to “catch-up” such that their high yield production from biomass can be synergized in a single pot reaction.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Antonov, Ivan O.; Zador, Judit; Rotavera, Brandon

Here, we report a combined experimental and quantum chemistry study of the initial reactions in low-temperature oxidation of tetrahydrofuran (THF). Using synchrotron-based time-resolved VUV photoionization mass spectrometry, we probe numerous transient intermediates and products at P = 10–2000 Torr and T = 400–700 K. A key reaction sequence, revealed by our experiments, is the conversion of THF-yl peroxy to hydroperoxy-THF-yl radicals (QOOH), followed by a second O 2 addition and subsequent decomposition to dihydrofuranyl hydroperoxide + HO 2 or to γ-butyrolactone hydroperoxide + OH. The competition between these two pathways affects the degree of radical chain-branching and is likely ofmore » central importance in modeling the autoignition of THF. We interpret our data with the aid of quantum chemical calculations of the THF-yl + O 2 and QOOH + O 2 potential energy surfaces. On the basis of our results, we propose a simplified THF oxidation mechanism below 700 K, which involves the competition among unimolecular decomposition and oxidation pathways of QOOH.« less

Enantiodiscrimination of flexible cyclic solutes using NMR spectroscopy in polypeptide chiral mesophases: investigation of cis-decalin and THF.

PubMed

Aroulanda, Christie; Lafon, Olivier; Lesot, Philippe

2009-08-06

The conformational dynamics and orientational behavior of two model cyclic molecules, cis-decalin (cis-dec) and tetrahydrofurane (THF), dissolved in weakly ordering, polypeptidic chiral liquid crystals (CLCs) are theoretically discussed and experimentally investigated using deuterium and carbon-13 NMR spectroscopies. The analysis of enantiomeric and enantiotopic discriminations in these compounds is shown to depend on the rate of conformational exchange regime, slow or fast. The slow exchange regime is illustrated through the case of cis-dec at low temperature (243 K). We show that the deuterium NMR spectra in this regime can be qualitatively and quantitatively interpreted by restricting the conformational pathway of cis-dec to two enantiomeric conformers of C(2)-symmetry. The orientational order parameters of these interconverting enantiomers are calculated by matching the (2)H quadrupolar splittings with calculated conformer structures. The fast exchange regime is investigated through the examples of cis-dec at high temperature (356 K) and THF at room temperature (300 K). The (2)H NMR spectra above the coalescence temperature are analyzed by introducing the concept of "average molecular structure". This fictitious structure allows easily identifying NMR equivalences of solutes dissolved in CLC. However, it cannot be applied to determine consistent orientational order parameters. This study emphasizes that enantiotopic discriminations observed for flexible molecules in the fast exchange regime can be quantitatively interpreted only by considering the orientational order of each conformer.

Key fuel properties and engine performances of diesel-ethanol blends, using tetrahydrofuran as surfactant additive

NASA Astrophysics Data System (ADS)

Molea, A.; Visuian, P.; Barabás, I.; Suciu, R. C.; Burnete, N. V.

2017-10-01

In this paper there were presented researches related to preparation and characterization of physicochemical properties of diesel-ethanol blends stabilized with tetrahydrofuran as surfactant, in order to be used as fuels in compression ignition engines. The main spray characteristics and engine performances of these blends were evaluated by using AVL Fire software. In the first stage of the studies, commercial diesel was mixed with ethanol, in different concentrations (between 2% and 15% v/v), followed by the addition of tetrahydrofuran (THF) until the blends were miscible, i.e. the blends were stabilized. The experiments were done at room temperature (22 °C). The obtained blends were characterized in order to determine the chemical composition and physicochemical properties, i.e. density, kinematic viscosity, surface tension. UV-Vis spectroscopy was utilized in order to determine a semi-quantitative evaluation regarding the chemical composition of the prepared blends and chemical interaction between diesel, ethanol and THF. Based on the determined properties, the fuel spray characteristics, engine performances and emission characteristics were evaluated by simulation using the AVL Fire software. The obtained results regarding physicochemical properties of blends were compared with diesel. Some improvements were observed when operating with the prepared blends compared to diesel with respect to engine performances and emission characteristics. Based on physicochemical evaluation and computer simulation, it was demonstrated that diesel-ethanol-tetrahydrofuran blends can be used as alternative fuel in compression ignition engines.

[Removal of mixed waste gases by the biotrickling filter].

PubMed

Zhang, Ding-Feng; Fang, Jun-Yi; Ye, Jie-Xu; Qiu, Song-Kai; Qian, Dong-Sheng; Dai, Qi-Zhou; Chen, Dong-Zhi

2013-06-01

A biotrickling filter (BTF) was designed for treating mixed waste gases, which contained hydrogen sulfide (H2S), tetrahydrofuran (THF) and dichloromethane (DCM) at the start-up and steady states. The removal efficiency of H2S and DCM could maintain about 99% and 60%, respectively, and the removal efficiency of DCM was reduced from 90% to 37% with the shortening empty bed retention time (EBRT) form 50 to 20 seconds when the inlet concentrations were 200, 100, 100 mg x m(-3) of H2S, THF, DCM, respectively. In the theoretical study, the biodegradation efficiency of contaminants was H2S > THF > DCM by analyzing the Michaelis-Menten Dynamic model.

Effect of solution concentration on MEH-PPV thin films

NASA Astrophysics Data System (ADS)

Affendi, I. H. H.; Sarah, M. S. P.; Alrokayan, Salman A. H.; Khan, Haseeb A.; Rusop, M.

2018-05-01

MEH-PPV thin films were prepared with a mixture of THF (tetrahydrofuran) solution deposited by spin coating method. The surface topology of MEH-PPV thin film were characterize by atomic force microscopy (AFM) and optical properties of absorption spectra were characterized by using Ultraviolet-visible-near-infrared (UV-Vis-NIR). The MEH-PPV concentration variation affects the surface and optical properties of the thin film where 0.5 mg/ml MEH-PPV concentration have a good surface topology provided the same film also gives the highest absorption coefficient were then deposited to a TiO2 thin film forming composite layer. The composite layer then shows low current flow of short circuit current of Isc = -5.313E-7 A.

Curcumin/poly(2-methyl-2-oxazoline-b-tetrahydrofuran-b-2-methyl-2-oxazoline) formulation: An improved penetration and biological effect of curcumin in F508del-CFTR cell lines.

PubMed

Gonçalves, Cristine; Gomez, Jean-Pierre; Même, William; Rasolonjatovo, Bazoly; Gosset, David; Nedellec, Steven; Hulin, Philippe; Huin, Cécile; Le Gall, Tony; Montier, Tristan; Lehn, Pierre; Pichon, Chantal; Guégan, Philippe; Cheradame, Hervé; Midoux, Patrick

2017-08-01

Neutral amphiphilic triblock ABA copolymers are of great interest to solubilize hydrophobic drugs. We reported that a triblock ABA copolymer consisting of methyl-2-oxazoline (MeOx) and tetrahydrofuran (THF) (MeOx 6 -THF 19 -MeOx 6 ) (TBCP2) can solubilize curcumin (Cur) a very hydrophobic molecule exhibiting multiple therapeutic effects but whose insolubility and low stability in water is a major drawback for clinical applications. Here, we provide evidences by flow cytometry and confocal microscopy that Cur penetration in normal and ΔF508-CFTR human airway epithelial cell lines is facilitated by TBCP2. When used on ΔF508-CFTR cell lines, the Cur/TBCP2 formulation promotes the restoration of the expression of the CFTR protein in the plasma membrane. Furthermore, patch-clamp and MQAE fluorescence experiments show that this effect is associated with a correction of a Cl - selective current at the membrane surface of F508del-CFTR cells. The results show the great potential of the neutral amphiphilic triblock copolymer MeOx 6 -THF 19 -MeOx 6 as carrier for curcumin in a Cystic Fibrosis context. We anticipate that other MeOx n -THF m -MeOx n copolymers could have similar behaviours for other highly insoluble therapeutic drugs or cosmetic active ingredients. Copyright © 2017 Elsevier B.V. All rights reserved.

Reactivity between biphenyl and precursor of solvated electrons in tetrahydrofuran measured by picosecond pulse radiolysis in near-ultraviolet, visible, and infrared.

PubMed

Saeki, Akinori; Kozawa, Takahiro; Ohnishi, Yuko; Tagawa, Seiichi

2007-02-22

The initial decrease of solvated electrons in tetrahydrofuran (THF) upon addition of biphenyl was investigated by picosecond pulse radiolysis. Transient absorption spectra derived from the biphenyl radical anion (centered at 408 and 655 nm) and solvated electrons of THF (infrared) were successfully measured in the wavelength region from 400 to 900 nm by the extension of a femtosecond continuum probe light to near-ultraviolet using a second harmonic generation of Ti:sapphire laser and a CaF2 plate. From the analysis of kinetic traces at 1300 nm considering the overlap of primary solvated electrons and partial biphenyl radical anion, C37, which is defined by the solute concentration to reduce the initial yield of solvated electrons to 1/e, was found to be 87 +/- 3 mM. The rate constant of solvated electrons with biphenyl was determined as 5.8 +/- 0.3 x 10(10) M(-1) s(-1). We demonstrate that the kinetic traces at both 408 nm mainly due to biphenyl radical anion and 1300 nm mainly due to solvated electrons are reproduced with high accuracy and consistency by a simple kinetic analysis. Much higher concentrations of biphenyl (up to 2 M) were examined, showing further increase of the initial yield of biphenyl radical anion accompanying a fast decay component. This observation is discussed in terms of geminate ion recombination, scavenging, delayed geminate ion recombination, and direct ionization of biphenyl at high concentration.

Unified analysis of optical absorption spectra of carotenoids based on a stochastic model.

PubMed

Uragami, Chiasa; Saito, Keisuke; Yoshizawa, Masayuki; Molnár, Péter; Hashimoto, Hideki

2018-05-03

The chemical structures of the carotenoid molecules are very simple and one might think that the electronic feature of it is easily predicted. However, it still has so much unknown information except the correlation between the electronic energy state and the length of effective conjugation chain of carotenoids. To investigate the electronic feature of the carotenoids, the most essential method is measuring the optical absorption spectra, but simulating it from the resonance Raman spectra is also the effective way. From this reason, we studied the optical absorption spectra as well as resonance Raman spectra of 15 different kinds of cyclic carotenoid molecules, recorded in tetrahydrofuran (THF) solutions at room temperature. The whole band shapes of the absorption spectra of all these carotenoid molecules were successfully simulated based on a stochastic model using Brownian oscillators. The parameters obtained from the simulation made it possible to discuss the intermolecular interaction between carotenoids and solvent THF molecules quantitatively. Copyright © 2018. Published by Elsevier Inc.

Chemical route for formation of intermetallic Zn 4Sb 3 phase

NASA Astrophysics Data System (ADS)

Denoix, A.; Solaiappan, A.; Ayral, R. M.; Rouessac, F.; Tedenac, J. C.

2010-05-01

Synthesis of intermetallic zinc antimonide phases via low temperature solution route was investigated. Trial experiments were carried out under inert atmosphere at 70 °C using metallic Zn, SbCl 3 and NaBH 4 as reactants and tetrahydrofuran (THF), dimethylsulfoxide (DMSO) as organic media. Powder X-ray analysis confirmed the nucleation and growth of ZnSb phases in presence of excess Zn. SEM analysis revealed the existence of core-shell structure comprising of Zn core and Sb shell. Such particles get transformed into Zn 4Sb 3 crystalline phases upon thermal treatment at 300 °C/6 h in a silica tube closed under high secondary vacuum.

Preparation of Radiolabeled Compounds for the U.S. Army Drug Development Program.

DTIC Science & Technology

1996-12-01

with borane -THF complex gave an 83% radiochemical yield of [14C]-19 after several recrystallizations from ethanol. In the master synthesis , alcohol...amide [14C]-15 in 88% radiochemical yield and 99% radiochemical purity after chromatography. Reduction of [14C]-15 with borane -THF complex afforded a...163 mCi) and tetrahydrofuran (freshly distilled) (28.6 mL) in a 1 00-mL RBF was cooled to 0 0C by an ice-bath. Borane -tetra- hydrofuran complex (10.8 mL

A thermodynamic study of complexation process between N, N'-dipyridoxylidene(1,4-butanediamine) and Cd2+ in some binary mixed solvents using conductometry

NASA Astrophysics Data System (ADS)

Ebrahimpoor, Sonia; Khoshnood, Razieh Sanavi; Beyramabadi, S. Ali

2016-12-01

Complexation of the Cd2+ ion with N, N'-dipyridoxylidene(1,4-butanediamine) Schiff base was studied in pure solvents including acetonitrile (AN), ethanol (EtOH), methanol (MeOH), tetrahydrofuran (THF), dimethylformamide (DMF), water (H2O), and various binary solvent mixtures of acetonitrile-ethanol (AN-EtOH), acetonitrile-methanol (AN-MeOH), acetonitrile-tetrahydrofuran (AN-THF), acetonitrile-dimethylformamide (AN-DMF), and acetonitrile-water (AN-H2O) systems at different temperatures using the conductometric method. The conductance data show that the stoichiometry of complex is 1: 1 [ML] in all solvent systems. A non-linear behavior was observed for changes of log K f of [Cd( N, N'-dipyridoxylidene(1,4-butanediamine)] complex versus the composition of the binary mixed solvents, which was explained in terms of solvent-solvent interactions. The results show that the thermodynamics of complexation reaction is affected by the nature and composition of the mixed solvents.

Electrospun Nanocomposite Materials, A Novel Synergy of Polyurethane and Bovine Derived Hydroxyapatite

NASA Astrophysics Data System (ADS)

Bozkurt, Y.; Sahin, A.; Sunulu, A.; Aydogdu, M. O.; Altun, E.; Oktar, F. N.; Ekren, N.; Gunduz, O.

2017-04-01

Polyurethane (PU) is a synthetic polymer that is used for construction of scaffold in tissue engineering applications in order to obtain desirable mechanical, physical and chemical properties like elasticity and durability. Bovine derived hydroxyapatite (BHAp) is a ceramic based natural polymer that is used as the most preferred implant material in orthopedics and dentistry due to their chemically and biologically similarity to the mineral phase found in the human bone structure. PU and bovine derived hydroxyapatite (BHAp) solutions with different concentrations were prepared with dissolving polyurethane and BHAp in Dimethylformamide (DMF) and Tetrahydrofuran (THF) solutions. Blended PU-BHAp solutions in different concentrations were used for electrospinning technique to create nanofiber scaffolds and new biocomposite material together. SEM, FTIR and physical analysis such as viscosity, electrical conductivity, density measurement and tensile strength measurement tests were carried out after production process.

Structural dependence of MEH-PPV chromism in solution.

PubMed

de Magalhães, Carlos E T; Savedra, Ranylson M L; Dias, Karina S; Ramos, Rodrigo; Siqueira, Melissa F

2017-03-01

The chromism observed in the MEH-PPV polymer in tetrahydrofuran (THF) solution is discussed as a function of the structural morphology of the backbone chains. To evaluate this phenomenon, we carried out simulations employing a hybrid methodology using molecular dynamics and quantum mechanical approaches. Our results support the hypothesis that the morphological order-disorder transition is related to the change from red to blue phase observed experimentally. The morphological disorder is associated with total or partial twisted arrangements in the polymer backbone, which induces an electronic conjugation length more confined to shorter segments. In addition, the main band of the MEH-PPV UV-Vis spectrum at the lower wavelength is related to the blue phase, in contrast to the red phase found for the more planar backbone chains.

Non-Leaching, Benign, Fouling Control, Multilayer Polymer Coatings for Marine Applications: PP-1274 Findings

DTIC Science & Technology

2003-09-01

transition temperature TBT tributyltin THF tetrahydrofuran TPE thermoplastic elastomer 4 EXECUTIVE SUMMARY The goal of this research is to...compounds that are environmentally persistant cause damage to the ecosystem, and enter the food chain. The ban on tributyltin ( TBT ) antifoulants by the

Oxidative stress-mediated hemolytic activity of solvent exchange-prepared fullerene (C60) nanoparticles

NASA Astrophysics Data System (ADS)

Trpkovic, Andreja; Todorovic-Markovic, Biljana; Kleut, Duska; Misirkic, Maja; Janjetovic, Kristina; Vucicevic, Ljubica; Pantovic, Aleksandar; Jovanovic, Svetlana; Dramicanin, Miroslav; Markovic, Zoran; Trajkovic, Vladimir

2010-09-01

The present study investigated the hemolytic properties of fullerene (C60) nanoparticles prepared by solvent exchange using tetrahydrofuran (nC60THF), or by mechanochemically assisted complexation with macrocyclic oligosaccharide gamma-cyclodextrin (nC60CDX) or the copolymer ethylene vinyl acetate-ethylene vinyl versatate (nC60EVA-EVV). The spectrophotometrical analysis of hemoglobin release revealed that only nC60THF, but not nC60CDX or nC60EVA-EVV, was able to cause lysis of human erythrocytes in a dose- and time-dependent manner. Atomic force microscopy revealed that nC60THF-mediated hemolysis was preceded by erythrocyte shrinkage and increase in cell surface roughness. A flow cytometric analysis confirmed a decrease in erythrocyte size and demonstrated a significant increase in reactive oxygen species production in red blood cells exposed to nC60THF. The nC60THF-triggered hemolytic activity was efficiently reduced by the antioxidants N-acetylcysteine and butylated hydroxyanisole, as well as by serum albumin, the most abundant protein in human blood plasma. These data indicate that nC60THF can cause serum albumin-preventable hemolysis through oxidative stress-mediated damage of the erythrocyte membrane.

Micro-Tomographic Investigation of Ice and Clathrate Formation and Decomposition under Thermodynamic Monitoring.

PubMed

Arzbacher, Stefan; Petrasch, Jörg; Ostermann, Alexander; Loerting, Thomas

2016-08-08

Clathrate hydrates are inclusion compounds in which guest molecules are trapped in a host lattice formed by water molecules. They are considered an interesting option for future energy supply and storage technologies. In the current paper, time lapse 3D micro computed tomographic (µCT) imaging with ice and tetrahydrofuran (THF) clathrate hydrate particles is carried out in conjunction with an accurate temperature control and pressure monitoring. µCT imaging reveals similar behavior of the ice and the THF clathrate hydrate at low temperatures while at higher temperatures (3 K below the melting point), significant differences can be observed. Strong indications for micropores are found in the ice as well as the THF clathrate hydrate. They are stable in the ice while unstable in the clathrate hydrate at temperatures slightly below the melting point. Significant transformations in surface and bulk structure can be observed within the full temperature range investigated in both the ice and the THF clathrate hydrate. Additionally, our results point towards an uptake of molecular nitrogen in the THF clathrate hydrate at ambient pressures and temperatures from 230 K to 271 K.

IRIS Toxicological Review of Tetrahydrofuran (THF) ...

EPA Pesticide Factsheets

EPA is releasing the draft report, Toxicological Review of Tetrahydrofuran, that was distributed to Federal agencies and White House Offices for comment during the Science Discussion step of the IRIS Assessment Development Process. Comments received from other Federal agencies and White House Offices are provided below with external peer review panel comments. EPA is undertaking an Integrated Risk Information System (IRIS) health assessment for tetrahydrofuran. IRIS is an EPA database containing Agency scientific positions on potential adverse human health effects that may result from chronic (or lifetime) exposure to chemicals in the environment. IRIS contains chemical-specific summaries of qualitative and quantitative health information in support of two steps of the risk assessment paradigm, i.e., hazard identification and dose-response evaluation. IRIS assessments are used in combination with specific situational exposure assessment information to evaluate potential public health risk associated with environmental contaminants.

1,4-Dioxane degradation potential of members of the genera Pseudonocardia and Rhodococcus.

PubMed

Inoue, Daisuke; Tsunoda, Tsubasa; Sawada, Kazuko; Yamamoto, Norifumi; Saito, Yuji; Sei, Kazunari; Ike, Michihiko

2016-11-01

In recent years, several strains capable of degrading 1,4-dioxane have been isolated from the genera Pseudonocardia and Rhodococcus. This study was conducted to evaluate the 1,4-dioxane degradation potential of phylogenetically diverse strains in these genera. The abilities to degrade 1,4-dioxane as a sole carbon and energy source and co-metabolically with tetrahydrofuran (THF) were evaluated for 13 Pseudonocardia and 12 Rhodococcus species. Pseudonocardia dioxanivorans JCM 13855 T , which is a 1,4-dioxane degrading bacterium also known as P. dioxanivorans CB1190, and Rhodococcus aetherivorans JCM 14343 T could degrade 1,4-dioxane as the sole carbon and energy source. In addition to these two strains, ten Pseudonocardia strains could degrade THF, but no Rhodococcus strains could degrade THF. Of the ten Pseudonocardia strains, Pseudonocardia acacia JCM 16707 T and Pseudonocardia asaccharolytica JCM 10410 T degraded 1,4-dioxane co-metabolically with THF. These results indicated that 1,4-dioxane degradation potential, including degradation for growth and by co-metabolism with THF, is possessed by selected strains of Pseudonocardia and Rhodococcus, although THF degradation potential appeared to be widely distributed in Pseudonocardia. Analysis of soluble di-iron monooxygenase (SDIMO) α-subunit genes in THF and/or 1,4-dioxane degrading strains revealed that not only THF and 1,4-dioxane monooxygenases but also propane monooxygenase-like SDIMOs can be involved in 1,4-dioxane degradation.

Polarization dependent two-photon absorption spectroscopy on a naturally occurring biomarker (curcumin) in solution: A theoretical-experimental study

NASA Astrophysics Data System (ADS)

Tiburcio-Moreno, Jose A.; Alvarado-Gil, J. J.; Diaz, Carlos; Echevarria, Lorenzo; Hernández, Florencio E.

2013-09-01

We report on the theoretical-experimental analysis of the two-photon absorption (TPA) and two-photon circular-linear dichroism (TPCLD) spectra of (1E,6E)-1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene-3,5-dione (curcumin) in Tetrahydrofuran (THF) solution. The measurement of the full TPA spectrum of this molecule reveals a maximum TPA cross-section at 740 nm, i.e. more than 10 times larger than the maximum reported in the literature at 800 nm for the application of curcumin in bioimaging. The TPCLD spectrum exposes the symmetry of the main excited-states involved in the two-photon excitation process. TD-DFT calculations support the experimental results. These outcomes are expected to expand the application of natural-occurring dyes in bioimaging.

Evaluation method of the performance of kinetic inhibitor for clathrate hydrate

NASA Astrophysics Data System (ADS)

Muraoka, M.; Susuki, N.; Yamamoto, Y.

2016-12-01

As a part of a Japanese National hydrate research program (MH21, funded by METI), we study the formation of tetrahydrofuran (THF) clathrate hydrate from polyvinylpyrrolidone (PVP) aqueous solution as a function of growth rate V and adsorbed PVP concentration c using the unidirectional growth technique. This study aims to propose a simple method for evaluating the performance of kinetic hydrate inhibitors (KHIs) for the clathrate hydrate-aqueous solution system. The degree of super cooling ΔT calculated from the growth-induced interface shift under steady-state conditions was used for evaluating the KHIs performance. Using this method, a single experimental run can be completed within 3.5 h of the compulsory nucleation by setting V = 5 μm s-1. We believe this method is useful for screening various KHIs and clarifying the inhibition mechanism of KHIs.

Solvent dependence of the activation energy of attachment determined by single molecule observations of surfactant adsorption.

PubMed

Honciuc, Andrei; Baptiste, Denver Jn; Campbell, Ian P; Schwartz, Daniel K

2009-07-07

Single-molecule total internal reflection fluorescence microscopy was used to obtain real-time images of fluorescently labeled hexadecanoic (palmitic) acid molecules as they adsorbed at the interface between fused silica and three different solvents: hexadecane (HD), tetrahydrofuran (THF), and water. These solvents were chosen to explore the effect of solvent polarity on the activation energy associated with the attachment rate, i.e., the rate at which molecules were transferred to the surface from the near-surface layer. Direct counting of single-molecule events, made under steady-state conditions at extremely low coverage, provided direct, model-independent measurements of this attachment rate, in contrast with conventional ensemble-averaged methods, which are influenced by bulk transport and competing detachment processes. We found that the attachment rate increased with increasing temperature for all solvents. Arrhenius analyses gave activation energies of 5+/-2 kJ/mol for adsorption from HD, 10+/-2 kJ/mol for adsorption from THF, and 19+/-2 kJ/mol for adsorption from water. These energies increased systematically with the solvent polarity and, therefore, with the expected strength of the solvent-substrate interaction. We hypothesize that the adsorption of amphiphilic solute molecules from solution can be regarded as a competitive exchange between solute molecules and surface-bound solvent. In this scenario, adsorption is an activated process, and the activation energy for attachment is associated with the solvent-substrate interaction energy.

Effect of reaction solvent on hydroxyapatite synthesis in sol-gel process

NASA Astrophysics Data System (ADS)

Nazeer, Muhammad Anwaar; Yilgor, Emel; Yagci, Mustafa Baris; Unal, Ugur; Yilgor, Iskender

2017-12-01

Synthesis of hydroxyapatite (HA) through sol-gel process in different solvent systems is reported. Calcium nitrate tetrahydrate (CNTH) and diammonium hydrogen phosphate (DAHP) were used as calcium and phosphorus precursors, respectively. Three different synthesis reactions were carried out by changing the solvent media, while keeping all other process parameters constant. A measure of 0.5 M aqueous DAHP solution was used in all reactions while CNTH was dissolved in distilled water, tetrahydrofuran (THF) and N,N-dimethylformamide (DMF) at a concentration of 0.5 M. Ammonia solution (28-30%) was used to maintain the pH of the reaction mixtures in the 10-12 range. All reactions were carried out at 40 ± 2°C for 4 h. Upon completion of the reactions, products were filtered, washed and calcined at 500°C for 2 h. It was clearly demonstrated through various techniques that the dielectric constant and polarity of the solvent mixture strongly influence the chemical structure and morphological properties of calcium phosphate synthesized. Water-based reaction medium, with highest dielectric constant, mainly produced β-calcium pyrophosphate (β-CPF) with a minor amount of HA. DMF/water system yielded HA as the major phase with a very minor amount of β-CPF. THF/water solvent system with the lowest dielectric constant resulted in the formation of pure HA.

Aggregation-Induced Emission Luminogen-Based Direct Visualization of Concentration Gradient Inside an Evaporating Binary Sessile Droplet.

PubMed

Cai, Xin; Xie, Ni; Qiu, Zijie; Yang, Junxian; He, Minghao; Wong, Kam Sing; Tang, Ben Zhong; Qiu, Huihe

2017-08-30

In this study, the concentration gradient inside evaporating binary sessile droplets of 30, 50, and 60 vol % tetrahydrofuran (THF)/water mixtures was investigated. The 5 μL THF/water droplets were evaporated on a transparent hydrophobic substrate. This is the first demonstration of local concentration mapping within an evaporating binary droplet utilizing the aggregation-induced emission material. During the first two evaporation stages of the binary droplet, the local concentration can be directly visualized by the change of fluorescence emission intensity. Time-resolved average and local concentrations can be estimated by using the pre-established function of fluorescence intensity versus water volume fraction.

Method to convert biomass to 5-(hydroxymethyl)-furfural (HMF) and furfural using lactones, furans, and pyrans as solvents

DOEpatents

Dumesic, James A.; Ribeiro Gallo, Jean Marcel; Alonso, David

2014-07-08

Described is a process to produce hydroxymethyl furfural (HMF) from biomass-derived sugars. The process includes the steps of reacting a C5 and/or C6 sugar-containing reactant derived from biomass in a monophasic or biphasic reaction solution comprising water and a co-solvent. The co-solvent can be beta-, gamma-, and/or delta-lactones derived from biomass, tetrahydrofuran (THF) derived from biomass, and/or methyltetrahydrofuran (MTHF) derived from biomass. The reaction takes place in the presence of an acid catalyst and a dehydration catalyst for a time and under conditions such that at least a portion of glucose or fructose present in the reactant is converted to HMF.

Local phase separation of co-solvents enhances pretreatment of biomass for bioenergy applications

DOE PAGES

Mostofian, Barmak; Cai, Charles M.; Smith, Micholas Dean; ...

2016-08-02

Pretreatment facilitates more complete deconstruction of plant biomass to enable more economic production of lignocellulosic biofuels and byproducts. Various co-solvent pretreatments have demonstrated advantages relative to aqueous-only methods by enhancing lignin removal to allow unfettered access to cellulose. However, there is a limited mechanistic understanding of the interactions between the co-solvents and cellulose that impedes further improvement of such pretreatment methods. Recently, tetrahydrofuran (THF) has been identified as a highly effective co-solvent for the pretreatment and fractionation of biomass. Here, to elucidate the mechanism of the THF water interactions with cellulose, we pair simulation and experimental data demonstrating that enhancedmore » solubilization of cellulose can be achieved by the THF water co-solvent system at equivolume mixtures and moderate temperatures (≤445 K). The simulations show that THF and water spontaneously phase separate on the local surface of a cellulose fiber, owing to hydrogen bonding of water molecules with the hydrophilic cellulose faces and stacking of THF molecules on the hydrophobic faces. Furthermore, a single fully solvated cellulose chain is shown to be preferentially bound by water molecules in the THF water mixture. In light of these findings, co-solvent reactions were performed on microcrystalline cellulose and maple wood to show that THF significantly enhanced cellulose deconstruction and lignocellulose solubilization at simulation conditions, enabling a highly versatile and efficient biomass pretreatment and fractionation method.« less

Photochemical organic oxidations and dechlorinations with a mu-oxo bridged heme/non-heme diiron complex.

PubMed

Wasser, Ian M; Fry, H Christopher; Hoertz, Paul G; Meyer, Gerald J; Karlin, Kenneth D

2004-12-27

Steady state and laser flash photolysis studies of the heme/non-heme mu-oxo diiron complex [((6)L)Fe(III)-O-Fe(III)-Cl](+) (1) have been undertaken. The anaerobic photolysis of benzene solutions of 1 did not result in the buildup of any photoproduct. However, the addition of excess triphenylphosphine resulted in the quantitative photoreduction of 1 to [((6)L)Fe(II)...Fe(II)-Cl](+) (2), with concomitant production by oxo-transfer of 1 equiv of triphenylphosphine oxide. Under aerobic conditions and excess triphenylphosphine, the reaction produces multiple turnovers (approximately 28) before the diiron complex is degraded. The anaerobic photolysis of tetrahydrofuran (THF) or toluene solutions of 1 likewise results in the buildup of 2. The oxidation products from these reactions included gamma-butyrolactone (approximately 15%) for the reaction in THF and benzaldehyde (approximately 23%) from the reaction in toluene. In either case, the O-atom which is incorporated into the carbonyl product is derived from dioxygen present under workup or under aerobic photolysis conditions. Transient absorption measurements of low-temperature THF solutions of 1 revealed the presence of an (P)Fe(II)-like [P = tetraaryl porphyrinate dianion] species suggesting that the reactive species is a formal (heme)Fe(II)/Fe(IV)=O(non-heme) pair. The non-heme Fe(IV)=O is thus most likely responsible for C-H bond cleavage and subsequent radical chemistry. The photolysis of 1 in chlorobenzene or 1,2-dichlorobenzene resulted in C-Cl cleavage reactions and the formation of [[((6)L)Fe(III)-Cl...Fe(III)-Cl](2)O](2+) (3), with chloride ligands that are derived from solvent dehalogenation chemistry. The resulting organic products are biphenyl trichlorides or biphenyl monochlorides, derived from dichlorobenzene and chlorobenzene, respectively. Similarly, product 3 is obtained by the photolysis of benzene-benzyl chloride solutions of 1; the organic product is benzaldehyde (approximately 70%). A brief discussion of the dehalogenation chemistry, along with relevant environmental perspectives, is included.

Micro-Tomographic Investigation of Ice and Clathrate Formation and Decomposition under Thermodynamic Monitoring

PubMed Central

Arzbacher, Stefan; Petrasch, Jörg; Ostermann, Alexander; Loerting, Thomas

2016-01-01

Clathrate hydrates are inclusion compounds in which guest molecules are trapped in a host lattice formed by water molecules. They are considered an interesting option for future energy supply and storage technologies. In the current paper, time lapse 3D micro computed tomographic (µCT) imaging with ice and tetrahydrofuran (THF) clathrate hydrate particles is carried out in conjunction with an accurate temperature control and pressure monitoring. µCT imaging reveals similar behavior of the ice and the THF clathrate hydrate at low temperatures while at higher temperatures (3 K below the melting point), significant differences can be observed. Strong indications for micropores are found in the ice as well as the THF clathrate hydrate. They are stable in the ice while unstable in the clathrate hydrate at temperatures slightly below the melting point. Significant transformations in surface and bulk structure can be observed within the full temperature range investigated in both the ice and the THF clathrate hydrate. Additionally, our results point towards an uptake of molecular nitrogen in the THF clathrate hydrate at ambient pressures and temperatures from 230 K to 271 K. PMID:28773789

New hexa-bodipy functionalized dendrimeric cyclotriphosphazene conjugates as highly selective and sensitive fluorescent chemosensor for Co2+ ions

NASA Astrophysics Data System (ADS)

Şenkuytu, Elif; Tanrıverdi Eçik, Esra

2018-06-01

In the study, the new hexa-bodipy functionalized dendrimeric cyclotriphosphazene conjugates (HBCP 1 and 2) have been successfully synthesized and characterized by using general spectroscopic techniques such as 1H, 13C and 31P NMR spectroscopies. The photophysical and metal sensing properties in THF solutions of dendrimeric cyclotriphosphazene conjugates (HBCP 1 and 2) were investigated by UV-Vis and fluorescence spectroscopies in dilute tetrahydrofuran solutions. These dendrimers showed strong absorption bands 501 and 641 nm at low concentration with high molar extinction coefficients. In addition, the stoichiometry of the complex between the conjugate (HBCP 2) and Co2+ ions were determined by a Job's plot obtained from fluorescence titrations. The metal sensing data showed that the hexa-bodipy functionalized dendrimeric cyclotriphosphazene conjugate (HBCP 2) is a candidate for fluorescent chemosensor for Co2+ ions due to showing high selectivity with a low limit of detection.

Impact of the Formulation Pathway on the Colloidal State and Crystallinity of Poly-ε-caprolactone Particles Prepared by Solvent Displacement.

PubMed

Pucci, Carlotta; Cousin, Fabrice; Dole, François; Chapel, Jean-Paul; Schatz, Christophe

2018-02-20

The formulation pathway and/or the mixing method are known to be relevant in many out-of-equilibrium processes. In this work, we studied the effect of the mixing conditions on the physicochemical properties of poly-ε-caprolactone (PCL) particles prepared by solvent displacement. More specifically, water was added in one shot (fast addition) or drop by drop to PCL solution in tetrahydrofuran (THF) to study the impact of the mixing process on particle properties including size, stability, and crystallinity. Two distinct composition maps representing the Ouzo domain characteristic of the presence of metastable nanoparticles have been established for each mixing method. Polymer nanoparticles are formed in the Ouzo domain according to a nucleation and growth (or aggregation) mechanism. The fast addition promotes a larger nucleation rate, thus favoring the formation of small and uniform particles. For the drop-by-drop addition, for which the polymer solubility gradually decreases, the composition trajectories systematically cross an intermediate unstable region between the solubility limit of the polymer and the Ouzo domain. This leads to heterogeneous nucleation as shown by the formation of larger and less stable particles. Particles formed in the Ouzo domain have semi-crystalline properties. The PCL melting point is decreased with the THF fraction trapped in particles in accordance with Flory's theory for melt crystallization. On the other hand, the degree of crystallinity is constant, around 20% regardless of the THF fraction. No difference between fast and slow addition could be detected on the semi-crystalline properties of the particles which emphasize that thermodynamic rather than kinetic factors drive the polymer crystallization in particles. The recovery of bulk PCL crystallinity after the removal of THF from particles tends to confirm this hypothesis.

Uranium(iii) complexes supported by hydrobis(mercaptoimidazolyl)borates: synthesis and oxidation chemistry.

PubMed

Maria, Leonor; Santos, Isabel C; Santos, Isabel

2018-05-23

The reaction of [UI3(thf)4] with the sodium or lithium salts of hydrobis(2-mercapto-1-methylimidazolyl)borate ligands ([H(R)B(timMe)2]-) in a 1 : 2 ratio, in tetrahydrofuran, gave the U(iii) complexes [UI{κ3-H,S,S'-H(R)B(timMe)2}2(thf)2] (R = H (1), Ph (2)) in good yields. Crystals of [UI{κ3-H,S,S'-H(Ph)B(timMe)2}2(thf)2] (2) were obtained by recrystallization from a tetrahydrofuran/acetonitrile solution, and the ion-separated uranium complex [U{κ3-H,S,S'-H(Ph)B(timMe)2}2(CH3CN)3][I] (3-I) was obtained by dissolution of 2 in acetonitrile followed by recrystallization. One-electron oxidation of 2 with AgBPh4 or I2 resulted in the formation of the cationic U(iv) complexes [U{κ3-H,S,S'-H(Ph)B(timMe)2}3][X] (X = BPh4 (6-BPh4), I (6-I)), due to a ligand redistribution process. These complexes are the first examples of homoleptic poly(azolyl)borate U(iv) complexes. Treatment of complex 2 with azobenzene led to the isolation of crystals of the U(iv) compound [UI{κ3-H(Ph)B(timMe)2}2(κ2-timMe)] (7). Treatment of 2 with pyridine-N oxide (pyNO) led to the formation of the uranyl complex [UO2{κ2-S,S'-H(Ph)B(timMe)2}2] (8) and of complex 6-I, while from the reaction of [U{κ3-H(Ph)B(timMe)2}2(thf)3][BPh4] (5) with pyNO, the oxo-bridged U(iv) complex [{U{κ3-H(Ph)B(timMe)2}2(pyNO)}2(μ-O)][BPh4]2 (9) was also obtained. In the U(iii) and U(iv) complexes, the bis(azolyl)borate ligands bind to the uranium center in a κ3-H,S,S' coordination mode, while in the U(vi) complex the ligands bind to the metal in a κ2-S,S' mode. The presence of UH-B interactions in the solid-state, for the nine-coordinate complexes 1, 2, 3, 6 and 7 and for the eight-coordinate complex 9, was supported by IR spectroscopy and/or X-ray diffraction analysis.

Novel approach for extraction of quercetin using molecular imprinted membranes

NASA Astrophysics Data System (ADS)

Kamarudin, Siti Fatimah; Ahmad, Mohd Noor; Dzahir, Irfan Hatim Mohamed; Nasir, Azalina Mohamed; Ishak, Noorhidayah; Halim, Nurul Farhanah

2017-12-01

Quercetin imprinted membrane (QIM) was synthesized and applied for the extraction of quercetin. The quercetin imprinted membranes (QIM) were fabricated through a non-covalent approach via surface thermal polymerization. Polyvinylidene fluoride (PVDF) microfiltration membrane was used as a support to improve mechanical stability of the membrane. The thin imprinted layer was formed by copolymerization of acrylamide (AA) as functional monomer and ethylene glycol dimethacrylate (EGDMA) as crosslinker in the presence of quercetin as template in tetrahydrofuran (THF) solution. The Atomic Force Microscopy (AFM) and Field Emission Scanning Electron Microscope (FESEM) were used to visualize the surface of membrane. Batch rebinding and binding kinetic experiments proved that the binding properties of the QIM are higher than non-imprinted membranes (NIM). QIM also have higher selectivity towards quercetin compared to sinensetin and rosmarinic acid.

Single-Molecule Tracking Study of the Permeability and Transverse Width of Individual Cylindrical Microdomains in Solvent-Swollen Polystyrene-block-poly(ethylene oxide) Films.

PubMed

Sapkota, Dol Raj; Tran-Ba, Khanh-Hoa; Elwell-Cuddy, Trevor; Higgins, Daniel A; Ito, Takashi

2016-12-01

Understanding the properties of solvent-swollen block copolymer (BCP) microdomains is important for better solvent-based control of microdomain morphology, orientation, and permeability. In this study, single-molecule tracking (SMT) was explored to assess the permeability and transverse width of individual cylindrical microdomains in solvent-swollen polystyrene-block-poly(ethylene oxide) (PS-b-PEO) films. PS-b-PEO films comprising shear-elongated cylindrical PEO microdomains were prepared by sandwiching its benzene or tetrahydrofuran (THF) solution between two glass substrates. SMT measurements were performed at different drying times to investigate the effects of solvent evaporation on the microdomain properties. SMT data showed one-dimensional (1D) motions of single fluorescent molecules (sulforhodamine B) based on their diffusion within the cylindrical microdomains. Microdomain permeability and transverse width were assessed from the single-molecule diffusion coefficients (D SMT ) and transverse variance of the 1D trajectories (σ δ 2 ), respectively. The D SMT and σ δ 2 values from individual 1D trajectories were widely distributed with no evidence of correlation on a single molecule basis, possibly because the individual microdomains in a film were swollen to different extents. On average, microdomain permeability (D) and effective radius (r) gradually decreased within the first 3 days of drying due to solvent evaporation, and changed negligibly thereafter. PS-b-PEO films prepared from THF solutions exhibited larger changes in D and r as compared with those from benzene solutions due to the better swelling of the PEO microdomains by THF. Importantly, changes in D were more prominent than those in r, suggesting that the permeability of the PEO microdomains is very susceptible to the presence of solvent. These results reveal the unique capability of SMT to assess the properties of individual cylindrical microdomains in a solvent-swollen BCP film.

Single-molecule tracking study of the permeability and transverse width of individual cylindrical microdomains in solvent-swollen polystyrene- block-poly(ethylene oxide) films

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sapkota, Dol Raj; Tran-Ba, Khanh-Hoa; Elwell-Cuddy, Trevor

Understanding the properties of solvent-swollen block copolymer (BCP) microdomains is important for better solvent-based control of microdomain morphology, orientation, and permeability. In this study, single-molecule tracking (SMT) was explored to assess the permeability and transverse width of individual cylindrical microdomains in solvent-swollen polystyrene- block-poly(ethylene oxide) (PS-b-PEO) films. PS-b-PEO films comprising shear-elongated cylindrical PEO microdomains were prepared by sandwiching its benzene or tetrahydrofuran (THF) solution between two glass substrates. In this paper, SMT measurements were performed at different drying times to investigate the effects of solvent evaporation on the microdomain properties. SMT data showed one-dimensional (1D) motions of single fluorescent moleculesmore » (sulforhodamine B) based on their diffusion within the cylindrical microdomains. Microdomain permeability and transverse width were assessed from the single-molecule diffusion coefficients (D SMT) and transverse variance of the 1D trajectories (σ δ 2), respectively. The D SMT and σ δ 2 values from individual 1D trajectories were widely distributed with no evidence of correlation on a single molecule basis, possibly because the individual microdomains in a film were swollen to different extents. On average, microdomain permeability (D) and effective radius (r) gradually decreased within the first 3 days of drying due to solvent evaporation, and changed negligibly thereafter. PS-b-PEO films prepared from THF solutions exhibited larger changes in D and r as compared with those from benzene solutions due to the better swelling of the PEO microdomains by THF. Importantly, changes in D were more prominent than those in r, suggesting that the permeability of the PEO microdomains is very susceptible to the presence of solvent. Finally, these results reveal the unique capability of SMT to assess the properties of individual cylindrical microdomains in a solvent-swollen BCP film.« less

Single-molecule tracking study of the permeability and transverse width of individual cylindrical microdomains in solvent-swollen polystyrene- block-poly(ethylene oxide) films

DOE PAGES

Sapkota, Dol Raj; Tran-Ba, Khanh-Hoa; Elwell-Cuddy, Trevor; ...

2016-11-04

Understanding the properties of solvent-swollen block copolymer (BCP) microdomains is important for better solvent-based control of microdomain morphology, orientation, and permeability. In this study, single-molecule tracking (SMT) was explored to assess the permeability and transverse width of individual cylindrical microdomains in solvent-swollen polystyrene- block-poly(ethylene oxide) (PS-b-PEO) films. PS-b-PEO films comprising shear-elongated cylindrical PEO microdomains were prepared by sandwiching its benzene or tetrahydrofuran (THF) solution between two glass substrates. In this paper, SMT measurements were performed at different drying times to investigate the effects of solvent evaporation on the microdomain properties. SMT data showed one-dimensional (1D) motions of single fluorescent moleculesmore » (sulforhodamine B) based on their diffusion within the cylindrical microdomains. Microdomain permeability and transverse width were assessed from the single-molecule diffusion coefficients (D SMT) and transverse variance of the 1D trajectories (σ δ 2), respectively. The D SMT and σ δ 2 values from individual 1D trajectories were widely distributed with no evidence of correlation on a single molecule basis, possibly because the individual microdomains in a film were swollen to different extents. On average, microdomain permeability (D) and effective radius (r) gradually decreased within the first 3 days of drying due to solvent evaporation, and changed negligibly thereafter. PS-b-PEO films prepared from THF solutions exhibited larger changes in D and r as compared with those from benzene solutions due to the better swelling of the PEO microdomains by THF. Importantly, changes in D were more prominent than those in r, suggesting that the permeability of the PEO microdomains is very susceptible to the presence of solvent. Finally, these results reveal the unique capability of SMT to assess the properties of individual cylindrical microdomains in a solvent-swollen BCP film.« less

Early Development of a Hazardous Chemical Protective Ensemble.

DTIC Science & Technology

1986-10-01

Insuff. Cyanides ( Sodium , Potassium, Sol’n) -- 5 Butyl Cyanogen Bromide CBR 2 Insuff. Cyanogen Chloride CCL NR Insuff. Cyclohexane --- 6 Butyl...SPILLED SUBSTANCES ANNUAL RECOMMENDED ALTERNATE COMPOUND CHRIS CODE NO. OF SPILLS MATERIAL MATERIALS Dimethyl Sulfate DSL 4 Insuff. Ethyl Acrylate EAC 38...Tetrachloride STC 2 Insuff. Sodium Hydroxide (sol’n or dry) SHD 193 Butyl Sulfuric Acid SFA 426 CPE Tetrahydrofuran THF 13 None Titanium Tetrachloride TTT

Dye sensitized solar cell applications of CdTiO3-TiO2 composite thin films deposited from single molecular complex

NASA Astrophysics Data System (ADS)

Ehsan, Muhammad Ali; Khaledi, Hamid; Pandikumar, Alagarsamy; Huang, Nay Ming; Arifin, Zainudin; Mazhar, Muhammad

2015-10-01

A heterobimetallic complex [Cd2Ti4(μ-O)6(TFA)8(THF)6]·1.5THF (1) (TFA=trifluoroacetato, THF=tetrahydrofuran) comprising of Cd:Ti (1:2) ratio was synthesized by a chemical reaction of cadmium (II) acetate with titanium (IV) isopropoxide and triflouroacetic acid in THF. The stoichiometry of (1) was recognized by single crystal X-ray diffraction, spectroscopic and elemental analyses. Thermal studies revealed that (1) neatly decomposes at 450 °C to furnish 1:1 ratio of cadmium titanate:titania composite oxides material. The thin films of CdTiO3-TiO2 composite oxides were deposited at 550 °C on fluorine doped tin oxide coated conducting glass substrate in air ambient. The micro-structure, crystallinity, phase identification and chemical composition of microspherical architectured CdTiO3-TiO2 composite thin film have been determined by scanning electron microscopy, X-ray diffraction, Raman spectroscopy and energy dispersive X-ray analysis. The scope of composite thin film having band gap of 3.1 eV was explored as photoanode for dye-sensitized solar cell application.

Dynamical cage behaviour and hydrogen migration in hydrogen and hydrogen-tetrahydrofuran clathrate hydrates

NASA Astrophysics Data System (ADS)

Gorman, Paul D.; English, Niall J.; MacElroy, J. M. D.

2012-01-01

Classical equilibrium molecular dynamics simulations have been performed to investigate dynamical properties of cage radial breathing modes and intra- and inter-cage hydrogen migration in both pure hydrogen and mixed hydrogen-tetrahydrofuran sII hydrates at 0.05 kbar and up to 250 K. For the mixed H2-THF system in which there is single H2 occupation of the small cage (labelled "1SC 1LC"), we find that no H2 migration occurs, and this is also the case for pure H2 hydrate with single small-cavity occupation and quadruple occupancy for large cages (dubbed "1SC 4LC"). However, for the more densely filled H2-THF and pure-H2 systems, in which there is double H2 occupation in the small cage (dubbed "2SC 1LC" and "2SC 4LC," respectively), there is an onset of inter-cage H2 migration events from the small cages to neighbouring cavities at around 200 K, with an approximate Arrhenius temperature-dependence for the migration rate from 200 to 250 K. It was found that these "cage hopping" events are facilitated by temporary openings of pentagonal small-cage faces with the relaxation and reformation of key stabilising hydrogen bonds during and following passage. The cages remain essentially intact up to 250 K, save for transient hydrogen bond weakening and reformation during and after inter-cage hydrogen diffusion events in the 200-250 K range. The "breathing modes," or underlying frequencies governing the variation in the cavities' radii, exhibit a certain overlap with THF rattling motion in the case of large cavities, while there is some overlap of small cages' radial breathing modes with lattice acoustic modes.

The roles of the solute and solvent cavities in charge-transfer-to-solvent dynamics: Ultrafast studies of potasside and sodide in diethyl ether

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cavanagh, Molly C.; Young, Ryan M.; Schwartz, Benjamin J.

2008-10-07

Although electron transfer reactions are among the most fundamental in chemistry, it is still not clear how to isolate the roles of the solute and solvent in moving charge between reactants in solution. In this paper, we address this question by comparing the ultrafast charge-transfer-to-solvent (CTTS) dynamics of potasside (K{sup -}) in diethyl ether (DEE) to those of sodide (Na{sup -}) in both DEE and tetrahydrofuran (THF). We find that for sodide in both DEE and THF, CTTS excitation leads to delayed ejection of a solvated electron that appears with its equilibrium absorption spectrum. This indicates that the ejected electronsmore » are localized in pre-existing solvent traps, suggesting that the structure of liquid DEE is characterized by cavities that are favorably polarized to localize an excess electron, as has been previously shown is the case for liquid THF. We also find that the geminate recombination dynamics following CTTS excitation of sodide in THF and DEE are similar, suggesting that the nature of the CTTS excited states and their coupling to the electronic states supported by the naturally occurring solvent cavities are similar in the two solvents. In contrast, the geminate recombination dynamics of potasside and sodide in DEE are different, with red-edge excitation of the K{sup -} CTTS band producing a greater number of long-lived electrons than is seen following the corresponding red-edge excitation of the Na{sup -} CTTS band. This indicates that the CTTS excited states of K{sup -} are better able to couple to the electronic states supported by the naturally occurring solvent cavities, allowing us to compare the energetic positions of the potasside and sodide ground and CTTS excited states on a common absolute scale. Finally, we also observe a strong transient absorption following the CTTS excitation of potasside in DEE that correlates well with the 766 nm position of the gas-phase potassium D-line. The data indicate that CTTS excitation of alkali metal anions essentially instantaneously produces a gas-phase-like neutral alkali metal atom, which then spontaneously undergoes partial ejection of the remaining valence electron to form a neutral alkali metal cation:solvated electron tight-contact pair.« less

Electrospun polyurethane/hydroxyapatite bioactive scaffolds for bone tissue engineering: the role of solvent and hydroxyapatite particles.

PubMed

Tetteh, G; Khan, A S; Delaine-Smith, R M; Reilly, G C; Rehman, I U

2014-11-01

Polyurethane (PU) is a promising polymer to support bone-matrix producing cells due to its durability and mechanical resistance. In this study two types of medical grade poly-ether urethanes Z3A1 and Z9A1 and PU-Hydroxyapatite (PU-HA) composites were investigated for their ability to act as a scaffold for tissue engineered bone. PU dissolved in varying concentrations of dimethylformamide (DMF) and tetrahydrofuran (THF) solvents were electrospun to attain scaffolds with randomly orientated non-woven fibres. Bioactive polymeric composite scaffolds were created using 15 wt% Z3A1 in a 70/30 DMF/THF PU solution and incorporating micro- or nano-sized HA particles in a ratio of 3:1 respectively, whilst a 25 wt% Z9A1 PU solution was doped in ratio of 5:1. Chemical properties of the resulting composites were evaluated by FTIR and physical properties by SEM. Tensile mechanical testing was carried out on all electrospun scaffolds. MLO-A5 osteoblastic mouse cells and human embryonic mesenchymal progenitor cells, hES-MPs were seeded on the scaffolds to test their biocompatibility and ability to support mineralised matrix production over a 28 day culture period. Cell viability was assayed by MTT and calcium and collagen deposition by Sirius red and alizarin red respectively. SEM images of both electrospun PU scaffolds and PU-HA composite scaffolds showed differences in fibre morphology with changes in solvent combinations and size of HA particles. Inclusion of THF eliminated the presence of beads in fibres that were present in scaffolds fabricated with 100% DMF solvent, and resulted in fibres with a more uniform morphology and thicker diameters. Mechanical testing demonstrated that the Young׳s Modulus and yield strength was lower at higher THF concentrations. Inclusion of both sizes of HA particles in PU-HA solutions reinforced the scaffolds leading to higher mechanical properties, whilst FTIR characterisation confirmed the presence of HA in all composite scaffolds. Although all scaffolds supported proliferation of both cell types and deposition of calcified matrix, PU-HA composite fibres containing nano-HA enabled the highest cell viability and collagen deposition. These scaffolds have the potential to support bone matrix formation for bone tissue engineering. Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.

New hexa-bodipy functionalized dendrimeric cyclotriphosphazene conjugates as highly selective and sensitive fluorescent chemosensor for Co2+ ions.

PubMed

Şenkuytu, Elif; Tanrıverdi Eçik, Esra

2018-06-05

In the study, the new hexa-bodipy functionalized dendrimeric cyclotriphosphazene conjugates (HBCP 1 and 2) have been successfully synthesized and characterized by using general spectroscopic techniques such as 1 H, 13 C and 31 P NMR spectroscopies. The photophysical and metal sensing properties in THF solutions of dendrimeric cyclotriphosphazene conjugates (HBCP 1 and 2) were investigated by UV-Vis and fluorescence spectroscopies in dilute tetrahydrofuran solutions. These dendrimers showed strong absorption bands 501 and 641nm at low concentration with high molar extinction coefficients. In addition, the stoichiometry of the complex between the conjugate (HBCP 2) and Co 2+ ions were determined by a Job's plot obtained from fluorescence titrations. The metal sensing data showed that the hexa-bodipy functionalized dendrimeric cyclotriphosphazene conjugate (HBCP 2) is a candidate for fluorescent chemosensor for Co 2+ ions due to showing high selectivity with a low limit of detection. Copyright © 2018 Elsevier B.V. All rights reserved.

On interfacial properties of tetrahydrofuran: Atomistic and coarse-grained models from molecular dynamics simulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Garrido, J. M.; Algaba, J.; Blas, F. J., E-mail: felipe@uhu.es

2016-04-14

We have determined the interfacial properties of tetrahydrofuran (THF) from direct simulation of the vapor-liquid interface. The molecules are modeled using six different molecular models, three of them based on the united-atom approach and the other three based on a coarse-grained (CG) approach. In the first case, THF is modeled using the transferable parameters potential functions approach proposed by Chandrasekhar and Jorgensen [J. Chem. Phys. 77, 5073 (1982)] and a new parametrization of the TraPPE force fields for cyclic alkanes and ethers [S. J. Keasler et al., J. Phys. Chem. B 115, 11234 (2012)]. In both cases, dispersive and coulombicmore » intermolecular interactions are explicitly taken into account. In the second case, THF is modeled as a single sphere, a diatomic molecule, and a ring formed from three Mie monomers according to the SAFT-γ Mie top-down approach [V. Papaioannou et al., J. Chem. Phys. 140, 054107 (2014)]. Simulations were performed in the molecular dynamics canonical ensemble and the vapor-liquid surface tension is evaluated from the normal and tangential components of the pressure tensor along the simulation box. In addition to the surface tension, we have also obtained density profiles, coexistence densities, critical temperature, density, and pressure, and interfacial thickness as functions of temperature, paying special attention to the comparison between the estimations obtained from different models and literature experimental data. The simulation results obtained from the three CG models as described by the SAFT-γ Mie approach are able to predict accurately the vapor-liquid phase envelope of THF, in excellent agreement with estimations obtained from TraPPE model and experimental data in the whole range of coexistence. However, Chandrasekhar and Jorgensen model presents significant deviations from experimental results. We also compare the predictions for surface tension as obtained from simulation results for all the models with experimental data. The three CG models predict reasonably well (but only qualitatively) the surface tension of THF, as a function of temperature, from the triple point to the critical temperature. On the other hand, only the TraPPE united-atoms models are able to predict accurately the experimental surface tension of the system in the whole temperature range.« less

Tuning the Morphology and Activity of Electrospun Polystyrene/UiO-66-NH2 Metal-Organic Framework Composites to Enhance Chemical Warfare Agent Removal.

PubMed

Peterson, Gregory W; Lu, Annie X; Epps, Thomas H

2017-09-20

This work investigates the processing-structure-activity relationships that ultimately facilitate the enhanced performance of UiO-66-NH 2 metal-organic frameworks (MOFs) in electrospun polystyrene (PS) fibers for chemical warfare agent detoxification. Key electrospinning processing parameters including solvent type (dimethylformamide [DMF]) vs DMF/tetrahydrofuran [THF]), PS weight fraction in solution, and MOF weight fraction relative to PS were varied to optimize MOF incorporation into the fibers and ultimately improve composite performance. It was found that composites spun from pure DMF generally resulted in MOF crystal deposition on the surface of the fibers, while composites spun from DMF/THF typically led to MOF crystal deposition within the fibers. For cases in which the MOF was incorporated on the periphery of the fibers, the composites generally demonstrated better gas uptake (e.g., nitrogen, chlorine) because of enhanced access to the MOF pores. Additionally, increasing both the polymer and MOF weight percentages in the electrospun solutions resulted in larger diameter fibers, with polymer concentration having a more pronounced effect on fiber size; however, these larger fibers were generally less efficient at gas separations. Overall, exploring the electrospinning parameter space resulted in composites that outperformed previously reported materials for the detoxification of the chemical warfare agent, soman. The data and strategies herein thus provide guiding principles applicable to the design of future systems for protection and separations as well as a wide range of environmental remediation applications.

Pentaarylcyclopentadienyl Iron, Cobalt, and Nickel Halides.

PubMed

Chakraborty, Uttam; Modl, Moritz; Mühldorf, Bernd; Bodensteiner, Michael; Demeshko, Serhiy; van Velzen, Niels J C; Scheer, Manfred; Harder, Sjoerd; Wolf, Robert

2016-03-21

The preparation of new stable half-sandwich transition metal complexes, having a bulky cyclopentadienyl ligand C5(C6H4-4-Et)5 (Cp(Ar1)) or C5(C6H4-4-nBu)5 (Cp(Ar2)), is reported. The tetrahydrofuran (THF) adduct [Cp(Ar1)Fe(μ-Br)(THF)]2 (1a) was synthesized by reacting K[Cp(Ar1)] with [FeBr2(THF)2] in THF, and its molecular structure was determined by X-ray crystallography. Complex 1a easily loses its coordinated THF molecules under vacuum to form the solvent-free complex [Cp(Ar1)Fe(μ-Br)]2 (1b). The analogous complexes [Cp(Ar1)Co(μ-Br)]2 (2), [Cp(Ar1)Ni(μ-Br)]2 (3), and [Cp(Ar2)Ni(μ-Br)]2 (4) were synthesized from CoBr2 and [NiBr2(1,2-dimethoxyethane)]. The mononuclear, low-spin cobalt(III) and nickel(III) complexes [Cp(Ar2)MI2] (5, M = Co; 6, M = Ni) were prepared by reacting the radical Cp(Ar2) with NiI2 and CoI2. The complexes were characterized by NMR and UV-vis spectroscopies and by elemental analyses. Single-crystal X-ray structure analyses revealed that the dimeric complexes 1a, 1b, and 3 have a planar M2Br2 core, whereas 2 and 4 feature a puckered M2Br2 ring.

Ultrafast responses of dipolar and V-shaped dipicolinate derivatives with potential applications in the labeling of biomolecules

NASA Astrophysics Data System (ADS)

Wang, Yaochuan; Liu, Siyuan; Liu, Dajun; Wang, Guiqiu; Xiao, Haibo

2016-02-01

A dipolar dipicolinate derivative, trans-dimethyl-4-[4'-(N,N-diphenylamino)-styry1]-pyridin-2,6-dicarboxylate (P-1), and a P-1based V-shaped compound, {4-[(E)-2-(2,6-dimethoxycarbonylpyridin-4-yl) vinyl]}-N-phenyl-N-{4-[(E)-2-(2,6-dimethoxycarbonylpyridin-4-yl)vinylphenyl]}aniline (P-2), with intense two-photon fluorescence emission properties were systematically investigated by using steady-state absorption and fluorescence spectroscopy, open-aperture Z-scans, and two-photon excited fluorescence (TPF). The two-photon absorption cross-section of the V-shaped compound P-2 in tetrahydrofuran (THF) was determined to be 208 GM, which represents a 6.5-fold enhancement compared with its dipolar counterpart P-1 (32 GM). Extension of the intramolecular charge transfer (ICT) in the V-shaped dipicolinate derivative has been suggested as the mechanism of enhancement. The excited state dynamics from transient absorption spectroscopy were analyzed and discussed. The formation and relaxation lifetimes of the ICT state for these dipicolinate derivatives in THF solutions were found to be several picoseconds and several hundred picoseconds, respectively. The results show an increased ICT character of the V-shaped compound and a potential application for this compound in two-photon fluorescence imaging fields.

Aggregation-induced emission enhancement of anthracene-derived Schiff base compounds and their application as a sensor for bovine serum albumin and optical cell imaging.

PubMed

Densil, Simon; Chang, Chien-Huei; Chen, Chia-Ling; Mathavan, Alagarsamy; Ramdass, Arumugam; Sathish, Veerasamy; Thanasekaran, Pounraj; Li, Wen-Shan; Rajagopal, Seenivasan

2018-06-01

Three anthracene-based Schiff base complexes, R1-R3 (R1 = (E)-N´-((anthracen-10-yl)methylene)benzohydrazide; R2 = (E)-1-((anthracen-10-yl)methylene)-4-phenylsemicarbazide; and R3 = (E)-1-((anthracen-10-yl)methylene)-4-phenylthiosemicarbazide) were synthesized from 9-anthracenecarboxaldehyde, benzohydrazide, 4-phenylsemicarbazide and 4-phenylthiosemi-carbazide respectively, and characterized by various spectral techniques. The absorption spectral characteristics of R1-R3 were bathochromically tuned to the visible region by extending the π conjugation. These target compounds were weakly fluorescent in tetrahydrofuran (THF) solution because of rapid isomerization of the C=N double bond in the excited state. However, the aqueous dispersion of R1-R3 in the THF/water mixture by the gradual addition of water up to 90% resulted in an increase in the fluorescence intensity mainly due to aggregation-induced emission enhancement (AIEE) properties. The formation of nanoaggregates of R1-R3 were confirmed by scanning electron microscopy (SEM) and atomic force microscopy (AFM) techniques. The compounds R1-R3 are ideal probes for the fluorescence sensing of bovine serum albumin (BSA) and breast cancer cells by optical cell imaging. Copyright © 2018 John Wiley & Sons, Ltd.

A Solvent-Vapor Approach toward the Control of Block Ionomer Morphologies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mineart, Kenneth P.; Lee, Byeongdu; Spontak, Richard J.

Sulfonated block ionomers possess advantageous properties for a wide range of diverse applications such as desalination membranes, fuel cells, electroactive media, and photovoltaic devices. Unfortunately, their inherently high incompatibilities and glass transition temperatures e ff ectively prevent the use of thermal annealing, routinely employed to re fi ne the morphologies of nonionic block copolymers. An alternative approach is therefore required to promote morphological equilibration in block ionomers. The present study explores the morphological characteristics of midblock- sulfonated pentablock ionomers (SBIs) di ff ering in their degree of sulfonation (DOS) and cast from solution followed by solvent-vapor annealing (SVA). Transmission electronmore » microscopy con fi rms that fi lms deposited from di ff erent solvent systems form nonequilibrium morphologies due to solvent-regulated self-assembly and drying. A series of SVA tests performed with solvents varying in polarity reveals that exposing cast fi lms to tetrahydrofuran (THF) vapor for at least 2 h constitutes the most e ff ective SVA protocol, yielding the anticipated equilibrium morphology. That is, three SBI grades subjected to THF-SVA self-assemble into well-ordered lamellae wherein the increase in DOS is accompanied by an increase in lamellar periodicity, as measured by small-angle X-ray scattering.« less

Magnesium Electrorefining in Non-Aqueous Electrolyte at Room Temperature

NASA Astrophysics Data System (ADS)

Kwon, Kyungjung; Park, Jesik; Kusumah, Priyandi; Dilasari, Bonita; Kim, Hansu; Lee, Churl Kyoung

Magnesium, of which application is often limited by its poor corrosion resistance, is more vulnerable to corrosion with existence of metal impurities such as Fe. Therefore, for the refining and recycling of magnesium, high temperature electrolysis using molten salts has been frequently adopted. In this report, the purification of magnesium scrap by electrolysis at room temperature is investigated with non-aqueous electrolytes. An aprotic solvent of tetrahydrofuran (THF) was used as a solvent of the electrolyte. Magnesium scrap was used as anode materials and ethyl magnesium bromide (EtMgBr) was dissolved in THF for magnesium source. The purified magnesium can be uniformly electrodeposited on copper electrode under potentiostatic conditions. The deposits were confirmed by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analysis.

Anionic polymerization of p-(2,2'-diphenylethyl)styrene and applications to graft copolymers.

PubMed

Huang, Minglu; Han, Bingyong; Lu, Jianmin; Yang, Wantai; Fu, Zhifeng

2017-01-01

Well-controlled anionic polymerization of an initiator-functionalized monomer, p -(2,2'-diphenylethyl)styrene (DPES), was achieved for the first time. The polymerization was performed in a mixed solvent of cyclohexane and tetrahydrofuran (THF) at 40 °C with n -BuLi as initiator. When the volume ratio of cyclohexane to THF was 20, the anionic polymerization of DPES showed living polymerization characteristics, and well-defined block copolymer PDPES- b -PS was successfully synthesized. Furthermore, radical polymerization of methyl methacrylate in the presence of PDPES effectively afforded a graft copolymer composed of a polystyrene backbone and poly(methyl methacrylate) branches. The designation of analogous monomers and polymers was of great significance to synthesize a variety of sophisticated copolymer and functionalize polymer materials.

Adding tetrahydrofuran to dilute acid pretreatment provides new insights into substrate changes that greatly enhance biomass deconstruction by Clostridium thermocellum and fungal enzymes

DOE PAGES

Thomas, Vanessa A.; Donohoe, Bryon S.; Li, Mi; ...

2017-11-30

Consolidated bioprocessing (CBP) by anaerobes, such as Clostridium thermocellum, which combine enzyme production, hydrolysis, and fermentation are promising alternatives to historical economic challenges of using fungal enzymes for biological conversion of lignocellulosic biomass. However, limited research has integrated CBP with real pretreated biomass, and understanding how pretreatment impacts subsequent deconstruction by CBP vs. fungal enzymes can provide valuable insights into CBP and suggest other novel biomass deconstruction strategies. This study focused on determining the effect of pretreatment by dilute sulfuric acid alone (DA) and with tetrahydrofuran (THF) addition via co-solvent-enhanced lignocellulosic fractionation (CELF) on deconstruction of corn stover and Populusmore » with much different recalcitrance by C. thermocellum vs. fungal enzymes and changes in pretreated biomass related to these differences.« less

Adding tetrahydrofuran to dilute acid pretreatment provides new insights into substrate changes that greatly enhance biomass deconstruction by Clostridium thermocellum and fungal enzymes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thomas, Vanessa A.; Donohoe, Bryon S.; Li, Mi

Consolidated bioprocessing (CBP) by anaerobes, such as Clostridium thermocellum, which combine enzyme production, hydrolysis, and fermentation are promising alternatives to historical economic challenges of using fungal enzymes for biological conversion of lignocellulosic biomass. However, limited research has integrated CBP with real pretreated biomass, and understanding how pretreatment impacts subsequent deconstruction by CBP vs. fungal enzymes can provide valuable insights into CBP and suggest other novel biomass deconstruction strategies. This study focused on determining the effect of pretreatment by dilute sulfuric acid alone (DA) and with tetrahydrofuran (THF) addition via co-solvent-enhanced lignocellulosic fractionation (CELF) on deconstruction of corn stover and Populusmore » with much different recalcitrance by C. thermocellum vs. fungal enzymes and changes in pretreated biomass related to these differences.« less

Absolute cross sections for electronic excitation of condensed tetrahydrofuran (THF) by 11-16 eV electrons.

PubMed

Lemelin, V; Bass, A D; Cloutier, P; Sanche, L

2016-11-07

Absolute cross section (CS) data on the interaction of low energy electrons with DNA and its molecular constituents are required as input parameters in Monte-Carlo type simulations, for several radiobiological applications. Previously [V. Lemelin et al., J. Chem. Phys. 144, 074701 (2016)], we measured absolute vibrational CSs for low-energy electron scattering from condensed tetrahydrofuran, a convenient surrogate for the deoxyribose. Here we report absolute electronic CSs for energy losses of between 6 and 11.5 eV, by electrons with energies between 11 and 16 eV. The variation of these CSs with incident electron energy shows no evidence of transient anion states, consistent with theoretical and other experimental results, indicating that initial electron capture leading to DNA strand breaks occurs primarily on DNA bases or the phosphate group.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chunshan Song; Hatcher, P.G.; Saini, A.K.

It has been indicated by DOE COLIRN panel that low-temperature catalytic pretreatment is a promising approach to the development of an improved liquefaction process. This work is a fundamental study on effects of pretreatments on coal structure and reactivity in liquefaction. The main objectives of this project are to study the coal structural changes induced by low-temperature catalytic and thermal pretreatments by using spectroscopic techniques; and to clarify the pretreatment-induced changes in reactivity or convertibility of coals. As the second volume of the final report, here we summarize our work on spectroscopic characterization of four raw coals including two subbituminousmore » coals and two bituminous coals, tetrahydrofuran (THF)-extracted but unreacted coals, the coals (THF-insoluble parts) that have been thermally pretreated. in the absence of any solvents and in the presence of either a hydrogen-donor solvent or a non-donor solvent, and the coals (THF-insoluble parts) that have been catalytically pretreated in the presence of a dispersed Mo sulfide catalyst in the absence of any solvents and in the presence of either a hydrogen-donor solvent or a non-donor solvent.« less

Fabrication of band gap engineered nanostructured tri-metallic (Mn-Co-Ti) oxide thin films

NASA Astrophysics Data System (ADS)

Mansoor, Muhammad Adil; Yusof, Farazila Binti; Nay-Ming, Huang

2018-04-01

In continuation of our previous studies on photoelectrochemical (PEC) properties of titanium based composite oxide thin films, an effort is made to develop thin films of 1:1:2 manganese-cobalt-titanium oxide composite, Mn2O3-Co2O3-4TiO2 (MCT), using Co(OAc)2 and a bimetallic manganese-titanium complex, [Mn2Ti4(TFA)8(THF)6(OH)4(O)2].0.4THF (1), where OAc = acetato, TFA = trifluoroacetato and THF = tetrahydrofuran, via aerosol-assisted chemical vapour deposition (AACVD) technique. The X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and energy dispersive X-ray (EDX) spectroscopic analyses confirmed formation of thin film of Mn2O3-Co2O3-4TiO2 composite material with uniformly distributed agglomerated particles. The average size of 39.5 nm, of the particles embedded inside agglomerates, was estimated by Scherer's equation. Further, UV-Vis spectroscopy was used to estimate the band gap of 2.62 eV for MCT composite thin film.

Venezenin: a new bioactive Annonaceous acetogenin from the bark of Xylopia aromatica.

PubMed

Colman-Saizarbitoria, T; Gu, Z M; Zhao, G X; Zeng, L; Kozlowski, J F; McLaughlin, J L

1995-04-01

Asimicin and a new cytotoxic Annonaceous acetogenin, venezenin [1], were isolated from the bark of Xylopia aromatica by bioactivity-directed fractionation using lethality to brine shrimp. Compound 1 represents an unusual type of C37 Annonaceous acetogenin, lacking either tetrahydrofuran (THF) or epoxide rings and possessing a double bond located two methylenes away from a vicinal diol in the hydrocarbon chain. The structure of 1 was elucidated by 1H- and 13C-nmr, COSY, single-relayed COSY, and by HMBC techniques, and derivatization. Annomontacin 10-one [6] and 18/21-cis-annomontacin-10-one [7], two semi-synthetic mono-THF acetogenins were prepared from 1. These acetogenins showed cytotoxicity, comparable or superior to adriamycin, against three human solid tumor cell lines. Reduction of the 10-keto of 1 to the racemic OH-10 derivative enhanced the bioactivity, as did the conversion of 1 to 6 and 7. Venezenin [1], like other Annonaceous acetogenins, showed inhibition of oxygen uptake by rat liver mitochondria and demonstrated that the THF ring may not be essential to this mode of action.

Electrospun cross linked rosin fibers

NASA Astrophysics Data System (ADS)

Baek, Woo-il; Nirmala, R.; Barakat, Nasser A. M.; El-Newehy, Mohamed H.; Al-Deyab, Salem S.; Kim, Hak Yong

2011-12-01

In this study, we describe the first reported preparation of rosin in fiber form through use of an electrospinning technique utilizing various solvent systems. The polymer concentration of the formed fiber was studied by using various solvents such as chloroform, ethanol, N-N dimethylformamide (DMF), tetrahydrofuran (THF), acetone, and methylene chloride (MC). An electrospray of the solution resulted in the beaded form of the rosin. By varying the polymer concentration with MC, we were then able to obtain uniform fibers. However, the fibers exhibited large diameter. We believe that it is possible to reduce the diameter of the rosin fibers through appropriate selection of electrospinning parameters. In addition, the morphological transitions from beads, to beaded fiber, to fiber were studied at different polymer concentrations. We propose a possible physical cross linking mechanism for the formation of rosin fibers during the electrospinning process. Our results demonstrate the feasibility of producing fiber nanostructures of rosin by using an electrospinning technique.

Multiwavelength laser light transmission of hollow optical fiber from the visible to the mid-infrared.

PubMed

Shi, Yi Wei; Ito, Kentaro; Matsuura, Yuji; Miyagi, Mitsunobu

2005-11-01

We report on low-loss multiwavelength laser delivery of hollow optical fiber in a wide wavelength region, from the visible to the infrared. Improved methods of liquid-phase coating were used to fabricate the hollow fiber with inner films of a silver and a cyclic olefin polymer (COP) layer. The surface roughness of the silver layer was reduced dramatically by pretreatment on the inner glass surface with an SnCl2 solution. The COP layer roughness was also decreased by using an ambient atmosphere of tetrahydrofuran (THF) solvent during the COP layer formation. Owing to the smooth surfaces, hollow fiber with optimum COP film thickness for CO2 laser light simultaneously yields low losses for a Er:YAG laser and a red pilot beam. The power durability of CO2 and Er:YAG lasers, as well as the loss properties for the pilot beam, is demonstrated.

Tautomerism of monochalcogenosilanoic acids CH3Si(＝O)XH (X D S, Se, Te) in the gas phase and in the polar and aprotic solution: An ab initio computational investigation

NASA Astrophysics Data System (ADS)

Li, Qiang-Gen; Deng, Chao; Ren, Yi; Wong, Ning-Bew; Chu, San-Yan; Wang, Xin

Computational investigations by an ab initio molecular orbital method (HF and MP2) with the 6-311+G(d,p) and 6-311++G(2df, 2pd) basis sets on the tautomerism of three monochalcogenosilanoic acids CH3Si(＝O)XH (X D S, Se, and Te) in the gas phase and a polar and aprotic solution tetrahydrofuran (THF) was undertaken. Calculated results show that the silanol forms CH3Si(＝X)OH are much more stable than the silanone forms CH3Si(＝O)XH in the gas-phase, which is different from the monochalcogenocarboxylic acids, where the keto forms CH3C(＝O)XH are dominant. This situation may be attributed to the fact that the Si＝O and O＝H single bonds in the silanol forms are stronger than the Si＝X and X＝H single bonds in the silanone forms, respectively, even though the Si＝X (X D S, Se, and Te) double bonds are much weaker than the Si＝O double bondE These results indicate that the stability of the monochalcogenosilanoic acid tautomers is not determined by the double bond energies, contrary to the earlier explanation based on the incorrect assumption that the Si＝S double bond is stronger than the S＝O double bond for the tautomeric equilibrium of RSi(＝O)SH (R＝H, F, Cl, CH3, OH, NH2) to shift towards the thione forms [RSi(＝S)OH]. The binding with CH3OCH3 enhances the preference of the silanol form in the tautomeric equilibrium, and meanwhile significantly lowers the tautomeric barriers by more than 34 kJ/mol in THF solution.0

Survismeter, 2-IN-1 for Viscosity and Surface Tension Measurement, AN Excellent Invention for Industrial Proliferation of Surface Forces in Liquids

NASA Astrophysics Data System (ADS)

Singh, Man

Viscosities (η, N s m-2) and surface tensions (γ, N m-1) of methanol, ethanol, glycerol, ethyl acetate, n-hexane, diethyl ether, chloroform, benzene, carbon tetrachloride (CCl4), tetrahydrofuran (THF), dimethylformamide (DMF), dimethylsulfoxide (DMSO), acetonitrile, and formic acid have been measured with survismeter and compared with the data obtained by Ubbehold viscometer and stalagmometer, respectively. The ±1.1 × 10-5 N s m-2 and ±1.3 × 10-6 N m-1 deviations are noted in the data, in fact literature data of surface tension and viscosity are available to 2nd and 3rd place of decimals, respectively, while the survismeter measures them to 3rd and 4th place of decimals, respectively. The survismeter is 2-in-1 for viscosity and surface tension measurements together with high accuracies several times better than those of the separately measured data. Viscosities and surface tensions of aqueous DMSO, THF, DMF, and acetonitrile from 0.01 to 0.20 mol kg-1 and mannitol from 0.005 to 0.02 mol kg-1 have been measured with survismeter with ±1.2 × 10-5 N s m-2 and ±1.3 × 10-6 N m-1 deviations, respectively. The data are used for friccohesity and dipole moment determination, the lower viscosities, surface tension, and friccohesity values are noted for mannitol as compared to DMSO, THF, DMF, and acetonitrile solutions. The weaker molecular interactions are noted for mannitol. As compared to viscometer and stalagmometer individually, it is inexpensive and minimizes 2/3rd of consumables, human efforts, and infrastructure with 10 times better accuracies.

Identification of critical process variables affecting particle size following precipitation using a supercritical fluid.

PubMed

Sacha, Gregory A; Schmitt, William J; Nail, Steven L

2006-01-01

The critical processing parameters affecting average particle size, particle size distribution, yield, and level of residual carrier solvent using the supercritical anti-solvent method (SAS) were identified. Carbon dioxide was used as the supercritical fluid. Methylprednisolone acetate was used as the model solute in tetrahydrofuran. Parameters examined included pressure of the supercritical fluid, agitation rate, feed solution flow rate, impeller diameter, and nozzle design. Pressure was identified as the most important process parameter affecting average particle size, either through the effect of pressure on dispersion of the feed solution into the precipitation vessel or through the effect of pressure on solubility of drug in the CO2/organic solvent mixture. Agitation rate, impeller diameter, feed solution flow rate, and nozzle design had significant effects on particle size, which suggests that dispersion of the feed solution is important. Crimped HPLC tubing was the most effective method of introducing feed solution into the precipitation vessel, largely because it resulted in the least amount of clogging during the precipitation. Yields of 82% or greater were consistently produced and were not affected by the processing variables. Similarly, the level of residual solvent was independent of the processing variables and was present at 0.0002% wt/wt THF or less.

Ultrafast spectroscopic investigation of a fullerene poly(3-hexylthiophene) dyad

NASA Astrophysics Data System (ADS)

Banerji, Natalie; Seifter, Jason; Wang, Mingfeng; Vauthey, Eric; Wudl, Fred; Heeger, Alan J.

2011-08-01

We present the femtosecond spectroscopic investigation of a covalently linked dyad, PCB-P3HT, formed by a segment of the conjugated polymer P3HT (regioregular poly(3-hexylthiophene)) that is end capped with the fullerene derivative PCB ([6,6]-phenyl-C61-butyric acid ester), adapted from PCBM. The fluorescence of the P3HT segment in tetrahydrofuran (THF) solution is reduced by 64% in the dyad compared to a control compound without attached fullerene (P3HT-OH). Fluorescence upconversion measurements reveal that the partial fluorescence quenching of PCB-P3HT in THF is multiphasic and occurs on an average time scale of 100 ps, in parallel to excited-state relaxation processes. Judging from ultrafast transient absorption experiments, the origin of the quenching is excitation energy transfer from the P3HT donor to the PCB acceptor. Due to the much higher solubility of P3HT compared to PCB in THF, the PCB-P3HT dyad molecules self-assemble into micelles. When pure C60 is added to the solution, it is incorporated into the fullerene-rich center of the micelles. This dramatically increases the solubility of C60 but does not lead to significant additional quenching of the P3HT fluorescence by the C60 contained in the micelles. In PCB-P3HT thin films drop-cast from THF, the micelle structure is conserved. In contrast to solution, quantitative and ultrafast (<150 fs) charge separation occurs in the solid-state films and leads to the formation of long-lived mobile charge carriers with characteristic transient absorption signatures similar to those that have been observed in P3HT:PCBM bulk heterojunction blends. While π-stacking interactions between neighboring P3HT chains are weak in the micelles, they are strong in thin films drop-cast from ortho-dichlorobenzene. Here, PCB-P3HT self-assembles into a network of long fibers, clearly seen in atomic force microscopy images. Ultrafast charge separation occurs also for the fibrous morphology, but the transient absorption experiments show fast loss of part of the charge carriers due to intensity-induced recombination and annihilation processes and monomolecular interfacial trap-mediated or geminate recombination. The yield of the long-lived charge carriers in the highly organized fibers is however comparable to that obtained with annealed P3HT:PCBM blends. PCB-P3HT can therefore be considered as an active material in organic photovoltaic devices.

Controlling morphology and chain aggregation in semiconducting conjugated polymers: the role of solvent on optical gain in MEH-PPV.

PubMed

Lampert, Zach E; Reynolds, C Lewis; Papanikolas, John M; Aboelfotoh, M Osama

2012-10-25

We report the results of a detailed investigation that addresses the influence of polymer morphology and chain aggregation, as controlled by the chemical nature of the solvent, on the optical gain properties of the conjugated polymer poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV). Using the variable stripe length technique in the picosecond regime, we have extensively studied the optical gain performance of asymmetric planar waveguides formed with thin MEH-PPV films spin-cast from concentrated chlorobenzene (CB) and tetrahydrofuran (THF) solutions onto thermally oxidized silicon substrates. CB and THF solvents were chosen based on their known ability to promote and effectively limit aggregate formation, respectively. Very large net gain coefficients are demonstrated, reaching values of 330 and 365 cm(-1), respectively, when optically pumping the waveguides with a maximum energy density of 85 μJ/cm(2). Our results clearly demonstrate that polymer morphology, and hence, the chain conformation dependence of the degree of aggregation in the films as controlled by the solvent, has minimal impact on the net gain. Moreover, the waveguides exhibit low loss coefficients of 10-20 cm(-1) at the ASE wavelength. These results question the importance of polymer morphology and aggregate formation in polymer-based optical devices operating at high excitation densities in the stimulated emission regime as would be characteristic of lasers and optical amplifiers.

Viscometric investigation of compatibilization of the poly(vinyl chloride)/poly(ethylene-co-vinyl acetate) blends by terpolymer of maleic anhydride styrene vinyl acetate

NASA Astrophysics Data System (ADS)

İmren, Dilek; Boztuğ, Ali; Yılmaz, Ersen; Zengin, H. Bayram

2008-11-01

In this study, a blend of poly(vinyl chloride) (PVC)/ethylene-co-vinyl acetate (EVA) was compatibilized by terpolymer of maleic anhydride-styrene-vinyl acetate (MAStVA) used as a compatibilizer. It was prepared the blends of 50/50 PVC/EVA containing 2-10% of the terpolymer. The compatibility experiences of these blends were investigated by using viscometric method in the range of concentrations (0.5-2.0 g dL -1) where tetrahydrofuran (THF) is the solvent. The interaction parameter (Δ b) was used to study the miscibility and compatibility of polymer blend in solution, obtained from the modified Krigbaum and Wall theory. Turbidity and FTIR measurements were also used to investigate the miscibility of this pair of polymers. The values of the relative viscosities of the each polymer solution and their blends were measured by a Cannon-Fenske type viscometer. In consequence of the study, it was observed that a considerable improvement was achieved in the miscibility of PVC/EVA blends by adding among 5 and 10 wt% of compatibilizer.

Development and Characterization of Novel Polyurethane Films Impregnated with Tolfenamic Acid for Therapeutic Applications

PubMed Central

Sheraz, Muhammad Ali; Rehman, Ihtesham ur

2013-01-01

The present study deals with the preparation of polyurethane (PU) films impregnated with a nonsteroidal anti-inflammatory drug, tolfenamic acid (TA). Solvent evaporation technique has been employed for the preparation of TA-PU films in two different ratios of 1 : 2 and 1 : 5 in Tetrahydrofuran (THF) or THF-ethanol mixtures. The prepared films were characterized using X-Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and release studies. The results indicate transformation of crystalline TA to its amorphous form. The degree of crystallinity changes both by increasing the polymer concentration and solvent used for the film preparations. The release profiles of TA were also found to be affected, showing a decrease from approximately 50% to 25% from 1 : 2 to 1 : 5 ratios, respectively. PMID:24073394

Acidic resin-catalysed conversion of fructose into furan derivatives in low boiling point solvents.

PubMed

Zhu, Hong; Cao, Quan; Li, Chunhu; Mu, Xindong

2011-09-27

Conversion of fructose into furan derivatives 5-hydroxymethylfurfural (HMF) and 5-methoxymethylfurfural (MMF) is performed in tetrahydrofuran (THF) and methanol-organic solvent systems, catalysed by an acidic resin Amberlyst-15. The melted fructose can be converted into HMF on the surface of the solid resin catalyst in the presence of THF as an extracting phase, which is a good solvent for HMF and other by-products. The solid resin catalyst can be reused eleven times without losing its catalytic ability, with an average HMF yield of approximately 50%. Upon the addition of methanol, the generated HMF can further react with methanol to form MMF, and the total yield of HMF and MMF could be promoted to 65%. GC-MS analysis confirms the formation of a small amount of methyl levulinate in methanolorganic solvent system. Copyright © 2011 Elsevier Ltd. All rights reserved.

Field and laboratory determination of a poly(vinyl/vinylidene chloride) additive in brick mortar.

PubMed

Law, S L; Newman, J H; Ptak, F L

1990-02-01

A polymerized vinyl/vinylidene chloride additive, used in brick mortar during the 60s and 70s, is detected at the building site by the field method, which employs a commercially available chloride test strip. The field test results can then be verified by the laboratory methods. In one method, total chlorine in the mortar is determined by an oxygen-bomb method and the additive chloride is determined by difference after water-soluble chlorides have been determined on a separate sample. In the second method, the polymerized additive is extracted directly from the mortar with tetrahydrofuran (THF). The difference in weight before and after extraction of the additive gives the weight of additive in the mortar. Evaporation of the THF from the extract leaves a thin film of the polymer, which gives an infrared "fingerprint" spectrum characteristic of the additive polymer.

Volumetric Properties of the Ionic Liquid, 1-Butyl-3-methylimidazolium Tetrafluoroborate, in Organic Solvents at T = 298.15K

NASA Astrophysics Data System (ADS)

Shekaari, Hemayat; Zafarani-Moattar, Mohammed Taghi

2008-04-01

Apparent molar volumes, V_φ , and compressibilities, kappa _φ , of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIm][BF4]) have been determined from precise density and speed-of-sound measurements in organic solvents, methanol (MeOH), acetonitrile (MeCN), tetrahydrofuran (THF), N, N-dimethylacetamide (DMA), and dimethylsulfoxide (DMSO) in the dilute region of the ionic liquid. Corresponding values at infinite dilution are estimated by the Redlich-Mayer and Pitzer equations. The results have been interpreted by the interaction of the [BMIm][BF4] in the organic solvents. Results show that the structure and dielectric constant of the organic solvents play an important role for the ion-solvent interactions in these mixtures. It was found that the strength of interaction between [BMIm][BF4] with the studied organic solvents has the order DMSO > DMA > MeOH > MeCN > THF.

Synthesis and characterization of biopolymer based mixed matrix membranes for pervaporative dehydration.

PubMed

Das, Paramita; Ray, Samit Kumar

2014-03-15

Several blend membranes were prepared from different weight ratios of polyvinyl alcohol (PVA) and hydroxyethyl cellulose (HEC) and these unfilled membranes were crosslinked with maleic acid. In a similar way mixed matrix blend membranes were also prepared by varying weight ratio of PVA and HEC with micro and nano bentonite filler in each of these blends. These membranes were used for pervaporative dehydration of 89 wt% tetrahydrofuran (THF). Three membranes designated as UF (unfilled), MF2 (containing 2 wt% micro filler) and NF2 (containing 2 wt% nano filler) showing the best results for flux and selectivity were identified. These membranes were characterized by FTIR, UV, XRD and DTA-TG and used for separation of 80-99 wt% THF from water by pervaporation. The NF2 membrane was found to show the best results in terms of flux and separation factor. Copyright © 2013 Elsevier Ltd. All rights reserved.

Effect of solvents on the optical and morphological properties of MEH-PPV: PC70BM nanocomposites

NASA Astrophysics Data System (ADS)

Mhamdi, Asya; Ltaief, Adnen; Bouazizi, Abdelaziz

2017-10-01

Focused on phase separation and morphologies of polymer poly [2-methoxy-5-(2'-ethyl) hexoxy-1,4-phenylenevinylene] (MEH-PPV) and [6,6]-phenylC71-butyric acid methyl ester (PC70BM) nanocomposite, we studied the effect of organic solvent on the optical and morphological properties of these blends. The MEH-PPV: PC70BM films was prepared using three different solvent; Tetrahydrofuran (THF), Chlorobenzene (CB) and Toluene. On the other hand, the effect of 1-8 octanedithiol additives is also studied with the same different solvents. These blend films are characterized by photoluminescence spectroscopy, UV-Vis absorption spectroscopy and atomic force microscopy (AFM). The photoluminescence results show that the THF solvent provide the better charge transfer. In a morphological view point, the phase segregation was clearly appearing by the addition of the additive on the surface of the blend films.

Exciplex formation in bimolecular photoinduced electron-transfer investigated by ultrafast time-resolved infrared spectroscopy.

PubMed

Koch, Marius; Letrun, Romain; Vauthey, Eric

2014-03-12

The dynamics of bimolecular photoinduced electron-transfer reactions has been investigated with three donor/acceptor (D/A) pairs in tetrahydrofuran (THF) and acetonitrile (ACN) using a combination of ultrafast spectroscopic techniques, including time-resolved infrared absorption. For the D/A pairs with the highest driving force of electron transfer, all transient spectroscopic features can be unambiguously assigned to the excited reactant and the ionic products. For the pair with the lowest driving force, three additional transient infrared bands, more intense in THF than in ACN, with a time dependence that differs from those of the other bands are observed. From their frequency and solvent dependence, these bands can be assigned to an exciplex. Moreover, polarization-resolved measurements point to a relatively well-defined mutual orientation of the constituents and to a slower reorientational time compared to those of the individual reactants. Thanks to the minimal overlap of the infrared signature of all transient species in THF, a detailed reaction scheme including the relevant kinetic and thermodynamic parameters could be deduced for this pair. This analysis reveals that the formation and recombination of the ion pair occur almost exclusively via the exciplex.

Polar aprotic solvent-water mixture as the medium for catalytic production of hydroxymethylfurfural (HMF) from bread waste.

PubMed

Yu, Iris K M; Tsang, Daniel C W; Chen, Season S; Wang, Lei; Hunt, Andrew J; Sherwood, James; De Oliveira Vigier, Karine; Jérôme, François; Ok, Yong Sik; Poon, Chi Sun

2017-12-01

Valorisation of bread waste for hydroxymethylfurfural (HMF) synthesis was examined in dimethyl sulfoxide (DMSO)-, tetrahydrofuran (THF)-, acetonitrile (ACN)-, and acetone-water (1:1v/v), under heating at 140°C with SnCl 4 as the catalyst. The overall rate of the process was the fastest in ACN/H 2 O and acetone/H 2 O, followed by DMSO/H 2 O and THF/H 2 O due to the rate-limiting glucose isomerisation. However, the formation of levulinic acid (via rehydration) and humins (via polymerisation) was more significant in ACN/H 2 O and acetone/H 2 O. The constant HMF maxima (26-27mol%) in ACN/H 2 O, acetone/H 2 O, and DMSO/H 2 O indicated that the rates of desirable reactions (starch hydrolysis, glucose isomerisation, and fructose dehydration) relative to undesirable pathways (HMF rehydration and polymerisation) were comparable among these mediums. They also demonstrated higher selectivity towards HMF production over the side reactions than THF/H 2 O. This study differentiated the effects of polar aprotic solvent-water mediums on simultaneous pathways during biomass conversion. Copyright © 2017 Elsevier Ltd. All rights reserved.

Photochemical dissolution of Turkish lignites in tetralin at different irradiation power and reaction times

DOE Office of Scientific and Technical Information (OSTI.GOV)

F. Karacan; T. Torul

2007-08-15

The effect of the power of ultraviolet (UV) irradiation on the tetrahydrofuran (THF) solubles yield (the total soluble product) and the soluble product distribution of the dissolution of Turkish lignites (Beypazari and Tuncbilek lignite) in tetralin at ambient temperatures has been investigated. The lignite samples were exposed to UV irradiation for 1, 2, 3, 5, and 10 days in the power of irradiation ranging from 0 to 180 W at 60 W intervals. The yields of THF solubles and oils increased with increasing irradiation power and time. The optimum irradiation power depends on the irradiation time to obtain the highestmore » degradation products. However, the yield of degradation products depends also on the lignite type. The largest fraction obtained from lignites by photochemical energy is oil. While the yields of THF solubles and oils sharply increased with irradiation power at longer reaction times, the yields of asphaltenes (AS) slightly decreased. Increasing oil yields is relatively larger when AS yields tend to decrease. These trends of AS and oil yields are ascribable to conversion of AS to oils at higher power. Small changes were observed in the PAS yields under all conditions. 27 refs., 5 figs., 1 tab.« less

Prediction of induction time for methane hydrate formation in the presence or absence of THF in flow loop system by Natarajan model

NASA Astrophysics Data System (ADS)

Talaghat, Mohammad Reza; Jokar, Seyyed Mohammad

2018-03-01

The induction time is a time interval to detect the initial hydrate formation, which is counted from the moment when the stirrer is turned on until the first detection of hydrate formation. The main objective of the present work is to predict and measure the induction time of methane hydrate formation in the presence or absence of tetrahydrofuran (THF) as promoter in the flow loop system. A laboratory flow mini-loop apparatus was set up to measure the induction time of methane hydrate formation. The induction time is predicted using developed Kashchiev and Firoozabadi model and modified model of Natarajan for a flow loop system. Furthermore, the effects of volumetric flow rate of the fluid on the induction time were investigated. The results of the models were compared with experimental data. They show that the induction time of hydrate formation in the presence of THF is very short at high pressure and high volumetric flow rate of the fluid. It decreases with increasing pressure and liquid volumetric flow rate. It is also shown that the modified Natarajan model is more accurate than the Kashchiev and Firoozabadi ones in prediction of the induction time.

Structural anomaly and dynamic heterogeneity in cycloether/water binary mixtures: Signatures from composition dependent dynamic fluorescence measurements and computer simulations

NASA Astrophysics Data System (ADS)

Indra, Sandipa; Guchhait, Biswajit; Biswas, Ranjit

2016-03-01

We have performed steady state UV-visible absorption and time-resolved fluorescence measurements and computer simulations to explore the cosolvent mole fraction induced changes in structural and dynamical properties of water/dioxane (Diox) and water/tetrahydrofuran (THF) binary mixtures. Diox is a quadrupolar solvent whereas THF is a dipolar one although both are cyclic molecules and represent cycloethers. The focus here is on whether these cycloethers can induce stiffening and transition of water H-bond network structure and, if they do, whether such structural modification differentiates the chemical nature (dipolar or quadrupolar) of the cosolvent molecules. Composition dependent measured fluorescence lifetimes and rotation times of a dissolved dipolar solute (Coumarin 153, C153) suggest cycloether mole-fraction (XTHF/Diox) induced structural transition for both of these aqueous binary mixtures in the 0.1 ≤ XTHF/Diox ≤ 0.2 regime with no specific dependence on the chemical nature. Interestingly, absorption measurements reveal stiffening of water H-bond structure in the presence of both the cycloethers at a nearly equal mole-fraction, XTHF/Diox ˜ 0.05. Measurements near the critical solution temperature or concentration indicate no role for the solution criticality on the anomalous structural changes. Evidences for cycloether aggregation at very dilute concentrations have been found. Simulated radial distribution functions reflect abrupt changes in respective peak heights at those mixture compositions around which fluorescence measurements revealed structural transition. Simulated water coordination numbers (for a dissolved C153) and number of H-bonds also exhibit minima around these cosolvent concentrations. In addition, several dynamic heterogeneity parameters have been simulated for both the mixtures to explore the effects of structural transition and chemical nature of cosolvent on heterogeneous dynamics of these systems. Simulated four-point dynamic susceptibility suggests formation of clusters inducing local heterogeneity in the solution structure.

Carboxylic and dicarboxylic acids extracted from crushed magnesium oxide single crystals

NASA Technical Reports Server (NTRS)

Freund, F.; Gupta, A. D.; Kumar, D.

1999-01-01

Carboxylic and dicarboxylic acids (glycolic, oxalic, malonic and succinic) have been extracted with tetrahydrofuran (THF) and H2O from large synthetic MgO crystals, crushed to a medium fine powder. The extracts were characterized by infrared spectroscopy and 1H-NMR. The THF extracts were derivatized with tert-butyldimethylsilyl (t-BDMS) for GC-MS analysis. A single crystal separated from the extract was used for an x-ray structure analysis, giving the monoclinic unit cell, space group P21/c with ao = 5.543 A, bo = 8.845 A, co = 5.086 A, and beta = 91.9 degrees, consistent with beta-succinic acid, HOOC(CH2)COOH. The amount of extracted acids is estimated to be of the order of 0.1 to 0.5 mg g-1 MgO. The MgO crystals from which these organic acids were extracted grew from the 2860 degrees C hot melt, saturated with CO/CO2 and H2O, thereby incorporating small amounts of the gaseous components to form a solid solution (ss) with MgO. Upon cooling, the ss becomes supersaturated, causing solute carbon and other solute species to segregate not only to the surface but also internally, to dislocations and subgrain boundaries. The organic acids extracted from the MgO crystals after crushing appear to derive from these segregated solutes that formed C-C, C-H and C-O bonds along dislocations and other defects in the MgO structure, leading to entities that can generically be described as (HxCyOz)n-. The processes underlying the formation of these precursors are fundamental in nature and expected to be operational in any minerals, preferentially those with dense structures, that crystallized in H2O-CO2-laden environments. This opens the possibility that common magmatic and metamorphic rocks when weathering at the surface of a tectonically active planet like Earth may be an important source of abiogenically formed complex organic compounds.

UV-LIGA Microfabrication of 220 GHz Sheet Beam Amplifier Gratings with SU-8 Photoresists

DTIC Science & Technology

2010-01-01

4 4 4a Diethyl ether 3d, RT 0 Tetrahydrofuran (THF) 3d, RT 1 2 4 3 3 Py + pyridinium (Pym) HBr crystals 2d, RT 1 2 3 2 Py + Pym HCl crystals 2d, RT 1...1 1 Acetone + Pym HBr crystals 2d, RT 1 0 Pym dichromate in Py 2d, RT 1 2 1 Pym chlorochromate in Py 2d, RT 4 1 2 1a Propylamine (PA) 2d, RT 1 2 3 2

TES buffer-induced phase separation of aqueous solutions of several water-miscible organic solvents at 298.15 K: phase diagrams and molecular dynamic simulations.

PubMed

Taha, Mohamed; Lee, Ming-Jer

2013-06-28

Water and the organic solvents tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, 1-propanol, 2-propanol, tert-butanol, acetonitrile, or acetone are completely miscible in all proportions at room temperature. Here, we present new buffering-out phase separation systems that the above mentioned organic aqueous solutions can be induced to form two liquid phases in the presence of a biological buffer 2-[[1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl]amino]ethanesulfonic acid (TES). The lower liquid phase is rich in water and buffer, and the upper phase is organic rich. This observation has both practical and mechanistic interests. The phase diagrams of these systems were constructed by experimental measurements at ambient conditions. Molecular dynamic (MD) simulations were performed for TES + water + THF system to understand the interactions between TES, water, and organic solvent at molecular level. Several composition-sets for this system, beyond and inside the liquid-liquid phase-splitting region, have been simulated. Interestingly, the MD simulation for compositions inside the phase separation region showed that THF molecules are forced out from the water network to start forming a new liquid phase. The hydrogen-bonds, hydrogen-bonds lifetimes, hydrogen-bond energies, radial distribution functions, coordination numbers, the electrostatic interactions, and the van der Waals interactions between the different pairs have been calculated. Additionally, MD simulations for TES + water + tert-butanol∕acetonitrile∕acetone phase separation systems were simulated. The results from MD simulations provide an explanation for the buffering-out phenomena observed in [TES + water + organic solvent] systems by a mechanism controlled by the competitive interactions of the buffer and the organic solvent with water. The molecular mechanism reported here is helpful for designing new benign separation materials.

Treatability Study of Pentaborane(9)

NASA Technical Reports Server (NTRS)

McDonald, Joseph K.; Wright, Jeffery S.; Gaines, Donald F.

2000-01-01

Procedures for the safe destruction of liquid pentaborane(9), B5H9, by solvolysis were investigated. The objective of the study was to establish the optimum conditions for a pilot plant operation that would use water, or alcohol, or water-alcohol mixtures as the solvolysis reagent Small amounts of B5H9 sprayed from a syringe will not necessarily enflame, nor will a small pool on a spot plate. Therefore, a procedure was developed to reproducibly demonstrate the flammability of B5H9 In these tests every sample of neat B5H9 ignited and burned with a very sooty flame till the sample was consumed. The spontaneous self-ignition of B5H9 was quenched by the addition of small concentrations of the ethers THF (tetrahydrofuran) or DME (1,2-dimethoxy ethane). It was found that 10% (volume) of either provided total quenching with a large margin of safety. When these stabilized solutions were exposed to air, they decomposed and evaporated leaving a residue that was identified by NMR analysis as boric acid. Most of the laboratory solvolysis experiments used the 90% B5H9, 10% THF solution. This mixture was safer to handle and its solvolysis reactivity was virtually identical to that of 100% B5H9. Reaction rates were analyzed by measurement of hydrogen evolved during the solvolysis reactions. In terms of the minimum overall complete reaction time, the data indicate that 50150 alcohol/water is the optimum solvolysis reagent. This reaction produced a mixture of boric acid, B(OH)3, and triethoxyborane, B(OEt)3 [Et = C2H5], and mixed exchange derivatives thereof.

Treatability Study of Pentaborane(9)

NASA Technical Reports Server (NTRS)

McDonald, Joseph K.; Wright, Jeffery S.; Gaines, Donald F.

2000-01-01

Procedures for the safe destruction of liquid pentaborane(9), B5H9, by solvolysis were investigated. The objective of the study was to establish the optimum conditions for a pilot plant operation that would use water, or alcohol, or water-alcohol mixtures as the solvolysis reagent. Small amounts of B5H9 sprayed from a syringe will not necessarily enflame, nor will a small pool on a spot plate. Therefore, a procedure was developed to reproducibly demonstrate the flammability of B5H9. In these tests every sample of neat B5H9 ignited and burned with a very sooty flame till the sample was consumed. The spontaneous self-ignition of B5H9 was quenched by the addition of small concentrations of ethers THF (tetrahydrofuran) or DME (1,2-dimethoxy ethane). It was found that ten percent (volume) of either provided total quenching with a large margin of safety. When these stabilized solutions were exposed to air, they decomposed and evaporated leaving a residue that was identified by nuclear magnetic resonance (NMR) analysis as boric acid. Most of the laboratory solvolysis experiments used the 90 percent B5H9, 10 percent THF solution. This mixture was safer to handle and its solvolysis reactivity was virtually identical to that of 100 percent B5H9. Reaction rates were analyzed by measurement of hydrogen evolved during the solvolysis reactions. In terms of the minimum overall complete reaction time, the data indicate that 50/50 alcohol/water is the optimum solvolysis reagent. This reaction produced a mixture of boric acid, B(OH)3, and triethoxyborane, B(OEt)3[Et = C2H5], and mixed exchange derivatives thereof.

Preparation and physical characterization of pure beta-carotene.

PubMed

Laughlin, Robert G; Bunke, Gregory M; Eads, Charles D; Laidig, William D; Shelley, John C

2002-05-01

Pure all-trans beta-carotene has been prepared on the 10's of grams scale by isothermal Fractional Dissolution (FD) of commercial laboratory samples in tetrahydrofuran (THF). beta-Carotene purified in this way is black, with a faint brownish tinge. The electronic spectra of black samples extend into the near infrared, with end-absorption past 750 nm. Black samples react directly with dioxygen under mild conditions to yield the familiar orange or red powders. Pure beta-carotene rigorously obeys Beer's Law in octane over the entire UV-Vis spectral range, while commercial laboratory samples and recrystallized samples do not. NMR self-diffusion coefficient data demonstrate that beta-carotene exists as simple molecular solutions in octane and toluene. The anomalously high crystallinity of beta-carotene can be attributed (from analysis using molecular mechanics) to the facts that: (1) the number of theoretically possible conformers of beta-carotene is extremely small, and (2) only a small fraction of these (ca. 12%, or 127) may actually exist in fluid phases.

Low-coordinate rare-earth complexes of the asymmetric 2,4-di-tert-butylphenolate ligand prepared by redox transmetallation/protolysis reactions, and their reactivity towards ring-opening polymerisation.

PubMed

Clark, Lawrence; Deacon, Glen B; Forsyth, Craig M; Junk, Peter C; Mountford, Philip; Townley, Josh P

2010-08-07

New trivalent lanthanoid aryloxide complexes have been prepared by redox transmetallation/protolysis (rtp) reactions using 2,4-di-tert-butylphenol (dbpH). Mononuclear octahedral complexes from tetrahydrofuran (thf) were of the type [Ln(dbp)(3)(thf)(3)] (Ln = La (1), Pr (2), Nd (3), Gd (4), Er (5)). The lanthanoid contraction results in the rather subtle change in stereochemistry from meridional (La, Pr, Nd, Gd) to facial (Er). An analogous reaction with neodymium in dimethoxyethane (dme), resulted in the isolation of the seven coordinate [Nd(dbp)(3)(dme)(2)] (6), and this is comparable with the thf complexes in terms of steric crowding. Dinuclear complexes of the type [Ln(2)(dbp)(6)(thf)(2)], (Ln = Nd (7), Er (8)) were obtained when 1 and 5 were recrystallised from toluene. These dimeric complexes contain two bridging and four terminal phenolates, as well as a single coordinated molecule of thf at each metal. A similar structural motif was observed for the products when the reaction was performed in diethyl ether, and in the absence of a solvent, yielding [Nd(2)(dbp)(6)(Et(2)O)(2)] (9) and [Nd(2)(dbp)(6)(dbpH)(2)] (10) respectively. Complexes 3 and 4 alone were efficient but poorly-controlled initiators for the ROP of rac-lactide, but with an excess of BnOH as a co-initiator they showed features consistent with immortal polymerisation. Use of BnNH(2) led to well-controlled, amine-initiated immortal ROP of rac-lactide, only the second report of this type of process for a group 3 or lanthanoid system.

Understanding the initial stages of reversible Mg deposition and stripping in inorganic nonaqueous electrolytes

DOE PAGES

Canepa, Pieremanuele; Gautam, Gopalakrishnan Sai; Malik, Rahul; ...

2015-04-08

Multivalent (MV) battery architectures based on pairing a Mg metal anode with a high-voltage (~3 V) intercalation cathode offer a realistic design pathway toward significantly surpassing the energy storage performance of traditional Li-ion-based batteries, but there are currently only few electrolyte systems that support reversible Mg deposition. Using both static first-principles calculations and ab initio molecular dynamics, we perform a comprehensive adsorption study of several salt and solvent species at the interface of Mg metal with an electrolyte of Mg 2+ and Cl–dissolved in liquid tetrahydrofuran (THF). Our findings not only provide a picture of the stable species at themore » interface but also explain how this system can support reversible Mg deposition, and as such, we provide insights in how to design other electrolytes for Mg plating and stripping. Furthermore, the active depositing species are identified to be (MgCl) + monomers coordinated by THF, which exhibit preferential adsorption on Mg compared to possible passivating species (such as THF solvent or neutral MgCl 2 complexes). We found that upon deposition, the energy to desolvate these adsorbed complexes and facilitate charge transfer is shown to be small (~61–46.2 kJ mol –1 to remove three THF from the strongest adsorbing complex), and the stable orientations of the adsorbed but desolvated (MgCl) + complexes appear to be favorable for charge transfer. Lastly, observations of Mg–Cl dissociation at the Mg surface at very low THF coordinations (0 and 1) suggest that deleterious Cl incorporation in the anode may occur upon plating. In the stripping process, this is beneficial by further facilitating the Mg removal reaction.« less

Understanding the initial stages of reversible Mg deposition and stripping in inorganic nonaqueous electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Canepa, Pieremanuele; Gautam, Gopalakrishnan Sai; Malik, Rahul

Multivalent (MV) battery architectures based on pairing a Mg metal anode with a high-voltage (~3 V) intercalation cathode offer a realistic design pathway toward significantly surpassing the energy storage performance of traditional Li-ion-based batteries, but there are currently only few electrolyte systems that support reversible Mg deposition. Using both static first-principles calculations and ab initio molecular dynamics, we perform a comprehensive adsorption study of several salt and solvent species at the interface of Mg metal with an electrolyte of Mg 2+ and Cl–dissolved in liquid tetrahydrofuran (THF). Our findings not only provide a picture of the stable species at themore » interface but also explain how this system can support reversible Mg deposition, and as such, we provide insights in how to design other electrolytes for Mg plating and stripping. Furthermore, the active depositing species are identified to be (MgCl) + monomers coordinated by THF, which exhibit preferential adsorption on Mg compared to possible passivating species (such as THF solvent or neutral MgCl 2 complexes). We found that upon deposition, the energy to desolvate these adsorbed complexes and facilitate charge transfer is shown to be small (~61–46.2 kJ mol –1 to remove three THF from the strongest adsorbing complex), and the stable orientations of the adsorbed but desolvated (MgCl) + complexes appear to be favorable for charge transfer. Lastly, observations of Mg–Cl dissociation at the Mg surface at very low THF coordinations (0 and 1) suggest that deleterious Cl incorporation in the anode may occur upon plating. In the stripping process, this is beneficial by further facilitating the Mg removal reaction.« less

Synthesis, spectroscopic characterization, and determination of the solution association energy of the dimer [Co{N(SiMe3)2}2]2: magnetic studies of low-coordinate Co(II) silylamides [Co{N(SiMe3)2}2L] (L = PMe3, pyridine, and THF) and related species that reveal evidence of very large zero-field splittings.

PubMed

Bryan, Aimee M; Long, Gary J; Grandjean, Fernande; Power, Philip P

2013-10-21

The synthesis, magnetic, and spectroscopic characteristics of the synthetically useful dimeric cobalt(II) silylamide complex [Co{N(SiMe3)2}2]2 (1) and several of its Lewis base complexes have been investigated. Variable-temperature nuclear magnetic resonance (NMR) spectroscopy of 1 showed that it exists in a monomer-dimer equilibrium in benzene solution and has an association energy (ΔGreacn) of -0.30(20) kcal mol(-1) at 300 K. Magnetic data for the polycrystalline, red-brown [Co{N(SiMe3)2}2]2 (1) showed that it displays strong antiferromagnetic exchange coupling, expressed as -2JexS1S2, between the two S = (3)/2 cobalt(II) centers with a Jex value of -215(5) cm(-1), which is consistent with its bridged dimeric structure in the solid state. The electronic spectrum of 1 in solution is reported for the first time, and it is shown that earlier reports of the melting point, synthesis, electronic spectrum, and magnetic studies of the monomer "Co{N(SiMe3)2}2" are consistent with those of the bright green-colored tetrahydrofuran (THF) complex [Co{N(SiMe3)2}2(THF)] (4). Treatment of 1 with various Lewis bases yielded monomeric three-coordinated species-[Co{N(SiMe3)2}2(PMe3)] (2), and [Co{N(SiMe3)2}2(THF)] (4), as well as the previously reported [Co{N(SiMe3)2}2(py)] (3)-and the four-coordinated species [Co{N(SiMe3)2}2(py)2] (5) in good yields. The paramagnetic complexes 2-4 were characterized by electronic and (1)H NMR spectroscopy, and by X-ray crystallography in the case of 2 and 4. Magnetic studies of 2-5 and of the known three-coordinated cobalt(II) species [Na(12-crown-4)2][Co{N(SiMe3)2}3] (6) showed that they have considerably larger χMT products and, hence, magnetic moments, than the spin-only values of 1.875 emu K mol(-1) and 3.87 μB, which is indicative of a significant zero-field splitting and g-tensor anisotropy resulting from the pseudo-trigonal crystal field. A fit of χMT for 2-6 yields a large g-tensor anisotropy, large negative D-values (between -62 cm(-1) and -82 cm(-1)), and E-values between ±10 cm(-1) and ±21 cm(-1).

Dye sensitized solar cell applications of CdTiO{sub 3}–TiO{sub 2} composite thin films deposited from single molecular complex

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ehsan, Muhammad Ali; Khaledi, Hamid; Pandikumar, Alagarsamy

2015-10-15

A heterobimetallic complex [Cd{sub 2}Ti{sub 4}(μ-O){sub 6}(TFA){sub 8}(THF){sub 6}]·1.5THF (1) (TFA=trifluoroacetato, THF=tetrahydrofuran) comprising of Cd:Ti (1:2) ratio was synthesized by a chemical reaction of cadmium (II) acetate with titanium (IV) isopropoxide and triflouroacetic acid in THF. The stoichiometry of (1) was recognized by single crystal X-ray diffraction, spectroscopic and elemental analyses. Thermal studies revealed that (1) neatly decomposes at 450 °C to furnish 1:1 ratio of cadmium titanate:titania composite oxides material. The thin films of CdTiO{sub 3}–TiO{sub 2} composite oxides were deposited at 550 °C on fluorine doped tin oxide coated conducting glass substrate in air ambient. The micro-structure, crystallinity,more » phase identification and chemical composition of microspherical architectured CdTiO{sub 3}–TiO{sub 2} composite thin film have been determined by scanning electron microscopy, X-ray diffraction, Raman spectroscopy and energy dispersive X-ray analysis. The scope of composite thin film having band gap of 3.1 eV was explored as photoanode for dye-sensitized solar cell application. - Graphical abstarct: Microspherical designed CdTiO{sub 3}–TiO{sub 2} composite oxides photoanode film has been fabricated from single source precursor [Cd{sub 2}Ti{sub 4}(μ-O){sub 6}(TFA){sub 8}(THF){sub 6}]·1.5THF via aerosol assisted chemical vapor deposition technique for dye sensitized solar cell application. - Highlights: • Synthesis and characterization of a heterobimetallic Cd–Ti complex. • Fabrication of CdTiO{sub 3}–TiO{sub 2} thin film photoelectrode. • Application as dye sensitized photoanode for solar application.« less

Influence of grafting solvents on the properties of polymer electrolyte membranes prepared by γ-ray preirradiation method

NASA Astrophysics Data System (ADS)

Kimura, Yosuke; Asano, Masaharu; Chen, Jinhua; Maekawa, Yasunari; Katakai, Ryoichi; Yoshida, Masaru

2008-07-01

The effect of grafting solvents, such as isopropanol (iPrOH), tetrachloroethane (TCE), tetrahydrofuran (THF), and toluene, on the preparation of poly(ethylene- co-tetrafluoroethylene)-graft-poly(styrene sulfonic acid) (ETFE-g-PSSA) electrolyte membranes by the γ-ray preirradiation grafting method was investigated. It was found that the iPrOH can drastically accelerate the grafting, resulting in a higher degree of grafting. However, for an appropriate degree of grafting of about 50%, the sulfonic acid groups in the ETFE-g-PSSA membrane prepared with the iPrOH were mainly distributed near the membrane surface, as shown by low proton conductivity in the membrane thickness direction. In contrast to this result, the ETFE-g-PSSA membranes prepared with the THF, toluene and TCE exhibited uniform distribution of the sulfonic acid groups in the membrane. Especially, in the case of the TCE grafting solvent, the chemical stability of the resultant electrolyte membrane was clearly higher than those prepared with the other grafting solvents.

One-Step Production of Amphiphilic Nanofibrillated Cellulose Using a Cellulose-Producing Bacterium.

PubMed

Tajima, Kenji; Kusumoto, Ryo; Kose, Ryota; Kono, Hiroyuki; Matsushima, Tokuo; Isono, Takuya; Yamamoto, Takuya; Satoh, Toshifumi

2017-10-09

Nanofibrillated bacterial cellulose (NFBC) is produced by culturing a cellulose-producing bacterium (Gluconacetobacter intermedius NEDO-01) with rotation or agitation in medium supplemented with carboxymethylcellulose (CMC). Despite a high yield and dispersibility in water, the product immediately aggregates in organic solvents. To broaden its applicability, we prepared amphiphilic NFBC by culturing strain NEDO-01 in medium supplemented with hydroxyethylcellulose or hydroxypropylcellulose instead of CMC. Transmission electron microscopy analysis revealed that the resultant materials (HE-NFBC and HP-NFBC, respectively) comprised relatively uniform fibers with diameters of 33 ± 7 and 42 ± 8 nm, respectively. HP-NFBC was dispersible in polar organic solvents such as methanol, acetone, isopropyl alcohol, acetonitrile, tetrahydrofuran (THF), and dimethylformamide, and was also dispersible in poly(methyl methacrylate) (PMMA) by solvent mixing using THF. HP-NFBC/PMMA composite films were highly transparent and had a higher tensile strength than neat PMMA film. Thus, HP-NFBC has a broad range of applications, including as a filler material.

Spontaneous Evolution of Nanostructure in Composite Films Consisting of Mixtures of Two Different Block Copolymer Micelles

NASA Astrophysics Data System (ADS)

Kim, Sehee; Char, Kookheon; Sohn, Byeong-Hyeok

2010-03-01

Diblock copolymers consisting of two immiscible polymer blocks covalently bonded together form various self-assembled nanostructures such as spheres, cylinders, and lamellae in bulk phase. In a selective solvent, however, they assemble into micelles with soluble corona brushes and immiscible cores. Both polystyrene-poly(4-vinylpyridine) (PS-b-P4VP) and polystyrene-poly(2-vinylpyridine) (PS-b-P2VP) diblock copolymers form micelles with PS coronas and P4VP or P2VP cores in a PS selective solvent (toluene). By varying the mixture ratio between PS-b-P4VP and PS-b-P2VP, composite films based on the micellar mixtures of PS-b-P4VP and PS-b-P2VP were obtained by spin-coating, followed by the solvent annealing with tetrahydrofuran (THF) vapor. Since THF is a solvent for both PS and P2VP blocks and, at the same time, a non-solvent for the P4VP block, PS-P2VP micelles transformed to lamellar multilayers while PS-P4VP micelles remained intact during the THF annealing. The spontaneous evolution of nanostructure in composite films consisting of lamellae layers with BCP micelles were investigated in detail by cross-sectional TEM and AFM.

Advanced liquefaction using coal swelling and catalyst dispersion techniques. Volume 2, appendices. Final technical report, October 1, 1991--September 30, 1994

DOE Office of Scientific and Technical Information (OSTI.GOV)

Curtis, C.W.; Chander, S.; Gutterman, C.

Liquefaction experiments were undertaken using subbituminous Black Thunder mine coal to observe the effects of aqueous SO{sub 2} coal beneficiation and the introduction of various coal swelling solvents and catalyst precursors. Aqueous SO{sub 2} beneficiation of Black Thunder coal removed alkali metals and alkaline earth metals, increased the sulfur content and increased the catalytic liquefaction conversion to THF solubles compared to untreated Black Thunder coal. The liquefaction solvent had varying effects on coal conversion, depending upon the type of solvent added. The hydrogen donor solvent, dihydroanthracene, was most effective, while a coal-derived Wilsonville solvent promoted more coal conversion than didmore » relatively inert 1-methylnaphthalene. Swelling of coal with hydrogen bonding solvents tetrahydrofuran (THF), isopropanol, and methanol, prior to reaction resulted in increased noncatalytic conversion of both untreated and SO{sub 2} treated Black Thunder coals, while dimethylsulfoxide (DMSO), which was absorbed more into the coal than any other swelling solvent, was detrimental to coal conversion. Swelling of SO{sub 2} treated coal before liquefaction resulted in the highest coal conversions; however, the untreated coal showed the most improvements in catalytic reactions when swelled in either THF, isopropanol, or methanol prior to liquefaction. The aprotic solvent DMSO was detrimental to coal conversion.« less

Chemical bonding and the equilibrium composition of Grignard reagents in ethereal solutions.

PubMed

Henriques, André M; Barbosa, André G H

2011-11-10

A thorough analysis of the electronic structure and thermodynamic aspects of Grignard reagents and its associated equilibrium composition in ethereal solutions is performed. Considering methylmagnesium halides containing fluorine, chlorine, and bromine, we studied the neutral, charged, and radical species associated with their chemical equilibrium in solution. The ethereal solvents considered, tetrahydrofuran (THF) and ethyl ether (Et(2)O), were modeled using the polarizable continuum model (PCM) and also by explicit coordination to the Mg atoms in a cluster. The chemical bonding of the species that constitute the Grignard reagent is analyzed in detail with generalized valence bond (GVB) wave functions. Equilibrium constants were calculated with the DFT/M06 functional and GVB wave functions, yielding similar results. According to our calculations and existing kinetic and electrochemical evidence, the species R(•), R(-), (•)MgX, and RMgX(2)(-) must be present in low concentration in the equilibrium. We conclude that depending on the halogen, a different route must be followed to produce the relevant equilibrium species in each case. Chloride and bromide must preferably follow a "radical-based" pathway, and fluoride must follow a "carbanionic-based" pathway. These different mechanisms are contrasted against the available experimental results and are proven to be consistent with the existing thermodynamic data on the Grignard reagent equilibria.

Effect of solvent type on the nanoparticle formation of atorvastatin calcium by the supercritical antisolvent process.

PubMed

Kim, Min-Soo; Song, Ha-Seung; Park, Hee Jun; Hwang, Sung-Joo

2012-01-01

The aims of this study were to identify how the solvent selection affects particle formation and to examine the effect of the initial drug solution concentration on mean particle size and particle size distribution in the supercritical antisolvent (SAS) process. Amorphous atorvastatin calcium was precipitated from seven different solvents using the SAS process. Particles with mean particle size ranging between 62.6 and 1493.7 nm were obtained by varying organic solvent type and solution concentration. By changing the solvent, we observed large variations in particle size and particle size distribution, accompanied by different particle morphologies. Particles obtained from acetone and tetrahydrofuran (THF) were compact and spherical fine particles, whereas those from N-methylpyrrolidone (NMP) and dimethylsulfoxide (DMSO) were agglomerated, with rough surfaces and relatively larger particle sizes. Interestingly, the mean particle size of atorvastatin calcium increased with an increase in the boiling point of the organic solvent used. Thus, for atorvastatin particle formation via the SAS process, particle size was determined mainly by evaporation of the organic solvent into the antisolvent phase. In addition, the mean particle size was increased with increasing drug solution concentration. In this study, from the aspects of particle size and solvent toxicity, acetone was the better organic solvent for controlling nanoparticle formation of atorvastatin calcium.

Thermodynamic properties of hyperbranched polymer, Boltorn U3000, using inverse gas chromatography.

PubMed

Domańska, Urszula; Zołek-Tryznowska, Zuzanna

2009-11-19

Mass-fraction activity coefficients at infinite dilution (Omega13(infinity)) of alkanes (C5-C10), cycloalkanes (C5-C8), alkenes (C5-C8), alkynes (C5-C8), aromatic hydrocarbons (benzene, toluene, ethylbenzene, o-, m-, p-xylene, thiophene), alcohols (C1-C5), water, ethers (tetrahydrofuran (THF), methyl-tert-butylether (MTBE), diethyl-, di-n-propyl-, di-n-butyl ether), and ketones (propanone, 2-pentanone, 3-pentanone, 2-hexanone, 3-hexanone, cyclopentanone) in the hyperbranched polymer, Boltorn U3000 (B-U3000), have been determined by inverse gas chromatography (IGC) using the polymer as the stationary phase. The measurements were carried out at different temperatures between 308.15 and 348.15 K. The density and thermophysical properties of polymer were described. The specific retention volume (V(g)), the Flory-Huggins interaction parameter (chi13(infinity)), the molar enthalpy of sorption (the partial molar enthalpies of solute dissolution) (Delta(s)H), the partial molar excess enthalpy at infinite dilution of the solute and polymer (DeltaH1(E,infinity)), the partial molar Gibbs excess energy at infinite dilution (DeltaG1(E,infinity)), and the solubility parameter (delta3) were calculated.

Guanidinophosphazenes: design, synthesis, and basicity in THF and in the gas phase.

PubMed

Kolomeitsev, Alexander A; Koppel, Ilmar A; Rodima, Toomas; Barten, Jan; Lork, Enno; Röschenthaler, Gerd-Volker; Kaljurand, Ivari; Kütt, Agnes; Koppel, Ivar; Mäemets, Vahur; Leito, Ivo

2005-12-21

A principle for creating a new generation of nonionic superbases is presented. It is based on attachment of tetraalkylguanidino, 1,3-dimethylimidazolidine-2-imino, or bis(tetraalkylguanidino)carbimino groups to the phosphorus atom of the iminophosphorane group using tetramethylguanidine or easily available 1,3-dimethylimidazolidine-2-imine. Seven new nonionic superbasic phosphazene bases, tetramethylguanidino-substituted at the P atom, have been synthesized. Their base strengths are established in tetrahydrofuran (THF) solution by means of spectrophotometric titration and compared with those of eight reference superbases designed specially for this study, P2- and P4-iminophosphoranes. The gas-phase basicities of several guanidino- and N',N',N'',N''-tetramethylguanidino (tmg)-substituted phosphazenes and their cyclic analogues are calculated, and the crystal structures of (tmg)3P=N-t-Bu and (tmg)3P=N-t-Bu x HBF4 are determined. The enormous basicity-increasing effect of this principle is experimentally verified for the tetramethylguanidino groups in the THF medium: the basicity increase when moving from (dma)3P=N-t-Bu (pKalpha = 18.9) to (tmg)3P=N-t-Bu (pKalpha = 29.1) is 10 orders of magnitude. A significantly larger basicity increase (up to 20 powers of 10) is expected (based on the high-level density functional theory calculations) to accompany the similar gas-phase transfer between the (dma)3P=NH and (tmg)3P=NH bases. Far stronger basicities still are expected when, in the latter two compounds, all three dimethylamino (or tetramethylguanidino) fragments are replaced by methylated triguanide fragments, (tmg)2C=N-. The gas-phase basicity (around 300-310 kcal/mol) of the resulting base, [(tmg)2C=N-]3P=NH, having only one phosphorus atom, is predicted to exceed the basicity of (dma)3P=NH by more than 40 powers of 10 and to surpass also the basicity of the widely used commercial [(dma)3P=N]3P=N-t-Bu (t-BuP4) superbase.

Phenoxide and alkoxide complexes of Mg, Al and Zn, and their use for the ring-opening polymerization of ℇ-caprolactone with initiators of different natures.

PubMed

Minyaev, Mikhail E; Nifant'ev, Ilya E; Shlyakhtin, Andrey V; Ivchenko, Pavel V; Lyssenko, Konstantin A

2018-05-01

A new packing polymorph of bis(2,6-di-tert-butyl-4-methylphenolato-κO)bis(tetrahydrofuran-κO)magnesium, [Mg(C 15 H 23 O) 2 (C 4 H 8 O) 2 ] or Mg(BHT) 2 (THF) 2 , (BHT is the 2,6-di-tert-butyl-4-methylphenoxide anion and THF is tetrahydrofuran), (1), has the same space group (P2 1 ) as the previously reported modification [Nifant'ev et al. (2017d). Dalton Trans. 46, 12132-12146], but contains three crystallographically independent molecules instead of one. The structure of (1) exhibits rotational disorder of the tert-butyl groups and positional disorder of a THF ligand. The complex of bis(2,6-di-tert-butyl-4-methylphenolato-κO)bis(μ 2 -ethyl glycolato-κ 2 O,O':κO)dimethyldialuminium, [Al 2 (CH 3 ) 2 (C 4 H 7 O 3 ) 2 (C 15 H 23 O) 2 ] or [(BHT)AlMe(OCH 2 COOEt)] 2 , (2), is a dimer located on an inversion centre and has an Al 2 O 2 rhomboid core. The 2-ethoxy-2-oxoethanolate ligand (OCH 2 COOEt) displays a μ 2 -κ 2 O,O':κO semi-bridging coordination mode, forming a five-membered heteronuclear Al-O-C-C-O ring. The same ligand exhibits positional disorder of the terminal methyl group. The redetermined structure of the heptanuclear complex octakis(μ 3 -benzyloxo-κO:κO:κO)hexaethylheptazinc, [Zn 7 (C 2 H 5 ) 6 (C 7 H 7 O) 8 ] or [Zn 7 (OCH 2 Ph) 8 Et 6 ], (3), possesses a bicubic Zn 7 O 8 core located at an inversion centre and demonstrates positional disorder of one crystallographically independent phenyl group. Cambridge Structural Database surveys are given for complexes structurally analogous to (2) and (3). Complexes (2) and (3), as well as derivatives of (1), are of interest as catalysts for the ring-opening polymerization of ℇ-caprolactone, and polymerization results are reported.

Highly stable red-emitting polymer dots for cellular imaging

NASA Astrophysics Data System (ADS)

Chelora, Jipsa; Zhang, Jinfeng; Chen, Rui; Thachoth Chandran, Hrisheekesh; Lee, Chun-Sing

2017-07-01

Polymer dots (Pdots) have emerged as a new type of fluorescent probe material for biomedical applications and have attracted great interest due to their excellent optical properties and biocompatability. In this work, we report on a red-emitting P3HT Pdot fluorescent probe for intracellular bioimaging. The as-prepared Pdot fluorescent probe exhibits good stability and has a large Stokes shift (121 nm) compared to molecules in tetrahydrofuran (THF). Furthermore, the probe shows low cytotoxicity, broad absorption spectrum, resistance against photodegradation, and good water dispersibility. These advantageous characteristics make P3HT Pdots a promising fluorescent probe material for bioimaging.

Highly stable red-emitting polymer dots for cellular imaging.

PubMed

Chelora, Jipsa; Zhang, Jinfeng; Chen, Rui; Chandran, Hrisheekesh Thachoth; Lee, Chun-Sing

2017-07-14

Polymer dots (Pdots) have emerged as a new type of fluorescent probe material for biomedical applications and have attracted great interest due to their excellent optical properties and biocompatability. In this work, we report on a red-emitting P 3 HT Pdot fluorescent probe for intracellular bioimaging. The as-prepared Pdot fluorescent probe exhibits good stability and has a large Stokes shift (121 nm) compared to molecules in tetrahydrofuran (THF). Furthermore, the probe shows low cytotoxicity, broad absorption spectrum, resistance against photodegradation, and good water dispersibility. These advantageous characteristics make P 3 HT Pdots a promising fluorescent probe material for bioimaging.

Solvent influence upon structure & throughput of poly vinyledene fluoride thin film nano-patterns by imprint lithography

NASA Astrophysics Data System (ADS)

Sankar, M. S. Ravi; Gangineni, R. B.

2018-04-01

This work aims at understanding the solvent influence upon the throughput and structure of poly vinyledene fluoride (PVDF)nano-patterned films. The PVDF thin films are deposited by spin coating method using Dimethylsulfoxide (DMSO), Tetrahydrofuran (THF) and 2-butanone solvents. The nano-patterns are realized by imprinting SONY 700 MB CD aluminum constructions on PVDF thin filmsusing imprint lithography technique under ambient annealing temperature and pressure. Surface morphology &imprint pattern transfer quality is evaluated with Atomic force microscopy (AFM). Raman spectroscopy is used for evaluating the structural evolutions with respect to solvent & patterning.

Advantages of using tetrahydrofuran-water as mobile phases in the quantitation of cyclosporin A in monkey and rat plasma by liquid chromatography-tandem mass spectrometry.

PubMed

Li, Austin C; Li, Yinghe; Guirguis, Micheal S; Caldwell, Robert G; Shou, Wilson Z

2007-01-04

A new analytical method is described here for the quantitation of anti-inflammatory drug cyclosporin A (CyA) in monkey and rat plasma. The method used tetrahydrofuran (THF)-water mobile phases to elute the analyte and internal standard, cyclosporin C (CyC). The gradient mobile phase program successfully eluted CyA into a sharp peak and therefore improved resolution between the analyte and possible interfering materials compared with previously reported analytical approaches, where CyA was eluted as a broad peak due to the rapid conversion between different conformers. The sharp peak resulted from this method facilitated the quantitative calculation as multiple smoothing and large number of bunching factors were not necessary. The chromatography in the new method was performed at 30 degrees C instead of 65-70 degrees C as reported previously. Other advantages of the method included simple and fast sample extraction-protein precipitation, direct injection of the extraction supernatant to column for analysis, and elimination of evaporation and reconstitution steps, which were needed in solid phase extraction or liquid-liquid extraction reported before. This method is amenable to high-throughput analysis with a total chromatographic run time of 3 min. This approach has been verified as sensitive, linear (0.977-4000 ng/mL), accurate and precise for the quantitation of CyA in monkey and rat plasma. However, compared with the usage of conventional mobile phases, the only drawback of this approach was the reduced detection response from the mass spectrometer that was possibly caused by poor desolvation in the ionization source. This is the first report to demonstrate the advantages of using THF-water mobile phases to elute CyA in liquid chromatography.

Size exclusion chromatography-gradients, an alternative approach to polymer gradient chromatography: 2. Separation of poly(meth)acrylates using a size exclusion chromatography-solvent/non-solvent gradient.

PubMed

Schollenberger, Martin; Radke, Wolfgang

2011-10-28

A gradient ranging from methanol to tetrahydrofuran (THF) was applied to a series of poly(methyl methacrylate) (PMMA) standards, using the recently developed concept of SEC-gradients. Contrasting to conventional gradients the samples eluted before the solvent, i.e. within the elution range typical for separations by SEC, however, the high molar mass PMMAs were retarded as compared to experiments on the same column using pure THF as the eluent. The molar mass dependence on retention volume showed a complex behaviour with a nearly molar mass independent elution for high molar masses. This molar mass dependence was explained in terms of solubility and size exclusion effects. The solubility based SEC-gradient was proven to be useful to separate PMMA and poly(n-butyl crylate) (PnBuA) from a poly(t-butyl crylate) (PtBuA) sample. These samples could be separated neither by SEC in THF, due to their very similar hydrodynamic volumes, nor by an SEC-gradient at adsorbing conditions, due to a too low selectivity. The example shows that SEC-gradients can be applied not only in adsorption/desorption mode, but also in precipitation/dissolution mode without risking blocking capillaries or breakthrough peaks. Thus, the new approach is a valuable alternative to conventional gradient chromatography. Copyright © 2011 Elsevier B.V. All rights reserved.

Effects of cyclic structure inhibitors on the morphology and growth of tetrahydrofuran hydrate crystals

NASA Astrophysics Data System (ADS)

Li, Sijia; Wang, Yanhong; Lang, Xuemei; Fan, Shuanshi

2013-08-01

Morphology and growth of hydrate crystals with cyclic structure inhibitors at a hydrate-liquid interface were directly observed through a microscopic manipulating apparatus. Tetrahydrofuran (THF) hydrate was employed as an objective. The effects of four kind of cyclic structure inhibitors, polyvinylpyrrolidone (PVP), poly(N-vinyl-2-pyrrolidone-co-2-vinyl pyridine) (PVPP), poly(2-vinyl pyridine-co-N-vinylcaprolactam) (PVPC) and poly(N-vinylcaprolactam) (PVCap), were investigated. Morphological patterns between each hydrate crystal growth from hydrate-liquid interface into droplet were found differ significantly. Lamellar structure growth of hydrate crystal was observed without inhibitor, while with PVP was featheriness-like, PVPP was like long dendritic crystal, PVPC was Mimosa pudica leaf-like and PVCap was like weeds. The growth rate of hydrate crystal without inhibitor was 0.00498 mm3/s, while with PVPP, PVPC and PVCap, were 0.00339 mm3/s, 0.00350 mm3/s, 0.00386 mm3/s and 0.00426 mm3/s, respectively. Cyclic structure inhibitors can decrease the growth rate, degree of reduction in growth rate of hydrate crystals decrease with the increase of cylinder number.

Effect of molecular conformation on the mechanofluorochromic properties based on DDIF

NASA Astrophysics Data System (ADS)

Mai, Runsheng; Peng, Huojun; Meng, Yuying; Chang, Xinyue; Jiang, Yue; Gao, Jinwei; Zhou, Guofu; Liu, Jun-ming

2017-07-01

Mechanofluorochromic (MFC) materials are smart materials in that their absorption and/or emission can respond to mechanical stimuli. They have received much attention recently. Although there have been several new material systems designed, little work has been done regarding the influence of molecular conformation on MFC properties. Herein, to disclose the relationship between molecular conformation and MFC properties, two molecules based on a 6, 12-Dihydro-6, 12-diaza-indeno[1,2-b]fluorine (DDIF) building block with thienyl linker, BDDIF-Th and BDDIF-BTh, have been designed and synthesized. Optical and electrochemical properties have been studied by UV-vis spectrometer and cyclic voltammetry measurements. Weak aggregation-induced emission (AIE) phenomena were obtained in the tetrahydrofuran (THF)/water solution. MFC behaviors suggest that BDDIF-Th is more sensible to the external mechanical forces than BDDIF-BTh. The color change could be attributed to the appearance of new emission peak instead of a bathochromic or hypsochromic effect. Theoretical calculations reveal that MFC performance is highly related to the molecular conformation, meaning that the BDDIF-BTh with perpendicular conformation is more difficult to flatten than the comparatively planar BDDIF-Th.

Retention mechanism of hypercrosslinked polystyrene silica hybrid phase in normal phase chromatography.

PubMed

Wu, Di; Nedev, Georgi K; Lucy, Charles A

2014-11-28

Hypercrosslinked polystyrene phases have been described as quasi-normal phase because they lack discrete polar sites. Retention on the HC-Tol column is investigated using the Snyder-Soczewinski model. Solvent strength of different hexane-solvent binary mobile phase compositions can be predicted with solvent strength of pure dichloromethane (DCM, 0.159), tetrahydrofuran (THF, 0.22), and benzene (0.127). The HC-Tol column is shown to be a localizing adsorptive phase. Also, site-competition delocalization on HC-Tol demonstrates that whatever its adsorption groups are, they are able to participate in lateral interactions. Copyright © 2014 Elsevier B.V. All rights reserved.

Dramatic Improvement of the Mechanical Strength of Silane-Modified Hydroxyapatite–Gelatin Composites via Processing with Cosolvent

PubMed Central

2018-01-01

Bone tissue engineering (BTE) requires a sturdy biomaterial for scaffolds for restoration of large bone defects. Ideally, the scaffold should have a mechanical strength comparable to the natural bone in the implanted site. We show that adding cosolvent during the processing of our previously developed composite of hydroxyapatite–gelatin with a silane cross-linker can significantly affect its mechanical strength. When processed with tetrahydrofuran (THF) as the cosolvent, the new hydroxyapatite–gelatin composite can demonstrate almost twice the compressive strength (97 vs 195 MPa) and biaxial flexural strength (222 vs 431 MPa) of the previously developed hydroxyapatite–gelatin composite (i.e., processed without THF), respectively. We further confirm that this mechanical strength improvement is due to the improved morphology of both the enTMOS network and the composite. Furthermore, the addition of cosolvents does not appear to negatively impact the cell viability. Finally, the porous scaffold can be easily fabricated, and its compressive strength is around 11 MPa under dry conditions. All these results indicate that this new hydroxyapatite–gelatin composite is a promising material for BTE application. PMID:29623305

Evolution of the Copper Surface in the Course of Oxidation by CCl4-L (L=THF, Dmf, Dmso): Scanning Probe Microscope Study

NASA Astrophysics Data System (ADS)

Panteleev, S. V.; Maslennikov, S. V.; Ignatov, S. K.; Spirina, I. V.; Kruglova, M. V.; Gribkov, B. A.; Vdovichev, S. N.

2013-04-01

The evolution of compact surface of the 100 nm copper film deposited on the glass-ceramics doped with vanadium coating in the course of the oxidation by the CCl4-L (L = dimethylformamide (DMF), tetrahydrofuran (THF), dimethylsulfoxide (DMSO), CCl4 concentration ≈ 1 mol/L) was studied by atomic force microscopy (AFM) in contact mode. The dynamics of active centers formation and destruction was investigated in the course of the oxidation process. The metallic sample dissolution rate was estimated as a function of the coordinating solvent nature. The development of the metal surface oxidation was established to lead to a significant increase of surface roughness. This phenomenon can be explained by the fact that different parts of the surface react at different rates. Further course of the reaction leads to a significant decrease of the surface roughness of copper films. The amount of the metal reacted has an almost linear dependence on the reaction time. AFM scans indicate that there is the same mechanism of the reaction between copper and carbon tetrachloride for all solvents.

Estimating thermal diffusivity and specific heat from needle probe thermal conductivity data

USGS Publications Warehouse

Waite, W.F.; Gilbert, L.Y.; Winters, W.J.; Mason, D.H.

2006-01-01

Thermal diffusivity and specific heat can be estimated from thermal conductivity measurements made using a standard needle probe and a suitably high data acquisition rate. Thermal properties are calculated from the measured temperature change in a sample subjected to heating by a needle probe. Accurate thermal conductivity measurements are obtained from a linear fit to many tens or hundreds of temperature change data points. In contrast, thermal diffusivity calculations require a nonlinear fit to the measured temperature change occurring in the first few tenths of a second of the measurement, resulting in a lower accuracy than that obtained for thermal conductivity. Specific heat is calculated from the ratio of thermal conductivity to diffusivity, and thus can have an uncertainty no better than that of the diffusivity estimate. Our thermal conductivity measurements of ice Ih and of tetrahydrofuran (THF) hydrate, made using a 1.6 mm outer diameter needle probe and a data acquisition rate of 18.2 pointss, agree with published results. Our thermal diffusivity and specific heat results reproduce published results within 25% for ice Ih and 3% for THF hydrate. ?? 2006 American Institute of Physics.

Pentynyl dextran as a support matrix for immobilization of serine protease subtilisin Carlsberg and its use for transesterification of N-acetyl-L-phenylalanine ethyl ester in organic media.

PubMed

Tahir, Muhammad Nazir; Cho, Eunae; Mischnick, Petra; Lee, Jae Yung; Yu, Jae-Hyuk; Jung, Seunho

2014-04-01

In this study, serine protease (subtilisin Carlsberg) was immobilized on pentynyl dextran (PyD, O-alkynyl ether of dextran, 1) and used for the transesterification of N-acetyl-L-phenylalanine ethyl ester (2) with different aliphatic (1-propanol, 1-butanol, 1-pentanol, 1-hexanol) and aromatic (benzyl alcohol, 2-phenyl ethanol, 4-phenyl-1-butanol) alcohols in tetrahydrofuran (THF). The effect of carbon chain length in aliphatic and aromatic alcohols on initial and average transesterification rate, transesterification activity of immobilized enzyme and yield of the reaction under selected reaction conditions was investigated. The transesterification reactivity of the enzyme and yield of the reaction increased as the chain length of the alcohols decreased. Furthermore, almost no change in yield was observed when the immobilized enzyme was repeatedly used for selected alcohols over six cycles. Intrinsic fluorescence analysis showed that the catalytic activity of the immobilized enzyme in THF was maintained due to retention of the tertiary structure of the enzyme after immobilization on PyD (1).

Direct functionalization of pristine single-walled carbon nanotubes by diazonium-based method with various five-membered S- or N- heteroaromatic amines

NASA Astrophysics Data System (ADS)

Leinonen, Heli; Lajunen, Marja

2012-09-01

Reactivity of five-membered, variously substituted, heteroaromatic diazonium salts was studied toward pristine single-walled carbon nanotubes (SWCNTs), prepared by high-pressure CO conversion (HiPCO) method. Average size range of individual HiPCO SWCNTs was 0.8-1.2 nm (diameter) and 100-1,000 nm (length). Functionalizations were performed by a one-pot diazotization-dediazotization method with methyl-2-aminothiophene-3-carboxylate, 2-aminothiophene-3-carbonitrile, 2-aminoimidazole sulfate, or 3-aminopyrazole in acetic acid using sodium nitrite at room temperature or by heating. According to Raman and Fourier transform infrared spectroscopy, all used heterocyclic diazonium salts formed a covalent bond with SWCNTs and yielded new kinds of five-membered heterocycle-functionalized SWCNTs. Methyl-2-thiophenyl-3-carboxylate-functionalized SWCNTs formed a highly soluble, stable dispersion in tetrahydrofuran (THF), 3-pyrazoyl-functionalized SWCNTs in ethanol, and 2-imidazoyl- or 2-thiophenyl-3-carbonitrile-functionalized SWCNTs in ethanol and THF. The thermogravimetric analysis as well as energy-filtered transmission electron microscopy imaging of the products confirmed the successful functionalization of SWCNTs.

Synthesis and characterization of a family of structurally characterized dysprosium alkoxides for improved fatigue-resistance characteristics of PDyZT thin films.

PubMed

Boyle, Timothy J; Bunge, Scott D; Clem, Paul G; Richardson, Jacob; Dawley, Jeffrey T; Ottley, Leigh Anna M; Rodriguez, Mark A; Tuttle, Bruce A; Avilucea, Gabriel R; Tissot, Ralph G

2005-03-07

Using either an ammoniacal route, the reaction between DyCl3, Na0, and HOR in liquid ammonia, or preferentially reacting Dy(N(SiMe3)2)3 with HOR in a solvent, we isolated a family of dysprosium alkoxides as [Dy(mu-ONep)2(ONep)]4 (1), (ONep)2Dy[(mu3-ONep)(mu-ONep)Dy(ONep)(THF)]2(mu-ONep) (2), (ONep)2Dy[(mu3-ONep)(mu-ONep)Dy(ONep)(py)]2(mu-ONep) (3), [Dy3(mu3-OBut)2(mu-OBut3(OBut)4(HOBut)2] (4), [Dy3(mu3-OBut)2(mu-OBut)3(OBut)4(THF)2] (5), [Dy3(mu3-OBut)2(mu-OBut)3(OBut)4(py)2] (6), (DMP)Dy(mu-DMP)4[Dy(DMP)2(NH3)]2 (7), [Dy(eta6-DMP)(DMP)2]2 (8), Dy(DMP)3(THF)3 (9), Dy(DMP)3(py)3 (10), Dy(DIP)3(NH3)2 (11), [Dy(eta6-DIP)(DIP)2]2 (12), Dy(DIP)3(THF)2 (13), Dy(DIP)3(py)3 (14), Dy(DBP)3(NH3) (15), Dy(DBP)3 (16), Dy(DBP)3(THF) (17), Dy(DBP)3(py)2 (18), [Dy(mu-TPS)(TPS2]2 (19), Dy(TPS)3(THF)3 (20), and Dy(TPS)3(py)3 (21), where ONep = OCH2CMe3, OBut) = OCMe3, DMP = OC6H3(Me)(2)-2,6, DIP = OC6H3(CHMe2)(2)-2,6, DBP = OC6H3(CMe3)(2)-2,6, TPS = OSi(C6H5)3, tol = toluene, THF = tetrahydrofuran, and py = pyridine. We were not able to obtain X-ray quality crystals of compounds 2, 8, and 9. The structures observed and data collected for the Dy compounds are consistent with those reported for its other congeners. A number of these precursors were used as Dy dopants in Pb(Zr0.3Ti0.7)O3 (PZT 30/70) thin films, with compound 12 yielding the highest-quality films. The resulting Pb0.94Dy0.04(Zr0.3Ti0.7)O3 [PDyZT (4/30/70)] had similar properties to PZT (30/70), but showed substantial resistance to polarization reversal fatigue.

Preparation of Carbon-Chitosan-Polyvinyl Chloride (CC-PVC) Material and its Application to Electrochemical Degradation of Methylene Blue in Sodium Chloride Solution

NASA Astrophysics Data System (ADS)

Riyanto; Prawidha, A. D.

2018-01-01

Electrochemical degradation of methylene blue using Carbon-Chitosan-Polyvinyl Chloride (CC-PVC) electrode in sodium chloride have been done. The aim of this work was to degradation of methylene blue using Carbon-Chitosan-Polyvinyl Chloride (CC-PVC). Carbon chitosan composite electrode was preparing by Carbon and Chitosan powder and PVC in 4 mL tetrahydrofuran (THF) solvent and swirled flatly to homogeneous followed by drying in an oven at 100 °C for 3 h. The mixture was placed in stainless steel mould and pressed at 10 ton/cm2. Sodium chloride was used electrolyte solution. The effects of the current and electrolysis time were investigated using spectrophotometer UV-Visible. The experimental results showed that the carbon-chitosan composite electrode have higher effect in the electrochemical degradation of methylene blue in sodium chloride. Based on UV-visible spectra analysis shows current and electrolysis time has high effect to degradation of methylene blue in sodium chloride. Chitosan and polyvinyl chloride can strengthen the bond between the carbons so that the material has the high stability and conductivity. As conclusions is Carbon-Chitosan-Polyvinyl Chloride (CC-PVC) electrode have a high electrochemical activity for degradation of methylene blue in sodium chloride.

Reaction pathway in vapour phase hydrogenation of maleic anhydride and its esters to {gamma}-butyrolactone

DOE Office of Scientific and Technical Information (OSTI.GOV)

Messori, M.; Vaccari, A.

1994-11-01

The catalytic reactivity of maleic anhydride (MA), succinic anhydride (SA) and their dimethyl esters (dimethyl maleate and dimethyl succinate) in the vapour phase hydrogenation to {gamma}-butyrolacetone (GBL) was investigated. In order to obtain general data, both a multicomponent catalyst (CAT 1: Cu/Zn/Mg/Cr = 40:5:5:50, atomic ratio %), obtained by reduction of a nonstoichiometric spinel-type precursor, and a commercial catalyst (CAT 2: Cu/Mn/Ba/Cr = 44:8:1:47, atomic ratio %) were used. The MA/GBL solution exhibited the highest GBL production, while the SA/GBL solution was converted only partially due to a competitive adsorption of GBL on the active sites, as evidenced by themore » similar reactivities observed with pure anhydrides. The best carbon balances were observed with the esters, probably the result of lowest light hydrocarbon synthesis and tar formation. With all the feedstocks, the activity of CAT 2 is higher than that of CAT 1, which, however, gives the best yield in GBL due its lower activity in the overhydrogenation and hydrogenolysis reaction. It was found that n-butanol (BuOH) and butyric acid (BuA) derived mainly from GBL. On this basis, the reactivities of the main products observed were investigated separately, confirming the stability of tetrahydrofuran (THF), which reacted only at high temperature with low conversions to ethanol. On the other hand, GBL gave rise to overhydrogenation and/or hydrogenolysis, with high conversion (mainly with CAT 2), confirming its key role in both reactions. Furthermore, the formation in the catalytic tests with BuA and BuOH of n-butanal, notwithstanding the high H{sub 2}/organic ratio, implies that it is the main intermediate in the hydrogenolysis reactions. A new reaction scheme is proposed, pointing out the key role of GBL as the {open_quotes}intersection{close_quotes} of two possible reaction pathways, giving rise to THF or overhydrogenation and hydrogenolysis products, respectively. 44 refs., 4 figs., 6 tabs.« less

The Scope of Direct Alkylation of Gold Surface with Solutions of C1-C4 n-Alkylstannanes.

PubMed

Kaletová, Eva; Kohutová, Anna; Hajduch, Jan; Kaleta, Jiří; Bastl, Zdeněk; Pospíšil, Lubomír; Stibor, Ivan; Magnera, Thomas F; Michl, Josef

2015-09-23

Treatment of cleaned gold surfaces with dilute tetrahydrofuran or chloroform solutions of tetraalkylstannanes (alkyl = methyl, ethyl, n-propyl, n-butyl) or di-n-butylmethylstannyl tosylate under ambient conditions causes a self-limited growth of disordered monolayers consisting of alkyls and tin oxide. Extensive use of deuterium labeling showed that the alkyls originate from the stannane and not from ambient impurities, and that trialkylstannyl groups are absent in the monolayers, contrary to previous proposals. Methyl groups attached to the Sn atom are not transferred to the surface. Ethyl groups are transferred slowly, and propyl and butyl rapidly. In all cases, tin oxide is codeposited in submonolayer amounts. The monolayers were characterized by ellipsometry, contact angle goniometry, polarization modulated IR reflection absorption spectroscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy with ferrocyanide/ferricyanide, which revealed a very low charge-transfer resistance. The thermal stability of the monolayers and their resistance to solvents are comparable with those of an n-octadecanethiol monolayer. A preliminary examination of the kinetics of monolayer deposition from a THF solution of tetra-n-butylstannane revealed an approximately half-order dependence on the bulk solution concentration of the stannane, hinting that more than one alkyl can be transferred from a single stannane molecule. A detailed structure of the attachment of the alkyl groups is not known, and it is proposed that it involves direct single or multiple bonding of one or more C atoms to one or more Au atoms.

5,10-Methylene-5,6,7,8-tetrahydrofolate conformational transitions upon binding to thymidylate synthase: molecular mechanics and continuum solvent studies

NASA Astrophysics Data System (ADS)

Jarmuła, Adam; Cieplak, Piotr; Montfort, William R.

2005-02-01

We applied the molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) approach to evaluate relative stability of the extended (flat) and C-shaped (bent) solution conformational forms of the 5,10-methylene-5,6,7,8-tetrahydrofolate (mTHF) molecule in aqueous solution. Calculations indicated that both forms have similar free energies in aqueous solution but detailed energy components are different. The bent solution form has lower intramolecular electrostatic and van der Waals interaction energies. The flat form has more favorable solvation free energy and lower contribution from the bond, angle and torsion angle molecular mechanical internal energies. We exploit these results and combine them with known crystallographic data to provide a model for the progressive binding of the mTHF molecule, a natural cofactor of thymidylate synthase (TS), to the complex forming in the TS-catalyzed reaction. We propose that at the time of initial weak binding in the open enzyme the cofactor molecule remains in a close balance between the flat and bent solution conformations, with neither form clearly favored. Later, thymidylate synthase undergoes conformational change leading to the closure of the active site and the mTHF molecule is withdrawn from the solvent. That effect shifts the thermodynamic equilibrium of the mTHF molecule toward the bent solution form. At the same time, burying the cofactor molecule in the closed active site produces numerous contacts between mTHF and protein that render change in the shape of the mTHF molecule. As a result, the bent solution conformer is converted to more strained L-shaped bent enzyme conformer of the mTHF molecule. The strain in the bent enzyme conformation allows for the tight binding of the cofactor molecule to the productive ternary complex that forms in the closed active site, and facilitates the protonation of the imidazolidine N10 atom, which promotes further reaction.

Structural insights into abasic site for Fpg specific binding and catalysis: comparative high-resolution crystallographic studies of Fpg bound to various models of abasic site analogues-containing DNA

PubMed Central

de Jésus, Karine Pereira; Serre, Laurence; Zelwer, Charles; Castaing, Bertrand

2005-01-01

Fpg is a DNA glycosylase that recognizes and excises the mutagenic 8-oxoguanine (8-oxoG) and the potentially lethal formamidopyrimidic residues (Fapy). Fpg is also associated with an AP lyase activity which successively cleaves the abasic (AP) site at the 3′ and 5′ sides by βδ-elimination. Here, we present the high-resolution crystal structures of the wild-type and the P1G defective mutant of Fpg from Lactococcus lactis bound to 14mer DNA duplexes containing either a tetrahydrofuran (THF) or 1,3-propanediol (Pr) AP site analogues. Structures show that THF is less extrahelical than Pr and its backbone C5′–C4′–C3′ diverges significantly from those of Pr, rAP, 8-oxodG and FapydG. Clearly, the heterocyclic oxygen of THF is pushed back by the carboxylate of the strictly conserved E2 residue. We can propose that the ring-opened form of the damaged deoxyribose is the structure active form of the sugar for Fpg catalysis process. Both structural and functional data suggest that the first step of catalysis mediated by Fpg involves the expulsion of the O4′ leaving group facilitated by general acid catalysis (involving E2), rather than the immediate cleavage of the N-glycosic bond of the damaged nucleoside. PMID:16243784

Organometallic oxides: Preparation, structure, and chemical and physical properties of paramagnetic ((. eta. -C sub 5 H sub 5 )NbCl(. mu. -A)) sup 3 (. mu. sub 3 -OH)(. mu. sub 3 -O) (A = Cl, OH) and other oxo-hydroxo clusters of niobium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bottomley, F.; Keizer, P.N.; White, P.S.

Hydrolysis of Cp{prime}NbCl{sub 4} (Cp{prime} = {eta}{sup 5}-C{sub 5}H{sub 5} (Cp), {eta}-C{sub 5}H{sub 4}Me (Cp{sup 1})) in tetrahydrofuran (THF) gave a mixture of products of general formula (Cp{prime}NbL{sub 4}){sub 2}({mu}-O), where L{sub 4} is a combination of H{sub 2}O and terminal or bridging Cl that gives eight-coordinate, pentavalent, niobium. For Cp{prime} = Cp, a major constituent of the mixture is (CpNb(H{sub 2}O)Cl{sub 3}){sub 2}({mu}-O) {times} 2THF {times} 0.05Et{sub 2}O (1), the structure of which was determined by X-ray diffraction. Reduction of (Cp{prime}NbL{sub 4}){sub 2}({mu}-O) with aluminum powder gave the cluster (Cp{prime}NbCl({mu}-Cl)){sub 3}({mu}{sub 3}-OH)({mu}{sub 3}-O) (2). The structure of 2 (Cp{prime}more » = Cp) as the THF adduct was determined by X-ray diffraction. Crystal data: monoclinic; P2{sub 1}/c; a = 9.966 (1) {angstrom}, b = 12.471 (2) {angstrom}, c = 20.321 (2) {angstrom}, {beta} = 93.86 (1){degree}.« less

Varying the Lewis base coordination of the Y2N2 core in the reduced dinitrogen complexes {[(Me3Si)2N]2(L)Y}2(μ-η2:η2-N2) (L = benzonitrile, pyridines, triphenylphosphine oxide, and trimethylamine N-oxide).

PubMed

Corbey, Jordan F; Farnaby, Joy H; Bates, Jefferson E; Ziller, Joseph W; Furche, Filipp; Evans, William J

2012-07-16

The effect of the neutral donor ligand, L, on the Ln(2)N(2) core in the (N═N)(2-) complexes, [A(2)(L)Ln](2)(μ-η(2):η(2)-N(2)) (Ln = Sc, Y, lanthanide; A = monoanion; L = neutral ligand), is unknown since all of the crystallographically characterized examples were obtained with L = tetrahydrofuran (THF). To explore variation in L, displacement reactions between {[(Me(3)Si)(2)N](2)(THF)Y}(2)(μ-η(2):η(2)-N(2)), 1, and benzonitrile, pyridine (py), 4-dimethylaminopyridine (DMAP), triphenylphosphine oxide, and trimethylamine N-oxide were investigated. THF is displaced by all of these ligands to form {[(Me(3)Si)(2)N](2)(L)Y}(2)(μ-η(2):η(2)-N(2)) complexes (L = PhCN, 2; py, 3; DMAP, 4; Ph(3)PO, 5; Me(3)NO, 6) that were fully characterized by analytical, spectroscopic, density functional theory, and X-ray crystallographic methods. The crystal structures of the Y(2)N(2) cores in 2-5 are similar to that in 1 with N-N bond distances between 1.255(3) Å and 1.274(3) Å, but X-ray analysis of the N-N distance in 6 shows it to be shorter: 1.198(3) Å.

A scattering function of star polymers including excluded volume effects

DOE PAGES

Li, Xin; Do, Changwoo; Liu, Yun; ...

2014-11-04

In this work we present a new model for the form factor of a star polymer consisting of self-avoiding branches. This new model incorporates excluded volume effects and is derived from the two point correlation function for a star polymer.. We compare this model to small angle neutron scattering (SANS) measurements from polystyrene (PS) stars immersed in a good solvent, tetrahydrofuran (THF). It is shown that this model provides a good description of the scattering signature originating from the excluded volume effect and it explicitly elucidates the connection between the global conformation of a star polymer and the local stiffnessmore » of its constituent branch.« less

Cobalt(II) chloride adducts with acetonitrile, propan-2-ol and tetrahydrofuran: considerations on nuclearity, reactivity and synthetic applications.

PubMed

Stinghen, Danilo; Rüdiger, André Luis; Giese, Siddhartha O K; Nunes, Giovana G; Soares, Jaísa F; Hughes, David L

2017-02-01

High-spin cobalt(II) complexes are considered useful building blocks for the synthesis of single-molecule magnets (SMM) because of their intrinsic magnetic anisotropy. In this work, three new cobalt(II) chloride adducts with labile ligands have been synthesized from anhydrous CoCl 2 , to be subsequently employed as starting materials for heterobimetallic compounds. The products were characterized by elemental, spectroscopic (EPR and FT-IR) and single-crystal X-ray diffraction analyses. trans-Tetrakis(acetonitrile-κN)bis(tetrahydrofuran-κO)cobalt(II) bis[(acetonitrile-κN)trichloridocobaltate(II)], [Co(C 2 H 3 N) 4 (C 4 H 8 O) 2 ][CoCl 3 (C 2 H 3 N)] 2 , (1), comprises mononuclear ions and contains both acetonitrile and tetrahydrofuran (thf) ligands, The coordination polymer catena-poly[[tetrakis(propan-2-ol-κO)cobalt(II)]-μ-chlorido-[dichloridocobalt(II)]-μ-chlorido], [Co 2 Cl 4 (C 3 H 8 O) 4 ], (2'), was prepared by direct reaction between anhydrous CoCl 2 and propan-2-ol in an attempt to rationalize the formation of the CoCl 2 -alcohol adduct (2), probably CoCl 2 (HO i Pr) m . The binuclear complex di-μ-chlorido-1:2κ 4 Cl:Cl-dichlorido-2κ 2 Cl-tetrakis(tetrahydrofuran-1κO)dicobalt(II), [Co 2 Cl 4 (C 4 H 8 O) 4 ], (3), was obtained from (2) after recrystallization from tetrahydrofuran. All three products present cobalt(II) centres in both octahedral and tetrahedral environments, the former usually less distorted than the latter, regardless of the nature of the neutral ligand. Product (2') is stabilized by an intramolecular hydrogen-bond network that appears to favour a trans arrangement of the chloride ligands in the octahedral moiety; this differs from the cis disposition found in (3). The expected easy displacement of the bound solvent molecules from the metal coordination sphere makes the three compounds good candidates for suitable starting materials in a number of synthetic applications.

Design of HIV-1 Protease Inhibitors with Amino-bis-tetrahydrofuran Derivatives as P2-Ligands to Enhance Backbone-Binding Interactions. Synthesis, Biological Evaluation, and Protein-Ligand X-ray Studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ghosh, Arun K.; Martyr, Cuthbert D.; Osswald, Heather L.

Structure-based design, synthesis, and biological evaluation of a series of very potent HIV-1 protease inhibitors are described. In an effort to improve backbone ligand–binding site interactions, we have incorporated basic-amines at the C4 position of the bis-tetrahydrofuran (bis-THF) ring. We speculated that these substituents would make hydrogen bonding interactions in the flap region of HIV-1 protease. Synthesis of these inhibitors was performed diastereoselectively. A number of inhibitors displayed very potent enzyme inhibitory and antiviral activity. Inhibitors 25f, 25i, and 25j were evaluated against a number of highly-PI-resistant HIV-1 strains, and they exhibited improved antiviral activity over darunavir. Two high resolutionmore » X-ray structures of 25f- and 25g-bound HIV-1 protease revealed unique hydrogen bonding interactions with the backbone carbonyl group of Gly48 as well as with the backbone NH of Gly48 in the flap region of the enzyme active site. These ligand–binding site interactions are possibly responsible for their potent activity.« less

Spectral and thermodynamic properties for the exciplexes of N-alkyl carbazoles with dicyanobenzenes in THF

NASA Astrophysics Data System (ADS)

Asim, Sadia; Mansha, Asim; Landgraf, Stephan; Grampp, Günter; Zahid, Muhammad; Bhatti, Haq Nawaz

2014-01-01

The exciplex emission spectra of N-ethylcarbazole with 1,2-dicyanobenzene (NEC/1,2-DCB), N-methylcarbazole with 1,2-dicyanobenzene (NMC/1,2-DCB), 1,3-dicyanobenzene (NMC/1,3-DCB), and 1,4-dicyanobenzene (NMC/1,4-DCB) are studied in tetrahydrofuran (THF) for the temperature range starting from 253 K to 334 K. Thermochromic shifts along with the spectral properties including change in peak intensities and the ratio of exciplex peak intensity to fluorophore peak intensity are studied. Effect of temperature on the energy of zero-zero transitions hνo‧, Huang-Rhys factor (S), Gauss broadening of vibronic level (σ) and the dominant high-frequency vibration (hνν) are also part of investigation. Enthalpy of exciplex formation (ΔHEX∗) calculated by the model proposed by A. Weller and the Gibb's energy of electron transfer (ΔGet∗) for all exciplex systems are also discussed in the present paper. All the exciplexes under study were observed to be dipolar in nature. The exciplex of the N-methylcarbazole/1,4-dicyanobenzene was found to be the most stable and the N-methylcarbazole/1,3-dicyanobenzene was the weakest exciplex system.

Purification of aflatoxin B1 antibody for the development of aflatoxin biosensor

NASA Astrophysics Data System (ADS)

Prihantoro, E. A. B.; Saepudin, E.; Ivandini, T. A.

2017-07-01

Aflatoxin B1 (AFB1) is produced from agricultural products especially peanuts overgrown with aspergillus flavus during the post-harvest process. Aflatoxin is classified as a highly toxic and carcinogenic substance to humans by the International Agency for Research on Cancer (IARC), WHO. This research was conducted to develop the AFB1 biosensor using antibody that specifically binds to aflatoxin B1. This antibody was produced by injecting an AFB1 hapten-protein (immunogen) to a rabbit. Antibody was obtained from rabbit's blood serum and purified using Protein A affinity chromatography and precipitation at the isoelectric point. The result showed that purification using protein A contains antibody of 4.0 mg/mL, whereas purification using precipitation at isoelectric pH contains antibody of 0.3 mg/mL. The pure antibody was tested for its specificity against AFB1, tetrahydrofuran (THF), dimethyl formamide (DMF), bovine serum albumin (BSA), and ethanol. The result revealed that THF, BSA, and ethanol were bound to antibody, while DMF showed no interaction. It was concluded that the polyclonal antibody which have been successfully purified from rabbit's blood serum using protein A affinity chromatography and precipitation methods showed an unspecific identification.

Understanding the influence of solvent field and fluctuations on the stability of photo-induced charge-separated state in molecular triad

NASA Astrophysics Data System (ADS)

Balamurugan, D.; Aquino, Adelia; Lischka, Hans; Dios, Francis; Flores, Lionel; Cheung, Margaret

2013-03-01

Molecular triad composed of fullerene, porphyrin, and carotene is an artificial analogue of natural photosynthetic system and is considered for applications in solar energy conversion because of its ability to produce long-lived photo-induced charge separated state. The goal of the present multiscale simulation is to understand how the stability of photo-induced charge-separated state in molecular triad is influenced by a polar organic solvent, namely tetrahydrofuran (THF). The multiscale approach is based on combined quantum, classical molecular dynamics, and statistical physics calculations. The quantum chemical calculations were performed on the triad using the second order algebraic diagrammatic perturbation and time-dependent density functional theory. Molecular dynamics simulations were performed on triad in a box of THF solvent with the replica exchange method. The two methods on different length and time scales are bridged through an important sampling technique. We have analyzed the free energy landscape, structural fluctuations, and the long- range electrostatic interactions between triad and solvent molecules. The results suggest that the polarity and re-organization of the solvent is critical in stabilization of charge-separated state in triad. Supported by DOE (DE-FG02-10ER16175)

Crystal structure of bis-[tetra-kis-(tetra-hydro-furan-κO)lithium] bis[μ-2,2',2''-methanetriyltris(4,6-di-tert-butylphenolato)-κ4O,O':O',O'']-dimagnesiate.

PubMed

Zhou, Hongyan; Wang, Lei

2017-07-01

The title ion-association metal complex, [Li(C 4 H 8 O) 4 ] 2 [Mg 2 (C 43 H 61 O 3 ) 2 ], has been synthesized from the tridentate phenolic ligand tris-(3,5-di- tert -butyl-2-hy-droxy-phen-yl)methane in tetra-hydro-furan (THF). The aryl-oxo magnesiate complex anion is binuclear with each Mg 2 O 4 complex unit inversion-related and bridged through the two tridentate chelating phenolate O-donors of the ligand. The complex centres have a distorted tetra-hedral stereochemistry [Mg-O range 1.8796 (17)-2.0005 (16) Å] and an Mg⋯Mg separation of 2.9430 (14) Å]. The LiO 4 coodination sphere of the cation comprises four THF O-donor atoms and has a slightly distorted tetra-hedral conformation [Li-O range 1.899 (5)- 1.953 (5) Å]. In the crystal, a number of stabilizing intra-anion C-H⋯O hydrogen-bonding inter-actions are present but no inter-species associations are found.

Synthesis and structural studies of lithium and sodium complexes with OOO-tridentate bis(phenolate) ligands: effective catalysts for the ring-opening polymerization of L-lactide.

PubMed

Huang, Yong; Tsai, Yueh-Hsuan; Hung, Wen-Chou; Lin, Chieh-Shen; Wang, Wei; Huang, Jui-Hsien; Dutta, Saikat; Lin, Chu-Chieh

2010-10-18

A series of lithium and sodium complexes with OOO-tridentate bis(phenolate) ligands have been synthesized and fully characterized. The reaction of 2,2'-dihydroxy-3,3',5,5'-tetrakis[(1-methyl-1-phenyl)ethyl]dibenzyl ether (L(1)-H(2)) with different ratios of (n)BuLi in toluene or tetrahydrofuran (THF) gave [Li(2)(L(1)-H)(2)] (1), [Li(4)L(1)(2)] (2), and [Li(2)L(1)(THF)(3)] (3), respectively. Similarly, [Na(L(1)-H)(THF)] (4), [Na(2)(L(1)-H)](2) (5), and [Na(4)L(1)(2)] (6) were prepared by the reaction of L(1)-H(2) and NaN[Si(CH(3))(3)](2) or sodium metal. In addition, the reaction of 2,2'-dihydroxy-3,3',5,5'-tetra-tert-butyldibenzyl ether (L(2)-H(2)) with (n)BuLi in toluene or THF yields Li(2)(L(2)-H)(2)] (7) and [Li(2)(L(2)-H)(2)(THF)(2)] (8), respectively. Further treatment of 7 with 2 mol equiv of benzyl alcohol provides [Li(2)(L(2)-H)(2)(BnOH)(2)] (9). Complexes 1-4 and 6-9 have been structurally characterized by single-crystal X-ray analysis. The dinuclear nature of complexes 1 and 3 was confirmed from their molecular structure. Complexes 2 and 6 illustrate tetranuclear species; however, complex 4 shows a mononuclear feature. A p-π interaction exists from the phenyl ring of the 2-(methyl-1-phenylethyl) groups to the central metal in complexes 2, 4, and 6, which could effectively stabilize the metal center. Among them, complexes 1, 2, and 5-9 displayed efficient catalytic behavior for the ring-opening polymerization of L-lactide in the presence of benzyl alcohol. Experimental results indicate that among these alkali-metal complexes, the sodium compound 6 displays a rapid catalytic polymerization of L-lactide in "living" fashion, yielding poly(L-lactide) with a controlled molecular weight and narrow polydispersity indices for a wide range of monomer-to-initiator ratios.

Thermal Transitions and Reaction Kinetics of Polyhederal Silsesquioxane Containing Phenylethynylphthalimides (Preprint)

DTIC Science & Technology

2010-03-18

Grignard reagent was added drop-wise to a well-stirred THF solution (10 mL) of trichloromethylsilane (5.431 g, 36.3 mmol) in a 250 mL flask. After...chloromethylsilane) The Grignard reagent , (Me3Si)2NC6H4MgBr was prepared exactly as previously described from 37.6 mmol of magnesium and 30 mmol of (N...trimethylsilyl)2-4-bromoaniline in THF (25 mL). This Grignard reagent was added drop-wise to a well-stirred THF solution (10 mL) of trichloromethylsilane

Devices and methods to detect and quantify trace gases

DOEpatents

Allendorf, Mark D.; Robinson, Alex

2016-05-03

Sensing devices based on a surface acoustic wave ("SAW") device coated with an absorbent crystalline or amorphous layer for detecting at least one chemical analyte in a gaseous carrier. Methods for detecting the presence of a chemical analyte in a gaseous carrier using such devices are also disclosed. The sensing devices and methods for their use may be configured for sensing chemical analytes selected from the group consisting of water vapor, carbon dioxide, methanol, ethanol, carbon monoxide, nitric oxide, nitrous oxide, organic amines, organic compounds containing NO.sub.2 groups, halogenated hydrocarbons, acetone, hexane, toluene, isopropanol, alcohols, alkanes, alkenes, benzene, functionalized aromatics, ammonia (NH.sub.3), phosgene (COCl.sub.2), sulfur mustard, nerve agents, sulfur dioxide, tetrahydrofuran (THF) and methyltertbutyl ether (MTBE) and combinations thereof.

A Second Glass Transition in Pressure Collapsed Type II Clathrate Hydrates.

PubMed

Andersson, Ove; Häussermann, Ulrich

2018-04-19

Type II clathrate hydrates (CHs) M·17 H 2 O, with M = tetrahydrofuran (THF) or 1,3-dioxolane, are known to collapse, or amorphize, on pressurization to ∼1.3 GPa in the temperature range 77-140 K. On heating at 1 GPa, these pressure-amorphized CH states show a weak, stretched sigmoid-shaped, heat-capacity increase because of a glass transition. Here we use thermal conductivity and heat capacity measurements to show that also type II CH with M = cyclobutanone (CB) collapses on isothermal pressurization and undergoes a similar, weak, glass transition upon heating at 1 GPa. Furthermore, we reveal for both THF CH and CB CH a second, much more pronounced, glass transition at temperatures above the thermally weak glass transition on heating in the 0.2-0.7 GPa range. This result suggests the general occurrence of two glass transitions in water-rich (94 mol %) pressure-collapsed CHs. Because of a large increase in dielectric permittivity concurrently as the weak heat capacity increase, the first glass transition must be due to kinetic unfreezing of water molecules. The thermal features of the second glass transition, measured on isobaric temperature cycling, are typical of a glass-liquid-glass transition, which suggests that pressure-amorphized CHs transform reversibly to liquids.

Kinetic and mechanistic studies of base-catalyzed phenylselenoetherification of (Z)- and (E)-hex-4-en-1-ols.

PubMed

Divac, Vera M; Puchta, Ralph; Bugarčić, Zorica M

2012-08-02

The mechanism of phenylselenoetherification of (Z)- and (E)-hex-4-en-1-ols using some bases (triethylamine, pyridine, quinoline, 2,2'-bipyridine) as catalysts and some solvents [tetrahydrofuran (THF) and CCl4] as reaction media was examined through studies of kinetics of the cyclization by UV-vis spectrophotometry. It was demonstrated that the intramolecular cyclization is facilitated in the presence of bases as a result of the hydrogen bond between the base and the alkenol's OH group. The rate constants in the base-catalyzed reactions are remarkably influenced by the bulkiness and basicity of the base used and the nature of the considered nitrogen donors. The obtained values for rate constants show that the reaction with triethylamine is the fastest one. THF with higher polarity and higher basic character is better as a solvent than CCl4. Quantum-chemical calculations [MP2(fc)/6-311+G**//B3LYP/6-311+G** + ZPE(B3LYP/6-311+G**] show that the cyclization of (Z)-hex-4-en-1-ol to a tetrahydrofuranoid five-membered ring is kinetically controlled, while the cyclization of (E)-hex-4-en-1-ol to the tetrahydropyranoid six-membered ring is thermodynamically controlled. This is in accordance with previous experimental findings.

Solvent recyclability in a multistep direct liquefaction process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hetland, M.D.; Rindt, J.R.

1995-12-31

Direct liquefaction research at the Energy & Environmental Research Center (EERC) has, for a number of years, concentrated on developing a direct liquefaction process specifically for low-rank coals (LRCs) through the use of hydrogen-donating solvents and solvents similar to coal-derived liquids, the water/gas shift reaction, and lower-severity reaction conditions. The underlying assumption of all of the research was that advantage could be taken of the reactivity and specific qualities of LRCs to produce a tetrahydrofuran (THF)-soluble material that might be easier to upgrade than the soluble residuum produced during direct liquefaction of high-rank coals. A multistep approach was taken tomore » produce the THF-soluble material, consisting of (1) preconversion treatment to prepare the coal for solubilization, (2) solubilization of the coal in the solvent, and (3) polishing to complete solubilization of the remaining material. The product of these three steps can then be upgraded during a traditional hydrotreatment step. The results of the EERC`s research indicated that additional studies to develop this process more fully were justified. Two areas were targeted for further research: (1) determination of the recyclability of the solvent used during solubilization and (2) determination of the minimum severity required for hydrotreatment of the liquid product. The current project was funded to investigate these two areas.« less

Matching organic libraries with protein-substructures

NASA Astrophysics Data System (ADS)

Preissner, R.; Goede, A.; Rother, K.; Osterkamp, F.; Koert, U.; Froemmel, C.

2001-09-01

We present a general approach which allows automatic identification of sub-structures in proteins that resemble given three-dimensional templates. This paper documents its success with non-peptide templates such as β-turn mimetics. We considered well-tested turn-mimetics such as the bicyclic turned dipeptide (BTD), spiro lactam (Spiro) and the 2,5-disubstituded tetrahydrofuran (THF), a new furan-derivative which was recently developed and characterized. The detected geometric similarity between the templates and the protein patches corresponds to r.m.s.-values of 0.3 Å for more than 80% of the constituting atoms, which is typical for active site comparisons of homologous proteins. This fast automatic procedure might be of biomedical value for finding special mimicking leads for particular protein sub-structures as well as for template-assembled synthetic protein (TASP) design.

Polypeptide Liquid Crystal Assisted Assembly of Cylindrically Symmetric Silica-Polypeptide Hybrid Microparticles

NASA Astrophysics Data System (ADS)

Russo, Paul; Rosu, Cornelia; Jacobeen, Shane; Park, Katherine; Yunker, Peter; Reichmanis, Elsa

Liquid crystals can organize dispersed particles into exotic structures. Matching the particle surface coating to the chemistry of the mesogenic phase permits a tight focus on factors such as extended particle shape. The colloidal particles developed for this work consist of a magnetic and fluorescent cylinder-like silica core. One end of the silica is rounded, almost hemispherical, giving the particles a bullet-like shape. These particles are functionalized with helical poly(γ-stearyl-L-glutamate) and dispersed, at different concentrations in cholesteric liquid crystals (ChLC) of the same polymer in tetrahydrofuran. Defects introduced by the particles to the director field of the bulk PSLG/THF host led to a variety of phases, including a quasi-hexagonal alignment of the particles. National Science Foundation.

Characterization of the coal biosolubilization process using gel permeation chromatography and CPMAS NMR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Linehan, J.C.; Bean, R.M.; Franz, J.A.

1990-05-01

Leonardite, an oxidized lignite, and Illinois {number sign}6 coal were treated with Trametes versicolor and Penicillium sp., respectively, and separately with aqueous base to yield soluble and insoluble products. The products and starting materials were analyzed by gel permeation chromatography (GPC), using both aqueous and organic eluents, and by high-field, high-speed-pinning (>10.0 kHz) {sup 13}C cross polarization/magic angle spinning (CPMAS) nuclear magnetic resonance spectroscopy (NMR). The weight average molecular weights (M{sub w}) of the fungal-and base-solubilized products determined by GPC using acidic tetrahydrofuran (THF) eluent were found to be consistently lower than the M{sub w} determined using basic aqueous eluents.more » The M{sub w} of the leonardite product was measured to be 1800 and 6100 daltons using the THF and aqueous eluents, respectively. The aqueous eluent (phosphate buffered at pH 11.5) was found to be superior to the THF eluent in its solubilizing power, with 10% more material analyzed with the basic eluent. The solubility of the biotreated products in aqueous base was greater than either the starting coal or the chemically solubilized product. The Trametes-solubilized leonardite was found to contain a higher percentage of aliphatic carbon than the raw lignite; the Penicillium- solubilized Illinois {number sign}6 contained more aromatic carbon than before fungal treatment as determined by {sup 13}C CPMAS NMR. Pre-oxidation of Illinois {number sign}6 decreases the relative amount of aliphatic carbon. The high-field, high-speed-spinning CPMAS NMR technique was quantitatively evaluated using Argonne premium coals,International Humic Society Standards, and model compounds at various temperatures. 7 refs., 4 figs., 3 tabs.« less

A selective naked-eye chemosensor derived from 2-methoxybenzylamine and 2,3-dihydroxybenzaldehyde - synthesis, spectral characterization and electrochemistry of its bis-bidentates Schiff bases metal complexes

NASA Astrophysics Data System (ADS)

Djouhra, Aggoun; Ali, Ourari; Ramiro, Ruiz-Rosas; Emilia, Morallon

2017-09-01

A new colorimetric receptor HL, acting as a bidentate Schiff base ligand, has been synthesized by condensation of 2-methoxybenzylamine on 2,3-dihydroxybenzaldehyde in a methanolic solution. Interestingly, this chelating agent can selectively detect Cu2 +, Co2 +, Fe2 + and Fe3 + ions with a simple and an easy-to-make, well defined naked-eye visible color changes in two different solvents like acetonitrile and methanol. This bidentate ligand coordinates three metal ions of Co(II), Cu(II) and Fe(II) via nitrogen and oxygen atoms. The molecular structures of the synthesized compounds were elucidated by various physicochemical properties such as the elemental analysis, FT-IR, HNMR, UV-Vis and the Mass spectrometry. The resulting general formulae [M(L)2·H2O] (M(II) = Cu, Fe, Co) are proposed as mononuclear complexes. The solvatochromism properties of these compounds were studied with their absorption spectra using different solvents as methanol (MeOH), acetonitrile (AN), tetrahydrofuran (THF), dimethylformamid (DMF), dimethylsulfoxid (DMSO) and dichloromethane (DC). The Electrochemical behavior of copper complex was explored in DMF solutions by cyclic voltammetry (CV) with two working electrodes: glassy carbon (GC) and platinum electrode (Pt). This study reveals that copper complex shows successively two redox systems as CuIII/II and CuII/I. The FeIII/II and CoII/I redox systems have also been studied in DMF and DMSO media.

Kinetics Tuning the Electrochemistry of Lithium Dendrites Formation in Lithium Batteries through Electrolytes

DOE PAGES

Tao, Ran; Bi, Xuanxuan; Li, Shu; ...

2017-02-13

Lithium batteries are one of the most advance energy storage devices in the world and have attracted extensive research interests. However, lithium dendrite growth was a safety issue which handicapped the application of pure lithium metal in the negative electrode. In this paper, two solvents, propylene carbonate (PC) and 2-methyl-tetrahydrofuran (2MeTHF), and four Li + salts, LiPF 6, LiAsF 6, LiBF 4 and LiClO 4 were investigated in terms of their effects on the kinetics of lithium dendrite formation in eight electrolyte solutions. The kinetic parameters of charge transfer step (exchange current density, j 0, transfer coefficient, α) of Limore » +/Li redox system, the mass transfer parameters of Li + (transfer number of Li +, t Li+, diffusion coefficient of Li +, D Li+), and the conductivity (κ) of each electrolyte were studied separately. The results demonstrate that the solvents play a critical role in the measured j 0, t Li+, D Li+, and κ of the electrolyte, while the choice of Li + salts only slightly affect the measured parameters. Finally, the understanding of the kinetics will gain insight into the mechanism of lithium dendrite formation and provide guidelines to the future application of lithium metal.« less

Kinetics Tuning the Electrochemistry of Lithium Dendrites Formation in Lithium Batteries through Electrolytes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tao, Ran; Bi, Xuanxuan; Li, Shu

Lithium batteries are one of the most advance energy storage devices in the world and have attracted extensive research interests. However, lithium dendrite growth was a safety issue which handicapped the application of pure lithium metal in the negative electrode. In this paper, two solvents, propylene carbonate (PC) and 2-methyl-tetrahydrofuran (2MeTHF), and four Li + salts, LiPF 6, LiAsF 6, LiBF 4 and LiClO 4 were investigated in terms of their effects on the kinetics of lithium dendrite formation in eight electrolyte solutions. The kinetic parameters of charge transfer step (exchange current density, j 0, transfer coefficient, α) of Limore » +/Li redox system, the mass transfer parameters of Li + (transfer number of Li +, t Li+, diffusion coefficient of Li +, D Li+), and the conductivity (κ) of each electrolyte were studied separately. The results demonstrate that the solvents play a critical role in the measured j 0, t Li+, D Li+, and κ of the electrolyte, while the choice of Li + salts only slightly affect the measured parameters. Finally, the understanding of the kinetics will gain insight into the mechanism of lithium dendrite formation and provide guidelines to the future application of lithium metal.« less

Plating and stripping calcium in an organic electrolyte

NASA Astrophysics Data System (ADS)

Wang, Da; Gao, Xiangwen; Chen, Yuhui; Jin, Liyu; Kuss, Christian; Bruce, Peter G.

2018-01-01

There is considerable interest in multivalent cation batteries, such as those based on magnesium, calcium or aluminium. Most attention has focused on magnesium. In all cases the metal anode represents a significant challenge. Recent work has shown that calcium can be plated and stripped, but only at elevated temperatures, 75 to 100 °C, with small capacities, typically 0.165 mAh cm-2, and accompanied by significant side reactions. Here we demonstrate that calcium can be plated and stripped at room temperature with capacities of 1 mAh cm-2 at a rate of 1 mA cm-2, with low polarization (~100 mV) and in excess of 50 cycles. The dominant product is calcium, accompanied by a small amount of CaH2 that forms by reaction between the deposited calcium and the electrolyte, Ca(BH4)2 in tetrahydrofuran (THF). This occurs in preference to the reactions which take place in most electrolyte solutions forming CaCO3, Ca(OH)2 and calcium alkoxides, and normally terminate the electrochemistry. The CaH2 protects the calcium metal at open circuit. Although this work does not solve all the problems of calcium as an anode in calcium-ion batteries, it does demonstrate that significant quantities of calcium can be plated and stripped at room temperature with low polarization.

Quantitative evaluation of inhibitory effect of various substances on anaerobic ammonia oxidation (anammox).

PubMed

Nakamura, Tomotaka; Harigaya, Yuhki; Kimura, Yuya; Kuroiwa, Megumi; Kurata, Yuhri; Isaka, Kazuichi; Suwa, Yuichi

2017-09-01

The inhibitory effect of 20 substances of various chemical species on the anaerobic ammonia oxidation (anammox) activity of an enrichment culture, predominated by Candidatus Brocadia, was determined systematically by using a 15 N tracer technique. The initial anammox rate was determined during first 25 min with a small-scale anaerobic batch incubation supplemented with possible inhibitors. Although Cu 2+ and Mn 2+ did not inhibit anammox, the remaining 18 substances [Ni 2+ , Zn 2+ , Co 2+ , [Formula: see text] , Fe 2+ , 4 amines, ethylenediaminetetraacetic acid (EDTA), ethylenediamine-N,N'-bis (2-hydroxyphenylacetic acid) (EDDHA), citric acid, nitrilotriacetic acid (NTA), N,N-dimethylacetamide (DMA), 1,4-dioxane, dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF) and tetrahydrofuran (THF)] were inhibitory. Inhibitory effect of NTA, EDDHA, THF, DMF, DMA and amines on anammox was first determined in this study. Inhibitory effects of metals were re-evaluated because chelators, which may interfere inhibitory effect, have been used to dissolve metal salts into assay solution. The relative anammox activities as a function of concentration of each substance were described successfully (R 2  > 0.91) either with a linear inhibition model or with a Michaelis-Menten-based inhibition model. IC 50 values were estimated based on either model, and were compared. The IC 50 values of the 4 chelators (0.06-2.7 mM) and 5 metal ions (0.02-1.09 mM) were significantly lower than those of the 4 amines (10.6-29.1 mM) and 5 organic solvents (3.5-82 mM). Although it did not show any inhibition within 25 min, 0.1 mM Cu 2+ completely inhibited anammox activity in 240 min, suggesting that the inhibitory effect caused by Cu 2+ is time-dependent. Copyright © 2017 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

21 CFR 178.3950 - Tetrahydrofuran.

Code of Federal Regulations, 2011 CFR

2011-04-01

... provisions of this section. (a) It is used as a solvent in the casting of film from a solution of polymeric... copolymerized with one another in any combination, or it may be used as a solvent in the casting of film... of tetrahydrofuran in the film does not exceed 1.5 percent by weight of film. ...

21 CFR 178.3950 - Tetrahydrofuran.

Code of Federal Regulations, 2013 CFR

2013-04-01

... provisions of this section. (a) It is used as a solvent in the casting of film from a solution of polymeric... copolymerized with one another in any combination, or it may be used as a solvent in the casting of film... of tetrahydrofuran in the film does not exceed 1.5 percent by weight of film. ...

21 CFR 178.3950 - Tetrahydrofuran.

Code of Federal Regulations, 2014 CFR

2014-04-01

... solvent in the casting of film from a solution of polymeric resins of vinyl chloride, vinyl acetate, or..., or it may be used as a solvent in the casting of film prepared from vinyl chloride copolymers complying with § 177.1980 of this chapter. (b) The residual amount of tetrahydrofuran in the film does not...

21 CFR 178.3950 - Tetrahydrofuran.

Code of Federal Regulations, 2012 CFR

2012-04-01

... provisions of this section. (a) It is used as a solvent in the casting of film from a solution of polymeric... copolymerized with one another in any combination, or it may be used as a solvent in the casting of film... of tetrahydrofuran in the film does not exceed 1.5 percent by weight of film. ...

Synthesis and Characterization of Dipolar Organic Molecules for Nonlinear Optical Materials

DTIC Science & Technology

1992-05-08

BH3, THF; then, aqueous NaOH; ii. pyridinium chlorochromate , methylene chloride; iii. lithium diisopropylamide, THF 50 effective. After purification... pyridinium chlorochromate (1.5 g, 6.96 mmol) was added. The solution was stirred at room temperature for 48 hours. The organic solution was decanted from...the alcohol was oxidized to the aldehyde. Swern oxidation5 was first attempted but gave very low yield in our hands. Alternatively, pyridinium chloro

Synthesis of the (N2)3- radical from Y2+ and its protonolysis reactivity to form (N2H2)2- via the Y[N(SiMe3)2]3/KC8 reduction system.

PubMed

Fang, Ming; Lee, David S; Ziller, Joseph W; Doedens, Robert J; Bates, Jefferson E; Furche, Filipp; Evans, William J

2011-03-23

Examination of the Y[N(SiMe(3))(2)](3)/KC(8) reduction system that allowed isolation of the (N(2))(3-) radical has led to the first evidence of Y(2+) in solution. The deep-blue solutions obtained from Y[N(SiMe(3))(2)](3) and KC(8) in THF at -35 °C under argon have EPR spectra containing a doublet at g(iso) = 1.976 with a 110 G hyperfine coupling constant. The solutions react with N(2) to generate (N(2))(2-) and (N(2))(3-) complexes {[(Me(3)Si)(2)N](2)(THF)Y}(2)(μ-η(2):η(2)-N(2)) (1) and {[(Me(3)Si)(2)N](2)(THF)Y}(2)(μ-η(2):η(2)-N(2))[K(THF)(6)] (2), respectively, and demonstrate that the Y[N(SiMe(3))(2)](3)/KC(8) reaction can proceed through an Y(2+) intermediate. The reactivity of (N(2))(3-) radical with proton sources was probed for the first time for comparison with the (N(2))(2-) and (N(2))(4-) chemistry. Complex 2 reacts with [Et(3)NH][BPh(4)] to form {[(Me(3)Si)(2)N](2)(THF)Y}(2)(μ-N(2)H(2)), the first lanthanide (N(2)H(2))(2-) complex derived from dinitrogen, as well as 1 as a byproduct, consistent with radical disproportionation reactivity.

Hydrogen storage in double clathrates with tert-butylamine.

PubMed

Prasad, Pinnelli S R; Sugahara, Takeshi; Sum, Amadeu K; Sloan, E Dendy; Koh, Carolyn A

2009-06-18

The first proof-of-concept of the formation of a double tert-butylamine (t-BuNH(2)) + hydrogen (H(2)) clathrate hydrate has been demonstrated. Binary clathrate hydrates with different molar concentrations of the large guest t-BuNH(2) (0.98-9.31 mol %) were synthesized at 13.8 MPa and 250 K, and characterized by powder X-ray diffraction and Raman microscopy. A structural transformation from sVI to sII of t-BuNH(2) hydrate was clearly observed under hydrogen pressures. Raman spectroscopic data suggested that the hydrogen molecules occupied the small cages and had similar occupancy to hydrogen in the double tetrahydrofuran (THF) + H(2) clathrate hydrate. The hydrogen storage capacity in this system was approximately 0.7 H(2) wt % at the molar concentration of t-BuNH(2) close to the sII stoichiometry.

Time-resolved analysis of nonlinear optical limiting for laser synthesized carbon nanoparticles

NASA Astrophysics Data System (ADS)

Chen, G. X.; Hong, M. H.

2010-11-01

Nonlinear optical limiting materials have attracted much research interest in recent years. Carbon nanoparticles suspended in liquids show a strong nonlinear optical limiting function. It is important to investigate the nonlinear optical limiting process of carbon nanoparticles for further improving their nonlinear optical limiting performance. In this study, carbon nanoparticles were prepared by laser ablation of a carbon target in tetrahydrofuran (THF). Optical limiting properties of the samples were studied with 532-nm laser light, which is in the most sensitive wavelength band for human eyes. The shape of the laser pulse plays an important role for initializing the nonlinear optical limiting effect. Time-resolved analysis of laser pulses discovered 3 fluence stages of optical limiting. Theoretical simulation indicates that the optical limiting is initialized by a near-field optical enhancement effect.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chew, K. W.; Chen, S. S.; Pang, W. L.

The effects of Lithium triflate salt (LiCF{sub 3}SO{sub 3}), on the poly (methyl methacrylate)(PMMA)-based solid polymer electrolytes plasticized with propylene carbonate (PC) solvated in Tetrahydrofuran (THF) have been studied through a.c impedance spectroscopy and infrared spectroscopy. Lithium triflate was incorporated into the predetermined PMMA/PC system that has the highest value of ionic conductivity. In current investigations, four combination systems: Pure PMMA, (PMMA+PC) systems, (PMMA+LiCF{sub 3}SO{sub 3}) and (PMMA+PC+LiCF{sub 3}SO{sub 3}) systems were prepared using the solution cast method. Solutions were stirred for numerous hours to obtain a homogenous solution before it is poured into the petri dishes under ambient temperaturemore » to form the solid electrolyte thin film. The films were then removed from petri discs and transferred into the dessicator for further drying prior to the different tests. From the characterization done through the a.c impedance spectroscopy, the highest room temperature ionic conductivity in the pure PMMA sample, (PMMA+PC) system and (PMMA+LiCF{sub 3}SO{sub 3}) system is 2.83x10{sup -12} Scm{sup -1}, 4.39x10{sup -11} Scm{sup -1} and 3.93x10{sup -6} Scm{sup -1} respectively. The conductivity for (PMMA+PC+LiCF{sub 3}SO{sub 3}) system was obtained with the 30 wt% of lithium triflate, which is 2.48x10{sup -5} Scm{sup -1}. Infrared spectroscopy shows that complexation occurred between the polymer and the plasticizer, and the polymer and plasticizer and salt. The interactions have been studied in the C=O band, C-O-C band and the O-CH{sub 3} band.« less

Alkaline earth metal complexes of a phosphine-borane-stabilized carbanion: synthesis, structures, and stabilities.

PubMed

Izod, Keith; Wills, Corinne; Clegg, William; Harrington, Ross W

2007-05-14

The reaction between either MgI2 or CaI2 and 2 equiv of [(Me3Si)2{Me2(H3B)P}C]K (2) in toluene gives the corresponding organo-alkaline earth metal compounds [(Me3Si)2{Me2(H3B)P}C]2M in moderate to good yields [M = Mg (3), Ca (4)]. Compound 3 crystallizes solvent-free, whereas X-ray quality crystals of 4 could not be obtained in the absence of coordinating solvents; crystallization of 4 from cold methylcyclohexane/THF gives the solvate [(Me3Si)2{Me2(H3B)P}C]2Ca(THF)4 (4a). The corresponding heavier alkaline earth metal complexes [(Me3Si)2{Me2(H3B)P}C]2M(THF)5 [M = Sr (7), Ba (8)] are obtained from the reaction between MI2 and 2 equiv of 2 in THF, followed by recrystallization from cold methylcyclohexane/THF. Compound 3 degrades over a period of several weeks at room-temperature both in the solid state and in toluene solution to give the free phosphine-borane (Me3Si)2{Me2(H3B)P}CH (5) as the sole phosphorus-containing product. In addition, compounds 3, 4, and 4a react rapidly with THF in toluene solution, yielding 5 as the sole phosphorus-containing product; in contrast, compounds 7 and 8 are stable toward this solvent.

Multidetector thermal field-flow fractionation as a novel tool for the microstructure separation of polyisoprene and polybutadiene.

PubMed

Greyling, Guilaume; Pasch, Harald

2014-11-01

For the first time, it is demonstrated that thermal field-flow fractionation (ThFFF) is an efficient tool for the fractionation of polyisoprene (PI) and polybutadiene (PB) with regard to molecular microstructure. ThFFF analysis of 1,4- and 3,4-PI as well as 1,4- and 1,2-PB samples in tetrahydrofuran (THF), THF/cyclohexane, and cyclohexane reveals that isomers of the same polymer family having similar molar masses exhibit different Soret coefficients depending on microstructure for each solvent. The separation according to microstructure is found to be based on the cooperative influence of the normal and the thermal diffusion coefficient. Of the three solvents, cyclohexane has the greatest influence on the fractionation of the isomers. In order to determine the distribution of isomeric structures in the PI and PB samples, the samples are fractionated by ThFFF in cyclohexane and subsequently analyzed by (1) H NMR. The isomeric distributions determined from NMR data correlate well with ThFFF retention data of the samples and thus further highlight the unique fractionating capabilities of ThFFF. The interplay of the normal and thermal diffusion coefficients that are influenced by temperature and the mobile phase opens the way to highly selective fractionations without the drawbacks of column-based separation methods. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Diimine triscarbonyl Re(I) of isomeric pyridyl-fulvene ligands: an electrochemical, spectroscopic, and computational investigation.

PubMed

Chartrand, Daniel; Castro Ruiz, Carlos A; Hanan, Garry S

2012-12-03

The synthesis and characterization of a novel family of positively charged fac-[Re(bpy)(CO)(3)(L)]PF(6) (bpy = 2,2'-bipyridine) complexes are reported, where L is a pyridine functionalized in para or meta position with a fulvene moiety, namely, 4-fluoren-9-ylidenemethyl-pyridine (pFpy) and 3-fluoren-9-ylidenemethyl-pyridine (mFpy). The complexes were prepared in high yield (86%) by direct addition at room temperature of the corresponding pyridine to the tetrahydrofuran (THF) adduct fac-[Re(bpy)(CO)(3)(THF)][PF(6)] precursor. Both ligand and complex structures were fully characterized by a variety of techniques including X-ray crystallography. The complexes did not exhibit the expected triplet mixed metal-ligand-to-ligand charge transfer (MLLCT) emission, because of its deactivation by the non-emissive triplet excited state of fulvene. The absorption profile shows that the MLLCT is overshadowed by the fulvene centered π-π* transition of higher molar absorptivity as shown by time dependent density functional theory (TD-DFT) calculations. The position of the fulvene on the pyridyl ring has a large effect on this transition, the para position displaying a much higher absorption coefficient (21.3 × 10(3) M(-1) cm(-1)) at lower energy (364 nm) than the meta position (331 nm, 16.0 × 10(3) M(-1) cm(-1)).

β-SiH-containing tris(silazido) rare-earth complexes as homogeneous and grafted single-site catalyst precursors for hydroamination

DOE PAGES

Eedugurala, Naresh; Wang, Zhuoran; Yan, KaKing; ...

2017-01-25

A series of homoleptic rare-earth silazido compounds and their silica-grafted derivatives were prepared to compare spectroscopic and catalytic features under homogeneous and interfacial conditions. Trivalent tris(silazido) compounds Ln{N(SiHMe 2) tBu} 3 (Ln = Sc (1), Y (2), Lu (3)) are prepared in high yield by salt metathesis reactions. Solution-phase and solid-state characterization of 1–3 by NMR and IR spectroscopy and X-ray diffraction reveals Ln←H–Si interactions. These features are retained in solvent-coordinated 2·Et 2O, 2·THF, and 3·THF. The change in spectroscopic features characterizing the secondary interactions (ν SiH, 1 J SiH) from the unactivated SiH in the silazane HN(SiHMe 2) tBumore » follows the trend 3 > 2 > 1 ≈ 2·Et 2O > 2·THF ≈ 3·THF. Ligand lability follows the same pattern, with Et 2O readily dissociating from 2·Et 2O while THF is displaced only during surface grafting reactions. 1 and 2·THF graft onto mesoporous silica nanoparticles (MSN) to give Ln{N(SiHMe 2) tBu} n@MSN (Ln = Sc (1@MSN), Y (2@MSN)) along with THF and protonated silazido as HN(SiHMe 2) tBu and H 2N tBu. The surface species are characterized by multinuclear and multidimensional solid-state (SS) NMR spectroscopic techniques, as well as diffuse reflectance FTIR, elemental analysis, and reaction stoichiometry. A key 1 J SiH SSNMR measurement reveals that the grafted sites most closely resemble Ln·THF adducts, suggesting that siloxane coordination occurs in grafted compounds. These species catalyze the hydroamination/bicyclization of aminodialkenes, and both solution-phase and interfacial conditions provide the bicyclized product with equivalent cis:trans ratios. As a result, similar diastereoselectivities mediated by catalytic sites under the two conditions suggest similar effective environments.« less

Conversion of lanthanide glutarate chlorides with interstitial THF into lanthanide glutarates with unprecedented topologies

DOE PAGES

Zehnder, Ralph A.; Jenkins, James; Zeller, Matthias; ...

2017-11-26

Here, using slow diffusion methods at room temperature (RT), we obtained four isomorphous lanthanide glutarate chlorides, accommodating interstitial THF and water molecules, [Ln 2(Glut) 2Cl 2(H 2O) 8]·2H 2O·THF, with Ln = La , Ce, Pr, Nd. They assemble as 3-dimensional (3D) lanthanide (Ln) coordination polymers with LnO 10 coordination polyhedra. Their topology was elucidated to be a 4-coordinated sql net. slowly dissolve in water liberating the entrapped THF molecules and reassemble as regular Ln-glutarate hydrates when the solution is deprived of THF and water by slow evaporation. The new products crystallize as [Ln 2(Glut) 3(H 2O) 3]·5H 2O, withmore » Ln = La, Ce, Pr, and [Nd 2(Glut) 3(H 2O) 2]·3.5H 2O.« less

Conversion of lanthanide glutarate chlorides with interstitial THF into lanthanide glutarates with unprecedented topologies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zehnder, Ralph A.; Jenkins, James; Zeller, Matthias

Here, using slow diffusion methods at room temperature (RT), we obtained four isomorphous lanthanide glutarate chlorides, accommodating interstitial THF and water molecules, [Ln 2(Glut) 2Cl 2(H 2O) 8]·2H 2O·THF, with Ln = La , Ce, Pr, Nd. They assemble as 3-dimensional (3D) lanthanide (Ln) coordination polymers with LnO 10 coordination polyhedra. Their topology was elucidated to be a 4-coordinated sql net. slowly dissolve in water liberating the entrapped THF molecules and reassemble as regular Ln-glutarate hydrates when the solution is deprived of THF and water by slow evaporation. The new products crystallize as [Ln 2(Glut) 3(H 2O) 3]·5H 2O, withmore » Ln = La, Ce, Pr, and [Nd 2(Glut) 3(H 2O) 2]·3.5H 2O.« less

Optical characterization of CdS nanoparticles embedded into the comb-type amphiphilic graft copolymer

NASA Astrophysics Data System (ADS)

Kalaycı, Özlem A.; Duygulu, Özgür; Hazer, Baki

2013-01-01

This study refers to the synthesis and characterization of a novel organic/inorganic hybrid nanocomposite material containing cadmium sulfide (CdS) nanoparticles. For this purpose, a series of polypropylene (PP)-g-polyethylene glycol (PEG), PP-g-PEG comb-type amphiphilic graft copolymers were synthesized. PEGs with Mn = 400, 2000, 3350, and 8000 Da were used and the graft copolymers obtained were coded as PPEG400, PPEG2000, PPEG3350, and PPEG8000. CdS nanoparticles were formed in tetrahydrofuran solution of PP-g-PEG amphiphilic comb-type copolymer by the reaction between aqueous solutions of Na2S and Cd(CH3COO)2 simultaneously. Micelle formation of PPEG2000 comb-type amphiphilic graft copolymer in both solvent/non-solvent (petroleum ether-THF) by transmission electron microscopy (TEM). The optical characteristics, size morphology, phase analysis, and dispersion of CdS nanoparticles embedded in PPEG400, PPEG2000, PPEG3350, and PPEG8000 comb-type amphiphilic graft copolymer micelles were determined by high resolution TEM (HRTEM), energy dispersive spectroscopy, UV-vis spectroscopy, and fluorescence emission spectroscopy techniques. The aggregate size of PPEG2000-CdS is between 10 and 50 nm; however, in the case of PPEG400-CdS, PPEG3350-CdS, and PPEG8000-CdS samples, it is up to approximately 100 nm. The size of CdS quantum dots in the aggregates for PPEG2000 and PPEG8000 samples was observed as 5 nm by HRTEM analysis, and this result was also supported by UV-vis absorbance spectra and fluorescence emission spectra.

Insight into substrate binding in Shibasaki's Li3(THF)n(BINOLate)3Ln complexes and implications in catalysis.

PubMed

Wooten, Alfred J; Carroll, Patrick J; Walsh, Patrick J

2008-06-11

Heterobimetallic Lewis acids M 3(THF) n (BINOLate) 3Ln [M = Li, Na, K; Ln = lanthanide(III)] are exceptionally useful asymmetric catalysts that exhibit high levels of enantioselectivity across a wide range of reactions. Despite their prominence, important questions remain regarding the nature of the catalyst-substrate interactions and, therefore, the mechanism of catalyst operation. Reported herein are the isolation and structural characterization of 7- and 8-coordinate heterobimetallic complexes Li 3(THF) 4(BINOLate) 3Ln(THF) [Ln = La, Pr, and Eu], Li 3(py) 5(BINOLate) 3Ln(py) [Ln = Eu and Yb], and Li 3(py) 5(BINOLate) 3La(py) 2 [py = pyridine]. Solution binding studies of cyclohexenone, DMF, and pyridine with Li 3(THF) n (BINOLate) 3Ln [Ln = Eu, Pr, and Yb] and Li 3(DMEDA) 3(BINOLate) 3Ln [Ln = La and Eu; DMEDA = N, N'-dimethylethylene diamine] demonstrate binding of these Lewis basic substrate analogues to the lanthanide center. The paramagnetic europium, ytterbium, and praseodymium complexes Li 3(THF) n (BINOLate) 3Ln induce relatively large lanthanide-induced shifts on substrate analogues that ranged from 0.5 to 4.3 ppm in the (1)H NMR spectrum. X-ray structure analysis and NMR studies of Li 3(DMEDA) 3(BINOLate) 3Ln [Ln = Lu, Eu, La, and the transition metal analogue Y] reveal selective binding of DMEDA to the lithium centers. Upon coordination of DMEDA, six new stereogenic nitrogen centers are formed with perfect diastereoselectivity in the solid state, and only a single diastereomer is observed in solution. The lithium-bound DMEDA ligands are not displaced by cyclohexenone, DMF, or THF on the NMR time scale. Use of the DMEDA adduct Li 3(DMEDA) 3(BINOLate) 3La in three catalytic asymmetric reactions led to enantioselectivities similar to those obtained with Shibasaki's Li 3(THF) n (BINOLate) 3La complex. Also reported is a unique dimeric [Li 6(en) 7(BINOLate) 6Eu 2][mu-eta (1),eta (1)-en] structure [en = ethylenediamine]. On the basis of these studies, it is hypothesized that the lanthanide in Shibasaki's Li 3(THF) n (BINOLate) 3Ln complexes cannot bind bidentate substrates in a chelating fashion. A hypothesis is also presented to explain why the lanthanide catalyst, Li 3(THF) n (BINOLate) 3La, is often the most enantioselective of the Li 3(THF) n (BINOLate) 3Ln derivatives.

Chemical and morphological characteristics of lithium electrode surfaces

NASA Technical Reports Server (NTRS)

Yen, S. P. S.; Shen, D.; Vasquez, R. P.; Grunthaner, F. J.; Somoano, R. B.

1981-01-01

Lithium electrode surfaces were analyzed for chemical and morphological characteristics, using electron spectroscopy chemical analysis (ESCA) and scanning electron microscopy (SEM). Samples included lithium metal and lithium electrodes which were cycled in a 1.5 M lithium arsenic hexafluoride/two-methyl tetrahydrofuran electrolyte. Results show that the surface of the as-received lithium metal was already covered by a film composed of LiO2 and an Li2O/CO2 adduct with a thickness of approximately 100-200 A. No evidence of Ni3 was found. Upon exposure of the lithium electrode to a 1.5 M LiAsF6/2-Me-THF electrochemical environment, a second film was observed to form on the surface, consisting primarily of As, Si, and F, possibly in the form of lithium arsenic oxyfluorides or lithium fluorosilicates. It is suggested that the film formation may be attributed to salt degradation.

Sample preparation for sequencing hits from one-bead-one-peptide combinatorial libraries by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

PubMed

Martínez-Ceron, María C; Giudicessi, Silvana L; Marani, Mariela M; Albericio, Fernando; Cascone, Osvaldo; Erra-Balsells, Rosa; Camperi, Silvia A

2010-05-15

Optimization of bead analysis by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) after the screening of one-bead-one-peptide combinatorial libraries was achieved, involving the fine-tuning of the whole process. Guanidine was replaced by acetonitrile (MeCN)/acetic acid (AcOH)/water (H(2)O), improving matrix crystallization. Peptide-bead cleavage with NH(4)OH was cheaper and safer than, yet as efficient as, NH(3)/tetrahydrofuran (THF). Peptide elution in microtubes instead of placing the beads in the sample plate yielded more sample aliquots. Successive dry layers deposit sample preparation was better than the dried droplet method. Among the matrices analyzed, alpha-cyano-4-hydroxycinnamic acid resulted in the best peptide ion yield. Cluster formation was minimized by the addition of additives to the matrix. Copyright 2010 Elsevier Inc. All rights reserved.

Robust Guar Gum/Cellulose Nanofibrils Multilayer Films with Good Barrier Properties.

PubMed

Dai, Lei; Long, Zhu; Chen, Jie; An, Xingye; Cheng, Dong; Khan, Avik; Ni, Yonghao

2017-02-15

The pursuit of sustainable functional materials requires development of materials based on renewable resources and efficient fabrication methods. Hereby, we fabricated all-polysaccharides multilayer films using cationic guar gum (CGG) and anionic cellulose nanofibrils (i.e., TEMPO-oxidized cellulose nanofibrils, TOCNs) through a layer-by-layer casting method. This technique is based on alternate depositions of oppositely charged water-based CGG and TOCNs onto laminated films. The resultant polyelectrolyte multilayer films were transparent, ductile, and strong. More importantly, the self-standing films exhibited excellent gas (water vapor and oxygen) and oil barrier performances. Another outstanding feature of these resultant films was their resistance to various organic solvents including methanol, acetone, N,N-dimethylacetamide (DMAc) and tetrahydrofuran (THF). The proposed film fabrication process is environmentally benign, cost-effective, and easy to scale-up. The developed CGG/TOCNs multilayer films can be used as a renewable material for industrial applications such as packaging.

Highly Sensitive and Selective Gas Sensor Using Hydrophilic and Hydrophobic Graphenes

PubMed Central

Some, Surajit; Xu, Yang; Kim, Youngmin; Yoon, Yeoheung; Qin, Hongyi; Kulkarni, Atul; Kim, Taesung; Lee, Hyoyoung

2013-01-01

New hydrophilic 2D graphene oxide (GO) nanosheets with various oxygen functional groups were employed to maintain high sensitivity in highly unfavorable environments (extremely high humidity, strong acidic or basic). Novel one-headed polymer optical fiber sensor arrays using hydrophilic GO and hydrophobic reduced graphene oxide (rGO) were carefully designed, leading to the selective sensing of volatile organic gases for the first time. The two physically different surfaces of GO and rGO could provide the sensing ability to distinguish between tetrahydrofuran (THF) and dichloromethane (MC), respectively, which is the most challenging issue in the area of gas sensors. The eco-friendly physical properties of GO allowed for faster sensing and higher sensitivity when compared to previous results for rGO even under extreme environments of over 90% humidity, making it the best choice for an environmentally friendly gas sensor. PMID:23736838

Single-photon and two-photon excited fluorescence behavior of a novel fluorene-based compound

NASA Astrophysics Data System (ADS)

Ma, Wenbo; Wu, Yiquan; Gu, Donghong; Gan, Fuxi

2005-09-01

A D-π-D type compound, 2,7-bis(4-methoxystyryl)-9,9-bis(2-ethylhexyl)-9H-fluorene (abbreviated as MO-Flu-MO), where electron-donor D is methoxy group andπis fluorene unit, has been synthesized. The molecular structures of the compound were characterized by elemental analyses, EI-MS and FT-IR spectra. UV-Vis spectra in the region 230--1000 nm and single-photon excited fluorescence in tetrahydrofuran (THF) of the compound were measured. It is found that the new compound exhibits strong two-photon excited fluorescence in the region 380--500 nm and moderate two-photon absorption (TPA) value in the femtoseconds regime (TPA cross-section as high as 55×10-50 cm4 s photon-1 with 13fs laser pulses). The results demonstrate that the compound is a promising candidate for two-photon three-dimensional (3D) optical data storage.

Solvothermal Vapor Annealing of Lamellar Poly(styrene)-block-poly(d,l-lactide) Block Copolymer Thin Films for Directed Self-Assembly Application.

PubMed

Cummins, Cian; Mokarian-Tabari, Parvaneh; Andreazza, Pascal; Sinturel, Christophe; Morris, Michael A

2016-03-01

Solvothermal vapor annealing (STVA) was employed to induce microphase separation in a lamellar forming block copolymer (BCP) thin film containing a readily degradable block. Directed self-assembly of poly(styrene)-block-poly(d,l-lactide) (PS-b-PLA) BCP films using topographically patterned silicon nitride was demonstrated with alignment over macroscopic areas. Interestingly, we observed lamellar patterns aligned parallel as well as perpendicular (perpendicular microdomains to substrate in both cases) to the topography of the graphoepitaxial guiding patterns. PS-b-PLA BCP microphase separated with a high degree of order in an atmosphere of tetrahydrofuran (THF) at an elevated vapor pressure (at approximately 40-60 °C). Grazing incidence small-angle X-ray scattering (GISAXS) measurements of PS-b-PLA films reveal the through-film uniformity of perpendicular microdomains after STVA. Perpendicular lamellar orientation was observed on both hydrophilic and relatively hydrophobic surfaces with a domain spacing (L0) of ∼32.5 nm. The rapid removal of the PLA microdomains is demonstrated using a mild basic solution for the development of a well-defined PS mask template. GISAXS data reveal the through-film uniformity is retained following wet etching. The experimental results in this article demonstrate highly oriented PS-b-PLA microdomains after a short annealing period and facile PLA removal to form porous on-chip etch masks for nanolithography application.

Micelles as Delivery Vehicles for Oligofluorene for Bioimaging

PubMed Central

Su, Fengyu; Alam, Ruhaniyah; Mei, Qian; Tian, Yanqing; Meldrum, Deirdre R.

2011-01-01

With the successful development of organic/polymeric light emitting diodes, many organic and polymeric fluorophores with high quantum efficiencies and optical stability were synthesized. However, most of these materials which have excellent optical properties are insoluble in water, limiting their applications in biological fields. Herein, we used micelles formed from an amino-group-containing poly(ε-caprolactone)-block-poly(ethylene glycol) (PCL-b-PEG-NH2) to incorporate a hydrophobic blue emitter oligofluorene (OF) to enable its application in biological conditions. Although OF is completely insoluble in water, it was successfully transferred into aqueous solutions with a good retention of its photophysical properties. OF exhibited a high quantum efficiency of 0.84 in a typical organic solvent of tetrahydrofuran (THF). In addition, OF also showed a good quantum efficiency of 0.46 after being encapsulated into micelles. Two cells lines, human glioblastoma (U87MG) and esophagus premalignant (CP-A), were used to study the cellular internalization of the OF incorporated micelles. Results showed that the hydrophobic OF was located in the cytoplasm, which was confirmed by co-staining the cells with nucleic acid specific SYTO 9, lysosome specific LysoTracker Red®, and mitochondria specific MitoTracker Red. MTT assay indicated non-toxicity of the OF-incorporated micelles. This study will broaden the application of hydrophobic functional organic compounds, oligomers, and polymers with good optical properties to enable their applications in biological research fields. PMID:21915324

Micelles as delivery vehicles for oligofluorene for bioimaging.

PubMed

Su, Fengyu; Alam, Ruhaniyah; Mei, Qian; Tian, Yanqing; Meldrum, Deirdre R

2011-01-01

With the successful development of organic/polymeric light emitting diodes, many organic and polymeric fluorophores with high quantum efficiencies and optical stability were synthesized. However, most of these materials which have excellent optical properties are insoluble in water, limiting their applications in biological fields. Herein, we used micelles formed from an amino-group-containing poly(ε-caprolactone)-block-poly(ethylene glycol) (PCL-b-PEG-NH(2)) to incorporate a hydrophobic blue emitter oligofluorene (OF) to enable its application in biological conditions. Although OF is completely insoluble in water, it was successfully transferred into aqueous solutions with a good retention of its photophysical properties. OF exhibited a high quantum efficiency of 0.84 in a typical organic solvent of tetrahydrofuran (THF). In addition, OF also showed a good quantum efficiency of 0.46 after being encapsulated into micelles. Two cells lines, human glioblastoma (U87MG) and esophagus premalignant (CP-A), were used to study the cellular internalization of the OF incorporated micelles. Results showed that the hydrophobic OF was located in the cytoplasm, which was confirmed by co-staining the cells with nucleic acid specific SYTO 9, lysosome specific LysoTracker Red®, and mitochondria specific MitoTracker Red. MTT assay indicated non-toxicity of the OF-incorporated micelles. This study will broaden the application of hydrophobic functional organic compounds, oligomers, and polymers with good optical properties to enable their applications in biological research fields.

Mapping CTTS dynamics of Na- in tetrahydrofurane with ultrafast multichannel pump-probe spectroscopy.

PubMed

Shoshana, O; Pérez Lustres, J L; Ernsting, N P; Ruhman, S

2006-06-14

Using multichannel femtosecond spectroscopy we have followed Na- charge transfer to solvent (CTTS) dynamics in THF solution. Absorption of the primary photoproducts in the visible, resolved here for the first time, consists of an asymmetric triplet centered at 595 nm, which we assign to a metastable incompletely solvated neutral atomic sodium species. Decay of this feature within approximately 1 ps to a broad and structureless solvated neutral is accompanied by broadening and loss of spectral detail. Kinetic analysis shows that both the spectral structure and the decay of this band are independent of the excitation photon frequency in the range 400-800 nm. With different pump-probe polarizations the anisotropy in transient transmission has been charted and its variation with excitation wavelength surveyed. The anisotropies are assigned to the reactant bleach, indicating that due to solvent-induced symmetry breaking, the CTTS absorption band of Na- is made up of discreet orthogonally polarized sub bands. None of the anisotropy in transient absorption could be associated with the photoproduct triplet band even at the earliest measurable time delays. Along with the documented differences in the spatial distribution of ejected electrons across the tested excitation wavelength range, these results lead us to conclude that photoejection is extremely rapid, and that loss of correlations between the departing electron and its neutral core is faster than our time resolution of approximately 60 fs.

Understanding the Phase Behavior of Tetrahydrofuran + Carbon Dioxide, + Methane, and + Water Binary Mixtures from the SAFT-VR Approach.

PubMed

Míguez, J M; Piñeiro, M M; Algaba, J; Mendiboure, B; Torré, J P; Blas, F J

2015-11-05

The high-pressure phase diagrams of the tetrahydrofuran(1) + carbon dioxide(2), + methane(2), and + water(2) mixtures are examined using the SAFT-VR approach. Carbon dioxide molecule is modeled as two spherical segments tangentially bonded, water is modeled as a spherical segment with four associating sites to represent the hydrogen bonding, methane is represented as an isolated sphere, and tetrahydrofuran is represented as a chain of m tangentially bonded spherical segments. Dispersive interactions are modeled using the square-well intermolecular potential. In addition, two different molecular model mixtures are developed to take into account the subtle balance between water-tetrahydrofuran hydrogen-bonding interactions. The polar and quadrupolar interactions present in water, tetrahydrofuran, and carbon dioxide are treated in an effective way via square-well potentials of variable range. The optimized intermolecular parameters are taken from the works of Giner et al. (Fluid Phase Equil. 2007, 255, 200), Galindo and Blas (J. Phys. Chem. B 2002, 106, 4503), Patel et al. (Ind. Eng. Chem. Res. 2003, 42, 3809), and Clark et al. (Mol. Phys. 2006, 104, 3561) for tetrahydrofuran, carbon dioxide, methane, and water, respectively. The phase diagrams of the binary mixtures exhibit different types of phase behavior according to the classification of van Konynenburg and Scott, ranging from types I, III, and VI phase behavior for the tetrahydrofuran(1) + carbon dioxide(2), + methane(2), and + water(2) binary mixtures, respectively. This last type is characterized by the presence of a Bancroft point, positive azeotropy, and the so-called closed-loop curves that represent regions of liquid-liquid immiscibility in the phase diagram. The system exhibits lower critical solution temperatures (LCSTs), which denote the lower limit of immiscibility together with upper critical solution temperatures (UCSTs). This behavior is explained in terms of competition between the incompatibility with the alkyl parts of the tetrahydrofuran ring chain and the hydrogen bonding between water and the ether group. A minimum number of unlike interaction parameters are fitted to give the optimal representation of the most representative features of the binary phase diagrams. In the particular case of tetrahydrofuran(1) + water(2), two sets of intermolecular potential model parameters are proposed to describe accurately either the hypercritical point associated with the closed-loop liquid-liquid immiscibility region or the location of the mixture lower- and upper-critical end-points. The theory is not only able to predict the type of phase behavior of each mixture, but also provides a reasonably good description of the global phase behavior whenever experimental data are available.

Highly enantioselective arylation of aldehydes and ketones using AlArEt(2)(THF) as aryl sources.

PubMed

Zhou, Shuangliu; Wu, Kuo-Hui; Chen, Chien-An; Gau, Han-Mou

2009-05-01

A series of AlArEt(2)(THF) (Ar = Ph (1a), 4-MeC(6)H(4) (1b), 4-MeOC(6)H(4) (1c), 4-Me(3)SiC(6)H(4) (1d), 2-naphthyl (1e)) were synthesized from reactions of AlEt(2)Br(THF) with ArMgBr. In CDCl(3) solution, the (1)H NMR spectra showed that AlArEt(2)(THF) compounds exist as a mixture of four species of formulas of AlAr(x)Et(3-x) (THF) (x = 0, 1, 2, or 3). AlArEt(2)(THF) compounds were found to be superior and atom-economic reagents for asymmetric aryl additions to organic carbonyls. Aryl additions of AlArEt(2)(THF) to aldehydes catalyzed by the titanium(IV) complex of (R)-H(8)-BINOL were efficient with a short reaction time of 1 h, affording aryl addition products as exclusive or main products in high yields and excellent enantioselectivities of up to 98% ee. Although ethyl additions to aldehydes occurred in minor extent, this study demonstrates that increasing the amount of AlArEt(2)(THF) from 1.2 to 1.4 or to 1.6 equiv significantly improved the aryl addition products of up to >99%. On the other hand, asymmetric arylations of AlArEt(2)(THF) to ketones employing a titanium(IV) catalyst of (S)-BINOL produced optically active tertiary alcohols exclusively in excellent enantioselectivities of up to 94% ee.

Evaluation of specimen preparation techniques for micro-PIXE localisation of elements in hyperaccumulating plants

NASA Astrophysics Data System (ADS)

Kachenko, Anthony G.; Siegele, Rainer; Bhatia, Naveen P.; Singh, Balwant; Ionescu, Mihail

2008-04-01

Hybanthus floribundus subsp. floribundus, a rare Australian Ni-hyperaccumulating shrub and Pityrogramma calomelanos var. austroamericana, an Australian naturalized As-hyperaccumulating fern are promising species for use in phytoremediation of contaminated sites. Micro-proton-induced X-ray emission (μ-PIXE) spectroscopy was used to map the elemental distribution of the accumulated metal(loid)s, Ca and K in leaf or pinnule tissues of the two plant species. Samples were prepared by two contrasting specimen preparation techniques: freeze-substitution in tetrahydrofuran (THF) and freeze-drying. The specimens were analysed to compare the suitability of each technique in preserving (i) the spatial elemental distribution and (ii) the tissue structure of the specimens. Further, the μ-PIXE results were compared with concentration of elements in the bulk tissue obtained by ICP-AES analysis. In H. floribundus subsp. floribundus, μ-PIXE analysis revealed Ni, Ca and K concentrations in freeze-dried leaf tissues were at par with bulk tissue concentrations. Elemental distribution maps illustrated that Ni was preferentially localised in the adaxial epidermal tissues (1% DW) and least concentration was found in spongy mesophyll tissues (0.53% DW). Conversely, elemental distribution maps of THF freeze-substituted tissues indicated significantly lower Ni, Ca and K concentrations than freeze-dried specimens and bulk tissue concentrations. Moreover, Ni concentrations were uniform across the whole specimen and no localisation was observed. In P. calomelanos var. austroamericana freeze-dried pinnule tissues, μ-PIXE revealed statistically similar As, Ca and K concentrations as compared to bulk tissue concentrations. Elemental distribution maps showed that As localisation was relatively uniform across the whole specimen. Once again, THF freeze-substituted tissues revealed a significant loss of As compared to freeze-dried specimens and the concentrations obtained by bulk tissue analysis. The results demonstrate that freeze-drying is a suitable sample preparation technique to study elemental distribution of ions in H. floribundus and P. calomelanos plant tissues using μ-PIXE spectroscopy. Furthermore, cellular structure was preserved in samples prepared using this technique.

NMR Stratagems for the Study of Multiple Kinetic Hydrogen/Deuterium Isotope Effectsof Proton Exchange. Example: Di-p-fluorophenylformamidine/THF

NASA Astrophysics Data System (ADS)

Limbach, Hans-Heinrich; Meschede, Ludger; Scherer, Gerd

1989-05-01

Stratagems are presented for the determination of kinetic isotope effects of proton exchange reactions by dynamic NMR spectroscopy. In such experiments, lineshape analyses and/or polarization transfer experiments are performed on the exchanging protons or deuterons as well as on remote spins, as a function of the deuterium fraction in the mobile proton sites. These methods are NMR analogs of previous proton inventory techniques involving classical kinetic methods. A theory is developed in order to derive the kinetic isotope effects as well as the number of transferred protons from the experimental NMR spectra. The technique is then applied to the problem of proton exchange in the system 15N,15N'-di-p-fluorophenylibrmamidine, a nitrogen analog of formic acid, dissolved in tetrahydrofuran-d8 (THF). DFFA forms two conformers in THF to which s-trans and s-cis structures have been assigned. Only the s-trans conformer is able to dimerize and exchange protons. Lineshape simulations and magnetization transfer experiments were carried out at 189,2 K, at a concentration of 0.02 mol l-1, as a function of the deuterium fraction D in the 1H-15N sites. Using 1H NMR spectroscopy, a linear dependence of the inverse proton lifetimes on D was observed. From this it was concluded that two protons are transported in the rate limiting step of the proton exchange. This result is expected for a double proton transfer in an s-trans dimer with a cyclic structure. The full kinetic HH/HD/DD isotope effects of 233:11:1 at 189 K were determined through 19F NMR experiments on the same samples. The deviation from the rule of geometric mean, although substantial, is much smaller than found in previous studies of intramolecular HH transfer reactions. Possible causes of this effect are discussed.

Sorting of large-diameter semiconducting carbon nanotube and printed flexible driving circuit for organic light emitting diode (OLED)

NASA Astrophysics Data System (ADS)

Xu, Wenya; Zhao, Jianwen; Qian, Long; Han, Xianying; Wu, Liangzhuan; Wu, Weichen; Song, Minshun; Zhou, Lu; Su, Wenming; Wang, Chao; Nie, Shuhong; Cui, Zheng

2014-01-01

A novel approach was developed to sort a large-diameter semiconducting single-walled carbon nanotube (sc-SWCNT) based on copolyfluorene derivative with high yield. High purity sc-SWCNTs inks were obtained by wrapping arc-discharge SWCNTs with poly[2,7-(9,9-dioctylfluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PFO-DBT) aided by sonication and centrifugation in tetrahydrofuran (THF). The sorted sc-SWCNT inks and nanosilver inks were used to print top-gated thin-film transistors (TFTs) on flexible substrates with an aerosol jet printer. The printed TFTs demonstrated low operating voltage, small hysteresis, high on-state current (up to 10-3 A), high mobility and on-off ratio. An organic light emitting diode (OLED) driving circuit was constructed based on the printed TFTs, which exhibited high on-off ratio up to 104 and output current up to 3.5 × 10-4 A at Vscan = -4.5 V and Vdd = 0.8 V. A single OLED was switched on with the driving circuit, showing the potential as backplanes for active matrix OLED applications.A novel approach was developed to sort a large-diameter semiconducting single-walled carbon nanotube (sc-SWCNT) based on copolyfluorene derivative with high yield. High purity sc-SWCNTs inks were obtained by wrapping arc-discharge SWCNTs with poly[2,7-(9,9-dioctylfluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PFO-DBT) aided by sonication and centrifugation in tetrahydrofuran (THF). The sorted sc-SWCNT inks and nanosilver inks were used to print top-gated thin-film transistors (TFTs) on flexible substrates with an aerosol jet printer. The printed TFTs demonstrated low operating voltage, small hysteresis, high on-state current (up to 10-3 A), high mobility and on-off ratio. An organic light emitting diode (OLED) driving circuit was constructed based on the printed TFTs, which exhibited high on-off ratio up to 104 and output current up to 3.5 × 10-4 A at Vscan = -4.5 V and Vdd = 0.8 V. A single OLED was switched on with the driving circuit, showing the potential as backplanes for active matrix OLED applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr04870e

Supramolecular architectures of iron phthalocyanine Langmuir-Blodgett films: The role played by the solution solvents

NASA Astrophysics Data System (ADS)

Rubira, Rafael Jesus Gonçalves; Aoki, Pedro Henrique Benites; Constantino, Carlos José Leopoldo; Alessio, Priscila

2017-09-01

The developing of organic-based devices has been widely explored using ultrathin films as the transducer element, whose supramolecular architecture plays a central role in the device performance. Here, Langmuir and Langmuir-Blodgett (LB) ultrathin films were fabricated from iron phthalocyanine (FePc) solutions in chloroform (CHCl3), dichloromethane (CH2Cl2), dimethylformamide (DMF), and tetrahydrofuran (THF) to determine the influence of different solvents on the supramolecular architecture of the ultrathin films. The UV-vis absorption spectroscopy shows a strong dependence of the FePc aggregation on these solvents. As a consequence, the surface pressure vs. mean molecular area (π-A) isotherms and Brewster angle microscopy (BAM) reveal a more homogeneous (surface morphology) Langmuir film at the air/water interface for FePc in DMF. The same morphological pattern observed for the Langmuir films is preserved upon LB deposition onto solid substrates. The Raman and FTIR analyses indicate the DMF-FePc interaction relies on coordination bonds between N atom (from DMF) and Fe atom (from FePc). Besides, the FePc molecular organization was also found to be affected by the DMF-FePc chemical interaction. It is interesting to note that, if the DMF-FePc leads to less aggregated FePc either in solution or ultrathin films (Langmuir and LB), with time (one week) the opposite trend is found. Taking into account the N-Fe interaction, the performance of the FePc ultrathin films with distinct supramolecular architectures composing sensing units was explored as proof-of-principle in the detection of trace amounts of atrazine herbicide in water using impedance spectroscopy. Further statistical and computational analysis reveal not only the role played by FePc supramolecular architecture but also the sensitivity of the system to detect atrazine solutions down to 10-10 mol/L, which is sufficient to monitor the quality of drinking water even according to the most stringent international regulations.

Miscibility and in vitro osteocompatibility of biodegradable blends of poly[(ethyl alanato) (p-phenyl phenoxy) phosphazene] and poly(lactic acid-glycolic acid).

PubMed

Deng, Meng; Nair, Lakshmi S; Nukavarapu, Syam P; Kumbar, Sangamesh G; Jiang, Tao; Krogman, Nicholas R; Singh, Anurima; Allcock, Harry R; Laurencin, Cato T

2008-01-01

Previously we demonstrated the ability of ethyl glycinato substituted polyphosphazenes to neutralize the acidic degradation products and control the degradation rate of poly(lactic acid-glycolic acid) (PLAGA) by blending. In this study, blends of high strength poly[(50% ethyl alanato) (50% p-phenyl phenoxy) phosphazene] (PNEA(50)PhPh(50)) and 85:15 PLAGA were prepared using a mutual solvent approach. Three different solvents, methylene chloride (MC), chloroform (CF) and tetrahydrofuran (THF) were studied to investigate solvent effects on blend miscibility. Three different blends were then fabricated at various weight ratios namely 25:75 (BLEND25), 50:50 (BLEND50), and 75:25 (BLEND75) using THF as the mutual solvent. The miscibility of the blends was evaluated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). Among these, BLEND25 was miscible while BLEND50 and BLEND75 were partially miscible. Furthermore, BLEND25 formed apatite layers on its surface as evidenced in a biomimetic study performed. These novel blends showed cell adhesion and proliferation comparable to PLAGA. However, the PNEA(50)PhPh(50) component in the blends was able to increase the phenotypic expression and mineralized matrix synthesis of the primary rat osteoblasts (PRO) in vitro. Blends of high strength PNEA(50)PhPh(50) and 85:15 PLAGA are promising biomaterials for a variety of musculoskeletal applications.

Enrichment Mechanism of Semiconducting Single-walled Carbon Nanotubes by Surfactant Amines

PubMed Central

Ju, Sang-Yong; Utz, Marcel; Papadimitrakopoulos, Fotios

2009-01-01

Utilization of single-walled carbon nanotubes (SWNTs) in high-end applications hinges on separating metallic (met-) from semiconducting (sem-) SWNTs. Surfactant amines, like octadecylamine (ODA) have proven instrumental for the selective extraction of sem-SWNTs from tetrahydrofuran (THF) nanotube suspensions. The chemical shift differences along the tail of an asymmetric, diacetylenic surfactant amine were used to probe the molecular dynamics in the presence and absence of nanotubes via NMR. The results suggest that the surfactant amine head is firmly immobilized onto the nanotube surface together with acidic water, while the aliphatic tail progressively gains larger mobility as it gets farther from the SWNT. X-ray and high-resolution TEM studies indicate that the sem-enriched sample is populated mainly by small nanotube bundles containing ca. three SWNTs. Molecular simulations in conjunction with previously determined HNO3/H2SO4 oxidation depths for met- and sem-SWNTs indicate that the strong pinning of the amine surfactants on the sem-enriched SWNTs bundles is a result of a well-ordered arrangement of nitrate/amine salts separated with a monomolecular layer of H2O. Such continuous 2D arrangement of nitrate/amine salts shields the local environment adjacent to sem-enriched SWNTs bundles and maintains an acidic pH that preserves nanotube oxidation (i.e. SWNTn+). This, in turn, results in strong interactions with charge-balancing NO3- counter ions that through their association with neutralized surfactant amines provide effective THF dispersion and consequent sem-enrichment. PMID:19397291

Synthesis and oxidation catalysis of [tris(oxazolinyl)borato]cobalt(II) scorpionates

DOE PAGES

Reinig, Regina R.; Mukherjee, Debabrata; Weinstein, Zachary B.; ...

2016-04-28

The reaction of CoCl 2·THF and thallium tris(4,4-dimethyl-2-oxazolinyl)phenylborate (TlTo M) in tetrahydrofuran (THF) provides To MCoCl (1) in 95 % yield; however, appropriate solvents and starting materials are required to favor 1 over two other readily formed side-products, (To M) 2Co (2) and {HTo M}CoCl 2 (3). ESR, NMR, FTIR, and UV/Vis spectroscopies were used to distinguish these cobalt(II) products and probe their electronic and structural properties. Even after the structures indicated by these methods were confirmed by X-ray crystallography, the spectroscopic identification of trace contaminants in the material was challenging. The recognition of possible contaminants in the synthesis ofmore » To MCoCl in combination with the paramagnetic nature of these complexes provided impetus for the utilization of X-ray powder diffraction to measure the purity of the To MCoCl bulk sample. Furthermore, the X-ray powder diffraction results provide support for the bulk-phase purity of To MCoCl in preparations that avoid 2 and 3. Thus, 1 is a precursor for new [tris(oxazolinyl)borato]cobalt chemistry, as exemplified by its reactions with KOtBu and NaOAc to give To MCoOtBu (4) and To MCoOAc (5), respectively. Compound 5 is a catalyst for the oxidation of cyclohexane with meta-chloroperoxybenzoic acid (mCPBA), and the rate constants and selectivity for cyclohexanol versus cyclohexanone and ϵ-caprolactone were assessed.« less

Conversion of calibration curves for accurate estimation of molecular weight averages and distributions of polyether polyols by conventional size exclusion chromatography.

PubMed

Xu, Xiuqing; Yang, Xiuhan; Martin, Steven J; Mes, Edwin; Chen, Junlan; Meunier, David M

2018-08-17

Accurate measurement of molecular weight averages (M¯ n, M¯ w, M¯ z ) and molecular weight distributions (MWD) of polyether polyols by conventional SEC (size exclusion chromatography) is not as straightforward as it would appear. Conventional calibration with polystyrene (PS) standards can only provide PS apparent molecular weights which do not provide accurate estimates of polyol molecular weights. Using polyethylene oxide/polyethylene glycol (PEO/PEG) for molecular weight calibration could improve the accuracy, but the retention behavior of PEO/PEG is not stable in THF-based (tetrahydrofuran) SEC systems. In this work, two approaches for calibration curve conversion with narrow PS and polyol molecular weight standards were developed. Equations to convert PS-apparent molecular weight to polyol-apparent molecular weight were developed using both a rigorous mathematical analysis and graphical plot regression method. The conversion equations obtained by the two approaches were in good agreement. Factors influencing the conversion equation were investigated. It was concluded that the separation conditions such as column batch and operating temperature did not have significant impact on the conversion coefficients and a universal conversion equation could be obtained. With this conversion equation, more accurate estimates of molecular weight averages and MWDs for polyether polyols can be achieved from conventional PS-THF SEC calibration. Moreover, no additional experimentation is required to convert historical PS equivalent data to reasonably accurate molecular weight results. Copyright © 2018. Published by Elsevier B.V.

Electron-Transfer-Enhanced Cation-Cation Interactions in Homo- and Heterobimetallic Actinide Complexes: A Relativistic Density Functional Theory Study.

PubMed

Zheng, Ming; Chen, Fang-Yuan; Tian, Jia-Nan; Pan, Qing-Jiang

2018-04-02

To provide deep insight into cation-cation interactions (CCIs) involving hexavalent actinyl species that are major components in spent nuclear fuel and pose important implications for the effective removal of radiotoxic pollutants in the environment, a series of homo- and heterobimetallic actinide complexes supported by cyclopentadienyl (Cp) and polypyrrolic macrocycle (H 4 L) ligands were systematically investigated using relativistic density functional theory. The metal sort in both parts of (THF)(H 2 L)(OAn VI O) and (An') III Cp 3 from U to Np to Pu, as well as the substituent bonding to Cp from electron-donating Me to H to electron-withdrawing Cl, SiH 3 , and SiMe 3 , was changed. Over 0.70 electrons are unraveled to transfer from the electron-rich U III to the electron-deficient An VI of the actinyl moiety, leading to a more stable An V -U IV isomer; in contrast, uranylneptunium and uranylplutonium complexes behave as electron-resonance structures between VI-III and V-IV. These were further corroborated by geometrical and electronic structures. The energies of CCIs (i.e., O exo -An' bonds) were calculated to be -19.6 to -41.2 kcal/mol, affording those of OUO-Np (-23.9 kcal/mol) and OUO-Pu (-19.6 kcal/mol) with less electron transfer (ET) right at the low limit. Topological analyses of the electron density at the O exo -An' bond critical points demonstrate that the CCIs are ET or dative bonds in nature. A positive correlation has been built between the CCIs' strength and corresponding ET amount. It is concluded that the CCIs of O exo -An' are driven by the electrostatic attraction between the actinyl oxo atom (negative) and the actinide ion (positive) and enhanced by their ET. Finally, experimental syntheses of (THF)(H 2 L)(OU VI O)(An') III Cp 3 (An' = U and Np) were well reproduced by thermodynamic calculations that yielded negative free energies in a tetrahydrofuran solution but a positive one for their uranylplutonium analogue, which was synthetically inaccessible. So, our thermodynamics would provide implications for the synthetic possibility of other theoretically designed bimetallic actinide complexes.

Dual fluorescence from an isonido ReIII rhenacarborane phosphine complex, [7,10-mu-H-7-CO-7,7-(PPh3)2-isonido-7,8,9-ReC2B7H9].

PubMed

Buckner, Steven W; Fischer, Matthew J; Jelliss, Paul A; Luo, Rensheng; Minteer, Shelley D; Rath, Nigam P; Siemiarczuk, Aleksander

2006-09-04

The complex [7,10-mu-H-7-CO-7,7-(PPh3)2-isonido-7,8,9-ReC2B7H9] has been synthesized by treatment of the complex salt [NHMe3][3,3-Cl2-3,3-(CO)2-closo-3,1,2-ReC2B9H11] with PPh3 in refluxing THF (tetrahydrofuran) and isolated as intensely colored orange-red microcrystals. Spectroscopic NMR and IR data have suggested that the product has a highly asymmetric structure with two inequivalent PPh3 ligands and a single CO ligand. Measurement of 11B NMR spectra in particular have indicated seven distinct boron vertexes, although the resulting cage degradation by removal of two BH vertexes was confirmed only following X-ray crystallographic analysis, which revealed the pentadecahedral isonido-7,8,9-ReC2B7 architecture. The 11B NMR resonances span an enormous chemical shift range (Deltadelta = 113), and this appears to be a direct consequence of the deshielding of the boron vertex directly opposite the quadrilateral |ReCCB| aperture. The new complex has been shown by electrochemical measurements to undergo a reversible one-electron oxidation. Digitally simulated cyclic voltammograms support a proposed square scheme (E(1/2) = 0.58, 0.69 V vs ferrocene) involving a reversible isonido-closo transition of the metallacarborane cage. Most unusually for a metallacarborane complex, ambient temperature solutions in CH2Cl2 and DMF have been shown to be intensely turquoise-blue fluorescent (lambda(em) = 442 nm, Phi = 0.012). Fluorescence spectroscopy measurements in MeTHF (2-methyltetrahydrofuran) glass at 77 K have indicated that the likely cause of such a broad emission is dual fluorescence (lambda(em) = 404, 505 nm), with both emissions displaying vibronic structure. Following excited-state lifetime decay analysis, the emissive behavior has been accredited to metal-perturbed 1IL states, with the lower energy emission arising from a slight geometric distortion of the initially excited complex.

Effect of chain length on thermal conversion of alkoxy-substituted copper phthalocyanine precursors.

PubMed

Fukuda, Takamitsu; Kikukawa, Yuu; Tsuruya, Ryota; Fuyuhiro, Akira; Ishikawa, Naoto; Kobayashi, Nagao

2011-11-21

A series of dialkoxy-substituted copper phthalocyanine (CuPc) precursors (4a-4d) have been prepared by treating phthalonitrile with the corresponding lithium alkoxide under mild conditions. The precursors exhibited high solubilities in common organic solvents, including acetone, toluene, tetrahydrofuran (THF), CH(2)Cl(2), and CHCl(3). Elongation of the alkoxy chains improved the solubilities of the precursors effectively, and accordingly, the butoxy-substituted derivative (4d) showed the highest solubility among 4a-4d. X-ray crystallography clarified that the conjugated skeletons of 4a-4d are all isostructural, and have two alkoxy groups in a syn-conformation fashion, leading to highly bent structures. Thermal conversions of the precursors examined by thermogravimetry (TG) and differential thermal analysis (DTA) demonstrate that 4a was converted into CuPc via two distinct exothermic processes in the 200-250 °C temperature range, while 4d exhibits only one exothermic signal in the DTA. In the field emission scanning electron microscopy (FESEM) images of 4a, the presence of two types of distinct crystal morphology (prismatic and plate-like crystals) can be recognized, implying that the two observed exothermic processes in the DTA can be attributed to the different crystal morphologies of the samples rather than the step-by-step elimination of the alkoxy groups. The thermal formation of CuPc from the precursors has been unambiguously confirmed by X-ray powder diffraction, UV-vis spectroscopy, and elemental analysis. The precursors were converted into CuPc at lower temperature with increasing chain length, presumably because of the increased void volume in the crystals. Thermal conversion performed in the solution phase results in a bright blue-colored solution with prominent absorption bands in the 650-700 nm region, strongly supporting the formation of CuPc.

Synthesis and structural characterization of (C sub 5 Me sub 5 )Zr(R) sub 2 (L) sub n sup + complexes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crowther, D.J.; Jordan, R.F.; Baenziger, N.C.

1990-09-01

The reaction of (C{sub 5}Me{sub 5})Zr(CH{sub 3}){sub 3} with ((C{sub 5}H{sub 4}Me){sub 2}Fe)(BPh{sub 4}) in THF yields ((C{sub 5}Me{sub 5})Zr(CH{sub 3}){sub 2}(THF){sub 2})(BPh{sub 4}) (1) via oxidative cleavage of a Zr-CH{sub 3} bond. X-ray diffraction reveals that the cation of 1 adopts a square-pyramidal/four-legged piano-stool structure with cis CH{sub 3} groups. The orientations of the THF ligands and the Zr-O bond distances suggest that Zr-O {pi}-bonding is important for at least one of the THF ligands. Data for 1: a = 14.551 (2) {angstrom}, b = 15.191 (4) {angstrom}, c = 17.852 (19) {angstrom}, {beta} = 92.26 (3){degree}, V =more » 3,943 (6) {angstrom}{sup 3}, Z = 4 in space group P2{sub 1}/c. Reaction of 1 with excess dmpe in THF solution yields ((C{sub 5}Me{sub 5})Zr(CH{sub 3}){sub 2}(dmpe)(THF))(BPh{sub 4}) (2), which also has been characterized by X-ray diffraction.« less

Electrolytic conditioning of a magnesium aluminum chloride complex for reversible magnesium deposition

DOE PAGES

Barile, Christopher J.; Barile, Elizabeth C.; Zavadil, Kevin R.; ...

2014-12-04

We describe in this report the electrochemistry of Mg deposition and dissolution from the magnesium aluminum chloride complex (MACC). The results define the requirements for reversible Mg deposition and definitively establish that voltammetric cycling of the electrolyte significantly alters its composition and performance. Elemental analysis, scanning electron microscopy, and energy-dispersive X-ray spectroscopy (SEM-EDS) results demonstrate that irreversible Mg and Al deposits form during early cycles. Electrospray ionization-mass spectrometry (ESI-MS) data show that inhibitory oligomers develop in THF-based solutions. These oligomers form via the well-established mechanism of a cationic ring-opening polymerization of THF during the initial synthesis of the MACC andmore » under resting conditions. In contrast, MACC solutions in 1,2-dimethoxyethane (DME), an acyclic solvent, do not evolve as dramatically at open circuit potential. Furthermore, we propose a mechanism describing how the conditioning process of the MACC in THF improves its performance by both tuning the Mg:Al stoichiometry and eliminating oligomers.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Carpenter, Alex E.; Chan, Chinglin; Rheingold, Arnold L.

The m-terphenyl isocyanide complex, HCo(CNAr Mes2) 4 (Ar Mes2 = 2,6-(2,4,6-Me 3C 6H 2) 2C 6H 3), serves as a unique example of a well-defined isocyano analogue to HCo(CO) 4. Given the well documented Brønsted acidity of HCo(CO) 4 in both protic and nonprotic media, the Brønsted acidity of HCo(CNAr Mes2) 4 was assessed for a quantitative comparison. Acid bracketing experiments in THF solution revealed that HCo(CNAr Mes2) 4 has a Morris relative pK α THF value of 38.5-40.7, which is considerably higher than that of HCo(CO) 4 (pK α THF (calc) = 11.4) and thereby indicates insignificant Brønsted acidity.more » Furthermore, the relative acidity of HCo(CNAr Mes2) 4 rivals that of tetra-phosphine cobalt hydrides (i.e., HCo(PR 3) 4; pK α THF (calc) ≥ 48), despite the good π-acidity properties of the isocyano unit. To systematically determine the effect of substituting an isocyanide for a CO ligand on the acidity of the Co-H unit in HCoL 4 complexes, the full series of HCo(CO) n(CNAr Mes2) 4-n monohydrides and [Co(CO) n(CNAr Mes2) 4-n] - (n = 1-4) metalates were prepared and characterized. Acid bracketing studies on the [Co(CO) n(CNAr Mes2) 4-n] - metalates in THF solution revealed a regular progression of increasing pK α THF values as isocyanides are added to the Co center. However, the monoisocyanide tricarbonyl hydride, HCo(CO) 3(CNAr Mes2), possesses a pK α THF value of 28.6-32.5, which is also significantly higher than that of HCo(CO) 4 and the monophosphine complex HCo(CO) 3(PPh 3). Accordingly, the unconventional ability of isocyanide ligands to function as stronger σ-donors than organophosphines is discussed within the context of both the Brønsted acidity and spectroscopic features of the HCo(CO) n(CNAr Mes2) 4-n monohydrides.« less

A Well-Defined Isocyano Analogue of HCo(CO) 4. 2: Relative Brønsted Acidity as a Function of Isocyanide Ligation

DOE PAGES

Carpenter, Alex E.; Chan, Chinglin; Rheingold, Arnold L.; ...

2016-07-07

The m-terphenyl isocyanide complex, HCo(CNAr Mes2) 4 (Ar Mes2 = 2,6-(2,4,6-Me 3C 6H 2) 2C 6H 3), serves as a unique example of a well-defined isocyano analogue to HCo(CO) 4. Given the well documented Brønsted acidity of HCo(CO) 4 in both protic and nonprotic media, the Brønsted acidity of HCo(CNAr Mes2) 4 was assessed for a quantitative comparison. Acid bracketing experiments in THF solution revealed that HCo(CNAr Mes2) 4 has a Morris relative pK α THF value of 38.5-40.7, which is considerably higher than that of HCo(CO) 4 (pK α THF (calc) = 11.4) and thereby indicates insignificant Brønsted acidity.more » Furthermore, the relative acidity of HCo(CNAr Mes2) 4 rivals that of tetra-phosphine cobalt hydrides (i.e., HCo(PR 3) 4; pK α THF (calc) ≥ 48), despite the good π-acidity properties of the isocyano unit. To systematically determine the effect of substituting an isocyanide for a CO ligand on the acidity of the Co-H unit in HCoL 4 complexes, the full series of HCo(CO) n(CNAr Mes2) 4-n monohydrides and [Co(CO) n(CNAr Mes2) 4-n] - (n = 1-4) metalates were prepared and characterized. Acid bracketing studies on the [Co(CO) n(CNAr Mes2) 4-n] - metalates in THF solution revealed a regular progression of increasing pK α THF values as isocyanides are added to the Co center. However, the monoisocyanide tricarbonyl hydride, HCo(CO) 3(CNAr Mes2), possesses a pK α THF value of 28.6-32.5, which is also significantly higher than that of HCo(CO) 4 and the monophosphine complex HCo(CO) 3(PPh 3). Accordingly, the unconventional ability of isocyanide ligands to function as stronger σ-donors than organophosphines is discussed within the context of both the Brønsted acidity and spectroscopic features of the HCo(CO) n(CNAr Mes2) 4-n monohydrides.« less

Rechargeable biofilm-controlling tubing materials for use in dental unit water lines.

PubMed

Luo, Jie; Porteous, Nuala; Sun, Yuyu

2011-08-01

A simple and practical surface grafting approach was developed to introduce rechargeable N-halamine-based antimicrobial functionality onto the inner surfaces of continuous small-bore polyurethane (PU) dental unit waterline (DUWL) tubing. In this approach, tetrahydrofuran (THF) solution of a free-radical initiator, dicumyl peroxide (DCP), flowed through the PU tubing (inner diameter of 1/16 in., or 1.6 mm) to diffuse DCP into the tubing's inner walls, which was used as initiator in the subsequent grafting polymerization of methacrylamide (MAA) onto the tubing. Upon chlorine bleach treatment, the amide groups of the grafted MAA side chains were transformed into acyclic N-halamines. The reactions were confirmed with attenuated total reflectance infrared (ATR) spectra and iodometric titration. The mechanical properties of the tubing were not significantly affected by the grafting reactions. The biofilm-controlling function of the new N-halamine-based PU tubing was evaluated with Pseudomonas aeruginosa (P. aeruginosa), one of the most isolated water bacteria from DUWLs, in a continuous bacterial flow model. Bacteria culturing and SEM studies showed that the inner surfaces of the new N-halamine-based PU tubing completely prevented bacterial biofilm formation for at least three to four weeks. After that, bacteria began to colonize the tubing surface. However, the lost function was fully regenerated by exposing the tubing inner surfaces to diluted chlorine bleach. The recharging process could be repeated periodically to further extend the biofilm-controlling duration for long-term applications.

Rechargeable Biofilm-Controlling Tubing Materials for Use in Dental Unit Water Lines

PubMed Central

Luo, Jie; Porteous, Nuala; Sun, Yuyu

2011-01-01

A simple and practical surface grafting approach was developed to introduce rechargeable N-halamine-based antimicrobial functionality onto the inner surfaces of continuous small-bore polyurethane (PU) dental unit waterline (DUWL) tubing. In this approach, tetrahydrofuran (THF) solution of a free-radical initiator, dicumyl peroxide (DCP), flowed through the PU tubing (inner diameter of 1/16 inch, or 1.6 mm) to diffuse DCP into the tube’s inner walls, which was used as initiator in the subsequent grafting polymerization of methacrylamide (MAA) onto the tubing. Upon chlorine bleach treatment, the amide groups of the grafted MAA side chains were transformed into acyclic N-halamines. The reactions were confirmed with attenuated total reflectance infrared (ATR) spectra and iodometric titration. The mechanical properties of the tubing were not significantly affected by the grafting reactions. The biofilm-controlling function of the new N-halamine-based PU tubing was evaluated with Pseudomonas aeruginosa (P. aeruginosa), one of the most isolated water bacteria from DUWLs, in a continuous bacterial flow model. Bacteria culturing and SEM studies showed that the inner surfaces of the new N-halamine-based PU tubing completely prevented bacterial biofilm formation for at least three to four weeks. After that, bacteria began to colonize the tubing surface. However, the lost function was fully regenerated by exposing the tubing inner surfaces to diluted chlorine bleach. The recharging process could be repeated periodically to further extend the biofilm-controlling duration for long-term applications. PMID:21721534

A solution-doped small molecule hole transport layer for efficient ITO-free organic solar cells (Presentation Recording)

NASA Astrophysics Data System (ADS)

Bormann, Ludwig; Selzer, Franz; Leo, Karl; Mueller-Meskamp, Lars

2015-10-01

Indium-tin-oxide-free (ITO-free) organic solar cells are an important, emerging research field because ITO transparent electrodes are a bottleneck for cheap large area devices on flexible substrates. Among highly conductive PEDOT:PSS and metal grids, percolation networks made of silver nanowires (AgNW) with a diameter in the nanoscale show a huge potential due to easy processing (e.g. spray coating), high aspect ratios and excellent electrical and optical properties like 15 Ohm/sq with a transmission of 83.5 % including the substrate. However, the inherent surface roughness of the AgNW film impedes the implementation as bottom electrode in organic devices, especially fully vacuum deposited ones, where often shunts are obtained. Here, we report about the solution processing of a small molecule hole transport layer (s-HTL) comprising N,N'-((Diphenyl-N,N'-bis)9,9,-dimethyl-fluoren-2-yl)-benzidine (BF-DPB, host material) and the proprietary NDP9 (p-dopant) deposited from tetrahydrofuran (THF) as non-halogenated, "green" solvent. We show, that the doping process already takes place in solution and that conductivities, achieved with this process at high doping efficiencies (4 * 10^-4 S/cm at 10 wt% doping concentration), are comparable to thermal co-evaporation of BF-DPB:NDP9 under high vacuum, which is the proven deposition method for doped small molecule films. Applying this s-HTL to AgNW films leads to well smoothened electrodes, ready for application in organic devices. Vacuum-deposited organic p-i-n solar cells with DCV2-5T-Me(3:3):C60 as active layer show a power conversion efficiency of 4.4% and 3.7% on AgNW electrode with 35nm and 90 nm wire diameter, compared to 4.1% on ITO with the s-HTL.

Selectivity in reversed-phase separations: general influence of solvent type and mobile phase pH.

PubMed

Neue, Uwe D; Méndez, Alberto

2007-05-01

The influence of the mobile phase on retention is studied in this paper for a group of over 70 compounds with a broad range of multiple functional groups. We varied the pH of the mobile phase (pH 3, 7, and 10) and the organic modifier (methanol, acetonitrile (ACN), and tetrahydrofuran (THF)), using 15 different stationary phases. In this paper, we describe the overall retention and selectivity changes observed with these variables. We focus on the primary effects of solvent choice and pH. For example, transfer rules for solvent composition resulting in equivalent retention depend on the packing as well as on the type of analyte. Based on the retention patterns, one can calculate selectivity difference values for different variables. The selectivity difference is a measure of the importance of the different variables involved in method development. Selectivity changes specific to the type of analyte are described. The largest selectivity differences are obtained with pH changes.

Glycyrrhiza glabra (Linn.) and Lavandula officinalis (L.) cell suspension cultures-based biotransformation of β-artemether.

PubMed

Patel, Suman; Gaur, Rashmi; Upadhyaya, Mohita; Mathur, Archana; Mathur, Ajay K; Bhakuni, Rajendra S

2011-07-01

The biotransformation of β-artemether (1) by cell suspension cultures of Glycyrrhiza glabra and Lavandula officinalis is reported here for the first time. The major biotransformed product appeared as a grayish-blue color spot on thin-layer chromatography (TLC) with transparent crystal-like texture. Based on its infrared (IR) and (1)H nuclear magnetic resonance (NMR) spectra, the product was characterized as a tetrahydrofuran (THF)-acetate derivative (2). The highest conversion efficiencies of 57 and 60% were obtained when 8-9-day-old cell suspensions of G. glabra and L. officinalis were respectively fed with 4-7 mg of compound 1 in 40 ml of medium per culture and the cells were harvested after 2-5 days of incubation. The addition of compound 1 at the beginning of the culture cycle caused severe growth depression in a dose-dependent manner, resulting in poor bioconversion efficiency of ~25% at 2-5 mg/culture dose only.

Acid proliferation to improve the sensitivity of EUV resists: a pulse radiolysis study

NASA Astrophysics Data System (ADS)

Enomoto, Kazuyuki; Arimitsu, Koji; Yoshizawa, Atsutaro; Yamamoto, Hiroki; Oshima, Akihiro; Kozawa, Takahiro; Tagawa, Seiichi

2011-04-01

The yields of acid have been measured in the electron-beam irradiation of triphenylsulfonium triflate (TPS-Tf) and pinanediol monosulfonates, which consist of tosylate (PiTs), 4-fluorobenzenesulfonate (Pi1F), or 4-trifluoromethylbenzenesulfonate (Pi3F), as an acid amplifier blended in 4-hydroxystyrene matrixes. The acid yields efficiency decreases when PiTs is present, while its efficiency increases in the presence of Pi3F. Reactions of the electrons with TPS-Tf and pinanediol monosulfonates have been studied using pulse radiolysis in liquid tetrahydrofuran (THF) to evaluate the kinetic contributions to acid production. The THF-solvated electrons react with PiTs, Pi1F, and Pi3F to produce the corresponding radical anions; the rate constants are estimated to be 4.1, 5.1, and 9.2 × 1010 M-1 s-1, respectively. Electron transfer from PiTs•-, Pi1F•-, and Pi3F•- radical anions to TPS-Tf occurs with the rate constants of 5.7×1010, 1.2×1011, and 6.3 × 1010 M-1 s-1, respectively. The long-lived Pi3F•- efficiently undergoes the electron transfer to TPS-Tf to form the TPS-Tf•-, which subsequently decompose to generate TfOH. On the other hand, the decay channels of PiTs•- and Pi1F•-, which possess a relatively short lifetime, are presumably dependent on its reactions with solvated protons (charge recombination) rather than the electron transfer to TPS-Tf. The novel acid production pathway via the electron transfer from pinanediol monosulfonate radical anions to TPS-Tf is presented.

Miscibility and in vitro osteocompatibility of biodegradable blends of poly[(ethyl alanato) (p-phenyl phenoxy) phosphazene] and poly(lactic acid-glycolic acid)

PubMed Central

Deng, Meng; Nair, Lakshmi S.; Nukavarapu, Syam P.; Kumbar, Sangamesh G.; Jiang, Tao; Krogman, Nicholas R.; Singh, Anurima; Allcock, Harry R.; Laurencin, Cato T.

2007-01-01

Previously we demonstrated the ability of ethyl glycinato substituted polyphosphazenes to neutralize the acidic degradation products and control the degradation rate of poly(lactic acid-glycolic acid) by blending. In this study, blends of high strength poly[(50% ethyl alanato) (50% p-phenyl phenoxy) phosphazene] (PNEA50PhPh50) and 85:15 poly(lactic acid-glycolic acid) (PLAGA) were prepared using a mutual solvent approach. Three different solvents, methylene chloride (MC), chloroform (CF) and tetrahydrofuran (THF) were studied to investigate solvent effects on blend miscibility. Three different blends were then fabricated at various weight ratios namely 25:75 (BLEND25), 50:50 (BLEND50), and 75:25 (BLEND75) using THF as the mutual solvent. The miscibility of the blends was evaluated by scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). Among these, BLEND25 was miscible while BLEND50 and BLEND75 were partially miscible. Furthermore, BLEND25 formed apatite layers on its surface as evidenced in a biomimetic study performed. These novel blends showed cell adhesion and proliferation comparable to PLAGA. However, the PNEA50PhPh50 component in the blends was able to increase the phenotypic expression and mineralized matrix synthesis of the primary rat osteoblasts (PRO) in vitro. Blends of high strength poly[(50% ethyl alanato) (50% p-phenyl phenoxy) phosphazene] (PNEA50PhPh50) and 85:15 poly(lactic acid-glycolic acid) (PLAGA) are promising biomaterials for a variety of musculoskeletal applications. PMID:17942150

Ga[OSi(O(t)Bu)3]3·THF, a thermolytic molecular precursor for high surface area gallium-containing silica materials of controlled dispersion and stoichiometry.

PubMed

Dombrowski, James P; Johnson, Gregory R; Bell, Alexis T; Tilley, T Don

2016-07-05

The molecular precursor tris[(tri-tert-butoxy)siloxy]gallium, as the tetrahydrofuran adduct Ga[OSi(O(t)Bu)3]3·THF (), was synthesized via the salt metathesis reaction of gallium trichloride with NaOSi(O(t)Bu)3. This complex serves as a model for isolated gallium in a silica framework. Complex decomposes thermally in hydrocarbon solvent, eliminating isobutylene, water, and tert-butanol to generate high surface area gallium-containing silica at low temperatures. When thermal decomposition was performed in the presence of P-123 Pluronic as a templating agent the generated material displayed uniform vermicular pores. Textural mesoporosity was evident in untemplated material. Co-thermolysis of with HOSi(O(t)Bu)3 in the presence of P-123 Pluronic led to materials with Ga : Si ratios ranging from 1 : 3 to 1 : 50, denoted UCB1-GaSi3, UCB1-GaSi10, UCB1-GaSi20 and UCB1-GaSi50. After calcination at 500 °C these materials exhibited decreasing surface areas and broadening pore distributions with increasing silicon content, indicating a loss of template effects. The position and dispersion of the gallium in UCB1-GaSi materials was investigated using (71)Ga MAS-NMR, powder XRD, and STEM/EDS elemental mapping. The results indicate a high degree of gallium dispersion in all samples, with gallium oxide clusters or oligomers present at higher gallium content.

THF water hydrate crystallization: an experimental investigation

NASA Astrophysics Data System (ADS)

Devarakonda, Surya; Groysman, Alexander; Myerson, Allan S.

1999-08-01

Supersaturated solutions of THF-water hydrate system were experimentally studied before and during crystallization, to examine the system's behavior in the metastable zone and observe any anomalies suggesting cluster formation. Nucleation induction time measurements, with and without additives, were performed to screen potential growth inhibitors. Shifts in the onset points of crystallization for water and THF-water mixtures with additives were measured using differential scanning calorimetry (DSC). Aspartame was among one of the few successfully screened inhibitors. Preliminary on-line crystal size distribution (CSD) measurements were performed on this system to monitor the crystal size during crystallization. The CSD data was also used to compute the hydrate crystal growth rates, which were found to be in the order of 145 μm/h.

Trinuclear alkyl hydrido rare-earth complexes supported by amidopyridinato ligands: synthesis, structures, C-Si bond activation and catalytic activity in ethylene polymerization.

PubMed

Lyubov, Dmitry M; Cherkasov, Anton V; Fukin, Georgy K; Ketkov, Sergey Yu; Shavyrin, Andrey S; Trifonov, Alexander A

2014-10-14

The reaction of Ap(9Me)Lu(CH2SiMe3)2(thf) (Ap(9Me) = (2,4,6-trimethylphenyl)[6-(2,4,6-triisopropylphenyl)pyridine-2-yl]amido ligand) with two molar equivalents of PhSiH3 affords a trinuclear alkyl-hydrido cluster [(Ap(9Me)Lu)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2]. The analogous reactions with Ap(9Me)Ln(CH2SiMe3)2(thf) (Ln = Y, Yb) are more complex and result in the formation of mixtures of two types of trinuclear alkyl-hydrido complexes [(Ap(9Me)Ln)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2] and [(Ap(9Me)Ln)3(μ(2)-H)3(μ(3)-H)2(CH2SiH2Ph)(thf)2] differing in the alkyl group. The DFT calculations of [(Ap*Y)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2] (Ap* = (2,6-diisopropylphenyl)[6-(2,4,6-triisopropylphenyl)pyridine-2-yl]amido ligand) confirm localization of the HOMO on the Ap*-Y(1A)-CH2SiMe3 fragment, thus explaining its enhanced reactivity. Analysis of the electron density distribution reveals the Y-H and H-H bonding interactions in the (Y)3(μ(2)-H)3(μ(3)-H)2 moiety. The NMR studies of diamagnetic complexes [(Ap(9Me)Lu)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2] and [(Ap*Y)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2] demonstrated that the trinuclear cores are retained in the solution and revealed exchange between μ(3)- and μ(2)-bridging hydrido ligands. Complexes [(Ap*Ln)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2], the cationic yttrium hydrido cluster [(Ap*Y)3(μ(2)-H)3(μ(3)-H)2(thf)3](+)[B(C6F5)4](-) as well as [(Ap(9Me)Ln)3(μ(2)-H)3(μ(3)-H)2(CH2SiMe3)(thf)2] proved to be active in catalysis of ethylene polymerization under mild conditions.

Preparation, characterization, physical properties, and photoconducting behaviour of anthracene derivative nanowires

NASA Astrophysics Data System (ADS)

Xiao, Jinchong; Yin, Zongyou; Yang, Bo; Liu, Yi; Ji, Li; Guo, Jun; Huang, Ling; Liu, Xuewei; Yan, Qingyu; Zhang, Hua; Zhang, Qichun

2011-11-01

Organic nanowires of 9,10-dibromoanthracene (DBA) and 9,10-dicyanoanthracene (DCNA) were obtained by adding the THF solution of DBA/DCNA into water containing P123 surfactants. The as-prepared nanowires were characterized by UV-vis, fluorescence spectra, Field Emission Scanning Electron Microscopy (FESEM), and Transmission Electron Microscopy (TEM). We found that DBA and DCNA nanowires emitted green light rather than blue light for molecules in THF solution. The red-shift UV and fluorescent spectra of DBA and DCNA nanowires implied that these nanowires were formed through J-aggregation. The photoconducting study of DBA/DCNA nanowire-based network on rGO/SiO2/Si shows different photocurrent behaviors upon irradiation, which displayed that electron transfer from DCNA nanowire to rGO was stronger than that of DBA nanowires to rGO.Organic nanowires of 9,10-dibromoanthracene (DBA) and 9,10-dicyanoanthracene (DCNA) were obtained by adding the THF solution of DBA/DCNA into water containing P123 surfactants. The as-prepared nanowires were characterized by UV-vis, fluorescence spectra, Field Emission Scanning Electron Microscopy (FESEM), and Transmission Electron Microscopy (TEM). We found that DBA and DCNA nanowires emitted green light rather than blue light for molecules in THF solution. The red-shift UV and fluorescent spectra of DBA and DCNA nanowires implied that these nanowires were formed through J-aggregation. The photoconducting study of DBA/DCNA nanowire-based network on rGO/SiO2/Si shows different photocurrent behaviors upon irradiation, which displayed that electron transfer from DCNA nanowire to rGO was stronger than that of DBA nanowires to rGO. Electronic supplementary information (ESI) available: XRD patterns and simulations, and FT-IR spectra. CCDC reference numbers 840471. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c1nr10655d

A fundamental study on the [(μ-Cl) 3 Mg 2 (THF) 6 ] + dimer electrolytes for rechargeable Mg batteries

DOE PAGES

Liu, Tianbiao; Cox, Jonathan T.; Hu, Dehong; ...

2015-01-05

We present a fundamental study on [(μ-Cl) 3 Mg 2 (THF) 6 ] + dimer electrolytes using various physical methods including Subambient Pressure Ionization with Nanoelectrospray Mass spectrometry (SPIN-MS), Raman spectroscopy, 25Mg{ 1H} NMR, 27Al{ 1H} NMR and electrochemical analysis. For the first time, long time sought THF solvated [MgCl] + species was experimentally characterized by SPIN mass spectrometry in the solution of the Mgdimer containing electrolyte, confirming the mono-Cl- abstraction reaction between MgCl 2 and an Al Lewis acid. Solvated MgCl 2 in the electrolyte was confirmed by Raman spectroscopy. The experimental results establish the previously proposed dimerization equilibriummore » of solvated [MgCl] + and MgCl2 with [(μ-Cl) 3Mg 2(THF)6] +. 25Mg{ 1H} NMR, 27Al{ 1H} NMR and electrochemical analysis on chloration reaction of [(μ-Cl) 3Mg 2(THF) 6]AlPh 3Cl with external Cl- led to further insights on the coordination chemistry of the dimer electrolyte. Finally, a comprehensive mechanism is proposed for the reversible electrochemical Mg deposition and stripping and Mg 2+ and Cl- ion transports of the Mg dimer electrolytes in rechargeable Mg batteries.« less

Exploring the synthesis and characterization of nanoenergetic materials from sol-gel chemistry

NASA Astrophysics Data System (ADS)

Walker, Jeremy D.

Nanoenergetic composite materials have been synthesized by a sol-gel chemical process where the addition of a weak base molecule induces the gelation of a hydrated metal salt solution. A proposed 'proton scavenging' mechanism, where a weak base molecule extracts a proton from the coordination sphere of the hydrated iron (III) complex in the gelation process to form iron (III) oxide/hydroxide, FeIIIxOyHz, has been confirmed for the weak base propylene oxide (PO), a 1,2 epoxide, as well as for the weak bases tetrahydrofuran (THF), a 1,4 epoxide, and pyridine, a heterocyclic nitrogen-containing compound. Gelation mechanisms for the formation of FeIIIxOyHz from THF and pyridine have been presented and confirmed through pH, XPS, and IR studies. THF follows a similar mechanism as PO, where the epoxide extracts a proton from the coordination sphere of the hydrated iron complex forming a protonated epoxide, which then undergoes irreversible ring-opening after reaction with a nucleophile in solution. Pyridine also extracts a proton from the hydrated metal complex, however, the stable six-membered molecule has low associated ring strain and does not endure ring-opening. Energetic properties for the Fe2O3/Al and RuO 2/Al sol-gel synthesized systems are also presented. Sol-gel chemistry synthesizes x-ray amorphous oxide matrices which contain substantial quantities of residual water and organic species. The iron (III) matrix, formed from the addition of a weak base epoxide molecule to a hydrated iron (III) nitrate solution, consists of stoichiometric Fe2O3, FeO(OH), and Fe(OH)3 and can only definitely be described as of Fe IIIxOyHz. XPS characterization of the metal oxide matrix synthesized from the addition of the weak base propylene oxide to a hydrated ruthenium (III) chloride solution corresponds to that of hydrous ruthenium (IV) oxide. Fe2O3/Al energetic systems were synthesized from the epoxides PO, trimethylene oxide (TMO) and 3,3 dimethyl oxetane (DMO). Energetic systems formed from each epoxide were each synthesized with different components, including: varying concentrations of nano-scale Al, micron Al, and carbon nanotubes. Surface area analysis of the synthesized matrices shows a direct correlation between the surface area of the iron (III) oxide matrix and the quantified exothermic heat of reaction of the energetic material due to the magnitude of the interfacial surface area contact between the iron (III) oxide matrix and the aluminum particles. The Fe2O3(PO)/Al systems possess the highest heat of reaction values due to the oxide surface area available for contact with the aluminum particles. Also, within systems, 1:1 Fe:nano Al samples possess the highest heat of reaction. Samples with nano-scale Al particles start reaction at 430°C, before the melting point of Al, whereas samples containing micron-Al do not react until ˜800°C, after the melting point of Al. The RuO2/Al energetic systems behave differently dependent on the atmosphere the sample is heated. Heating the RuO2/Al samples in an inert atmosphere results in the complete reduction of the ruthenium oxide matrix to Ru(0) before reaction with the aluminum particles. This results in the exothermic formation of RuxAly intermetallics, with the stoichiometry dependent on the initial Ru:Al concentration. However, heating the samples in an oxygen-rich atmosphere results in an exothermic reaction between RuO2 and Al. Post-reaction analysis of these samples reveals the sole existence of ruthenium (IV) oxide as the exothermic reaction vaporizes the aluminum particles.

Carboxylic and Dicarboxylic Acids Extracted from Crushed Magnesium Oxide Single Crystals

NASA Technical Reports Server (NTRS)

Freund, Friedemann; Gupta, Alka D.; Kumar, Devendra; DeVincenzi, Donald (Technical Monitor)

1998-01-01

Carboxylic and dicarboxylic acids (glycolic, oxalic, malonic and succinic) have been extracted with tetrahydrofuran (THE) and H2O from large synthetic MgO crystals, crushed to a medium fine powder. The extracts were characterized by infrared spectroscopy and (sup 1)H-NMR (Nuclear Magnetic Resonance). The THF extracts were derivatized with tert-butyldimethylsilyl (t-BDMS) for GC-MS (Gas Chromatography - Mass Spectroscopy) analysis. A single crystal separated from the extract was used for an x-ray structure analysis, giving the monoclinic unit cell, space group P2(sub 1)/c with a(sub o) = 5.543 A, b(sub o) = 8.845 A, c(sub o) = 5.086 A, and beta = 91.9 degrees, consistent with beta-succinic acid, HOOC(CH2)COOH. The amount of extracted acids is estimated to be of the order of 0.1 to 0.5 mg/g MgO. The MgO crystals from which these organic acids were extracted grew from the 2360 C hot melt, saturated with CO/CO2 and H2O, thereby incorporating small amounts of the gaseous components to form a solid solution (ss) with MgO. Upon cooling, the ss becomes supersaturated, causing solute carbon and other solute species to segregate not only to the surface but also internally, to dislocations and subgrain boundaries. The organic acids extracted from the MgO crystals after crushing appear to derive from these segregated solutes that formed C-C, C-H, and C-O bonds along dislocations and other defects in the MgO structure, leading to entities that can generically be described as (HxCyOz)(sup n-). The processes underlying the formation of these precursors are fundamental in nature and expected to be operational in any minerals, preferentially those with dense structures, that crystallized in H2O-CO2-laden environments. This opens the possibility that common magmatic and metamorphic rocks when weathering at the surface of a tectonically active planet like Earth may be an important source of abiogenically formed complex organic compounds.

Ionic Liquid as an Effective Additive for Rechargeable Magnesium Batteries

DOE PAGES

Pan, Baofei; Lau, Ka -Cheong; Vaughey, John T.; ...

2017-03-02

Here, the effect of the addition of an ionic liquid DEME•TFSI to an electrolyte solution of Mg(HMDS) 2-MgCl 2 in THF was studied electrochemically and spectroscopically. Reversible magnesium deposition/dissolution was achieved with the DEME•TFSI-modified electrolyte. This electrolyte shows higher ionic conductivity, and a linear relationship was observed between the ionic conductivity and the concentration of DEME•TFSI in THF solution of Mg(HMDS) 2-MgCl 2. Mg-Mo 6S 8 coin cells have also been successfully cycled using Mg(HMDS) 2-MgCl 2 electrolyte with the addition of DEME•TFSI. Raman and NMR spectroscopy suggest that DEME•TFSI facilitates magnesium deposition/dissolution by improving ionic conductivity of the electrolyte.

Charge transfer fluorescence and 34 nm exciton diffusion length in polymers with electron acceptor end traps

DOE PAGES

Zaikowski, Lori; Mauro, Gina; Bird, Matthew; ...

2014-12-22

Photoexcitation of conjugated poly-2,7-(9,9-dihexylfluorene) polyfluorenes with naphthylimide (NI) and anthraquinone (AQ) electron-acceptor end traps produces excitons that form charge transfer states at the end traps. Intramolecular singlet exciton transport to end traps was examined by steady state fluorescence for polyfluorenes of 17 to 127 repeat units in chloroform, dimethylformamide (DMF), tetrahydrofuran (THF), and p-xylene. End traps capture excitons and form charge transfer (CT) states at all polymer lengths and in all solvents. The CT nature of the end-trapped states is confirmed by their fluorescence spectra, solvent and trap group dependence and DFT descriptions. Quantum yields of CT fluorescence are asmore » large as 46%. This strong CT emission is understood in terms of intensity borrowing. Energies of the CT states from onsets of the fluorescence spectra give the depths of the traps which vary with solvent polarity. For NI end traps the trap depths are 0.06 (p-xylene), 0.13 (THF) and 0.19 eV (CHCl 3). For AQ, CT fluorescence could be observed only in p-xylene where the trap depth is 0.27 eV. Quantum yields, emission energies, charge transfer energies, solvent reorganization and vibrational energies were calculated. Fluorescence measurements on chains >100 repeat units indicate that end traps capture ~50% of the excitons, and that the exciton diffusion length L D =34 nm, which is much larger than diffusion lengths reported in polymer films or than previously known for diffusion along isolated chains. As a result, the efficiency of exciton capture depends on chain length, but not on trap depth, solvent polarity or which trap group is present.« less

Escape of anions from geminate recombination in THF due to charge delocalization

DOE PAGES

Chen, Hung -Cheng; Cook, Andrew R.; Asaoka, Sadayuki; ...

2017-11-24

Geminate recombination of 24 radical anions (M˙ –) with solvated protons (RH 2 +) was studied in tetrahydrofuran (THF) with pulse radiolysis. The recombination has two steps: (1) diffusion of M˙ – and RH 2 + together to form intimate (contact and solvent separated) ion pairs, driven by Coulomb attraction; (2) annihilation of anions due to proton transfer (PT) from RH 2 + to M˙ –. The non-exponential time-dependence of the geminate diffusion was determined. For all molecules protonated on O or N atoms the subsequent PT step is too fast (<0.2 ns) to measure, except for the anion ofmore » TCNE which did not undergo proton transfer. PT to C atoms was as slow as 70 ns and was always slow enough to be observable. A possible effect of charge delocalization on the PT rates could not be clearly separated from other factors. For 21 of the 24 molecules studied here, a free ion yield (71.6 ± 6.2 nmol J –1) comprising ~29% of the total, was formed. This yield of “Type I” free ions is independent of the PT rate because it arises entirely by escape from the initial distribution of ion pair distances without forming intimate ion pairs. Furthermore, three anions of oligo(9,9-dihexyl)fluorenes, F n˙ – (n = 2–4) were able to escape from intimate ion-pairs to form additional yields of “Type II” free ions with escape rate constants near 3 × 10 6 s –1. These experiments find no evidence for an inverted region for proton transfer.« less

Effect of dynamic surface polarization on the oxidative stability of solvents in nonaqueous Li-O 2 batteries

NASA Astrophysics Data System (ADS)

Khetan, Abhishek; Pitsch, Heinz; Viswanathan, Venkatasubramanian

2017-09-01

Polarization-induced renormalization of the frontier energy levels of interacting molecules and surfaces can cause significant shifts in the excitation and transport behavior of electrons. This phenomenon is crucial in determining the oxidative stability of nonaqueous electrolytes in high-energy density electrochemical systems such as the Li-O2 battery. On the basis of partially self-consistent first-principles Sc G W0 calculations, we systematically study how the electronic energy levels of four commonly used solvent molecules, namely, dimethylsulfoxide (DMSO), dimethoxyethane (DME), tetrahydrofuran (THF), and acetonitrile (ACN), renormalize when physisorbed on the different stable surfaces of Li2O2 , the main discharge product. Using band level alignment arguments, we propose that the difference between the solvent's highest occupied molecular orbital (HOMO) level and the surface's valence-band maximum (VBM) is a refined metric of oxidative stability. This metric and a previously used descriptor, solvent's gas phase HOMO level, agree quite well for physisorbed cases on pristine surfaces where ACN is oxidatively most stable followed by DME, THF, and DMSO. However, this effect is intrinsically linked to the surface chemistry of the solvent's interaction with the surface states and defects, and depends strongly on their nature. We conclusively show that the propensity of solvent molecules to oxidize will be significantly higher on Li2O2 surfaces with defects as compared to pristine surfaces. This suggests that the oxidative stability of a solvent is dynamic and is a strong function of surface electronic properties. Thus, while gas phase HOMO levels could be used for preliminary solvent candidate screening, a more refined picture of solvent stability requires mapping out the solvent stability as a function of the state of the surface under operating conditions.

Programmatic Summary: Self-Regulating, Self-Pressurizing Tubules for Integrated Circulatory Systems

DTIC Science & Technology

2009-02-01

Conditions: (i) 3- aminopropyl silane; (ii) 2-furoyl chloride, Et3N, CH2Cl2, 0 C to RT, 24 h; (iii) Compound 2, THF, RT, 24 h.; and (iv) Toluene, reflux... aminopropyl )trimethoxy silane. Next, we treated the amino-terminated slides with a solution of 2-furoyl chloride to yield furan functionalized slides...Conditions: (i) 3- aminopropyl silane; (ii) 2-furoyl chloride, Et3N, CH2Cl2, 0 C to RT, 24 h; (iii) Compound 2, THF, RT, 24 h.; and (iv) Toluene, reflux

Polymerization of Enantiomerically Pure 2,3-Dicarboalkoxy Norbornadienes and 5,6-Disubstituted Norbornenes by Well-Characterized Molybdenum ROMP catalysts

DTIC Science & Technology

1993-10-29

menthol , R-(-)-pantalactone, BBr3 (IM in CH2C12), PhMe2SiCI and t-BuLi were purchased from Aldrich and used as received. Mo(CHCMe2Ph)(NAr)(O-t-Bu)2 was...2,3- (COCl)2norbornadiene1 9 (9.05 g, 41.7 mmol) in THF (50 mL) was added dropwise to a stirred THF (200 mL) solution of IR, 2S, 5R-(-)- menthol (14.33 g

Structure of block copolymer micelles in the presence of co-solvents

NASA Astrophysics Data System (ADS)

Robertson, Megan; Wang, Shu; Le, Kim Mai; Piemonte, Rachele; Madsen, Louis

2015-03-01

Amphiphilic block copolymer micelles in water are under broad exploration for drug delivery applications due to their high loading capacity and targeted drug delivery. We aim to understand the kinetic and thermodynamic processes that underlie the self-assembly of diblock copolymer micelle systems. The present work focuses on diblock copolymers containing poly(ethylene oxide) (a hydrophilic polymer) and polycaprolactone (a hydrophobic polymer), which spontaneously self-assemble into spherical micelles in water. Addition of a common good solvent (a co-solvent) for both of the constituting blocks, such as tetrahydrofuran (THF), reduces the interfacial tension at the core-corona interface. We are currently investigating the effect of this phenomenon on the micelle structural properties, using scattering experiments and nuclear magnetic resonance. We have characterized the hydrodynamic radius, core radius, corona thickness, aggregation number, degree of swelling of the micelle core with the co-solvent, and unimer (free chain) concentration, as a function of the co-solvent concentration. Fundamental knowledge from these studies will inform design of drug delivery systems by allowing us to tailor micelle properties for optimal cargo loading.

Assessment of Blend PVDF Membranes, and the Effect of Polymer Concentration and Blend Composition

PubMed Central

Bamaga, Omar A.; Abdel-Aziz, M. H.

2018-01-01

In this work, PVDF homopolymer was blended with PVDF-co-HFP copolymer and studied in terms of morphology, porosity, pore size, hydrophobicity, permeability, and mechanical properties. Different solvents, namely N-Methyl-2 pyrrolidone (NMP), Tetrahydrofuran (THF), and Dimethylformamide (DMF) solvents, were used to fabricate blended PVDF flat sheet membranes without the introduction of any pore forming agent, through a non-solvent induced phase separation (NIPS) technique. Furthermore, the performance of the fabricated membranes was investigated for pressure and thermal driven applications. The porosity of the membranes was slightly increased with the increase in the overall content of PVDF and by the inclusion of PVDF copolymer. Total PVDF content, copolymer content, and mixed-solvent have a positive effect on mechanical properties. The addition of copolymer increased the hydrophobicity when the total PVDF content was 20%. At 25% and with the inclusion of mixed-solvent, the hydrophobicity was adversely affected. The permeability of the membranes increased with the increase in the overall content of PVDF. Mixed-solvents significantly improved permeability. PMID:29510555

Influencing the structure of block copolymer micelles with small molecule additives

NASA Astrophysics Data System (ADS)

Robertson, Megan; Singh, Avantika; Cooksey, Tyler; Kidd, Bryce; Piemonte, Rachele; Wang, Shu; Mai Le, Kim; Madsen, Louis

Amphiphilic block copolymer micelles in water are under broad exploration for drug delivery applications due to their high loading capacity and targeted drug delivery. We aim to understand the kinetic and thermodynamic processes that underlie the self-assembly of diblock copolymer micelle systems. The present work focuses on diblock copolymers containing poly(ethylene oxide) (a hydrophilic polymer) and polycaprolactone (a hydrophobic polymer), which spontaneously self-assemble into spherical micelles in water. Addition of a common good solvent (a co-solvent) for both of the constituting blocks, such as tetrahydrofuran (THF), reduces the interfacial tension at the core-corona interface. We are currently investigating the effect of this phenomenon on the micelle structural properties, using small-angle scattering and nuclear magnetic resonance. We have characterized the hydrodynamic radius, core radius, corona thickness, aggregation number, degree of swelling of the micelle core with the co-solvent, and unimer (free chain) concentration, as a function of the co-solvent concentration. Fundamental knowledge from these studies will inform design of drug delivery systems by allowing us to tailor micelle properties for optimal cargo loading.

Hydrogen-Bond and Supramolecular-Contact Mediated Fluorescence Enhancement of Electrochromic Azomethines.

PubMed

Wałęsa-Chorab, Monika; Tremblay, Marie-Hélène; Skene, William G

2016-08-01

An electronic push-pull fluorophore consisting of an intrinsically fluorescent central fluorene capped with two diaminophenyl groups was prepared. An aminothiophene was conjugated to the two flanking diphenylamines through a fluorescent quenching azomethine bond. X-ray crystallographic analysis confirmed that the fluorophore formed multiple intermolecular supramolecular bonds. It formed two hydrogen bonds involving a terminal amine, resulting in an antiparallel supramolecular dimer. Hydrogen bonding was also confirmed by FTIR and NMR spectroscopic analyses, and further validated theoretically by DFT calculations. Intrinsic fluorescence quenching modes could be reduced by intermolecular supramolecular contacts. These contacts could be engaged at high concentrations and in thin films, resulting in fluorescence enhancement. The fluorescence of the fluorophore could also be restored to an intensity similar to its azomethine-free counterpart with the addition of water in >50 % v/v in tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), and acetonitrile. The fluorophore also exhibited reversible oxidation and its color could be switched between yellow and blue when oxidized. Reversible electrochemically mediated fluorescence turn-off on turn-on was also possible. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Tetrahydrofuran Calpha-tetrasubstituted amino acids: two consecutive beta-turns in a crystalline linear tripeptide.

PubMed

Maity, Prantik; Zabel, Manfred; König, Burkhard

2007-10-12

The synthesis of tetrahydrofuran Calpha-tetrasubstituted amino acids (TAAs) and their effect on the conformation in small peptides are reported. The synthesis starts from the protein amino acid methionine, which is protected at the C and N terminus and converted into the corresponding sulfonium salt by alkylation. Simple base treatment in the presence of an aryl aldehyde leads to the formation of tetrahydrofuran tetrasubstituted Calpha-amino acids in a highly diastereoselective (trans/cis ratio up to 97:3) reaction with moderate to good yields (35-78%) depending on the aldehyde used. Palladium-catalyzed coupling reactions allow a subsequent further functionalization of the TAA. The R,S,S-TAA-Ala dipeptide amide adopts a beta-turn type I conformation, whereas its S,R,S isomer does not. The R,S,S-Gly-TAA-Ala tripeptide amide shows in the solid state and in solution a conformation of two consecutive beta-turn type III structures, stabilized by i+3-->i intramolecular hydrogen bonds.

Modified zeolitic imidazolate framework-8 as solid-phase microextraction Arrow coating for sampling of amines in wastewater and food samples followed by gas chromatography-mass spectrometry.

PubMed

Lan, Hangzhen; Rönkkö, Tuukka; Parshintsev, Jevgeni; Hartonen, Kari; Gan, Ning; Sakeye, Motolani; Sarfraz, Jawad; Riekkola, Marja-Liisa

2017-02-24

In this study, a novel solid phase microextration (SPME) Arrow was prepared for the sampling of volatile low molecular weight alkylamines (trimethylamine (TMA) and triethylamine (TEA)) in wastewater, salmon and mushroom samples before gas chromatographic separation with mass spectrometer as detector. Acidified zeolitic imidazolate framework-8 (A-ZIF-8) was utilized as adsorbent and poly(vinyl chloride) (PVC) as the adhesive. The custom SPME Arrow was fabricated via a physical adhesion: (1) ZIF-8 particles were suspended in a mixture of tetrahydrofuran (THF) and PVC to form a homogeneous suspension, (2) a non-coated stainless steel SPME Arrow was dipped in the ZIF-8/PVC suspension for several times to obtain a uniform and thick coating, (3) the pore size of ZIF-8 was modified by headspace exposure to hydrochloric acid in order to increase the extraction efficiency for amines. The effect of ZIF-8 concentration in PVC solution, dipping cycles and aging temperature on extraction efficiency was investigated. In addition, sampling parameters such as NaCl concentration, sample volume, extraction time, potassium hydroxide concentration, desorption temperature and desorption time were optimized. The Arrow-to-Arrow reproducibilities (RSDs) for five ZIF-8 coated Arrows were 15.6% and 13.3% for TMA and TEA, respectively. The extraction with A-ZIF-8/PVC Arrow was highly reproducible for at least 130 cycles without noticeable decrease of performance (RSD<12.5%). Headspace SPME of 7.5mL sample solution with the fabricated ZIF-8 coated Arrow achieved linear ranges of 1-200ngmL -1 for both TMA and TEA. The limit of quantitation (LOQ) was 1ngmL -1 for both TMA and TEA. The method was successfully applied to the determination of TMA and TEA in wastewater, salmon and mushroom samples giving satisfactory selectivity towards the studied amines. Copyright © 2016 Elsevier B.V. All rights reserved.

Homoleptic 2,2'-bipyridine metalates(-I) of iron and cobalt, one cocrystallized with an anthracene radical anion and the other with neutral anthracene.

PubMed

Brennessel, William W; Ellis, John E

2014-08-01

Homoleptic 2,2'-bipyridine (bipy) metalates of iron and cobalt have been synthesized directly from the corresponding homoleptic anthracene metalates. In the iron structure, bis[([2.2.2]cryptand)potassium(I)] tris(2,2'-bipyridine)ferrate(-I) anthracene(-I), [K(C18H36N2O6)]2[Fe(C10H8N2)3](C14H10), the asymmetric unit contains one potassium complex cation in a general position, the Fe center and one and a half bipy ligands of the ferrate complex on a crystallographic twofold axis that includes the Fe atom, and one half of an anthracene radical anion whose other half is generated by a crystallographic inversion center. The cations and anions are well separated and the geometry about the Fe center is essentially octahedral. In the cobalt structure, ([2.2.2]cryptand)potassium(I) bis(2,2'-bipyridine)cobaltate(-I) anthracene hemisolvate tetrahydrofuran (THF) disolvate, [K(C18H36N2O6)][Co(C10H8N2)2]·0.5C14H10·2C4H8O, the asymmetric unit contains the cation, anion, and both cocrystallized THF solvent molecules in general positions, and one half of a cocrystallized anthracene molecule whose other half is generated by a crystallographic inversion center. The cation and anion are well separated and the ligand planes in the cobaltate anion are periplanar. Each anthracene molecule is midway between and is oriented perpendicular to a pair of symmetry-related bipy ligands such that aromatic donor-acceptor interactions may play a role in the packing arrangement. The lengths of the bonds that connect the bipy rings support the assertion that the ligands are bipy radical anions in the iron structure. However, in the case of cobalt, these lengths are between the known ranges for a bipy radical anion and a bipy dianion, and therefore no conclusion can be made from the crystallography alone. One cocrystallized THF solvent molecule in the cobalt structure was modeled as disordered over three positions with appropriate geometric and thermal restraints, which resulted in a refined component mass ratio of 0.412 (4):0.387 (3):0.201 (3).

Method of producing thin cellulose nitrate film

DOEpatents

Lupica, S.B.

1975-12-23

An improved method for forming a thin nitrocellulose film of reproducible thickness is described. The film is a cellulose nitrate film, 10 to 20 microns in thickness, cast from a solution of cellulose nitrate in tetrahydrofuran, said solution containing from 7 to 15 percent, by weight, of dioctyl phthalate, said cellulose nitrate having a nitrogen content of from 10 to 13 percent.

Diphenylacrylonitrile-connected BODIPY dyes: fluorescence enhancement based on dark and AIE resonance energy transfer.

PubMed

Lin, Liangbin; Lin, Xiaoru; Guo, Hongyu; Yang, Fafu

2017-07-19

This study focuses on the construction of novel diphenylacrylonitrile-connected BODIPY dyes with high fluorescence in both solution and an aggregated state by combining DRET and FRET processes in a single donor-acceptor system. The first BODIPY derivatives with one, two, or three AIE-active diphenylacrylonitrile groups were designed and synthesized in moderate yields. Strong fluorescence emissions were observed in the THF solution under excitation at the absorption wavelength of non-emissive diphenylacrylonitrile chromophores, implying the existence of the DRET process between the dark diphenylacrylonitrile donor and the emissive BODIPY acceptor. In the THF/H 2 O solution, the fluorescence intensity of the novel BODIPY derivatives gradually increased under excitation at the absorption wavelength of diphenylacrylonitrile chromophores, suggesting a FRET process between diphenylacrylonitrile and BODIPY moieties. A greater number of diphenylacrylonitrile units led to higher energy-transfer efficiencies. The pseudo-Stokes shift for both DRET and FRET processes was as large as 190 nm.

Molecular Interactions in 1,4-Dioxane, Tetrahydrofuran, and Ethyl Acetate Solutions of 1,1'-Bis(4-isopropyloxyacetylphenoxy)cyclohexane on Reological, Density, and Acoustic Behavior

NASA Astrophysics Data System (ADS)

Dhaduk, B. B.; Patel, Ch. B.; Parsania, P. H.

2017-12-01

Various thermo-acoustical parameters of 1,4-dioxane, tetrahydofuran and ethylacetae solutions of 1,1'-bis(4-isopropyloxyacetylphenoxy)cyclohexane were determined at different temperatures using density, viscosity and ultrasonic speed and correlated with concentration. Linear increase of ultrasonic speed, specific acoustical impedance, Rao's molar sound function, Van der Waals constant and free volume with concentration C and decreased with temperature. Linear decrease of adiabatic compressibility, internal pressure, intermolecular free path length, classical absorption coefficient, and viscous relaxation time with concentration and increased with temperature indicated existence of strong molecular interactions in solutions and further supported by positive values of solvation number. Gibbs free energy of activation decreased with C in all three systems. It is decreased with T in 1,4-dioxane, while increased in tetrahydrofuran and ethyl acetate. Both enthalpy of activation and entropy of activation are increased gradually with C in 1,4-dioxane, while they are negative and remained practically independent of concentration in 1,4-dioxane and tetrahydofuran systems.

The solvation structure of Mg ions in dichloro complex solutions from first-principles molecular dynamics and simulated X-ray absorption spectra.

PubMed

Wan, Liwen F; Prendergast, David

2014-10-15

The knowledge of Mg solvation structure in the electrolyte is requisite to understand the transport behavior of Mg ions and their dissolution/deposition mechanism at electrolyte/electrode interfaces. In the first established rechargeable Mg-ion battery system [D. Aurbach et al. Nature 2000, 407, 724], the electrolyte is of the dichloro complex (DCC) solution family, Mg(AlCl2BuEt)2/THF, resulting from the reaction of Bu2Mg and EtAlCl2 with a molar ratio of 1:2. There is disagreement in the literature regarding the exact solvation structure of Mg ions in such solutions, i.e., whether Mg(2+) is tetra- or hexacoordinated by a combination of Cl(-) and THF. In this work, theoretical insight into the solvation complexes present is provided based on first-principles molecular dynamics simulations (FPMD). Both Mg monomer and dimer structures are considered in both neutral and positively charged states. We found that, at room temperature, the Mg(2+) ion tends to be tetracoordinated in the THF solution phase instead of hexacoordinated, which is the predominant solid-phase coordination. Simulating the X-ray absorption spectra (XAS) at the Mg K-edge by sampling our FPMD trajectories, our predicted solvation structure can be readily compared with experimental measurements. It is found that when changing from tetra- to hexacoordination, the onset of X-ray absorption should exhibit at least a 1 eV blue shift. We propose that this energy shift can be used to monitor changes in the Mg solvation sphere as it migrates through the electrolyte to electrolyte/electrode interfaces and to elucidate the mechanism of Mg dissolution/deposition.

Thermal conductivity of hydrate-bearing sediments

USGS Publications Warehouse

Cortes, Douglas D.; Martin, Ana I.; Yun, Tae Sup; Francisca, Franco M.; Santamarina, J. Carlos; Ruppel, Carolyn D.

2009-01-01

A thorough understanding of the thermal conductivity of hydrate-bearing sediments is necessary for evaluating phase transformation processes that would accompany energy production from gas hydrate deposits and for estimating regional heat flow based on the observed depth to the base of the gas hydrate stability zone. The coexistence of multiple phases (gas hydrate, liquid and gas pore fill, and solid sediment grains) and their complex spatial arrangement hinder the a priori prediction of the thermal conductivity of hydrate-bearing sediments. Previous studies have been unable to capture the full parameter space covered by variations in grain size, specific surface, degree of saturation, nature of pore filling material, and effective stress for hydrate-bearing samples. Here we report on systematic measurements of the thermal conductivity of air dry, water- and tetrohydrofuran (THF)-saturated, and THF hydrate–saturated sand and clay samples at vertical effective stress of 0.05 to 1 MPa (corresponding to depths as great as 100 m below seafloor). Results reveal that the bulk thermal conductivity of the samples in every case reflects a complex interplay among particle size, effective stress, porosity, and fluid-versus-hydrate filled pore spaces. The thermal conductivity of THF hydrate–bearing soils increases upon hydrate formation although the thermal conductivities of THF solution and THF hydrate are almost the same. Several mechanisms can contribute to this effect including cryogenic suction during hydrate crystal growth and the ensuing porosity reduction in the surrounding sediment, increased mean effective stress due to hydrate formation under zero lateral strain conditions, and decreased interface thermal impedance as grain-liquid interfaces are transformed into grain-hydrate interfaces.

Theophylline cocrystals prepared by spray drying: physicochemical properties and aerosolization performance.

PubMed

Alhalaweh, Amjad; Kaialy, Waseem; Buckton, Graham; Gill, Hardyal; Nokhodchi, Ali; Velaga, Sitaram P

2013-03-01

The purpose of this work was to characterize theophylline (THF) cocrystals prepared by spray drying in terms of the physicochemical properties and inhalation performance when aerosolized from a dry powder inhaler. Cocrystals of theophylline with urea (THF-URE), saccharin (THF-SAC) and nicotinamide (THF-NIC) were prepared by spray drying. Milled THF and THF-SAC cocrystals were also used for comparison. The physical purity, particle size, particle morphology and surface energy of the materials were determined. The in vitro aerosol performance of the spray-dried cocrystals, drug-alone and a drug-carrier aerosol, was assessed. The spray-dried particles had different size distributions, morphologies and surface energies. The milled samples had higher surface energy than those prepared by spray drying. Good agreement was observed between multi-stage liquid impinger and next-generation impactor in terms of assessing spray-dried THF particles. The fine particle fractions of both formulations were similar for THF, but drug-alone formulations outperformed drug-carrier formulations for the THF cocrystals. The aerosolization performance of different THF cocrystals was within the following rank order as obtained from both drug-alone and drug-carrier formulations: THF-NIC>THF-URE>THF-SAC. It was proposed that micromeritic properties dominate over particle surface energy in terms of determining the aerosol performance of THF cocrystals. Spray drying could be a potential technique for preparing cocrystals with modified physical properties.

F-element metalated dipyrrins: synthesis and characterization of a family of uranyl bis(dipyrrinate) complexes.

PubMed

Bolotaulo, Duer; Metta-Magaña, Alejandro; Fortier, Skye

2017-03-07

Using an improved, chromatography-free dipyrrin synthesis, the α,β-unsubstituted dipyrrins [RC(C 4 H 2 N) 2 H] (2) (R = tolyl (2toly l ), p-OMe-C 6 H 4 (2anis), mesityl (2mes), ferrocenyl (2Fc)) were isolated in good to excellent yields. Deprotonation of 2 with Na[N(SiMe 3 ) 2 ] gives the alkali metal salts [Na(DME) n ][RC(C 4 H 2 N) 2 ] (3) which reacts with UO 2 Cl 2 (THF) 3 to give the uranyl bis(dipyrrinates) UO 2 [RC(C 4 H 2 N) 2 ] 2 (L) (L = THF (4R-THF); DMAP (4R-DMAP)) (R = tolyl, p-OMe-C 6 H 4 , mesityl, ferrocenyl). The THF adducts, 4R-THF, are unstable in aromatic and nonpolar solvents and rapidly decompose to 2 and an intractable uranium-containing solid. On the other hand, the DMAP adducts, 4R-DMAP, are indefinitely stable in solution. The solid-state structures of 4R-THF and 4R-DMAP reveal distorted trigonal bipyramidal geometries. In the solid-state, the dipyrrinate ligands exhibit significant distortions including bowing and, in some instances, out-of-plane equatorial N-atom coordination, likely as a consequence of steric crowding and interligand repulsion. The complexes, 4R-DMAP, have been fully characterized by NMR, UV/Vis, and fluorescence spectroscopies, and their electrochemical properties have been investigated through cyclic voltammetry. The cyclic voltammograms of 4R-DMAP display several redox features but present a reversible wave at ca. -1.9 V (vs. Fc 0/+ ) attributable to a ligand centred reduction. Fluorescence measurements of all compounds reveal that only the mesityl derivatives 2mes, 3mes, and 4mes fluoresce with modest Stokes shift that ranges from ca. 30-70 nm, with 4mes displaying the greatest relative emission intensity.

Intramolecular, Exciplex-Mediated, Proton-Coupled, Charge-Transfer Processes in N,N-Dimethyl-3-(1-pyrenyl)propan-1-ammonium Cations: Influence of Anion, Solvent Polarity, and Temperature.

PubMed

Safko, Trevor M; Faleiros, Marcelo M; Atvars, Teresa D Z; Weiss, Richard G

2016-06-16

An intramolecular exciplex-mediated, proton-coupled, charge-transfer (PCCT) process has been investigated for a series of N,N-dimethyl-3-(1-pyrenyl)propan-1-ammonium cations with different anions (PyS) in solvents of low to intermediate polarity over a wide temperature range. Solvent mediates both the equilibrium between conformations of the cation that place the pyrenyl and ammonium groups in proximity (conformation C) or far from each other (conformation O) and the ability of the ammonium group to transfer a proton adiabatically in the PyS excited singlet state. Thus, exciplex emission, concurrent with the PCCT process, was observed only in hydrogen-bond accepting solvents of relatively low polarity (tetrahydrofuran, ethyl acetate, and 1,4-dioxane) and not in dichloromethane. From the exciplex emission and other spectroscopic and thermodynamic data, the acidity of the ammonium group in conformation C of the excited singlet state of PyS (pKa*) has been estimated to be ca. -3.4 in tetrahydrofuran. The ratios between the intensities of emission from the exciplex and the locally excited state (IEx/ILE) appear to be much more dependent on the nature of the anion than are the rates of exciplex formation and decay, although the excited state data do not provide a quantitative measure of the anion effect on the C-O equilibrium. The activation energies associated with exciplex formation in THF are calculated to be 0.08 to 0.15 eV lower than for the neutral amine, N,N-dimethyl-3-(1-pyrenyl)propan-1-amine. Decay of the exciplexes formed from the deprotonation of PyS is hypothesized to occur through charge-recombination processes. To our knowledge, this is the first example in which photoacidity and intramolecular exciplex formation (i.e., a PCCT reaction) are coupled.

Trivalent Rare-Earth-Metal Bis(trimethylsilyl)amide Halide Complexes by Targeted Oxidations.

PubMed

Bienfait, André M; Wolf, Benjamin M; Törnroos, Karl W; Anwander, Reiner

2018-05-07

In contrast to previously applied salt metathesis protocols the targeted rare-earth-metal compounds Ln[N(SiMe 3 ) 2 ] 2 (halogenido) were accessed by oxidation of Ln(II) silylamide precursors. Treatment of Sm[N(SiMe 3 ) 3 ] 2 (thf) 2 with 0.5 equiv of C 2 Cl 6 or 0.25 equiv of TeBr 4 in thf and crystallization thereof gave [Sm{N(SiMe 3 ) 2 } 2 (μ-X)(thf)] 2 (X = Cl, Br). A similar reaction/crystallization procedure performed with 0.5 equiv of 1,2-diiodoethane gave monomeric Sm[N(SiMe 3 ) 2 ] 2 I(thf) 2 . Switching to Yb[N(SiMe 3 ) 2 ] 2 (thf) 2 , the aforementioned oxidants generated monomeric five-coordinate complexes Yb[N(SiMe 3 ) 2 ] 2 X(thf) 2 (X = Cl, Br, I). The reaction of Eu[N(SiMe 3 ) 2 ] 2 (thf) 2 with 0.5 equiv of C 2 Cl 6 in thf yielded the separated ion pair [Eu{N(SiMe 3 ) 2 } 3 Cl][(thf) 5 Eu(μ-Cl) 2 Eu(thf) 5 ]. Performing the chlorination in n-hexane led to oxidation followed by rapid disproportionation into EuCl 3 (thf) x and Eu[N(SiMe 3 ) 2 ] 3 . The bromination reaction did not afford crystalline material, while the iodination gave crystals of divalent EuI 2 (thf) 5 . Use of trityl chloride (Ph 3 CCl) as the oxidant in thf accomplished the Eu(III) species [Eu{N(SiMe 3 ) 2 } 2 (μ-Cl)(thf)] 2 . In situ oxidation of putative [Tm{N(SiMe 3 ) 2 } 2 (thf) x ] using 0.5 equiv of C 2 Cl 6 in thf followed by crystallization from n-hexane led to the formation of a mixture of [Tm{N(SiMe 3 ) 2 } 2 (μ-Cl)(thf)] 2 and Tm[N(SiMe 3 ) 2 ] 3 . Switching the oxidant to 0.5 equiv of 1,2-diiodoethane and crystallizing from thf repeatedly afforded the bis-halogenated complex Tm[N(SiMe 3 ) 2 ]I 2 (thf) 3 .

Electrospinning of Polyvinylidene Fluoride and Polyetherimide From Mixed Solvents

NASA Technical Reports Server (NTRS)

Morgret, Leslie D.; Pawlowski, Kristin J.; Hinkley, Jeffrey A.

2005-01-01

Polyvinylidene fluoride and Ultem(TradeMark) polyetherimide were dissolved in 50/50 acetone/N,N dimethylformamide (DMF) and 80/20 tetrahydrofuran/DMF, respectively, and electrospun. Polymer solution concentrations and molecular weights were changed while other spinning parameters (voltage, distance, solution feed rate) were held constant. Fiber diameters in the resulting electrospun mats varied from 0.25 to 4.4 microns, increasing with polymer concentration and molecular weight; trends in diameter were compared with trends in viscosities and surface tensions of the spinning solutions.

Multiply Reduced Oligofluorenes: Their Nature and Pairing with THF-Solvated Sodium Ions

DOE PAGES

Wu, Qin; Zaikowski, Lori; Kaur, Parmeet; ...

2016-07-01

Conjugated oligofluorenes are chemically reduced up to five charges in tetrahydrofuran solvent and confirmed with clear spectroscopic evidence. Stimulated by these experimental results, we have conducted a comprehensive computational study of the electronic structure and the solvation structure of representative oligofluorene anions with a focus on the pairing between sodium ions and these multianions. In addition, using density functional theory (DFT) methods and a solvation model of both explicit solvent molecules and implicit polarizable continuum, we first elucidate the structure of tightly solvated free sodium ions, and then explore the pairing of sodium ions either in contact with reduced oligofluorenesmore » or as solvent-separated ion pairs. Computed time-dependent-DFT absorption spectra are compared with experiments to assign the dominant ion pairing structure for each multianion. Computed ion pair binding energies further support our assignment. Lastly, the availability of different length and reducing level of oligofluorenes enables us to investigate the effects of total charge and charge density on the binding with sodium ions, and our results suggest both factors play important roles in ion pairing for small molecules. However, as the oligofluorene size grows, its charge density determines the binding strength with the sodium ion.« less

Feedback System Control Optimized Electrospinning for Fabrication of an Excellent Superhydrophobic Surface.

PubMed

Yang, Jian; Liu, Chuangui; Wang, Boqian; Ding, Xianting

2017-10-13

Superhydrophobic surface, as a promising micro/nano material, has tremendous applications in biological and artificial investigations. The electrohydrodynamics (EHD) technique is a versatile and effective method for fabricating micro- to nanoscale fibers and particles from a variety of materials. A combination of critical parameters, such as mass fraction, ratio of N, N-Dimethylformamide (DMF) to Tetrahydrofuran (THF), inner diameter of needle, feed rate, receiving distance, applied voltage as well as temperature, during electrospinning process, to determine the morphology of the electrospun membranes, which in turn determines the superhydrophobic property of the membrane. In this study, we applied a recently developed feedback system control (FSC) scheme for rapid identification of the optimal combination of these controllable parameters to fabricate superhydrophobic surface by one-step electrospinning method without any further modification. Within five rounds of experiments by testing totally forty-six data points, FSC scheme successfully identified an optimal parameter combination that generated electrospun membranes with a static water contact angle of 160 degrees or larger. Scanning electron microscope (SEM) imaging indicates that the FSC optimized surface attains unique morphology. The optimized setup introduced here therefore serves as a one-step, straightforward, and economic approach to fabricate superhydrophobic surface with electrospinning approach.

Buoyancy driven mixing of miscible fluids by volumetric energy deposition of microwaves.

PubMed

Wachtor, Adam J; Mocko, Veronika; Williams, Darrick J; Goertz, Matthew P; Jebrail, Farzaneh F

2013-01-01

An experiment that seeks to investigate buoyancy driven mixing of miscible fluids by microwave volumetric energy deposition is presented. The experiment involves the use of a light, non-polar fluid that initially rests on top of a heavier fluid which is more polar. Microwaves preferentially heat the polar fluid, and its density decreases due to thermal expansion. As the microwave heating continues, the density of the lower fluid eventually becomes less than that of the upper, and buoyancy driven Rayleigh-Taylor mixing ensues. The choice of fluids is crucial to the success of the experiment, and a description is given of numerous fluid combinations considered and characterized. After careful consideration, the miscible pair of toluene/tetrahydrofuran (THF) was determined as having the best potential for successful volumetric energy deposition buoyancy driven mixing. Various single fluid calibration experiments were performed to facilitate the development of a heating theory. Thereafter, results from two-fluid mixing experiments are presented that demonstrate the capability of this novel Rayleigh-Taylor driven experiment. Particular interest is paid to the onset of buoyancy driven mixing and unusual aspects of the experiment in the context of typical Rayleigh-Taylor driven mixing.

Sorting of large-diameter semiconducting carbon nanotube and printed flexible driving circuit for organic light emitting diode (OLED).

PubMed

Xu, Wenya; Zhao, Jianwen; Qian, Long; Han, Xianying; Wu, Liangzhuan; Wu, Weichen; Song, Minshun; Zhou, Lu; Su, Wenming; Wang, Chao; Nie, Shuhong; Cui, Zheng

2014-01-01

A novel approach was developed to sort a large-diameter semiconducting single-walled carbon nanotube (sc-SWCNT) based on copolyfluorene derivative with high yield. High purity sc-SWCNTs inks were obtained by wrapping arc-discharge SWCNTs with poly[2,7-(9,9-dioctylfluorene)-alt-4,7-bis(thiophen-2-yl)benzo-2,1,3-thiadiazole] (PFO-DBT) aided by sonication and centrifugation in tetrahydrofuran (THF). The sorted sc-SWCNT inks and nanosilver inks were used to print top-gated thin-film transistors (TFTs) on flexible substrates with an aerosol jet printer. The printed TFTs demonstrated low operating voltage, small hysteresis, high on-state current (up to 10(-3) A), high mobility and on-off ratio. An organic light emitting diode (OLED) driving circuit was constructed based on the printed TFTs, which exhibited high on-off ratio up to 10(4) and output current up to 3.5 × 10(-4) A at V(scan) = -4.5 V and Vdd = 0.8 V. A single OLED was switched on with the driving circuit, showing the potential as backplanes for active matrix OLED applications.

A High-Throughput Process for the Solid-Phase Purification of Synthetic DNA Sequences

PubMed Central

Grajkowski, Andrzej; Cieślak, Jacek; Beaucage, Serge L.

2017-01-01

An efficient process for the purification of synthetic phosphorothioate and native DNA sequences is presented. The process is based on the use of an aminopropylated silica gel support functionalized with aminooxyalkyl functions to enable capture of DNA sequences through an oximation reaction with the keto function of a linker conjugated to the 5′-terminus of DNA sequences. Deoxyribonucleoside phosphoramidites carrying this linker, as a 5′-hydroxyl protecting group, have been synthesized for incorporation into DNA sequences during the last coupling step of a standard solid-phase synthesis protocol executed on a controlled pore glass (CPG) support. Solid-phase capture of the nucleobase- and phosphate-deprotected DNA sequences released from the CPG support is demonstrated to proceed near quantitatively. Shorter than full-length DNA sequences are first washed away from the capture support; the solid-phase purified DNA sequences are then released from this support upon reaction with tetra-n-butylammonium fluoride in dry dimethylsulfoxide (DMSO) and precipitated in tetrahydrofuran (THF). The purity of solid-phase-purified DNA sequences exceeds 98%. The simulated high-throughput and scalability features of the solid-phase purification process are demonstrated without sacrificing purity of the DNA sequences. PMID:28628204

Understanding and controlling the rest potential of carbon nanotube-based supercapacitors for energy density enhancement

NASA Astrophysics Data System (ADS)

Yoo, Young-Eun; Park, Jinwoo; Kim, Woong

2018-03-01

We present a novel method for enhancing the energy density of an electrical double layer capacitor (EDLC). Surface modification of single-walled carbon nanotube (SWNT) electrodes significantly affects the rest potential (E0) of EDLCs; acid treatment and polyethyleneimine (PEI) coating of SWNTs shift E0 toward more positive and more negative values, respectively. Adjusting E0 towards the center of the electrolyte stability window can increase the cell voltage and hence the energy density. PEI coating on SWNTs increases the cell voltage from 0.8 V to 1.7 V in tetrabutylammonium perchlorate (TBAP)/tetrahydrofuran (THF) electrolyte, and from 2.5 V to 3.1 V in tetraethylammonium tetrafluoroborate (TEABF4)/3-cyanopropionic acid methyl ester (CPAME), respectively. Moreover, PEI-SWNT EDLCs exhibit excellent cycling stability (92% of capacitance retention over 10000 cycles). We attribute the shift in E0 to a change in the Fermi level of SWNTs owing to the surface charge modification. Injection of electrical charge into PEI-SWNTs consistently yielded similar trends and thus validated our hypothesis. Our results may help to push various electrolytes that have been overlooked so far to new frontiers for obtaining high energy-density supercapacitors.

Mechanical and electromagnetic properties of northern Gulf of Mexico sediments with and without THF hydrates

USGS Publications Warehouse

Lee, J.Y.; Santamarina, J.C.; Ruppel, C.

2008-01-01

Using an oedometer cell instrumented to measure the evolution of electromagnetic properties, small strain stiffness, and temperature, we conducted consolidation tests on sediments recovered during drilling in the northern Gulf of Mexico at the Atwater Valley and Keathley Canyon sites as part of the 2005 Chevron Joint Industry Project on Methane Hydrates. The tested specimens include both unremolded specimens (as recovered from the original core liner) and remolded sediments both without gas hydrate and with pore fluid exchanged to attain 100% synthetic (tetrahydrofuran) hydrate saturation at any stage of loading. Test results demonstrate the extent to which the electromagnetic and mechanical properties of hydrate-bearing marine sediments are governed by the vertical effective stress, stress history, porosity, hydrate saturation, fabric, ionic concentration of the pore fluid, and temperature. We also show how permittivity and electrical conductivity data can be used to estimate the evolution of hydrate volume fraction during formation. The gradual evolution of geophysical properties during hydrate formation probably reflects the slow increase in ionic concentration in the pore fluid due to ion exclusion in closed systems and the gradual decrease in average pore size in which the hydrate forms. During hydrate formation, the increase in S-wave velocity is delayed with respect to the decrease in permittivity, consistent with hydrate formation on mineral surfaces and subsequent crystal growth toward the pore space. No significant decementation/debonding occurred in 100% THF hydrate-saturated sediments during unloading, hence the probability of sampling hydrate-bearing sediments without disturbing the original sediment fabric is greatest for samples in which the gas hydrate is primarily responsible for maintaining the sediment fabric and for which the time between core retrieval and restoration of in situ effective stress in the laboratory is minimized. In evaluating the impact of core retrieval on specimen properties, it is also important to consider how far removed hydrate-bearing samples are from hydrate stability conditions. ?? 2008 Elsevier Ltd.

Determination of the Solubility Limit of Tris(dibenzylideneacetone) Dipalladium(0) in Tetrahydrofuran/Water Mixtures

ERIC Educational Resources Information Center

Franzen, Stefan

2011-01-01

Determination of the solubility limit of a strongly colored organometallic reagent in a mixed-solvent system provides an example of quantitative solubility measurement appropriate to understand polymer, nanoparticle, and other macromolecular aggregation processes. The specific example chosen involves a solution of tris(dibenzylideneacetone)…

21 CFR 178.3950 - Tetrahydrofuran.

Code of Federal Regulations, 2010 CFR

2010-04-01

... section. (a) It is used as a solvent in the casting of film from a solution of polymeric resins of vinyl... another in any combination, or it may be used as a solvent in the casting of film prepared from vinyl... in the film does not exceed 1.5 percent by weight of film. ...

The formal combination of three singlet biradicaloid entities to a singlet hexaradicaloid metalloid Ge14[Si(SiMe3)3]5[Li(THF)2]3 cluster.

PubMed

Schenk, Christian; Kracke, Andreas; Fink, Karin; Kubas, Adam; Klopper, Wim; Neumaier, Marco; Schnöckel, Hansgeorg; Schnepf, Andreas

2011-03-02

The reaction of GeBr with LiSi(SiMe(3))(3) leads to the metalloid cluster compound [(THF)(2)Li](3)Ge(14)[Si(SiMe(3))(3)](5) (1). After the introduction of a first cluster of this type, in which 14 germanium atoms form an empty polyhedron, [(THF)(2)Li](3)Ge(14)[Ge(SiMe(3))(3)](5) (2), we present here further investigations on 1 to obtain preliminary insight into its chemical and bonding properties. The molecular structure of 1 is determined via X-ray crystal structure solution using synchrotron radiation. The electronic structure of the Ge(14) polyhedron is further examined by quantum chemical calculations, which indicate that three singlet biradicaloid entities formally combine to yield the singlet hexaradicaloid character of 1. Moreover, the initial reactions of 1 after elimination of the [Li(THF)(2)](+) groups by chelating ligands (e.g., TMEDA or 12-crown-4) are presented. Collision induced dissociation experiments in the gas phase, employing FT-ICR mass spectrometry, lead to the elimination of the singlet biradicaloid Ge(5)H(2)[Si(SiMe(3))(3)](2) cluster. The unique multiradicaloid bonding character of the metalloid cluster 1 might be used as a model for reactions and properties in the field of surface science and nanotechnology.

Closer insight into the reactivity of TMP-dialkyl zincates in directed ortho-zincation of anisole: experimental evidence of amido basicity and structural elucidation of key reaction intermediates.

PubMed

Clegg, William; Conway, Ben; Hevia, Eva; McCall, Matthew D; Russo, Luca; Mulvey, Robert E

2009-02-18

The new dialkyl(aryl) lithium zincates [(THF)(2)Li(C(6)H(4)-OMe)MeZnMe] (4), [(TMEDA)Li(C(6)H(4)-OMe)MeZnMe] (6), [(THF)(3)Li(C(6)H(4)-OMe)(t)BuZn(t)Bu] (7), and [(PMDETA)Li(C(6)H(4)-OMe)(t)BuZn(t)Bu] (8) have been prepared by co-complexation reactions of lithiated anisole with the relevant dialkylzinc compound and the relevant Lewis base. These new heterobimetallic compounds have been characterized in solution using (1)H, (13)C{H}, and (7)Li NMR spectroscopy, and the molecular structures of 6 and 8 have been elucidated by X-ray crystallography. In 6 the distinct metals are connected through the anisole ligand which binds in an ambidentate fashion (through carbon-zinc and oxygen-lithium contacts) and also through one of the methyl groups, to close a [LiOCCZnC] six-membered ring; whereas 8 displays an open structure where anisole connects the two metals (in the same mode as in 6) but with the tert-butyl groups exclusively bonded terminally to zinc. Reactivity studies of zincates 4 and 7 with the amine TMP(H) supply experimental evidence that these heterobimetallic compounds are intermediates in the two-step deprotonation reaction of anisole by TMP-dialkyl zincates and show the relevance of the alkyl groups in the efficiency of TMP-dialkyl zincate bases. In addition, important solvent effects have also been evaluated. When hexane is added to THF solutions of compounds 4 or 7, the homoleptic tetraorganozincate [(THF)(2)Li(2)Zn(C(6)H(4)-OMe)(4)] (5) is obtained as the result of a disproportionation process. This lithium-rich zincate has also been spectroscopically and crystallographically characterized.

Kinetic control of block copolymer self-assembly into multicompartment and novel geometry nanoparticles

NASA Astrophysics Data System (ADS)

Chen, Yingchao; Wang, Xiaojun; Zhang, Ke; Wooley, Karen; Mays, Jimmy; Percec, Virgil; Pochan, Darrin

2012-02-01

Micelles with the segregation of hydrophobic blocks trapped in the same nanoparticle core have been produced through co-self-assembly of two block copolymers in THF/water dilute solution. The dissolution of two block copolymer sharing the same polyacrylic acid PAA blocks in THF undergoes consequent aggregation and phase separation through either slow water titration or quick water addition that triggers the micellar formation. The combination and comparison of the two water addition kinetic pathways are the keys of forming multicompartment structures at high water content. Importantly, the addition of organic diamine provides for acid-base complexation with the PAA side chains which, in turn, plays the key role of trapping unlike hydrophobic blocks from different block copolymers into one nanoparticle core. The kinetic control of solution assembly can be applied to other molecular systems such as dendrimers as well as other block copolymer molecules. Transmission electron microscopy, cryogenic transmission electron microscopy, light scattering have been applied to characterize the micelle structures.

Halogen-free boron based electrolyte solution for rechargeable magnesium batteries

NASA Astrophysics Data System (ADS)

Zhu, Jinjie; Guo, Yongsheng; Yang, Jun; Nuli, Yanna; Zhang, Fan; Wang, Jiulin; Hirano, Shin-ichi

2014-02-01

All halogen containing electrolytes for Mg battery are apt to corrode conventional metal current collectors. In this paper, a new type of halogen-free boron based electrolyte (Mg[Mes3BPh]2/THF) is designed and prepared. Electrochemical tests show that this electrolyte system possesses high ion conductivity (1.5 × 10-3 S cm-1) and good Mg deposition-dissolution reversibility. More importantly, the same electrochemical window (2.6 V vs. Mg RE) of the electrolyte on Pt and stainless steel electrodes indicates that halogen-free electrolyte indeed lessens the corrosion to conventional metal current collectors. The surface morphologies of stainless steel, aluminum and copper are further observed after their anodic potentiostatic polarization in 0.25 mol L-1 Mg[Mes3BPh]2/THF electrolyte solution for 2 days. A comparison with halogen containing electrolytes proves that the presence of halogen in electrolyte is the reason for corrosion. This work provides a stepping stone for developing new halogen-free electrolyte systems for rechargeable Mg batteries.

Utilization of Network-Forming Block Copolymers and Ionomers in the Development of Novel Nanostructures and Responsive Media

NASA Astrophysics Data System (ADS)

Mineart, Kenneth

Network forming block copolymers, i.e. thermoplastic elastomers (TPEs), are one of the highest commodity forms of block copolymers due to their competitive elasticity and extendability as well as their ability to be melt and solution processed. TPEs owe many of their advantages to a combination of hard and soft blocks. The soft blocks, which must be covalently bound at both ends to hard blocks, connect adjacent hard domains resulting in physically cross-linked systems. Herein, simulations and theory are used to provide a molecular-level depiction of the evolution from diblock copolymers, which do not contain the ability to form physical cross-links, to network forming triblock copolymers. In addition, systems with high interblock incompatibility that are within the diblock-to-triblock transition (i.e. having high molecular asymmetry) are identified to form three component (ABC triblock copolymer) phases from copolymer containing only two chemically distinct blocks. Following this work, which emphasizes the fundamental principle of TPEs, the dissertation shifts focus to physically- and chemically-modified triblock and pentablock copolymer TPEs. Recent progress has sought to broaden TPEs to include properties that are above and beyond their inherent mechanical benefits, including responsiveness to external stimuli. The first examples presented here consist of TPEs prepared in combination with amorphous hydrocarbon additives to yield TPE gels (TPEGs). The resulting TPEGs, which maintain the beneficial processing properties of TPEs, are subsequently molded into 1- and 2-D arrays of microchannels that are filled with liquid metal. The final devices exhibit strain-sensitive electrical conductivity to at least 600% strain, have tunable compliance (ease of stretching), and are fully recyclable. The substitution of the amorphous hydrocarbon component for crystalline analogues with melting points <100 °C yield TPE composites (TPECs). The TPECs gain the added capability of thermally-triggered shape-memory actuation, which results in a number of design possibilities including: (i) multiple-transition shape-memory in single a composite, (ii) complex actuation in laminates and, (iii) thermally-responsive electrical conductivity in microchannel-molded composites filled with liquid metal. These shape-memory TPECs can also be tuned to have different shape-memory response rates through the addition of an amorphous hydrocarbon tackifier, which serves to dilute the crystalline content without altering TPE concentration. The second set of functionalized TPEs examined are midblock-sulfonated block copolymers, which have substantial ion and water transport abilities, but are often restricted in thermal processability. The casting solvent-dependent morphology of a midblock sulfonated pentablock copolymer highlights the impact of solvent templating on resulting film domain structures. It is shown that film deposition from a miscible mixture of toluene and isopropanol (TIPA) leads to spherical sulfonated domains within a nonpolar matrix whereas deposition from neat tetrahydrofuran (THF) produces a combination of lamellar and hexagonally-pack cylinder nanostructures. These morphologies can both be converted to the anticipated equilibrium morphology, alternating lamellae, using THF vapor-annealing. Further, the morphology resulting from each solvent-casting approach impacts the rate and overall capacity at which films absorb water. Specifically, THF-cast copolymers swell faster and to a greater extent. However, some intrigue lies in the transformation of the TIPA-cast copolymer upon swelling, which yields disordered, but continuous, hydrophilic domains. The disordered morphology outperforms ordered analogues in solar simulation experiments indicating higher ion conductivity.

7, 8, 3′-Trihydroxyflavone Promotes Neurite Outgrowth and Protects Against Bupivacaine-Induced Neurotoxicity in Mouse Dorsal Root Ganglion Neurons

PubMed Central

Shi, Haohong; Luo, Xingjing

2016-01-01

Background 7, 8, 3′-trihydroxyflavone (THF) is a novel pro-neuronal small molecule that acts as a TrkB agonist. In this study, we examined the effect of THF on promoting neuronal growth and protecting anesthetics-induced neurotoxicity in dorsal root ganglion (DRG) neurons in vitro. Material/Methods Neonatal mouse DRG neurons were cultured in vitro and treated with various concentrations of THF. The effect of THF on neuronal growth was investigated by neurite outgrowth assay and Western blot. In addition, the protective effects of THF on bupivacaine-induced neurotoxicity were investigated by apoptosis TUNEL assay, neurite outgrowth assay, and Western blot, respectively. Results THF promoted neurite outgrowth of DRG neurons in dose-dependent manner, with an EC50 concentration of 67.4 nM. Western blot analysis showed THF activated TrkB signaling pathway by inducing TrkB phosphorylation. THF also rescued bupivacaine-induced neurotoxicity by reducing apoptosis and protecting neurite retraction in DRG neurons. Furthermore, the protection of THF in bupivacaine-injured neurotoxicity was directly associated with TrkB phosphorylation in a concentration-dependent manner in DRG neurons. Conclusions THF has pro-neuronal effect on DRG neurons by promoting neurite growth and protecting against bupivacaine-induced neurotoxicity, likely through TrkB activation. PMID:27371503

Rh-Catalyzed annulations of N-methoxybenzamides with ketenimines: synthesis of 3-aminoisoindolinones and 3-diarylmethyleneisoindolinones with strong aggregation induced emission properties.

PubMed

Zhou, Xiaorong; Peng, Zhixing; Zhao, Hongyang; Zhang, Zhiyin; Lu, Ping; Wang, Yanguang

2016-08-23

Rhodium-catalyzed C-H activation/annulation reactions of ketenimines with N-methoxybenzamides furnished 3-aminoisoindolin-1-ones and 3-(diarylmethylene)isoindolin-1-ones. The synthesized 3-(diarylmethylene)isoindolin-1-ones exhibited aggregation induced emissions in aqueous tetrahydrofuran solution and strong green-yellow emissions in solids.

Facilitated preparation of bioconjugatable zwitterionic quantum dots using dual-lipid encapsulation.

PubMed

Shrake, Robert; Demillo, Violeta G; Ahmadiantehrani, Mojtaba; Zhu, Xiaoshan; Publicover, Nelson G; Hunter, Kenneth W

2015-01-01

Zwitterionic quantum dots prepared through incorporated zwitterionic ligands on quantum dot surfaces, are being paid significant attention in biomedical applications because of their excellent colloidal stability across a wide pH and ionic strength range, antifouling surface, good biocompatibility, etc. In this work, we report a dual-lipid encapsulation approach to prepare bioconjugatable zwitterionic quantum dots using amidosulfobetaine-16 lipids, dipalmitoyl-sn-glycero-3-phosphoethanolamine lipids with functional head groups, and CuInS2/ZnS quantum dots in a tetrahydrofuran/methanol/water solvent system with sonication. Amidosulfobetaine-16 is a zwitterionic lipid and dipalmitoyl-sn-glycero-3-phosphoethanolamine, with its functional head, provides bioconjugation capability. Under sonication, tetrahydrofuran/methanol containing amidosulfobetaine-16, dipalmitoyl-sn-glycero-3-phosphoethanolamine, and hydrophobic quantum dots are dispersed in water to form droplets. Highly water-soluble tetrahydrofuran/methanol in droplets is further displaced by water, which induces the lipid self-assembling on hydrophobic surface of quantum dots and thus forms water soluble zwitterionic quantum dots. The prepared zwitterionic quantum dots maintain colloidal stability in aqueous solutions with high salinity and over a wide pH range. They are also able to be conjugated with biomolecules for bioassay with minimal nonspecific binding. Copyright © 2014 Elsevier Inc. All rights reserved.

Lif Spectroscopy of ThF and the Preparation of ThF^{+} for the Jila eEDM Experiment

NASA Astrophysics Data System (ADS)

Ng, Kia Boon; Zhou, Yan; Gresh, Dan; Cairncross, William; Roussy, Tanya; Shagam, Yuval; Cheng, Lan; Ye, Jun; Cornell, Eric

2017-06-01

ThF^{+} is a promising candidate for a second-generation molecular ion-based measurement of the permanent electric dipole moment of the electron (eEDM). Compared to the current HfF^{+} eEDM experiment, ThF^{+} has several advantages: (i) the eEDM-sensitive ^{3}Δ_1 electronic state is the ground state, which facilitates a long measurement coherence time; (ii) its effective electric field (38 GV/cm) is 50% larger than that of HfF+, which promises a direct increase of the eEDM sensitivity; and (iii) the ionization energy of neutral ThF is lower than its dissociation energy, which introduces a greater flexibility for rotational state-selective photoionization via core-nonpenetrating Rydberg states. We use laser-induced fluorescence (LIF) spectroscopy to find suitable intermediate states required for the state selective ionization process. We present the results of our LIF spectroscopy of ThF, and our current progress on efficient ThF ionization and on ThF^{+} dissociation.

Synthesis of Synthetic Hydrocarbons Via Alpha Olefins.

DTIC Science & Technology

1985-05-01

THF complex, 0OC; (e) Pyridinium chlorochromate , dry CH2 CL29 room temperature; b (f) methyltriphenylphosphonium bromide, dimethyl sulfoxide, room...vigorously stirred solution of pyridinium chlorochromate (27.91 g, 0.13 mol) in dry methylene chloride (175 mL) was added all at once a solution of l... pyridinium chlorochroniate. 3 Our four-step synthesis of l-decene-2-1 3 C from 1-bromooctane is outlined in the Scheme. This synthetic sequence provides the

A facile synthesis of poly(aniline-co-o-bromoaniline) copolymer: Characterization and application as semiconducting material

NASA Astrophysics Data System (ADS)

Mahudeswaran, A.; Vivekanandan, J.; Vijayanand, P. S.; Kojima, T.; Kato, S.

2016-01-01

Poly(aniline-co-o-bromoaniline) (p(an-co-o-BrAn)) copolymer has been synthesized using chemical oxidation method in the hydrochloric acid medium. Copolymerization of aniline with o-bromoaniline of different compositions, such as 1:1, 1:2, 2:1, 1:3 and 3:1 molar ratios were prepared. The synthesized copolymer is soluble in polar solvents like dimethyl sulphoxide (DMSO), dimethyl formamide (DMF), Tetrahydrofuran (THF) and 1-methyl 2-pyrrolidone (NMP). The copolymer is analyzed by various characterization techniques, such as FTIR, UV-Visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), conductivity, Differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). FTIR spectrum confirms the characteristic peaks of the copolymer containing benzenoid and quinoid ring stretching. UV spectrum reveals the formation of π-π∗ transition and n-π∗ transition between the energy levels. XRD peaks reveal that the copolymer possesses amorphous nature. Morphological study reveals that the agglomerated particles form globular structure and size of the each particle is about 100 nm. The electrical conductivity of the copolymers is found in the range of 10-5Scm-1. These organic semiconductor materials can be used to fabricate thinner and cheaper environmental friendly optoelectronic devices that will replace the conventional inorganic semiconductors.

Silver nanoparticles synthesized with Rumex hymenosepalus extracts: effective broad-spectrum microbicidal agents and cytotoxicity study.

PubMed

Rodríguez-León, Ericka; Íñiguez-Palomares, Ramón A; Navarro, Rosa Elena; Rodríguez-Beas, César; Larios-Rodríguez, Eduardo; Alvarez-Cirerol, Francisco J; Íñiguez-Palomares, Claudia; Ramírez-Saldaña, Maricela; Hernández Martínez, Javier; Martínez-Higuera, Aarón; Galván-Moroyoqui, José Manuel; Martínez-Soto, Juan Manuel

2017-08-21

We synthesized silver nanoparticles using Rumex hymenosepalus root extract (Rh). Nanoparticles were subjected to a purification process and final product is a composite of Rh and silver nanoparticles (AgNPsC). Transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used to perform a microstructure study. Additionally, two fractions (RhA and RhB) were obtained from the original extract by filtration with tetrahydrofuran (THF); both fractions were analyzed using UV-Vis spectroscopy, Fourier transform infrared spectroscopy (FT-IR), and 2,2-diphenyl-1-picrylhydrazyl (DPPH); total polyphenol content was also determined. Separate inhibition tests for AgNPsC and RhA and RhB were applied to Gram-positive bacteria, Gram-negative bacteria, and yeast (Candida albicans) using the well diffusion method. Extract fractions were found to have inhibitory effects only over Gram-positive bacteria, and silver nanoparticles showed inhibitory effects over all the evaluated microorganisms. Cytotoxicity was evaluated using the tetrazolium dye (MTT) assay in mononuclear peripheral blood cells. In addition, we assessment AgNPsC in THP-1 monocyte cell line, using the cell viability estimation by trypan blue dye exclusion test (TB) and Live/Dead (LD) cell viability assays by confocal microscopy.

Co-pyrolysis of rice straw and polypropylene using fixed-bed pyrolyzer

NASA Astrophysics Data System (ADS)

Izzatie, N. I.; Basha, M. H.; Uemura, Y.; Mazlan, M. A.; Hashim, M. S. M.; Amin, N. A. M.; Hamid, M. F.

2016-11-01

The present work encompasses the impact of temperature (450, 500, 550, 600 °C) on the properties of pyrolysis oil and on other product yield for the co-pyrolysis of Polypropylene (PP) plastics and rice straw. Co-pyrolysis of PP plastic and rice straw were conducted in a fixed-bed drop type pyrolyzer under an inert condition to attain maximum oil yield. Physically, the pyrolysis oil is dark-brown in colour with free flowing and has a strong acrid smell. Copyrolysis between these typically obtained in maximum pyrolysis oil yields up to 69% by ratio 1:1 at a maximum temperature of 550 °C. From the maximum yield of pyrolysis oil, characterization of pyrolysis product and effect of biomass type of the composition were evaluated. Pyrolysis oil contains a high water content of 66.137 wt.%. Furfural, 2- methylnaphthalene, tetrahydrofuran (THF), toluene and acetaldehyde were the major organic compounds found in pyrolysis oil of rice straw mixed with PP. Bio-char collected from co-pyrolysis of rice straw mixed with PP plastic has high calorific value of 21.190 kJ/g and also carbon content with 59.02 wt.% and could contribute to high heating value. The non-condensable gases consist of hydrogen, carbon monoxide, and methane as the major gas components.

Engineering the Re-Entrant Hierarchy and Surface Energy of PDMS-PVDF Membrane for Membrane Distillation Using a Facile and Benign Microsphere Coating.

PubMed

Lee, Eui-Jong; Deka, Bhaskar Jyoti; Guo, Jiaxin; Woo, Yun Chul; Shon, Ho Kyong; An, Alicia Kyoungjin

2017-09-05

To consolidate the position of membrane distillation (MD) as an emerging membrane technology that meets global water challenges, it is crucial to develop membranes with ideal material properties. This study reports a facile approach for a polyvinylidene fluoride (PVDF) membrane surface modification that is achieved through the coating of the surface with poly(dimethylsiloxane) (PDMS) polymeric microspheres to lower the membrane surface energy. The hierarchical surface of the microspheres was built without any assistance of a nano/microcomposite by combining the rapid evaporation of tetrahydrofuran (THF) and the phase separation from condensed water vapor. The fabricated membrane exhibited superhydrophobicity-a high contact angle of 156.9° and a low contact-angle hysteresis of 11.3°-and a high wetting resistance to seawater containing sodium dodecyl sulfate (SDS). Compared with the control PVDF-hexafluoropropylene (HFP) single-layer nanofiber membrane, the proposed fabricated membrane with the polymeric microsphere layer showed a smaller pore size and higher liquid entry pressure (LEP). When it was tested for the direct-contact MD (DCMD) in terms of the desalination of seawater (3.5% of NaCl) containing SDS of a progressively increased concentration, the fabricated membrane showed stable desalination and partial wetting for the 0.1 and 0.2 mM SDS, respectively.

The effect of silica particle sizes and promoters to equilibrium moisture content for CO2 hydrate formation in HPVA

NASA Astrophysics Data System (ADS)

Hassan, Mohd Hafiz Abu; Snape, Colin Edwards; Steven, Lee

2018-06-01

The formation of CO2 hydrate (CO2:6H2O) in this work was experimentally investigated in batch mode inside a high pressure volumetric analyser (HPVA). The investigations in pure CO2 gas systems highlighted the effect of type of silicas used and the concentration of promoters used on the amount of equilibrium moisture content available for formation of hydrate. Standard silica gel was the only silica found to show hydrate formation due to the best distribution of pore size with the amount of equilibrium moisture content of 14.8 wt%. The high amount of bulk water inside zeolites 13X and spherical MCF-17 (21.3 and 50.8 wt% respectively) was the main reason of no hydrate formation observed due to the interstitial spaces between both silica particles were fully occupied by water. In other words, diffusion of gas molecules into the water is required for hydrate nucleation as well as hydrate growth. Additionally, the combined-promoters designated type T1-5 (0.01 mol% sodium dodecyl sulphate (SDS)+5.6 mol% tetrahydrofuran (THF)) was the best obtaining a CO2 uptake of 5.95 mmol of CO2 per g of H2O with the amount of equilibrium moisture content of 13.28 wt%.

Effects of Coordinating a Hemilabile Ligand to 14e Cp*M(NO) Scaffolds (M = Mo, W).

PubMed

Handford, Rex C; Patrick, Brian O; Legzdins, Peter

2017-10-16

This article describes the differing chemical properties imparted by the two ligands, hemilabile 2-[(diisopropylphosphino)methyl]-3-methylpyridine ( i Pr 2 PN) and the related 1,2-bis(dimethylphosphino)ethane (dmpe), when attached to the 14e Cp*M(NO) scaffolds (Cp* = η 5 -C 5 Me 5 ; M = W, Mo). For instance, the treatment of [Cp*W(NO)Cl 2 ] 2 with 2 or 1 equiv of dmpe in C 6 H 6 affords excellent yields of [Cp*W(NO)(κ 2 -dmpe)Cl]Cl (1) or [Cp*W(NO)Cl 2 ] 2 [μ-dmpe] (2). In contrast, the treatment of [Cp*W(NO)Cl 2 ] 2 with 1 equiv of i Pr 2 PN in C 6 H 6 does not produce the complex analogous to 1 but rather affords orange [Cp*W(NO)(κ 2 -P-N- i Pr 2 PN)Cl][Cp*W(NO)Cl 3 ] (3) in 90% yield. Furthermore, subsequent reduction of 1 or 2 with 2 or 4 equiv of Cp 2 Co in tetrahydrofuran (THF), respectively, results in the production of orange Cp*W(NO)(κ 2 -dmpe) (4) in good yields. However, a similar treatment of 3 with 1 equiv of Cp 2 Co in THF does not result in the production of Cp*W(NO)(κ 2 -P,N- i Pr 2 PN), the analogue of 4, but rather generates a 1:1 mixture of the novel complexes Cp*W(NO)(H)(κ 1 -P- i Pr 2 PN)Cl (5) and Cp*W(NO)(κ 2 -P,N- i Pr 2 PCH-2-(3-Me-C 5 H 3 N))Cl (6), which are separable by crystallization from pentane and diethyl ether solutions, respectively. The divergent reactivity imparted by the dmpe and i Pr 2 PN proligands is a unique demonstration of the unusual properties of a mixed-donor ligand. In the case of molybdenum, the reaction of [Cp*Mo(NO)Cl 2 ] 2 with 2 equiv of i Pr 2 PN in C 6 H 6 first forms Cp*Mo(NO)(κ 1 -P- i Pr 2 PN)Cl 2 , which then converts to [Cp*Mo(NO)(κ 2 -P,N- i Pr 2 PN)Cl][Cp*Mo(NO)Cl 3 ], the analogue of 3. Reduction of the Cp*Mo(NO)(κ 1 -P- i Pr 2 PN)Cl 2 intermediate complex with 2 equiv of Cp 2 Co affords dark-green Cp*Mo(NO)(κ 2 -P,N- i Pr 2 PN) (7). All new complexes have been characterized by conventional spectroscopic and analytical methods, and the solid-state molecular structures of most of them have been established by single-crystal X-ray crystallographic analyses.

Water dissociation in a radio-frequency electromagnetic field with ex situ electrodes—decomposition of perfluorooctanoic acid and tetrahydrofuran

NASA Astrophysics Data System (ADS)

Schneider, Jens; Holzer, Frank; Kraus, Markus; Kopinke, Frank-Dieter; Roland, Ulf

2016-10-01

The application of radio waves with a frequency of 13.56 MHz on electrolyte solutions in a capillary reactor led to the formation of reactive hydrogen and oxygen species and finally to molecular oxygen and hydrogen. This process of water splitting can be principally used for the elimination of hazardous chemicals in water. Two compounds, namely perfluorooctanoic acid (PFOA) and tetrahydrofuran, were converted using this process. Their main decomposition products were highly volatile and therefore transferred to a gas phase, where they could be identified by GC-MS analyses. It is remarkable that the chemical reactions could benefit from both the oxidizing and reducing species formed in the plasma process, which takes place in gas bubbles saturated with water vapor. The breaking of C-C and C-F bonds was proven in the case of PFOA, probably initiated by electron impacts and radical reactions.

Synthesis and structural characterisation of alkali metal complexes of heteroatom-stabilised 1,4- and 1,6-dicarbanions.

PubMed

Izod, Keith; Bowman, Lyndsey J; Wills, Corinne; Clegg, William; Harrington, Ross W

2009-05-07

A straightforward Peterson olefination reaction between either [{(Me(2)PhSi)(3)C}Li(THF)] or in situ-generated [(Me(3)Si)(2){Ph(2)P(BH(3))}CLi(THF)(n)] and paraformaldehyde gives the alkenes (Me(2)PhSi)(2)C[double bond, length as m-dash]CH(2) () and (Me(3)Si){Ph(2)P(BH(3))}C[double bond, length as m-dash]CH(2) (), respectively, in good yield. Ultrasonic treatment of with lithium in THF yields the lithium complex [{(Me(2)PhSi)(2)C(CH(2))}Li(THF)(n)](2) (), which reacts in situ with one equivalent of KOBu(t) in diethyl ether to give the potassium salt [{(Me(2)PhSi)(2)C(CH(2))}K(THF)](2) (). Similarly, ultrasonic treatment of with lithium in THF yields the lithium complex [[{Ph(2)P(BH(3))}(Me(3)Si)C(CH(2))]Li(THF)(3)](2).2THF (). The bis(phosphine-borane) [(Me(3)Si){Me(2)(H(3)B)P}CH(Me(2)Si)(CH(2))](2) () may be prepared by the reaction of [Me(2)P(BH(3))CH(SiMe(3))]Li with half an equivalent of ClSiMe(2)CH(2)CH(2)SiMe(2)Cl in refluxing THF. Metalation of with two equivalents of MeLi in refluxing THF yields the lithium complex [[{Me(2)P(BH(3))}(Me(3)Si)C{(SiMe(2))(CH(2))}]Li(THF)(3)](2) (), whereas metalation with two equivalents of MeK in cold diethyl ether yields the potassium complex [[{Me(2)P(BH(3))}(Me(3)Si)C{(SiMe(2))(CH(2))}](2)K(2)(THF)(4)](infinity) () after recrystallisation. X-Ray crystallography shows that, whereas the lithium complex crystallises as a discrete molecular species, the potassium complexes and crystallise as sheet and chain polymers, respectively.

A convenient enantioselective CBS-reduction of arylketones in flow-microreactor systems.

PubMed

De Angelis, Sonia; De Renzo, Maddalena; Carlucci, Claudia; Degennaro, Leonardo; Luisi, Renzo

2016-05-04

A convenient, versatile, and green CBS-asymmetric reduction of aryl and heteroaryl ketones has been developed by using the microreactor technology. The study demonstrates that it is possible to handle borane solution safely within microreactors and that the reaction performs well using 2-MeTHF as a greener solvent.

Magnetic Solid Phase Extraction Based on Oleic Acid Coated Fe3O4 for the Determination of Benzo[α]pyrene in Cigarette Smoke Coupled with High-Performance Liquid Chromatography.

PubMed

Feng, Shouai; Wei, Kang; Tian, Zhaofu; Li, Xiaolan; Meng, Dongling; Liao, Wenlong; Miao, Mingming; Yang, Yaling

2016-07-29

In this work, a simple and effective method based on magnetic solid-phase extraction combined with high-performance liquid chromatography was developed for the determination of benzo[α]pyrene (BaP) in cigarette smoke. Oleic acid coated Fe 3 O 4 (Fe 3 O 4 -OA) was synthesized and directly used as an efficient sorbent for the first time in magnetic solid-phase extraction (MSPE) procedure for the clean-up of BaP in cigarette smoke extracts. The synthesized Fe 3 O 4 -OA was characterized by transmission electron microscopy, X-ray diffraction and Fourier transformed infrared spectroscopy. The extraction via Fe 3 O 4 -OA was dispersed in the extracts of cigarette smoke followed by the magnetic isolation, acetonitrile-tetrahydrofuran (ACN-THF; v/v = 9:1) was used for desorption of the analyte. The effects of important parameters such as the amount of adsorbent, solution pH, the content of acetonitrile, temperature and sorption time were investigated. The method showed good linearity for the determination of BaP in the concentration range of 0.5-50 ng mL -1 with a regression coefficient (R 2 ) of 0.9987. The limit of detection and limit of quantification for BaP were obtained to be 0.12 and 0.41 ng mL -1 , respectively. The mean recoveries were in the range from 81.0% to 97.6% at low, medium, high spiked levels, and the relative standard deviations were in the range of 2.7-6.8%. Combined with high-performance liquid chromatography and fluorescence detection, a simple and effective method was developed for the analysis of BaP in cigarette smoke. © The Author 2016. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Structural and Spectroscopic Characterization of 17- and 18-Electron Piano-Stool Complexes of Chromium. Thermochemical Analyses of Weak Cr–H Bonds

DOE Office of Scientific and Technical Information (OSTI.GOV)

van der Eide, Edwin F.; Helm, Monte L.; Walter, Eric D.

2013-02-04

The 17-electron radical CpCr(CO)2(IMe)• (IMe = 1,3-dimethylimidazol-2-ylidene) was synthesized by the reaction of IMe with [CpCr(CO)3]2, and characterized by single crystal X-ray diffraction and by EPR, IR and variable temperature 1H NMR spectroscopy. The metal-centered radical is monomeric under all conditions and exhibits Curie paramagnetic behavior in solution. An electrochemically reversible reduction to 18-electron CpCr(CO)2(IMe)- takes place at E½ = -1.89(1) V vs Cp2Fe+•/0 in MeCN, and was accomplished chemically with KC8 in THF. The salts K+(18-crown-6)[CpCr(CO)2(IMe)]- • ½THF and K+[CpCr(CO)2(IMe)]- • ¾THF were crystallographically characterized. Monomeric ion pairs are found in the former, whereas the latter has a polymericmore » structure due to a network of K∙∙∙O(CO) interactions. Protonation of K+(18-crown-6)[CpCr(CO)2(IMe)]- • ½THF gives the hydride CpCr(CO)2(IMe)H, which could not be isolated, but was characterized in solution; a pKa of 27.2(4) was determined in MeCN. A thermochemical analysis provides the Cr-H bond dissociation free energy (BDFE) for CpCr(CO)2(IMe)H in MeCN solution as 47.3(6) kcal mol-1. This value is exceptionally low for a transition metal hydride, and implies that the reaction 2 [Cr-H] → 2 [Cr•] + H2 is exergonic (ΔG = -9.0(8) kcal mol-1). This analysis explains the experimental observation that generated solutions of the hydride produce CpCr(CO)2(IMe)• (typically on the timescale of days). By contrast, CpCr(CO)2(PCy3)H has a higher Cr-H BDFE (52.9(4) kcal mol-1), is more stable with respect to H2 loss, and is isolable. We thank the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences for support. M.L.H. carried out the crystallographic studies and was supported as part of the Center for Molecular Electrocatalysis, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. The EPR studies were performed at the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by the Department of Energy’s Office of Biological and Environmental Research located at PNNL. Pacific Northwest National Laboratory is a multiprogram national laboratory operated by Battelle for the U.S. Department of Energy.« less

13C nuclear magnetic resonance detection of interactions of serine hydroxymethyltransferase with C1-tetrahydrofolate synthase and glycine decarboxylase complex activities in Arabidopsis.

PubMed Central

Prabhu, V; Chatson, K B; Abrams, G D; King, J

1996-01-01

In C3 plants, serine synthesis is associated with photorespiratory glycine metabolism involving the tetrahydrofolate (THF)-dependent activities of the glycine decarboxylase complex (GDC) and serine hydroxymethyl transferase (SHMT). Alternatively, THF-dependent serine synthesis can occur via the C1-THF synthase/SHMT pathway. We used 13C nuclear magnetic resonance to examine serine biosynthesis by these two pathways in Arabidopsis thaliana (L.) Heynh. Columbia wild type. We confirmed the tight coupling of the GDC/ SHMT system and observed directly in a higher plant the flux of formate through the C1-THF synthase/SHMT system. The accumulation of 13C-enriched serine over 24 h from the GDC/SHMT activities was 4-fold greater than that from C1-THF synthase/SHMT activities. Our experiments strongly suggest that the two pathways operate independently in Arabidopsis. Plants exposed to methotrexate and sulfanilamide, powerful inhibitors of THF biosynthesis, reduced serine synthesis by both pathways. The results suggest that continuous supply of THF is essential to maintain high rates of serine metabolism. Nuclear magnetic resonance is a powerful tool for the examination of THF-mediated metabolism in its natural cellular environment. PMID:8819325

Equatorially connected diruthenium(II,III) units toward paramagnetic supramolecular structures with singular magnetic properties.

PubMed

Barral, M Carmen; Gallo, Teresa; Herrero, Santiago; Jiménez-Aparicio, Reyes; Torres, M Rosario; Urbanos, Francisco A

2006-05-01

The reaction of Ru2Cl(O2CMe)(DPhF)3 (DPhF = N,N'-diphenylformamidinate) with mono- and polycarboxylic acids gives a clean substitution of the acetate ligand, leading to the formation of complexes Ru2Cl(O2CC6H5)(DPhF)3 (1), Ru2Cl(O2CC6H4-p-CN)(DPhF)3 (2), [Ru2Cl(DPhF)3(H2O)]2(O2C)2 (3), [Ru2Cl(DPhF)3]2[C6H4-p-(CO2)2] (4), and [Ru2Cl(DPhF)3]3[C6H3-1,3,5-(CO2)3] (5). The preparation of [Ru2(NCS)(DPhF)3]3[C6H3-1,3,5-(CO2)3] (6) and {[Ru2(DPhF)3(H2O)]3[C6H3-1,3,5-(CO2)3]}(SO3CF3)3 (7) from 5 is also described. All complexes are characterized by elemental analysis, IR and electronic spectroscopy, mass spectrometry, cyclic voltammetry, and variable-temperature magnetic measurements. The crystal structure determinations of complexes 2.0.5THF and 3.THF.4H2O (THF = tetrahydrofuran) are reported. The reactions carried out demonstrate the high chemical stability of the fragment [Ru2(DPhF)3]2+, which is preserved in all tested experimental conditions. The stability of this fragment is also corroborated by the mass spectra. Electrochemical measurements reveal in all complexes one redox process due to the equilibrium Ru2(5+) <--> Ru2(6+). In the polynuclear complex 7, some additional oxidation processes are also observed that have been ascribed to the presence of two types of dimetallic units rather than two consecutive reversible oxidations. The magnetic behavior toward temperature for complexes 1-7 from 300 to 2 K is analyzed. Complexes 1-7 show low values of antiferromagnetic coupling in accordance with the molecular nature in 1 and 2 and the absence of important antiferromagnetic interaction through the carboxylate bridging ligands in 3-7, respectively. In addition, the magnetic properties of complex 7 do not correspond to any magnetic behavior described for diruthenium(II,III) complexes. The experimental data of compound 7 are simulated considering a physical mixture of S = 1/2 and 3/2 spin states. This magnetic study demonstrates the high sensitivity of the electronic configuration of the unit [Ru2(DPhF)3]2+ to small changes in the nature of the axial ligands. Finally, the energy gap between the pi and delta orbitals in these types of compounds allows the tentative assignment of the transition pi --> delta.

High-yield synthesis of a unique Mn(iii) siloxide complex through KMnO4 oxidation of a Mn(ii) precursor.

PubMed

Lorenz, Volker; Ehle, Sophie; Liebing, Phil; Engelhardt, Felix; Hashemi-Haeri, Haleh; Oehler, Florian; Hinderberger, Dariush; Busse, Sabine; Urbaschok, Jens; Edelmann, Frank T

2017-12-19

A unique trivalent manganese siloxide complex, blue-violet Mn III Li 2 Cl[(Ph 2 SiO) 2 O] 2 (THF) 4 ·2THF (3) has been prepared by a straightforward two-step synthetic protocol. Lithiation of (Ph 2 SiOH) 2 O (1) followed by reaction with MnCl 2 (THF) 2 gave the structurally remarkable Mn(ii) precursor Mn II Li 4 Cl 2 [(Ph 2 SiO) 2 O] 2 (THF) 5 ·2THF (2). Surprisingly, the final oxidation step could be achieved using KMnO 4 in THF to provide the Mn(iii) species 3 in high yield (91%). Both title compounds were structurally characterized by single-crystal X-ray diffraction.

The Synthesis of 1,1’-Bicobaltocene Salts of Tetracyano-P-Quinodimethanide and the Sturcture of 1,1’-Bicobaltocene (Co (III) Co (III)) (TCNQ)3,

DTIC Science & Technology

1981-06-03

Salts of Bicobaltocenet-The hexafluorophosphate salt of bicobaltocene(III,III) was prepared by the method of Davison and Smart 4 and the orange product...tetrahydrofuran. The lithium salt of TCNO was prepared by adding a boiling solution of lithium iodide in acetonitrile to a boiling solution of TCNQ in...compound 1,1’-bicobaltocene[Co(III)Co(III)[TCNQJ 3 resulted from the reaction of the mixed valence hexafluorophosphate salt with a mixture of [Et3NH

Curing and Characterization of Siloxanecarbonate Polymers

DTIC Science & Technology

1980-01-01

to 93 percent yields of p-bromophenol-Z-tetrahydropyranyl ether. The Grignard reagent made from the protected phenol in tetrahydrofuran was added to...iodomethane and heating. When all of the magnesium appeared to have been consumed, the resulting Grignard reagent was added via a double-tipped needle...7-dichlorooctamethyltetrasiloxane via the Grignard reaction. Workup of the reaction product with aqueous ammonium chloride solution kept the molecule

Lithium Enolates of Simple Ketones: Structure Determination Using the Method of Continuous Variation

PubMed Central

Liou, Lara R.; McNeil, Anne J.; Ramirez, Antonio; Toombes, Gilman E. S.; Gruver, Jocelyn M.

2009-01-01

The method of continuous variation in conjunction with 6Li NMR spectroscopy was used to characterize lithium enolates derived from 1-indanone, cyclohexanone, and cyclopentanone in solution. The strategy relies on forming ensembles of homo- and heteroaggregated enolates. The enolates form exclusively chelated dimers in N,N,N’,N’-tetramethylethylenediamine and cubic tetramers in tetrahydrofuran and 1,2-dimethoxyethane. PMID:18336025

Purified low-density lipoprotein and bovine serum albumin efficiency to internalise lycopene into adipocytes.

PubMed

Gouranton, Erwan; Yazidi, Claire El; Cardinault, Nicolas; Amiot, Marie Josèphe; Borel, Patrick; Landrier, Jean-François

2008-12-01

Epidemiological studies have suggested that lycopene has protective effects against various diseases including cardiovascular diseases. However, mechanistic studies to understand these effects are difficult due to the insolubility of lycopene in aqueous culture medium. The objective of the present study was to use LDL or BSA as physiological vehicles for lycopene and to compare them with various classical vehicles. Among tested vehicles, only LDL, BSA, THF/BHT, beadlets, and liposomes were able to solubilise lycopene. No cytotoxicity was observed with these vehicles. LDL and BSA allowed good stability of lycopene during incubation (52% and 43% for 2microM lycopene solutions), but remained less efficient than THF/BHT or beadlets (67% and 62%). Incubation of adipocytes (3T3-L1) with the different vehicles for 24 and 48h showed that beadlets best delivered lycopene to cells. Finally, whatever the vehicle used, intracellular localization of lycopene was the same: lipid droplets (32-51%), plasma membrane (32-37%) and nuclear membrane (19-29%). As a conclusion, LDL or BSA display comparable properties to THF/BHT or beadlets. It is the first time that lycopene carried by physiological vehicles is shown to reach different subcellular compartments supporting molecular effects in adipocyte, such as cell signaling or nuclear receptor interacting.

Stereochemical inversion of a cyano-stabilized grignard reagent: remarkable effects of the ethereal solvent structure and concentration.

PubMed

Gao, Ming; Patwardhan, Neeraj N; Carlier, Paul R

2013-09-25

Chiral organometallic reagents are useful in asymmetric synthesis, and configurational stability of these species is critical to success. In this study we followed the epimerization of a chiral Grignard reagent, prepared by Mg/Br exchange of bromonitrile trans-2b. This compound underwent highly retentive Mg/Br exchange in Et2O; less retention was observed in 2-MeTHF and THF. Epimerization rate constants k(tc) were determined at 195 K by measuring the diastereomer ratio of deuteration product d1-3b as a function of the delay time before quench. Studies were also performed at varying concentrations of Et2O in toluene. Remarkable dynamic range in k(tc) was seen: relative to reaction at 0.12 M Et2O in toluene, epimerization was 26-, 800-, and 1300-fold faster in Et2O, 2-MeTHF, and THF, respectively. Thus, the identity and concentration of an ethereal solvent can dramatically affect configurational stability. Reaction stoichiometry experiments suggested that, in Et2O, the Grignard reagent derived from trans-2b exists as an i-PrMgCl heterodimer; the invariance of k(tc) over a 20-fold range in [Mg]total ruled out mandatory deaggregation (or aggregation) on the epimerization path. Analysis of the dependency of k(tc) on [Et2O] and temperature in Et2O/toluene solution at 195, 212, and 231 K indicated fast incremental solvation before rate-limiting ion-pair separation and provided an estimate of the entropic cost of capturing a solvent ligand (-13 ± 3 eu). Calculations at the MP2/6-31G*(PCM)//B3LYP/6-31G* level provide support for these conclusions and map out a possible "ionogenic conducted tour" pathway for epimerization.

[Studies for analyzing restricted ingredients such as phenylbenzoimidazole sulfonic acid].

PubMed

Tokunaga, Hiroshi; Mori, Kenichiro; Onuki, Nahomi; Nosaka, Tomio; Doi, Kayo; Sakaguchi, Hiroshi; Fujii, Makiko; Takano, Katuhiro; Hayashi, Masato; Yoshizawa, Kenichi; Shimamura, Kimio; Sato, Nobuo

2006-01-01

Phenylbenzoimidazol sulfonic acid (PBS) is a kind of sunscreens in cosmetics and is nominated as the restricted ingredients in cosmetics in Japanese Pharmaceutical Affairs Act. So the analytical method for PBS was investigated by HPLC. 1.0 g of the lotions with 1.0% PBS was exactly weighed, put into a 50-mL volumetric flask. Water was added to make exactly 50 mL and this mixture was used as the sample solution. On the other hand, 1.0 g of the creams with 1.0% PBS was exactly weighed, put into a beaker. After adding 1 mL of tetrahydrofuran and dissolving the cream, that mixture was transferred to a 50-mL volumetric flask. And then the beaker was rinsed with 1 mL of tetrahydrofuran and the rinsed solution was put together into the volumetric flask. After adding water to the volumetric flask to make exactly 50 mL, this mixture was used as the sample solution. If necessary, the mixture was filtrated with a membrane filter (0.45 microm). 5.0 mL of the sample solution was pipetted and put into a 200-mL volumetric flask. After adding water to make exactly 200 mL, 20 microL of this solution was analyzed by HPLC using the ODS column (CAPCELL PAK C18 column, 4.6 mm i.d. x 250 mm), the mixture of 40 mmol/L acetic buffer (pH 3.4) and acetonitrile (3:1) with 0.8 mmol/L dodecyltrimethyl ammonium bromide and the detection wavelength of 305 nm. The working curve from 0.5 to 20.0 microg/mL showed a linear line between the concentrations of PBS and the peak areas. There was no interference of peak of PBS from the lotion and cream.

Synthesis and molecular structures of phenylamides of magnesium, calcium, strontium, and barium--from molecular to polymeric structures.

PubMed

Gärtner, Martin; Görls, Helmar; Westerhausen, Matthias

2007-09-03

Several preparative procedures for the synthesis of the THF complexes of the alkaline earth metal bis(phenylamides) of Mg (1), Ca (2), Sr (3), and Ba (4) are presented such as metalation of aniline with strontium and barium, metathesis reactions of MI2 with KN(H)Ph, and metalation of aniline with arylcalcium compounds or dialkylmagnesium. The THF content of these compounds is rather low and an increasing aggregation is observed with the size of the metal atom. Thus, tetrameric [(THF)2Ca{mu-N(H)Ph}2]4 (2) and polymeric [(THF)2Sr{mu-N(H)Ph}2]infinity and {[(THF)2Ba{mu-N(H)Ph}2]2[(THF)Ba{mu-N(H)Ph}2]2}infinity show six-coordinate metal atoms with increasing interactions to the pi systems of the phenyl groups with increasing the radius of the alkaline earth metal atom.

Spectroscopic investigations of ThF and ThF+.

PubMed

Barker, Beau J; Antonov, Ivan O; Heaven, Michael C; Peterson, Kirk A

2012-03-14

The electronic spectra of ThF and ThF(+) have been examined using laser induced fluorescence and resonant two-photon ionization techniques. The results from high-level ab initio calculations have been used to guide the assignment of these data. Spectra for ThF show that the molecule has an X (2)Δ(3/2) ground state. The upper spin-orbit component, X (2)Δ(5/2) was found at an energy of 2575(15) cm(-1). The low-lying states of ThF(+) were probed using dispersed fluorescence and pulsed field ionization-zero kinetic energy (PFI-ZEKE) photoelectron spectroscopy. Vibronic progressions belonging to four electronic states were identified. The lowest energy states were clearly (1)Σ(+) and (3)Δ(1). Although the energy ordering could not be rigorously determined, the evidence favors assignment of (1)Σ(+) as the ground state. The (3)Δ(1) state, of interest for investigation of the electron electric dipole moment, is just 315.0(5) cm(-1) above the ground state. The PFI-ZEKE measurements for ThF yielded an ionization energy of 51 581(3) cm(-1). Molecular constants show that the vibrational constant increases and the bond length shortens on ionization. This is consistent with removal of a non-bonding Th-centered 6d or 7s electron. Laser excitation of ThF(+) was used to probe electronically excited states in the range of 19,000-21,500 cm(-1).

Asymmetric Aryl Polyhedral Oligomeric SilSesquioxanes (ArPOSS) with Enhanced Solubility (Preprint)

DTIC Science & Technology

2011-03-23

by reaction of an aryl Grignard or lithium reagent with SiCl4 under reaction conditions s imilar to those previously reported [22]. The aryl...cooling to room temperature, this Grignard reagent w as added via canula to a SiCl 4 (25.1 g, 0.148 m ol) THF (70 mL) solution and stirred overnight

Folate status and concentrations of serum folate forms in the US population: National Health and Nutrition Examination Survey 2011–2

PubMed Central

Pfeiffer, Christine M.; Sternberg, Maya R.; Fazili, Zia; Lacher, David A.; Zhang, Mindy; Johnson, Clifford L.; Hamner, Heather C.; Bailey, Regan L.; Rader, Jeanne I.; Yamini, Sedigheh; Berry, R. J.; Yetley, Elizabeth A.

2016-01-01

Serum and red blood cell (RBC) total folate are indicators of folate status. No nationally representative population data exist for folate forms. We measured serum folate forms [5-methyltetrahydrofolate (5-methylTHF), unmetabolized folic acid (UMFA), non-methyl folate (sum of THF, 5-formylTHF, 5,10-methenylTHF), and MeFox (5-methylTHF oxidation product)] by HPLC-MS/MS and RBC total folate by microbiologic assay in US persons ≥1 year (n ~7500) participating in the National Health and Nutrition Examination Survey 2011–2. Data analysis for serum total folate was conducted including and excluding MeFox. Concentrations (geometric mean; detection rate) of 5-methylTHF (37.5 nmol/L; 100%), UMFA (1.21 nmol/L; 99.9%), MeFox (1.53 nmol/L; 98.8%), and THF (1.01 nmol/L; 85.2%) were mostly detectable. 5-FormylTHF (3.6%) and 5,10-methenylTHF (4.4%) were rarely detected. The biggest contributor to serum total folate was 5-methylTHF (86.7%); UMFA (4.0%), non-methyl folate (4.7%), and MeFox (4.5%) contributed smaller amounts. Age was positively related to MeFox but showed a U-shaped pattern for other folates. We generally noted sex and race-ethnic biomarker differences and weak (Spearman r <0.4) but significant (P <0.05) correlations with physiologic and lifestyle variables. Fasting, kidney function, smoking, and alcohol intake showed negative associations. BMI and body surface area showed positive associations with MeFox but negative associations with other folates. All biomarkers showed significantly higher concentrations with recent folic acid-containing dietary supplement use. These first-time population data for serum folate forms generally show similar associations with demographic, physiologic, and lifestyle variables as serum total folate. Patterns observed for MeFox may suggest altered folate metabolism dependent on biological characteristics. PMID:25917925

Widely Tunable Morphologies in Block Copolymer Thin Films Through Solvent Vapor Annealing Using Mixtures of Selective Solvents

PubMed Central

Chavis, Michelle A.; Smilgies, Detlef-M.; Wiesner, Ulrich B.; Ober, Christopher K.

2015-01-01

Thin films of block copolymers are extremely attractive for nanofabrication because of their ability to form uniform and periodic nanoscale structures by microphase separation. One shortcoming of this approach is that to date the design of a desired equilibrium structure requires synthesis of a block copolymer de novo within the corresponding volume ratio of the blocks. In this work, we investigated solvent vapor annealing in supported thin films of poly(2-hydroxyethyl methacrylate)-block-poly(methyl methacrylate) [PHEMA-b-PMMA] by means of grazing incidence small angle X–ray scattering (GISAXS). A spin-coated thin film of lamellar block copolymer was solvent vapor annealed to induce microphase separation and improve the long-range order of the self-assembled pattern. Annealing in a mixture of solvent vapors using a controlled volume ratio of solvents (methanol, MeOH, and tetrahydrofuran, THF), which are chosen to be preferential for each block, enabled selective formation of ordered lamellae, gyroid, hexagonal or spherical morphologies from a single block copolymer with a fixed volume fraction. The selected microstructure was then kinetically trapped in the dry film by rapid drying. To our knowledge, this paper describes the first reported case where in-situ methods are used to study the transition of block copolymer films from one initial disordered morphology to four different ordered morphologies, covering much of the theoretical diblock copolymer phase diagram. PMID:26819574

Progress in donor assisted coal liquefaction: Hydroaromatic compound formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kottenstette, R.J.; Stephens, H.P.

1993-12-31

The role of hydrogen donor compounds in coal liquefaction has been extensively investigated since the mid 1960`s using model compounds and process derived hydrogen donor solvents. Our recent research and that of other investigators have shown that two model compounds in particular have great efficacy in solvating low rank coals. 1,2,3,10b tetrahydrofluoranthene (H{sub 4}Fl) and 1,2,3,6,7,8 hexahydropyrene (H{sub 6}Py) have been used to dissolve Wyodak coal to > 95% soluble material as measured by tetrahydrofuran (THF). Although these hydrogen donors are very effective, they may not be found in any significant concentrations in actual liquefaction process recycle solvents. Therefore, studiesmore » with process derived recycle materials are necessary to understand donor solvent chemistry. The objective of this paper is to present results of solvent hydrogenation experiments using heavy distillate solvents produced during testing at the Wilsonville Advanced Coal Liquefaction Test Facility. We evaluated the impact of hydrogenation conditions upon hydrogen donor formation in process derived distillates and compared these process derived solvents with the highly effective H{sub 4}Fl and H{sub 6}Py donors in coal liquefaction tests. This paper presents data on reaction conditions used for distillate hydrotreating and subsequent coal liquefaction, with an aim toward understanding the relationship between reaction conditions and donor solvent quality in recycle distillates.« less

A Dioxane Template for Highly Selective Epoxy Alcohol Cyclizations

PubMed Central

Mousseau, James J.; Morten, Christopher J.

2013-01-01

Ladder polyether natural products are a class of natural products denoted by their high functional group density and large number of well-defined stereocenters. They comprise the toxic component of harmful algal blooms (HABs), having significant negative economic and environmental ramifications. However, their mode of action, namely blocking various cellular ion channels, also denotes their promise as potential anticancer agents. Understanding their potential mode of biosynthesis will not only help with developing ways to limit the damage of HABs, but would also facilitate the synthesis of a range of analogues with interesting biological activity. 1,3-Dioxan-5-ol substrates display remarkable ‘enhanced template effects’ in water-promoted epoxide cyclization processes en route to the synthesis of these ladder polyether natural products. In many cases they provide near complete endo to exo selectivity in the cyclization of epoxy alcohols, thereby strongly favouring the formation of tetrahydropyran (THP) over tetrahydrofuran (THF) rings. The effects of various Brønsted and Lewis acidic and basic conditions are explored to demonstrate the superior selectivity of the template over the previously reported THP-based epoxy alcohols. In addition, the consideration of other synthetic routes are also considered with the goal of gaining rapid access to a plethora of potential starting materials applicable towards the synthesis of ladder polyethers. Finally, cascade sequences with polyepoxides are investigated, further demonstrating the versatility of this new reaction template. PMID:23775936

[Macromolecular aromatic network characteristics of Chinese power coal analyzed by synchronous fluorescence and X-ray diffraction].

PubMed

Ye, Cui-Ping; Feng, Jie; Li, Wen-Ying

2012-07-01

Coal structure, especially the macromolecular aromatic skeleton structure, has a strong influence on coke reactivity and coal gasification, so it is the key to grasp the macromolecular aromatic skeleton coal structure for getting the reasonable high efficiency utilization of coal. However, it is difficult to acquire their information due to the complex compositions and structure of coal. It has been found that the macromolecular aromatic network coal structure would be most isolated if small molecular of coal was first extracted. Then the macromolecular aromatic skeleton coal structure would be clearly analyzed by instruments, such as X-ray diffraction (XRD), fluorescence spectroscopy with synchronous mode (Syn-F), Gel permeation chromatography (GPC) etc. Based on the previous results, according to the stepwise fractional liquid extraction, two Chinese typical power coals, PS and HDG, were extracted by silica gel as stationary phase and acetonitrile, tetrahydrofuran (THF), pyridine and 1-methyl-2-pyrollidinone (NMP) as a solvent group for sequential elution. GPC, Syn-F and XRD were applied to investigate molecular mass distribution, condensed aromatic structure and crystal characteristics. The results showed that the size of aromatic layers (La) is small (3-3.95 nm) and the stacking heights (Lc) are 0.8-1.2 nm. The molecular mass distribution of the macromolecular aromatic network structure is between 400 and 1 130 amu, with condensed aromatic numbers of 3-7 in the structure units.

Synthesis and coordination chemistry of TpC*MI complexes where M=Mg, Ca, Sr, Ba and Zn and TpC*=tris[3-(2-methoxy-1,1-dimethyl)pyrazolyl]hydroborate.

PubMed

Chisholm, Malcolm H; Gallucci, Judith C; Yaman, Gulsah

2009-01-14

Reactions involving MI2 where M=Mg, Ca, Sr, Ba or Zn and M'TpC* where M'=Na or Tl and TpC*=tris[3-methoxy-1,1-dimethyl)pyrazolyl]hydroborate in tetrahydrofuran are described leading to the isolation and characterization of the complexes TpC*MgI, , TpC*CaI, , TpC*SrI, , TpC*SrI(THF), , TpC*BaI, , TpC*BaI(pz*H), , where pz*H=3-(2-methoxyl-1,1-dimethyl)pyrazole, TpC*BaI.1/2toluene, and TpC*ZnI, . The compounds , , , , and have been characterized by single-crystal X-ray crystallography. Compounds and are isostructural and are salt-like containing kappa6-TpM+ cations and I- anions. In all other structures, the iodide is bound to the metal and TpC* is kappa6 bonded to the group 2 M(2+) ions. Reactions involving TpC*CaI, , and sodium or lithium alkoxides or amides failed to yield the amide or alkoxide calcium TpC* derivative, though related reactions involving TpC*ZnI, , and KOSiMe3 proceeded quantitatively to yield kappa3TpC*ZnOSiMe3, , which was also structurally characterized and shown to have the kappa3-TpC* bound ligand.

Preparation of enhanced hydrophobic poly(L-lactide-co-ɛ-caprolactone) films surface and its blood compatibility

NASA Astrophysics Data System (ADS)

Kim, Seung Il; Lim, Jin Ik; Jung, Youngmee; Mun, Cho Hay; Kim, Ji Heung; Kim, Soo Hyun

2013-07-01

Hydrophobicity-enhanced poly(L-lactide-co-ɛ-caprolactone) (PLCL) (50:50) films were cast by using the solvent-nonsolvent casting method. PLCL (50:50) was synthesized by the well-known random copolymerization process and confirmed by 1H NMR analysis. The molecular weight of the synthesized PLCL was measured by gel permeation chromatography (GPC). Number-average (Mn), weight-average (Mw) molecular weights and polydispersity (Mw/Mn) were 7 × 104, 1.2 × 105, and 1.7, respectively. PLCL films were cast in vacuum condition with various nonsolvents and nonsolvent ratios. Tetrahydrofuran (THF) was used as the solvent and three different alcohols were used as the nonsolvent: methanol, ethanol, and isopropyl alcohol (IPA). Surface hydrophobicity was confirmed by water contact angle. The water contact angle was increased from 81° ± 2° to 107° ± 2°. Water contact angle was influenced by surface porosity and topography. The prepared film surfaces were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The change of crystalline property was characterized by X-ray diffraction (XRD). Platelet adhesion tests on the modified PLCL film surfaces were evaluated by platelet-rich plasma (PRP). The modified film surface exhibited enhanced hydrophobicity and reduced platelet adhesion ratio depending on the surface topography. One of the candidate products proposed as a potential blood compatible material showed a markedly reduced platelet adhesion property.

Cu(II) binding by a pH-fractionated fulvic acid

USGS Publications Warehouse

Brown, G.K.; Cabaniss, S.E.; MacCarthy, P.; Leenheer, J.A.

1999-01-01

The relationship between acidity, Cu(II) binding and sorption to XAD resin was examined using Suwannee River fulvic acid (SRFA). The work was based on the hypothesis that fractions of SRFA eluted from an XAD column at various pH's from 1.0 to 12.0 would show systematic variations in acidity and possibly aromaticity which in turn would lead to different Cu(II) binding properties. We measured equilibrium Cu(II) binding to these fractions using Cu2+ ion-selective electrode (ISE) potentiometry at pH 6.0. Several model ligands were also examined, including cyclopentane-1,2,3,4-tetracarboxylic acid (CP-TCA) and tetrahydrofuran-2,3,4,5-tetracarboxylic acid (THF-TCA), the latter binding Cu(II) much more strongly as a consequence of the ether linkage. The SRFA Cu(II) binding properties agreed with previous work at high ionic strength, and binding was enhanced substantially at lower ionic strength, in agreement with Poisson-Boltzmann predictions for small spheres. Determining Cu binding constants (K(i)) by non-linear regression with total ligand concentrations (L(Ti)) taken from previous work, the fractions eluted at varying pH had K(i) similar to the unfractionated SRFA, with a maximum enhancement of 0.50 log units. We conclude that variable-pH elution from XAD does not isolate significantly strong (or weak) Cu(II)-binding components from the SRFA mixture. Copyright (C) 1999 Elsevier Science B.V.

Rapid and extensive debromination of decabromodiphenyl ether by smectite clay-templated subnanoscale zero-valent iron.

PubMed

Yu, Kai; Gu, Cheng; Boyd, Stephen A; Liu, Cun; Sun, Cheng; Teppen, Brian J; Li, Hui

2012-08-21

Subnanoscale zerovalent iron (ZVI) synthesized using smectite clay as a template was utilized to investigate reduction of decabromodiphenyl ether (DBDE). The results revealed that DBDE was rapidly debrominated by the prepared smectite-templated ZVI with a reaction rate 10 times greater than that by conventionally prepared nanoscale ZVI. This enhanced reduction is plausibly attributed to the smaller-sized smectite-templated ZVI clusters (∼0.5 nm) vs that of the conventional nanoscale ZVI (∼40 nm). The degradation of DBDE occurred in a stepwise debromination manner. Pentabromodiphenyl ethers were the terminal products in an alkaline suspension (pH 9.6) of smectite-templated ZVI, whereas di-, tri-, and tetrabromodiphenyl ethers formed at the neutral pH. The presence of tetrahydrofuran (THF) as a cosolvent at large volume fractions (e.g., >70%) in water reduced the debromination rates due to enhanced aggregation of clay particles and/or diminished adsorption of DBDE to smectite surfaces. Modification of clay surfaces with tetramethylammonium (TMA) attenuated the colsovent effect on the aggregation of clay particles, resulting in enhanced debromination rates. Smectite clay provides an ideal template to form subnanoscale ZVI, which demonstrated superior debromination reactivity with DBDE compared with other known forms of ZVIs. The ability to modify the nature of smectite clay surface by cation exchange reaction utilizing organic cations can be harnessed to create surface properties compatible with various contaminated sites.

Calculated and Experimental Vibrational Properties of P700 and the Iron Sulfur Cluster in Photosystem I

NASA Astrophysics Data System (ADS)

Lamichhane, Hari; Hastings, Gary

2009-11-01

Density functional theory (DFT) based vibrational frequency calculations of Fe4S4(SR)4^n- clusters show that the intense iron-sulfur stretching modes lie in the frequency region between 300-400 cm-1. Among them the iron-sulfur ligand (Fe-S^t) stretching modes are more intense and ˜ 30 cm-1 lower in frequency than the iron-sulfur body (Fe-S^b) stretching modes. Calculations in tetrahydrofuran (THF) show that all these iron-sulfur stretching modes of vibration downshift by ˜ 20 cm-1 upon reduction of the molecule. On the other hand, we have not observed any intense bands from chlorophyll a in the frequency region 400 to 320 cm-1 from the calculations. In an attempt to detect modes associated with iron sulfur clusters in PS I we have obtained light induced (P700^+ - P700) FTIR difference spectra for PSI particles from S. 6803 in the far infrared region. We observe difference bands at many frequencies in the 600-300 cm-1 region. Based on our calculations and literature values we claim that the negative bands at 388 cm-1 and 353 cm-1 in the (P700^+ - P700) FTIR difference spectra be assigned to Fe-S^b and Fe-S^t stretching modes of the ground state of the iron-sulfur cluster FB.

2-Isopropenyl-2-oxazoline: Well-Defined Homopolymers and Block Copolymers via Living Anionic Polymerization

DOE PAGES

Feng, Hongbo; Changez, Mohammad; Hong, Kunlun; ...

2016-12-23

Poly(2-isopropenyl-2-oxazoline) (PIPOx) has drawn significant attention for numerous applications. However, the successful living anionic polymerization of 2-isopropenyl-2-oxazoline has not been reported previously. In this paper, we describe how well-defined PIPOx with quantitative yields, controlled molecular weights from 6800 to over 100 000 g/mol and low polydispersity indices (PDI ≤ 1.17) were synthesized successfully via living anionic polymerization using diphenylmethylpotassium/diethylzinc (DPM-K/Et 2Zn) in tetrahydrofuran (THF) at 0 °C. In particular, we report the precise synthesis of well-defined PIPOx with the highest molecular weight ever reported (over 100 000 g/mol) and low PDI of 1.17. The resulting polymers were characterized by 1Hmore » and 13C nuclear magnetic resonance spectroscopy (NMR) along with size exclusion chromatography (SEC). Additionally, the reactivity of living PIPOx was investigated by crossover block copolymerization with styrene (St), 2-vinylpyridine (2VP), and methyl methacrylate (MMA). It was found that the nucleophilicity of living PIPOx is of this order: living PS > living P2VP > living PMMA > living PIPOx. The self-assembly behavior in bulk of PIPOx-b-PS-b-PIPOx triblock copolymers having different block ratios of 10:80:10 and 25:50:25 was studied using transmission electron microscopy (TEM). Finally, the formation of spherical and lamellar nanostructures, respectively, was observed.« less

2-Isopropenyl-2-oxazoline: Well-Defined Homopolymers and Block Copolymers via Living Anionic Polymerization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, Hongbo; Changez, Mohammad; Hong, Kunlun

Poly(2-isopropenyl-2-oxazoline) (PIPOx) has drawn significant attention for numerous applications. However, the successful living anionic polymerization of 2-isopropenyl-2-oxazoline has not been reported previously. In this paper, we describe how well-defined PIPOx with quantitative yields, controlled molecular weights from 6800 to over 100 000 g/mol and low polydispersity indices (PDI ≤ 1.17) were synthesized successfully via living anionic polymerization using diphenylmethylpotassium/diethylzinc (DPM-K/Et 2Zn) in tetrahydrofuran (THF) at 0 °C. In particular, we report the precise synthesis of well-defined PIPOx with the highest molecular weight ever reported (over 100 000 g/mol) and low PDI of 1.17. The resulting polymers were characterized by 1Hmore » and 13C nuclear magnetic resonance spectroscopy (NMR) along with size exclusion chromatography (SEC). Additionally, the reactivity of living PIPOx was investigated by crossover block copolymerization with styrene (St), 2-vinylpyridine (2VP), and methyl methacrylate (MMA). It was found that the nucleophilicity of living PIPOx is of this order: living PS > living P2VP > living PMMA > living PIPOx. The self-assembly behavior in bulk of PIPOx-b-PS-b-PIPOx triblock copolymers having different block ratios of 10:80:10 and 25:50:25 was studied using transmission electron microscopy (TEM). Finally, the formation of spherical and lamellar nanostructures, respectively, was observed.« less

Enzymatically and chemically oxidized lignin nanoparticles for biomaterial applications.

PubMed

Mattinen, Maija-Liisa; Valle-Delgado, Juan José; Leskinen, Timo; Anttila, Tuomas; Riviere, Guillaume; Sipponen, Mika; Paananen, Arja; Lintinen, Kalle; Kostiainen, Mauri; Österberg, Monika

2018-04-01

Cross-linked and decolorized lignin nanoparticles (LNPs) were prepared enzymatically and chemically from softwood Kraft lignin. Colloidal lignin particles (CLPs, ca. 200 nm) in a non-malodorous aqueous dispersion could be dried and redispersed in tetrahydrofuran (THF) or in water retaining their stability i.e. spherical shape and size. Two fungal laccases, Trametes hirsuta (ThL) and Melanocarpus albomyces (MaL) were used in the cross-linking reactions. Reactivity of ThL and MaL on Lignoboost™ lignin and LNPs was confirmed by high performance size exclusion chromatography (HPSEC) and oxygen consumption measurements with simultaneous detection of red-brown color due to the formation of quinones. Zeta potential measurements verified oxidation of LNPs via formation of surface-oriented carboxylic acid groups. Dynamic light scattering (DLS) revealed minor changes in the particle size distributions of LNPs after laccase catalyzed radicalization, indicating preferably covalent intraparticular cross-linking over polymerization. Changes in the surface morphology of laccase treated LNPs were imaged by atomic force (AFM) and transmission emission (TEM) microscopy. Furthermore, decolorization of LNPs without degradation was obtained using ultrasonication with H 2 O 2 in alkaline reaction conditions. The research results have high impact for the utilization of Kraft lignin as nanosized colloidal particles in advanced bionanomaterial applications in medicine, foods and cosmetics including different sectors from chemical industry. Copyright © 2018 The Author(s). Published by Elsevier Inc. All rights reserved.

Advanced direct liquefaction concepts for PETC generic units. Quarterly technical progress report, October 1992--December 1992

DOE Office of Scientific and Technical Information (OSTI.GOV)

Not Available

The reactivity of the THF insoluble fraction of the ashy resid component of Wilsonville recycle oil (WRO) during liquefaction of Black Thunder coal in tetralin was determined at 415{degrees}C and 60 minutes. The liquefaction runs were made by combining this material with Black Thunder coal at the same ratio used in the WRO coal runs. THF conversion and product distribution from liquefaction in tetralin in the presence of the THF insoluble fraction of the ashy resid were similar to results from liquefaction in WRO. THF conversion was greater than loot with an oil yield that was somewhat higher than inmore » WRO. Differences in HC gas yield and H{sub 2} consumption were slight, while conversion and product distribution from liquefaction of Black Thunder coal in tetralin or in the WRO distillate were quite different. In both these solvents the 85--86% THF conversions were less than for runs in which the THF insoluble fraction of the ashy resid was present. This establishes that the THF insoluble fraction of the ashy resid is the reactive fraction of the WRO.« less

Association and Dissociation of Grignard Reagents RMgCl and Their Turbo Variant RMgCl⋅LiCl.

PubMed

Schnegelsberg, Christoph; Bachmann, Sebastian; Kolter, Marlene; Auth, Thomas; John, Michael; Stalke, Dietmar; Koszinowski, Konrad

2016-06-01

Grignard reagents RMgCl and their so-called turbo variant, the highly reactive RMgCl⋅LiCl, are of exceptional synthetic utility. Nevertheless, it is still not fully understood which species these compounds form in solution and, in particular, in which way LiCl exerts its reactivity-enhancing effect. A combination of electrospray-ionization mass spectrometry, electrical conductivity measurements, NMR spectroscopy (including diffusion-ordered spectroscopy), and quantum chemical calculations is used to analyze solutions of RMgCl (R=Me, Et, Bu, Hex, Oct, Dec, iPr, tBu, Ph) in tetrahydrofuran and other ethereal solvents in the absence and presence of stoichiometric amounts of LiCl. In tetrahydrofuran, RMgCl forms mononuclear species, which are converted into trinuclear anions as a result of the concentration increase experienced during the electrospray process. These trinuclear anions are theoretically predicted to adopt open cubic geometries, which remarkably resemble structural motifs previously found in the solid state. The molecular constituents of RMgCl and RMgCl⋅LiCl are interrelated via Schlenk equilibria and fast intermolecular exchange processes. A small portion of the Grignard reagent also forms anionic ate complexes in solution. The abundance of these more electron-rich and hence supposedly more nucleophilic ate complexes strongly increases upon the addition of LiCl, thus rationalizing its beneficial effect on the reactivity of Grignard reagents. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Steric modulation of coordination number and reactivity in the synthesis of lanthanoid(III) formamidinates.

PubMed

Cole, Marcus L; Deacon, Glen B; Forsyth, Craig M; Junk, Peter C; Konstas, Kristina; Wang, Jun

2007-01-01

Reactions of a range of the readily prepared and sterically tunable N,N'-bis(aryl)formamidines with lanthanoid metals and bis(pentafluorophenyl)mercury (Hg(C6F5)2) in THF have given an extensive series of tris(formamidinato)lanthanoid(III) complexes, [Ln(Form)3(thf)n], namely [La(o-TolForm)3(thf)2], [Er(o-TolForm)3(thf)], [La(XylForm)3(thf)], [Sm(XylForm)3], [Ln(MesForm)3] (Ln=La, Nd, Sm and Yb), [Ln(EtForm)3] (Ln=La, Nd, Sm, Ho and Yb), and [Ln(o-PhPhForm)3] (Ln=La, Nd, Sm and Er). [For an explanation of the N,N'-bis(aryl)formamidinate abbreviations used see Scheme 1.] Analogous attempts to prepare [Yb(o-TolForm)3] by this method invariably yielded [{Yb(o-TolForm)2(mu-OH)(thf)}2], but [Yb(o-TolForm)3] was isolated from a metathesis synthesis. X-ray crystal structures show exclusively N,N'-chelation of the Form ligands and a gradation in coordination number with Ln3+ size and with Form ligand bulk. The largest ligands, MesForm, EtForm and o-PhPhForm give solely homoleptic complexes, the first two being six-coordinate, the last having an eta1-pi-Ar--Ln interaction. Reaction of lanthanoid elements and Hg(C6F5)2 with the still bulkier DippFormH in THF resulted in C--F activation and formation of [Ln(DippForm)2F(thf)] (Ln=La, Ce, Nd, Sm and Tm) complexes, and o-HC6F4O(CH2)4DippForm in which the formamidine is functionalised by a ring-opened THF that has trapped tetrafluorobenzyne. Analogous reactions between Ln metals, Hg(o-HC6F4)2 and DippFormH yielded [Ln(DippForm)2F(thf)] (Ln=La, Sm and Nd) and 3,4,5-F3C6H2O(CH2)4DippForm. X-ray crystal structures of the heteroleptic fluorides show six-coordinate monomers with two chelating DippForm ligands and cisoid fluoride and THF ligands in a trigonal prismatic array. The organometallic species [Ln(DippForm)2(C[triple chemical bond]CPh)(thf)] (Ln=Nd or Sm) are obtained from reaction of Nd metal, bis(phenylethynyl)mercury (Hg(C[triple chemical bond]CPh)2) and DippFormH, and the oxidation of [Sm(DippForm)2(thf)2] with Hg(C[triple chemical bond]CPh)2, respectively. The monomeric, six-coordinate, cisoid [Ln(DippForm)2(C[triple chemical bond]CPh)(thf)] complexes have trigonal prismatic geometries and rare (for Ln) terminal C[triple chemical bond]CPh groups with contrasting Ln--C[triple chemical bond]C angles (Ln=Nd, 170.9(4) degrees; Ln=Sm, 142.9(7) degrees). Their formation lends support to the view that [Ln(DippForm)2F(thf)] complexes arise from oxidative formation and C--F activation of [Ln(DippForm)2(C6F5)] intermediates.

About the solubility of reduced SWCNT in DMSO

NASA Astrophysics Data System (ADS)

Guan, Jingwen; Martinez-Rubi, Yadienka; Dénommée, Stéphane; Ruth, Dean; Kingston, Christopher T.; Daroszewska, Malgosia; Barnes, Michael; Simard, Benoit

2009-06-01

Single-walled carbon nanotubes (SWCNT) have been reduced with sodium naphthalide in THF. The reduced SWCNT are not only soluble in dimethylsulfoxide (DMSO) to form a stable solution/suspension, but also react spontaneously at room temperature with DMSO to evolve hydrocarbon gases and are converted into functionalized SWCNT. The degree of functionalization is about 2C% and the addends are mainly methyl and small oxygen-containing hydrocarbons. The functionalized SWCNT are apparently more soluble and stable in DMSO solution. It may open a new era for further processing and applications.

Di and trinuclear rare-earth metal complexes supported by 3-amido appended indolyl ligands: synthesis, characterization and catalytic activity towards isoprene 1,4-cis polymerization.

PubMed

Zhang, Guangchao; Deng, Baojia; Wang, Shaowu; Wei, Yun; Zhou, Shuangliu; Zhu, Xiancui; Huang, Zeming; Mu, Xiaolong

2016-10-21

Different di and trinuclear rare-earth metal complexes supported by 3-amido appended indolyl ligands were synthesized and their catalytic activities towards isoprene polymerization were investigated. Treatment of [RE(CH 2 SiMe 3 ) 3 (thf) 2 ] with 1 equiv. of 3-(CyN[double bond, length as m-dash]CH)C 8 H 5 NH in toluene or in THF afforded dinuclear rare-earth metal alkyl complexes having indolyl ligands in different hapticities with central metals {[η 2 :η 1 -μ-η 1 -3-(CyNCH(CH 2 SiMe 3 ))Ind]RE-(thf)(CH 2 SiMe 3 )} 2 (Cy = cyclohexyl, Ind = Indolyl, RE = Yb (1), Er (2), Y (3)) or {[η 1 -μ-η 1 -3-(CyNCH(CH 2 SiMe 3 ))Ind]RE-(thf) 2 (CH 2 SiMe 3 )} 2 (RE = Yb (4), Er (5), Y (6), Gd (7)), respectively. These two series of dinuclear complexes could be transferred to each other easily by only changing the solvents in the process. Reaction of [Er(CH 2 SiMe 3 ) 3 (thf) 2 ] with 1 equiv. of 3-t-butylaminomethylindole 3-( t BuNHCH 2 )C 8 H 5 NH in THF afforded the unexpected trinuclear erbium alkyl complex [η 2 :η 1 -μ-η 1 -3-( t BuNCH 2 )Ind] 4 Er 3 (thf) 5 (CH 2 SiMe 3 ) (8), which can also be prepared by reaction of 3 equiv. of [Er(CH 2 SiMe 3 ) 3 (thf) 2 ] with 4 equiv. of 3-( t BuNHCH 2 )C 8 H 5 NH in THF. Accordingly, complexes [η 2 :η 1 -μ-η 1 -3-( t BuNCH 2 )Ind] 4 RE 3 (thf) 5 (CH 2 SiMe 3 ) (RE = Y (9), Dy (10)) were prepared by reactions of 3 equiv. of [RE(CH 2 SiMe 3 ) 3 (thf) 2 ] with 4 equiv. of 3-( t BuNHCH 2 )C 8 H 5 NH in THF. Reactions of [RE(CH 2 SiMe 3 ) 3 (thf) 2 ] with 1 equiv. of 3-t-butylaminomethylindole 3-( t BuNHCH 2 )C 8 H 5 NH in THF, followed by treatment with 1 equiv. of [(2,6- i Pr 2 C 6 H 3 )N[double bond, length as m-dash]CHNH(C 6 H 3 i Pr 2 -2,6)] afforded, after workup, the dinuclear rare-earth metal complexes [η 1 -μ-η 1 :η 1 -3-( t BuNCH 2 )Ind][η 1 -μ-η 1 :η 3 -3-( t BuNCH 2 )Ind]RE 2 (thf)[(η 3 -2,6- i Pr 2 C 6 H 3 )NCHN(C 6 H 3 i Pr 2 -2,6)] 2 (RE = Er (11), Y (12)) having the indolyl ligands bonded with the rare-earth metal in different ligations. All new complexes 1-12 were fully characterized by spectroscopic methods and elemental analyses, and their structures were determined by X-ray crystallographic analyses. It was found that, except for complexes 1, 4, 11 and 12, all complexes were highly efficient catalysts for selective isoprene polymerization (up to 99% 1,4-cis selectivity) with the cooperation of co-catalysts, and the trinuclear complexes displayed advantages over dinuclear complexes in terms of molecular weight of polymers.

An excellent fluorescent dye with a twistable aromatic chain and its axially chiral crystals.

PubMed

Ma, Yan; Hao, Rui; Shao, Guangsheng; Wang, Yuan

2009-04-30

A new organic fluorescent dye, 2,4-dichloro-6-[p-(N,N-diethylamino)biphenylyl]-1,3,5-triazine (DBQ), with an electron withdrawing-donating pair bridged by a twistable aromatic chain has been synthesized. DBQ exhibits high fluorescence quantum yields (0.96 in hexane and 0.71 in THF), high extinction coefficients, and an excitation window extending up to approximately 480 nm. Due to the strong intramolecular charge transfer character, DBQ shows obviously solvent-dependent Stokes shifts with a value as high as 6360 cm(-1) in THF and controllable fluorescence emission in the visible region from "blue" to "orange". The axially chiral structures of DBQ crystals were clearly revealed by the X-ray analyses and CD spectroscopy measurements. Two enantiomers of DBQ were obtained by spontaneous resolution upon crystallization without any chiral auxiliary. The low rotation barriers around the interannular bonds in DBQ molecules resulted in an efficient and selective multiplication of each of the chiral structures when DBQ crystallized in THF at room temperature in the presence of an enantiopure crystal seed, leaving racemized DBQ molecules in the solution. The special crystalline properties of DBQ provided a new approach to the design and synthesis of organic chiral crystals. The photophysical properties of DBQ make it promising in the preparation of new fluorescent probes with high sensitivity.

Selective Anion Binding by a Cofacial Binuclear Zinc Complex of a Schiff-Base Pyrrole Macrocycle

PubMed Central

Devoille, Aline M. J.; Richardson, Patricia; Bill, Nathan; Sessler, Jonathan L.; Love, Jason B.

2011-01-01

The synthesis of the new cofacial binuclear zinc complex [Zn2(L)] of a Schiff-base pyrrole macrocycle is reported. It was discovered that the binuclear microenvironment between the two metals of [Zn2(L)] is suited for the encapsulation of anions, leading to the formation of [K(THF)6][Zn2(μ-Cl)(L)].2THF and [Bun4N][Zn2(μ-OH)(L)] which were characterized by X-ray crystallography. Unusually obtuse Zn-X-Zn angles (X=Cl: 150.54(9)° and OH: 157.4(3)°) illustrate the weak character of these interactions and the importance of the cleft pre-organization to stabilize the host. In the absence of added anion, aggregation of [Zn2(L)] was inferred and investigated by successive dilutions and by the addition of coordinating solvents to [Zn2(L)] solutions using NMR spectroscopy as well as isothermal microcalorimetry (ITC). On anion addition, evidence for de-aggregation of [Zn2(L)], combined with the formation of the 1:1 host-guest complex, was observed by NMR spectroscopy and ITC titrations. Furthermore, [Zn2(L)] binds to Cl− selectively in THF as deduced from the ITC analyses, while other halides induce only de-aggregation. These conclusions were reinforced by DFT calculations, which indicated that the binding energies of OH− and Cl− were significantly greater than for the other halides. PMID:21391550

The Control of Orbital Mixing in Ruthenium Complexes Containing Quinone Related Ligands

DTIC Science & Technology

1991-04-04

and sodium, respectively. Tetrabutylammonium perchlorate (TBAP) and tetrabutylammonium hexafluorophosphate (Kodak; TBAH) were recrystallized from...solution. Lithium perchlorate trihydrate (0.036 g; 0.23 mmol) in methanol (2 mL) was added to the hot reaction mixture. The mixture was cooled to room...and lithium aluminum hydride suspension in THF (this required the use of the 4,5-dimethylated orthophenylenediamine complex for solubility reasons

Technical note: Simultaneous carotenoid and vitamin analysis of milk from total mixed ration-fed cows optimized for xanthophyll detection.

PubMed

Stout, M A; Benoist, D M; Drake, M A

2018-06-01

Concentrations of retinol, α-tocopherol, and major carotenoids in dairy products are often determined simultaneously by liquid chromatography. These compounds have different polarity and solubility; thus, extracting them simultaneously can be difficult and inefficient. In milks with low carotenoid concentrations, the xanthophylls lutein and zeaxanthin may not be completely resolved using common extraction techniques. A simplified method was developed to optimize extraction efficiency and the limit of detection and limit of quantification (LoQ) of lutein and zeaxanthin in bovine milk without decreasing sensitivity to other vitamins or carotenoids. The developed method evaluates lutein, zeaxanthin, β-carotene, retinol, and α-tocopherol simultaneously by ultra-high performance liquid chromatography-photodiode array detection. Common saponification temperatures (40-60°C) and concentrations of KOH in water (10-50% KOH wt/vol) were evaluated. Multiple solvents were evaluated for optimal xanthophyll extraction (diethyl ether, dichloromethane, hexane, and tetrahydrofuran) following saponification. The limit of detection and LoQ were defined as 3:1 and 10:1 signal-to-noise ratio, respectively. All experiments were performed in triplicate. The optimal saponification procedure was a concentration of 25% KOH at either 40 or 50°C. Saponified extracts solubilized in solutions containing diethyl ether had greater concentrations of lutein- than hexane- or tetrahydrofuran-based solutions, with peak areas above LoQ values. The solution containing diethyl ether solubilized similar concentrations of retinol, α-tocopherol, and β-carotene when compared with other solutions. The proposed optimized method allows for the simultaneous determination of carotenoids from milk with increased lutein and zeaxanthin sensitivity without sacrificing recovery of retinol, α-tocopherol, and β-carotene. Copyright © 2018 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Folate status and concentrations of serum folate forms in the US population: National Health and Nutrition Examination Survey 2011-2.

PubMed

Pfeiffer, Christine M; Sternberg, Maya R; Fazili, Zia; Lacher, David A; Zhang, Mindy; Johnson, Clifford L; Hamner, Heather C; Bailey, Regan L; Rader, Jeanne I; Yamini, Sedigheh; Berry, R J; Yetley, Elizabeth A

2015-06-28

Serum and erythrocyte (RBC) total folate are indicators of folate status. No nationally representative population data exist for folate forms. We measured the serum folate forms (5-methyltetrahydrofolate (5-methylTHF), unmetabolised folic acid (UMFA), non-methyl folate (sum of tetrahydrofolate (THF), 5-formyltetrahydrofolate (5-formylTHF), 5,10-methenyltetrahydrofolate (5,10-methenylTHF)) and MeFox (5-methylTHF oxidation product)) by HPLC-MS/MS and RBC total folate by microbiologic assay in US population ≥ 1 year (n approximately 7500) participating in the National Health and Nutrition Examination Survey 2011-2. Data analysis for serum total folate was conducted including and excluding MeFox. Concentrations (geometric mean; detection rate) of 5-methylTHF (37·5 nmol/l; 100 %), UMFA (1·21 nmol/l; 99·9 %), MeFox (1·53 nmol/l; 98·8 %), and THF (1·01 nmol/l; 85·2 %) were mostly detectable. 5-FormylTHF (3·6 %) and 5,10-methenylTHF (4·4 %) were rarely detected. The biggest contributor to serum total folate was 5-methylTHF (86·7 %); UMFA (4·0 %), non-methyl folate (4·7 %) and MeFox (4·5 %) contributed smaller amounts. Age was positively related to MeFox, but showed a U-shaped pattern for other folates. We generally noted sex and race/ethnic biomarker differences and weak (Spearman's r< 0·4) but significant (P< 0·05) correlations with physiological and lifestyle variables. Fasting, kidney function, smoking and alcohol intake showed negative associations. BMI and body surface area showed positive associations with MeFox but negative associations with other folates. All biomarkers showed significantly higher concentrations with recent folic acid-containing dietary supplement use. These first-time population data for serum folate forms generally show similar associations with demographic, physiological and lifestyle variables as serum total folate. Patterns observed for MeFox may suggest altered folate metabolism dependent on biological characteristics.

Moonlighting Glutamate Formiminotransferases Can Functionally Replace 5-Formyltetrahydrofolate Cycloligase*

PubMed Central

Jeanguenin, Linda; Lara-Núñez, Aurora; Pribat, Anne; Mageroy, Melissa Hamner; Gregory, Jesse F.; Rice, Kelly C.; de Crécy-Lagard, Valérie; Hanson, Andrew D.

2010-01-01

5-Formyltetrahydrofolate (5-CHO-THF) is formed by a side reaction of serine hydroxymethyltransferase. Unlike other folates, it is not a one-carbon donor but a potent inhibitor of folate enzymes and must therefore be metabolized. Only 5-CHO-THF cycloligase (5-FCL) is generally considered to do this. However, comparative genomic analysis indicated (i) that certain prokaryotes lack 5-FCL, implying that they have an alternative 5-CHO-THF-metabolizing enzyme, and (ii) that the histidine breakdown enzyme glutamate formiminotransferase (FT) might moonlight in this role. A functional complementation assay for 5-CHO-THF metabolism was developed in Escherichia coli, based on deleting the gene encoding 5-FCL (ygfA). The deletion mutant accumulated 5-CHO-THF and, with glycine as sole nitrogen source, showed a growth defect; both phenotypes were complemented by bacterial or archaeal genes encoding FT. Furthermore, utilization of supplied 5-CHO-THF by Streptococcus pyogenes was shown to require expression of the native FT. Recombinant bacterial and archaeal FTs catalyzed formyl transfer from 5-CHO-THF to glutamate, with kcat values of 0.1–1.2 min−1 and Km values for 5-CHO-THF and glutamate of 0.4–5 μm and 0.03–1 mm, respectively. Although the formyltransferase activities of these proteins were far lower than their formiminotransferase activities, the Km values for both substrates relative to their intracellular levels in prokaryotes are consistent with significant in vivo flux through the formyltransferase reaction. Collectively, these data indicate that FTs functionally replace 5-FCL in certain prokaryotes. PMID:20952389

Formation of unexpected silicon- and disiloxane-bridged multiferrocenyl derivatives bearing Si-O-CH[double bond, length as m-dash]CH2 and Si-(CH2)2C(CH3)3 substituents via cleavage of tetrahydrofuran and trapping of its ring fragments.

PubMed

Bruña, Sonia; González-Vadillo, Ana Mª; Ferrández, Marta; Perles, Josefina; Montero-Campillo, M Merced; Mó, Otilia; Cuadrado, Isabel

2017-09-12

The formation of a family of silicon- and siloxane-bridged multiferrocenyl derivatives carrying different functional groups attached to silicon, including Fc 2 (CH 3 ) 3 C(CH 2 ) 2 SiCH[double bond, length as m-dash]CH 2 (5), Fc 2 (CH 2 [double bond, length as m-dash]CH-O)SiCH[double bond, length as m-dash]CH 2 (6), Fc 2 (OH)SiCH[double bond, length as m-dash]CH 2 (7), Fc 2 (CH 2 [double bond, length as m-dash]CH-O)Si-O-Si(O-CH[double bond, length as m-dash]CH 2 )Fc 2 (8) and Fc 2 (CH 2 [double bond, length as m-dash]CH-O)Si-O-SiFc 3 (9) is described. Silyl vinyl ether molecules 6, 8 and 9 and the heteroleptic vinylsilane 5 resulted from the competing metathesis reaction of lithioferrocene (FcLi), CH 2 [double bond, length as m-dash]CH-OLi or (CH 3 ) 3 C(CH 2 ) 2 Li with the corresponding multifunctional chlorosilane, Cl 3 SiCH[double bond, length as m-dash]CH 2 or Cl 3 Si-O-SiCl 3 . The last two organolithium species have been likely formed in situ by fragmentation of the tetrahydrofuran solvent. Diferrocenylvinyloxyvinylsilane 6 is noteworthy since it represents a rare example of a redox-active silyl mononomer in which two different C[double bond, length as m-dash]C polymerisable groups are directly connected to silicon. The molecular structures of the silicon-containing multiferrocenyl species 5, 6, 8 and 9 have been investigated by single-crystal X-ray diffraction studies, demonstrating the capture and storage processes of two ring fragments resulting from the cleavage of cyclic THF in redox-active and stable crystalline organometallic compounds. From electrochemical studies we found that by changing the anion of the supporting electrolyte from [PF 6 ] - to [B(C 6 F 5 ) 4 ] - , the redox behaviour of tetrametallic disiloxane 8 can be switched from a poorly resolved multistep redox process to four consecutive well-separated one-electron oxidations, corresponding to the sequential oxidation of the four ferrocenyl moieties.

Alteration of the alkaloid profile in genetically modified tobacco reveals a role of methylenetetrahydrofolate reductase in nicotine N-demethylation

USDA-ARS?s Scientific Manuscript database

Methylenetetrahydrofolate reductase (MTHFR) is a key enzyme of the tetrahydrofolate (THF)-mediated one-carbon (C1) metabolic network. This enzyme catalyzes reduction of 5,10-methylene-THF to 5-methyl-THF. The latter donates its methyl group to homocysteine forming Met, which is then used for the syn...

Preparation of polydopamine nanocapsules in a miscible tetrahydrofuran-buffer mixture.

PubMed

Ni, Yun-Zhou; Jiang, Wen-Feng; Tong, Gang-Sheng; Chen, Jian-Xin; Wang, Jie; Li, Hui-Mei; Yu, Chun-Yang; Huang, Xiao-hua; Zhou, Yong-Feng

2015-01-21

A miscible tetrahydrofuran-tris buffer mixture has been used to fabricate polydopamine hollow capsules with a size of 200 nm and with a shell thickness of 40 nm. An unusual non-emulsion soft template mechanism has been disclosed to explain the formation of capsules. The results indicate that the capsule structure is highly dependent on the volume fraction of tetrahydrofuran as well as the solvent, and the shell thickness of capsules can be controlled by adjusting the reaction time and dopamine concentration.

Metal–Organic Frameworks Stabilize Solution-Inaccessible Cobalt Catalysts for Highly Efficient Broad-Scope Organic Transformations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Teng; Manna, Kuntal; Lin, Wenbin

New and active earth-abundant metal catalysts are critically needed to replace precious metal-based catalysts for sustainable production of commodity and fine chemicals. We report here the design of highly robust, active, and reusable cobalt-bipyridine- and cobalt-phenanthroline-based metal–organic framework (MOF) catalysts for alkene hydrogenation and hydroboration, aldehyde/ketone hydroboration, and arene C–H borylation. In alkene hydrogenation, the MOF catalysts tolerated a variety of functional groups and displayed unprecedentedly high turnover numbers of ~2.5 × 10 6 and turnover frequencies of ~1.1 × 10 5 h –1. Structural, computational, and spectroscopic studies show that site isolation of the highly reactive (bpy)Co(THF) 2 speciesmore » in the MOFs prevents intermolecular deactivation and stabilizes solution-inaccessible catalysts for broad-scope organic transformations. Computational, spectroscopic, and kinetic evidence further support a hitherto unknown (bpy•–)CoI(THF) 2 ground state that coordinates to alkene and dihydrogen and then undergoing σ-complex-assisted metathesis to form (bpy)Co(alkyl)(H). Reductive elimination of alkane followed by alkene binding completes the catalytic cycle. MOFs thus provide a novel platform for discovering new base-metal molecular catalysts and exhibit enormous potential in sustainable chemical catalysis.« less

Structural and fluorescence properties of the 2,2‧-methylenediphenoxy and 1,1‧-methylenedi-2-naphthoxy cyclotriphosphazene derivatives

NASA Astrophysics Data System (ADS)

Yenilmez Çiftçi, Gönül; Eker, Yakup; Şenkuytu, Elif; Yuksel, Fatma

2016-08-01

In the present work, the partially or fully substituted spiro-, ansa, open-chain forms of 2,2'-methylenediphenoxy, 1,1'-methylenedi-2-naphthoxy cyclotriphosphazene derivatives and their spectral properties were reported. The reactions of hexachlorocyclotriphosphazene [trimer, N3P3Cl6, (1)] with 2,2'-methylenediphenol (2) and 1,1'-methylenedi-2-naphthol (3) in THF produced new cyclotriphosphazene compounds (4-11). All these compounds (4-11) were fully characterized by elemental analysis, FT-IR, MALDI-TOF mass spectrometry, UV Vis, 1H, 13C and 31P NMR spectroscopy. The molecular structures of 4, 5, 7, 9 and 10 were also determined by X-ray crystallography. All five structures were found in monoclinic system, C2/c, P21/n or P21/c space groups. The fluorescence behaviour of the studied cyclotriphosphazene derivatives (9-11) were also examined in THF solution. Compound 11 showed the highest fluorescence emission behaviour that of compounds 4-10.

Investigation of the spectral properties of a squarylium near-infrared dye and its complexation with Fe(III) and Co(II) ions

NASA Astrophysics Data System (ADS)

Tarazi, Leila; Narayanan, Nara; Sowell, John; Patonay, Gabor; Strekowski, Lucjan

2002-01-01

The spectral features of the squarylium dye NN525 in different solutions and its complexation with several metal ions were investigated. The absorbance maximum of the dye is at 669 nm in tetrahydrofuran. This value matches the output of a commercially available laser diode (650 nm), thus making use of such a source practical for excitation. The emission maximum of the dye in tetrahydrofuran is at 676 nm. The addition of either Fe(III) ion or Co(II) ion resulted in fluorescence quenching of the dye. The detection limit is 6.24×10 -8 M for Fe(III) ion and 1.55×10 -8 M for Co(II) ion. The molar ratio of the metal to the dye was established to be 1:1 for both metal ions. The stability constant KS of the metal-dye complex was calculated to be 3.14×10 6 M -1 for the Fe-dye complex and 2.64×10 5 M -1 for the Co-dye complex.

Investigation of the spectral properties of a squarylium near-infrared dye and its complexation with Fe(III) and Co(II) ions.

PubMed

Tarazi, Leila; Narayanan, Nara; Sowell, John; Patonay, Gabor; Strekowski, Lucjan

2002-01-15

The spectral features of the squarylium dye NN525 in different solutions and its complexation with several metal ions were investigated. The absorbance maximum of the dye is at 669 nm in tetrahydrofuran. This value matches the output of a commercially available laser diode (650 nm), thus making use of such a source practical for excitation. The emission maximum of the dye in tetrahydrofuran is at 676 nm. The addition of either Fe(III) ion or Co(II) ion resulted in fluorescence quenching of the dye. The detection limit is 6.24 x 10(-8) M for Fe(III) ion and 1.55 x 10(-8) M for Co(II) ion. The molar ratio of the metal to the dye was established to be 1:1 for both metal ions. The stability constant Ks of the metal-dye complex was calculated to be 3.14 x 10(6) M(-1) for the Fe-dye complex and 2.64 x 10(5) M(-1) for the Co-dye complex.

Template directed assembly of nanoelements in viscous polymer environments

NASA Astrophysics Data System (ADS)

Modi, Satyamkumar

Polymer melt-based manufacturing methods, such as injection molding, offer the potential of directly fabricating three-dimensional parts with nanostructured surfaces in a one-step, high-rate, and solventless process. Electrophoretic deposition has the potential to produce in-mold assembly of nanoparticles during injection molding. The process is fast, is cost effective and can be automated. This electrophoretic deposition, however, has been performed from low-viscosity media and polymer melts are far more viscous. This research provided a fundamental understanding of the electrophoretic deposition process in viscous media. Electrophoresis was performed using a model system of carbon black and polystyrene in tetrahydrofuran (THF). Examined were the effects of processing parameters, polystyrene molecular weight, and carbon black charge. The presence of polystyrene did not prevent deposition of carbon black, but deposition rates decreased at shorter deposition times; deposition was not linear with increasing applied voltage; and greater solution concentrations reduced the critical voltages. A comparison of experimental data with Hamaker's model showed that about 1.6% of the available polystyrene was initially deposited with the carbon black. At voltages above the critical voltage, the deposited mass indicated formation of electrically insulating layers on the electrodes. Increases in polystyrene molecular weight reduced the electrophoretic deposition of the carbon black particles due to increases in suspension viscosity and preferential adsorption of the longer polystyrene chains on the carbon black particles. At low deposition times (≤ 5 seconds), only carbon black deposited onto the electrodes. For longer deposition times, polystyrene co-deposited with the carbon black, with the amount of polystyrene increasing with molecular weight and decreasing with greater charge on the polystyrene molecules. The additional of function groups to the carbon black surface decoupled the carbon black and polystyrene, however, the deposition of the carbon black particles, followed by deposition of a thick layer of polystyrene was observed. This polystyrene deposition was present regardless of the applied voltage, the deposition time, the polystyrene molecular weight, polystyrene material (i.e., charge), and solvent polarity. This deposition behavior suggests that use of lower molecular polymers and unmodified carbon blacks, and control of electrical properties will permit electrophoretic deposition of nanoparticles from polymer melts.

Reactivity of lanthanocene hydroxides toward ketene, isocyanate, lanthanocene alkyl, and triscyclopentadienyllanthanide complexes.

PubMed

Zhang, Chunmei; Liu, Ruiting; Zhang, Jie; Chen, Zhenxia; Zhou, Xigeng

2006-07-24

The reactivity of [Cp(2)Ln(mu-OH)(THF)]2 (Ln = Y (1), Er (2), Yb (3)) toward PhEtCCO, PhNCO, Cp3Ln, [Cp2Ln(mu-CH3)]2, and the LiCl adduct of Cp2Ln(n)Bu(THF)x was examined. In all cases, OH-centered reactivity is observed: complexes 1-3 react with PhEtCCO to form the O-H addition products [Cp2Ln(mu-eta1:eta2-O2CCHEtPh)]2 (Ln = Yb (5), Er (6), Y (7), respectively, for 1-3), whereas treatment of 1 with PhNCO affords the addition/CpH-elimination/rearrangement product [{Cp2Y(THF)}2(mu-eta2:eta2-O2CNPh)] (8), which contains an unusual PhNCO(2) dianionic ligand. Analogous compound [Cp2Ln(THF)]2(mu-eta2:eta2-O2CNPh) (Ln = Yb (9), Er (10)) and 8 can be obtained in a higher yield by treatment of [Cp2Ln(mu-OH)(THF)]2 with PhNCO followed by reaction with the corresponding Cp3Ln. However, attempts to prepare the corresponding heterobimetallic complex by reacting stoichiometric amounts of [Cp2Y(mu-OH)(THF)]2 with PhNCO followed by treating it with Cp3Yb are unsuccessful. Instead, only rearrangement products 8 and 9 are obtained. Furthermore, the reaction of 3 with [Cp2Yb(mu-CH3)]2 or Cp3Yb forms oxo-bridged compound [Cp2Yb(THF)]2(mu-O) (11), whereas the reaction of [Cp2ErCl]2 with Li(n)Bu followed by treatment with 2 affords unexpected mu-oxo lanthanocene cluster (Cp2Er)3(mu-OH)(mu3-O)(mu-Cl)Li(THF)4 (12). In contrast to 1 and 2, 3 shows a strong tendency to undergo the intermolecular elimination of CpH at room temperature, giving trinuclear species [Cp2Yb(mu-OH)]2[CpYb(THF)](mu3-O) (4). The single-crystal X-ray diffraction structures of 1, 2, and 4-12 are described. All the results offer an interesting contrast to transition- and main-metal hydroxide complexes.

Parametric study of the physical properties of hydrate-bearing sand, silt, and clay sediments: 1. Electromagnetic properties

USGS Publications Warehouse

Lee, J.Y.; Santamarina, J.C.; Ruppel, C.

2010-01-01

The marked decrease in bulk electrical conductivity of sediments in the presence of gas hydrates has been used to interpret borehole electrical resistivity logs and, to a lesser extent, the results of controlled source electromagnetic surveys to constrain the spatial distribution and predicted concentration of gas hydrate in natural settings. Until now, an exhaustive laboratory data set that could be used to assess the impact of gas hydrate on the electromagnetic properties of different soils (sand, silt, and clay) at different effective stress and with different saturations of hydrate has been lacking. The laboratory results reported here are obtained using a standard geotechnical cell and the hydrate-formed tetrahydrofuran (THF), a liquid that is fully miscible in water and able to produce closely controlled saturations of hydrate from dissolved phase. Both permittivity and electrical conductivity are good indicators of the volume fraction of free water in the sediment, which is in turn dependent on hydrate saturation. Permittivity in the microwave frequency range is particularly predictive of free water content since it is barely affected by ionic concentration, pore structure, and surface conduction. Electrical conductivity (or resistivity) is less reliable for constraining water content or hydrate saturation: In addition to fluid-filled porosity, other factors, such as the ionic concentration of the pore fluid and possibly other conduction effects (e.g., surface conduction in high specific surface soils having low conductivity pore fluid), also influence electrical conductivity.

Facile solid-phase synthesis of C-terminal peptide aldehydes and hydroxamates from a common Backbone Amide-Linked (BAL) intermediate.

PubMed

Gazal, S; Masterson, L R; Barany, G

2005-12-01

C-Terminal peptide aldehydes and hydroxamates comprise two separate classes of effective inhibitors of a number of serine, aspartate, cysteine, and metalloproteases. Presented here is a method for preparation of both classes of peptide derivatives from the same resin-bound Weinreb amide precursor. Thus, 5-[(2 or 4)-formyl-3,5-dimethoxyphenoxy]butyramido-polyethylene glycol-polystyrene (BAL-PEG-PS) was treated with methoxylamine hydrochloride in the presence of sodium cyanoborohydride to provide a resin-bound methoxylamine, which was efficiently acylated by different Fmoc-amino acids upon bromo-tris-pyrrolidone-phosphonium hexafluorophosphate (PyBrOP) activation. Solid-phase chain elongation gave backbone amide-linked (BAL) peptide Weinreb amides, which were cleaved either by trifluoroacetic acid (TFA) in the presence of scavengers to provide the corresponding peptide hydroxamates, or by lithium aluminum hydride in tetrahydrofuran (THF) to provide the corresponding C-terminal peptide aldehydes. With several model sequences, peptide hydroxamates were obtained in crude yields of 68-83% and initial purities of at least 85%, whereas peptide aldehydes were obtained in crude yields of 16-53% and initial purities in the range of 30-40%. Under the LiAlH4 cleavage conditions used, those model peptides containing t-Bu-protected aspartate residues underwent partial side chain reduction to the corresponding homoserine-containing peptides. Similar results were obtained when working with high-load aminomethyl-polystyrene, suggesting that this chemistry will be generally applicable to a range of supporting materials.

A highly selective and sensitive ultrasonic assisted dispersive liquid phase microextraction based on deep eutectic solvent for determination of cadmium in food and water samples prior to electrothermal atomic absorption spectrometry.

PubMed

Zounr, Rizwan Ali; Tuzen, Mustafa; Deligonul, Nihal; Khuhawar, Muhammad Yar

2018-07-01

A simple, fast, green, sensitive and selective ultrasonic assisted deep eutectic solvent liquid-phase microextraction technique was used for preconcentration and extraction of cadmium (Cd) in water and food samples by electrothermal atomic absorption spectrometry (ETAAS). In this technique, a synthesized reagent (Z)-N-(3,5-diphenyl-1H-pyrrol-2-yl)-3,5-diphenyl-2H-pyrrol-2-imine (Azo) was used as a complexing agent for Cd. The main factors effecting the pre-concentration and extraction of Cd such as effect of pH, type and composition of deep eutectic solvent (DES), volume of DES, volume of complexing agent, volume of tetrahydrofuran (THF) and ultrasonication time have been examined in detail. At optimum conditions the value of pH and molar ratio of DES were found to be 6.0 and 1:4 (ChCl:Ph), respectively. The detection limit (LOD), limit of quantification (LOQ), relative standard deviation (RSD) and preconcentration factor (PF) were observed as 0.023 ng L -1 , 0.161 ng L -1 , 3.1% and 100, correspondingly. Validation of the developed technique was observed by extraction of Cd in certified reference materials (CRMs) and observed results were successfully compared with certified values. The developed procedure was practiced to various food, beverage and water samples. Copyright © 2018 Elsevier Ltd. All rights reserved.

Tetrahydrofuran

Integrated Risk Information System (IRIS)

Tetrahydrofuran ; CASRN 109 - 99 - 9 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic E

Synthesis of 2-(3'-Indolyl)tetrahydrofurans by oxidative cycloetherification.

PubMed

Gillard, Rachel M; Sperry, Jonathan

2015-03-06

A series of 2-(3'-indolyl)tetrahydrofurans have been prepared by a DDQ-mediated oxidative cycloetherification process. Performing the reaction under biphasic conditions prevents reductive cleavage of the products by the spent oxidant (DDQH2).

Cross sections for ionization of tetrahydrofuran by protons at energies between 300 and 3000 keV

NASA Astrophysics Data System (ADS)

Wang, Mingjie; Rudek, Benedikt; Bennett, Daniel; de Vera, Pablo; Bug, Marion; Buhr, Ticia; Baek, Woon Yong; Hilgers, Gerhard; Rabus, Hans

2016-05-01

Double-differential cross sections for ionization of tetrahydrofuran by protons with energies from 300 to 3000 keV were measured at the Physikalisch-Technische Bundesanstalt ion accelerator facility. The electrons emitted at angles between 15∘ and 150∘ relative to the ion-beam direction were detected with an electrostatic hemispherical electron spectrometer. Single-differential and total ionization cross sections have been derived by integration. The experimental results are compared to the semiempirical Hansen-Kocbach-Stolterfoht model as well as to the recently reported method based on the dielectric formalism. The comparison to the latter showed good agreement with experimental data in a broad range of emission angles and energies of secondary electrons. The scaling property of ionization cross sections for tetrahydrofuran was also investigated. Compared to molecules of different size, the ionization cross sections of tetrahydrofuran were found to scale with the number of valence electrons at large impact parameters.

Impact of Na- and K-C pi-interactions on the structure and binding of M3(sol)n(BINOLate)3Ln catalysts.

PubMed

Wooten, Alfred J; Carroll, Patrick J; Walsh, Patrick J

2007-08-16

Shibasaki's heterobimetallic complexes M3(THF)n(BINOLate)3Ln [M = Li, Na, K; Ln = lanthanide(III)] are among the most successful asymmetric Lewis acid catalysts. Why does M3(THF)n(BINOLate)3Ln readily bind substrates when M = Li but not when M = Na or K? Structural studies herein indicate Na- and K-C cation-pi interactions and alkali metal radius may be more important than even lanthanide radius. Also reported is a novel polymeric [K3(THF)2(BINOLate)3Yb]n structure that provides the first evidence of interactions between M3(THF)n(BINOLate)3Ln complexes.

Impact of Na- and K-C π-Interactions on the Structure and Binding of M3(sol)n(BINOLate)3Ln Catalysts

PubMed Central

Wooten, Alfred J.; Carroll, Patrick J.; Walsh, Patrick J.

2008-01-01

Shibasaki’s heterobimetallic complexes M3(THF)n(BINOLate)3Ln [M = Li, Na, K, Ln = lanthanide(III)] are among the most successful asymmetric Lewis acid catalysts. Why does M3(THF)n(BINOLate)3Ln readily bind substrates when M = Li but not when M = Na or K? Structural studies herein indicate Na- and K-C cation-π interactions and alkali metal radius may be more important than even lanthanide radius. Also reported is a novel polymeric [K3(THF)2(BINOLate)3Yb]n structure that provides the first evidence of interactions between M3(THF)n(BINOLate)3Ln complexes. PMID:17658838

Defining the Structural Basis for Allosteric Product Release from E. coli Dihydrofolate Reductase Using NMR Relaxation Dispersion.

PubMed

Oyen, David; Fenwick, R Bryn; Aoto, Phillip C; Stanfield, Robyn L; Wilson, Ian A; Dyson, H Jane; Wright, Peter E

2017-08-16

The rate-determining step in the catalytic cycle of E. coli dihydrofolate reductase is tetrahydrofolate (THF) product release, which can occur via an allosteric or an intrinsic pathway. The allosteric pathway, which becomes accessible when the reduced cofactor NADPH is bound, involves transient sampling of a higher energy conformational state, greatly increasing the product dissociation rate as compared to the intrinsic pathway that obtains when NADPH is absent. Although the kinetics of this process are known, the enzyme structure and the THF product conformation in the transiently formed excited state remain elusive. Here, we use side-chain proton NMR relaxation dispersion measurements, X-ray crystallography, and structure-based chemical shift predictions to explore the structural basis of allosteric product release. In the excited state of the E:THF:NADPH product release complex, the reduced nicotinamide ring of the cofactor transiently enters the active site where it displaces the pterin ring of the THF product. The p-aminobenzoyl-l-glutamate tail of THF remains weakly bound in a widened binding cleft. Thus, through transient entry of the nicotinamide ring into the active site, the NADPH cofactor remodels the enzyme structure and the conformation of the THF to form a weakly populated excited state that is poised for rapid product release.

The modulation of corticosteroid metabolism by hydrocortisone therapy in patients with hypopituitarism increases tissue glucocorticoid exposure.

PubMed

Sherlock, Mark; Behan, Lucy Ann; Hannon, Mark J; Alonso, Aurora Aragon; Thompson, Christopher J; Murray, Robert D; Crabtree, Nicola; Hughes, Beverly A; Arlt, Wiebke; Agha, Amar; Toogood, Andrew A; Stewart, Paul M

2015-11-01

Patients with hypopituitarism have increased morbidity and mortality. There is ongoing debate about the optimum glucocorticoid (GC) replacement therapy. To assess the effect of GC replacement in hypopituitarism on corticosteroid metabolism and its impact on body composition. We assessed the urinary corticosteroid metabolite profile (using gas chromatography/mass spectrometry) and body composition (clinical parameters and full body DXA) of 53 patients (19 female, median age 46 years) with hypopituitarism (33 ACTH-deficient/20 ACTH-replete) (study A). The corticosteroid metabolite profile of ten patients with ACTH deficiency was then assessed prospectively in a cross over study using three hydrocortisone (HC) dosing regimens (20/10 mg, 10/10 mg and 10/5 mg) (study B) each for 6 weeks. 11 beta-hydroxysteroid dehydrogenase 1 (11β-HSD1) activity was assessed by urinary THF+5α-THF/THE. Endocrine Centres within University Teaching Hospitals in the UK and Ireland. Urinary corticosteroid metabolite profile and body composition assessment. In study A, when patients were divided into three groups - patients not receiving HC and patients receiving HC≤20 mg/day or HC>20 mg/day - patients in the group receiving the highest daily dose of HC had significantly higher waist-to-hip ratio (WHR) than the ACTH replete group. They also had significantly elevated THF+5α-THF/THE (P=0.0002) and total cortisol metabolites (P=0.015). In study B, patients on the highest HC dose had significantly elevated total cortisol metabolites and all patients on HC had elevated THF+5α-THF/THE ratios when compared to controls. In ACTH-deficient patients daily HC doses of >20 mg/day have increased WHR, THF+5α-THF/THE ratios and total cortisol metabolites. GC metabolism and induction of 11β-HSD1 may play a pivitol role in the development of the metabolically adverse hypopituitary phenotype. © 2015 European Society of Endocrinology.

Truxene-cored π-expanded triarylborane dyes as single- and two-photon fluorescent probes for fluoride.

PubMed

Yuan, Mao-Sen; Wang, Qi; Wang, Wenji; Wang, Dong-En; Wang, Junru; Wang, Jinyi

2014-03-21

Fluoride anion (F(-)) significantly affects chemical, biological, and environmental processes. Fluoride recognition and detection have received increasing attention. Convenient, effective, and sensitive fluorescent probes for F(-) should urgently be designed and synthesized. In this study, we describe a strategy for constructing two triarylborane-based fluoride fluorescent probes: 2,7,12-tri(2-(5-(dimesitylboryl)thiophen-2-yl)ethynyl)-5,5',10,10',15,15'-hexaethyltruxene (C3B3) with π-3A (acceptor) configuration and 2,7-di(N,N-diphenylamino)-12-(5-(dimesitylboryl)thiophen-2-yl)-5,5',10,10',15,15'-hexaethyltruxene (N2SB) with 2D (donor)-π-A configuration. The loss of color of the tetrahydrofuran solution of these probes from greenish yellow suggests that they can conveniently monitor F(-) at a low concentration (10 μM) free of apparatus. The different structural features of these probes varied their fluorescent responses to F(-). The single-photon fluorescence intensity of C3B3 declined to 90% upon the addition of 4.5 equivalents of F(-) to its tetrahydrofuran solution. However, the single-photon fluorescence intensity of N2SB was enhanced six-fold upon addition of 2.5 equivalents of the F(-). Under the experimental conditions, the detection limits of the two probes for F(-) can reach 12-13 μM (C3B3) and 3-5 μM (N2SB). The ability of the two probes in detecting F(-) in their toluene solutions in the two-photon mode was also investigated. The sensitive two-photon fluorescence responses of both probes make them excellent two-photon fluorescence probes.

Photo-physical properties and triplet-triplet absorption of platinum(II) acetylides in solid PMMA matrices

NASA Astrophysics Data System (ADS)

Glimsdal, Eirik; Westlund, Robert; Lindgren, Mikael

2009-05-01

Because of their strong nonlinear optical properties, Platinum(II) acetylides are investigated as potential chromophores for optical power limiting (OPL) applications. The strong excited state absorption and efficient intersystem crossing to the triplet states in these materials are desired properties for good OPL performance. We recently reported on OPL and photo-physical properties of Pt(II)-acetylide chromophores in solution, modified with thiophenyl or triazole groups. [R. Westlund et al. J. Mater. Chem. 18, 166 (2008); E. Glimsdal et al. Proc. SPIE 6740, 67400M (2007)] The chromophores were later incorporated into poly(methyl-methacrylate) (PMMA) glasses. A variety of doped organic solids were prepared, reaching concentrations of up to 13 wt% of the guest molecule. Raman spectra of the doped solid devices proved that the chemical structure of the nonlinear dyes remains intact upon the polymerization of the solid matrix. Luminescence spectra confirm that the basic photo-physical properties (absorption, emission and inter-system crossing) observed for the solute molecules in THF are maintained also in the solid state. In particular, the phosphorescence lifetime stays in the order of μs to ms, just as in the oxygen evacuated liquid samples. Also, the wavelength dependence and time-dynamics of the triplet absorption spectra of the dyes, dissolved in THF solution and dispersed in solid PMMA matrices, were investigated and compared. Ground state UV absorption spectra between 300 and 420 nm have corresponding broad band visible triplet-triplet absorption between 400 and 800 nm. The triplet state extinction coefficients were determined to be in the order of 104 M-1cm-1.

Analogs of Estrogen Metabolites as Probes of Estrogen-Induced Tumorigenesis

DTIC Science & Technology

1999-07-01

bromination reaction by reverse phase HPLC revealed a mixture of 4-bromoestradiol (5-10%), 2-bromoestradiol 28 (’-15%) and 2,4- dibromoestradiol 29...mixture. HPLC analysis of the reaction mixture revealed that the estradiol was completely consumed and 2,4-dibromoestradiol 29 was the major product...purification by HPLC .5 A solution of 30 in THF at -78’C was treated with various organolithium reagents and stirred for three hours after which the

Computer Solutions to Heat and Diffraction Equations in High Energy Laser Windows. Volume II

DTIC Science & Technology

1976-11-01

IF L =2 AND TI2.1) = T(l.l)» Gn TO 135 TO FOLLOW UP THp IMPRESSION THAT INTERGRANn IS STRAIGHT LINE. .tQ. 1ABS ) 60 TO ,135 LACllLATE NEXT...IJA ’.(M MUMBFR OF "DAIAIM« ARRAYS -rAPO UDA »? CONTAIN THE TViDTCtb DI" DATA IM ’DATAIN1 WHICH ARF (0 iE PLOTTED AT THF BFGTNMT’MR 0^ EACH

3',4',7-Trihydroxyflavone prevents apoptotic cell death in neuronal cells from hydrogen peroxide-induced oxidative stress.

PubMed

Kwon, Seung-Hwan; Hong, Sa-Ik; Ma, Shi-Xun; Lee, Seok-Yong; Jang, Choon-Gon

2015-06-01

In this study, we investigated the mechanisms of 3',4',7-trihydroxyflavone (THF) protection of neuronal cells from neuronal cell death induced by the oxidative stress-related neurotoxin hydrogen peroxide (H2O2). Pretreatment with THF significantly elevated cell viability, reduced H2O2-induced lactate dehydrogenase (LDH) release, reactive oxygen species (ROS) production, glutathione (GSH) content, superoxide dismutase (SOD) activity, catalase (CAT) activity, and mitochondria membrane potential (MMP) loss. Western blot data demonstrated that THF inhibited the H2O2-induced up- or down-regulation of cleaved caspase-3, cleaved caspase-9, cleaved poly-ADP-ribose polymerase (PARP), Bax, Bcl-2, and Bcl-xL, and attenuated the H2O2-induced release of cytochrome c from the mitochondria to the cytosol. In addition, pretreatment with THF attenuated H2O2-induced rapid and significant phosphorylation of c-Jun N-terminal kinase (JNK), p38 mitogen-activated protein kinase (MAPK), and phosphatidylinositol 3-kinases (PI3K)/Akt. THF also inhibited nuclear factor-κB (NF-κB) translocation to the nucleus induced by H2O2, down-stream of H2O2-induced phosphorylation of MAPKs and PI3K/Akt. These data provide the first evidence that THF protects neuronal cells against H2O2-induced oxidative stress, possibly through ROS reduction, mitochondria protection, and NF-κB modulation via MAPKs and PI3K/Akt pathways. The neuroprotective effects of THF make it a promising candidate as a therapeutic agent for neurodegenerative diseases. Copyright © 2015 Elsevier Ltd. All rights reserved.

11β-Hydroxysteroid dehydrogenase type-2 and type-1 (11β-HSD2 and 11β-HSD1) and 5β-reductase activities in the pathogenia of essential hypertension.

PubMed

Campino, Carmen; Carvajal, Cristian A; Cornejo, Javiera; San Martín, Betty; Olivieri, Oliviero; Guidi, Giancesare; Faccini, Giovanni; Pasini, Francesco; Sateler, Javiera; Baudrand, Rene; Mosso, Lorena; Owen, Gareth I; Kalergis, Alexis M; Padilla, Oslando; Fardella, Carlos E

2010-02-01

Cortisol availability is modulated by several enzymes: 11β-HSD2, which transforms cortisol (F) to cortisone (E) and 11β-HSD1 which predominantly converts inactive E to active F. Additionally, the A-ring reductases (5α- and 5β-reductase) inactivate cortisol (together with 3α-HSD) to tetrahydrometabolites: 5αTHF, 5βTHF, and THE. The aim was to assess 11β-HSD2, 11β-HSD1, and 5β-reductase activity in hypertensive patients. Free urinary F, E, THF, and THE were measured by HPLC-MS/MS in 102 essential hypertensive patients and 18 normotensive controls. 11β-HSD2 enzyme activity was estimated by the F/E ratio, the activity of 11β-HSD1 in compare to 11β-HSD2 was inferred by the (5αTHF + 5βTHF)/THE ratio and 5β-reductase activity assessed using the E/THE ratio. Activity was considered altered when respective ratios exceeded the maximum value observed in the normotensive controls. A 15.7% of patients presented high F/E ratio suggesting a deficit of 11β-HSD2 activity. Of the remaining 86 hypertensive patients, two possessed high (5αTHF + 5βTHF)/THE ratios and 12.8% had high E/THE ratios. We observed a high percentage of alterations in cortisol metabolism at pre-receptor level in hypertensive patients, previously misclassified as essential. 11β-HSD2 and 5β-reductase decreased activity and imbalance of 11β-HSDs should be considered in the future management of hypertensive patients.

The Chloroplastic Protein THF1 Interacts with the Coiled-Coil Domain of the Disease Resistance Protein N′ and Regulates Light-Dependent Cell Death1[OPEN

PubMed Central

Sekine, Ken-Taro; Wallon, Thérèse; Sugiwaka, Yuji; Kobayashi, Kappei

2016-01-01

One branch of plant immunity is mediated through nucleotide-binding/Leu-rich repeat (NB-LRR) family proteins that recognize specific effectors encoded by pathogens. Members of the I2-like family constitute a well-conserved subgroup of NB-LRRs from Solanaceae possessing a coiled-coil (CC) domain at their N termini. We show here that the CC domains of several I2-like proteins are able to induce a hypersensitive response (HR), a form of programmed cell death associated with disease resistance. Using yeast two-hybrid screens, we identified the chloroplastic protein Thylakoid Formation1 (THF1) as an interacting partner for several I2-like CC domains. Co-immunoprecipitations and bimolecular fluorescence complementation assays confirmed that THF1 and I2-like CC domains interact in planta and that these interactions take place in the cytosol. Several HR-inducing I2-like CC domains have a negative effect on the accumulation of THF1, suggesting that the latter is destabilized by active CC domains. To confirm this model, we investigated N′, which recognizes the coat protein of most Tobamoviruses, as a prototypical member of the I2-like family. Transient expression and gene silencing data indicated that THF1 functions as a negative regulator of cell death and that activation of full-length N′ results in the destabilization of THF1. Consistent with the known function of THF1 in maintaining chloroplast homeostasis, we show that the HR induced by N′ is light-dependent. Together, our results define, to our knowledge, novel molecular mechanisms linking light and chloroplasts to the induction of cell death by a subgroup of NB-LRR proteins. PMID:26951433

Folic acid and L-5-methyltetrahydrofolate: comparison of clinical pharmacokinetics and pharmacodynamics.

PubMed

Pietrzik, Klaus; Bailey, Lynn; Shane, Barry

2010-08-01

There is a large body of evidence to suggest that improving periconceptional folate status reduces the risk of neonatal neural tube defects. Thus increased folate intake is now recommended before and during the early stages of pregnancy, through folic acid supplements or fortified foods. Furthermore, there is growing evidence that folic acid may have a role in the prevention of other diseases, including dementia and certain types of cancer. Folic acid is a synthetic form of the vitamin, which is only found in fortified foods, supplements and pharmaceuticals. It lacks coenzyme activity and must be reduced to the metabolically active tetrahydrofolate form within the cell. L-5-methyl-tetrahydrofolate (L-5-methyl-THF) is the predominant form of dietary folate and the only species normally found in the circulation, and hence it is the folate that is normally transported into peripheral tissues to be used for cellular metabolism. L-5-methyl-THF is also available commercially as a crystalline form of the calcium salt (Metafolin(R)), which has the stability required for use as a supplement. Studies comparing L-5-methyl-THF and folic acid have found that the two compounds have comparable physiological activity, bioavailability and absorption at equimolar doses. Bioavailability studies have provided strong evidence that L-5-methyl-THF is at least as effective as folic acid in improving folate status, as measured by blood concentrations of folate and by functional indicators of folate status, such as plasma homocysteine. Intake of L-5-methyl-THF may have advantages over intake of folic acid. First, the potential for masking the haematological symptoms of vitamin B(12) deficiency may be reduced with L-5-methyl-THF. Second, L-5-methyl-THF may be associated with a reduced interaction with drugs that inhibit dihydrofolate reductase.

Development of Organic Nonlinear Optical Materials

DTIC Science & Technology

1992-10-22

been used by Casstevens, et al, to analyze DFWM results on Langmuir - Blodgett films of SiPc derivatives and evaporated films of metal free phthalocyanine...of poly (THF) (MW = 650 g/mol), a soluble branched polymer was produced. The reaction was carried out either neat, or in THF without addition of any...substantially and poly (THF) proved suitable. The resultant polymer was soluble with a lower Tg due to plasticizing effects. A major cause of concern in this work

Lanthanide(II) complexes of a phosphine-borane-stabilised carbanion.

PubMed

Izod, Keith; Clegg, William; Harrington, Ross W

2010-08-07

The reaction between two equivalents of the potassium salt [(Me(3)Si)(2){Me(2)P(BH(3))}C]K (4) and SmI(2)(THF)(2) in refluxing THF yields the dialkylsamarium(II) compounds [(Me(3)Si)(2){Me(2)P(BH(3))}C](2)Sm(THF) (5a) or [(Me(3)Si)(2){Me(2)P(BH(3))}C](2)Sm(THF)(3) (5b), depending on the crystallisation conditions, in good yield as air- and moisture-sensitive crystalline solids. X-ray crystallography shows that, whereas both alkyl ligands chelate the samarium(II) ion in 5a, in 5b one alkyl ligand chelates the metal centre and one binds the metal only through its borane hydrogen atoms. The reaction between YbI(2) and two equivalents of 4 in refluxing benzene yields the solvent-free dialkylytterbium(II) compound [(Me(3)Si)(2){Me(2)P(BH(3))}C](2)Yb (8). In contrast to 5a and 5b, compound 8 reacts rapidly with THF to give the free phosphine-borane (Me(3)Si)(2){Me(2)P(BH(3))}CH as the only identifiable product.

Aminotroponiminate calcium and strontium complexes.

PubMed

Datta, Simmi; Gamer, Michael T; Roesky, Peter W

2008-06-07

Heteroleptic aminotroponiminate complexes of calcium and strontium have been prepared. The monomeric calcium complex [((iPr)2ATI)CaI(THF)3] 1 ((iPr)2ATI = N-isopropyl-2-(isopropylamino)troponiminate) and the corresponding dimeric strontium compound [( (iPr)2ATI)SrI(THF)2]2 2 were obtained by reaction of [((iPr)2ATI)K] and MI2. Whereas the mixed ligand compound of composition [((iPr)2ATI)Ca(iPrAT)]2 3 (iPrAT = 2-(isopropylamino)troponate) was not obtained via a salt metathesis but by reaction of [Ca(N(SiMe3)2)2(THF)2] with ( (iPr)2ATI)H and (iPrAT)H, the diphosphanylamido complex [( (iPr)2ATI)Ca((Ph2P)2N)(THF)2] was obtained by reaction of CaI2 with the potassium compounds [( (iPr)2ATI)K] and [K(THF)n][N(PPh2)2]. The single crystal X-ray structures of all compounds were established and the latter compound shows a eta2-coordination mode of the ligand via the nitrogen and one phosphorus atom.

Adipic acid production catalyzed by a combination of a solid acid and an iodide salt from biomass-derived tetrahydrofuran-2,5-dicarboxylic acid

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gilkey, Matthew J.; Balakumar, Rachana; Vlachos, Dionisios G.

We recently reported biomass-derived tetrahydrofuran-2,5-dicarboxylic acid (THFDCA) as a potential renewable feedstock for adipic acid (AA) production by combining HI and molecular H 2 in organic acid solvents.

Adipic acid production catalyzed by a combination of a solid acid and an iodide salt from biomass-derived tetrahydrofuran-2,5-dicarboxylic acid

DOE PAGES

Gilkey, Matthew J.; Balakumar, Rachana; Vlachos, Dionisios G.; ...

2018-01-01

We recently reported biomass-derived tetrahydrofuran-2,5-dicarboxylic acid (THFDCA) as a potential renewable feedstock for adipic acid (AA) production by combining HI and molecular H 2 in organic acid solvents.

Synthesis and redox properties of fac-BrRe(CO)3[1,2-(PPh2)2-closo-1,2-C2B10H10]: The first structurally characterized rhenium carbonyl containing a carboranyl-based diphosphine ligand

NASA Astrophysics Data System (ADS)

Lin, Chen-Hao; Nesterov, Vladimir N.; Richmond, Michael G.

2018-03-01

The diphosphine 1,2-(PPh2)2-closo-1,2-C2B10H10 reacts with BrRe(CO)5 and fac-BrRe(CO)3(THF)2 to give fac-BrRe(CO)3[1,2-(PPh2)2-closo-1,2-C2B10H10] (1) in high yields (>80%). Compound 1 is the first structurally characterized rhenium carbonyl that contains an ancillary carborane-based diphosphine ligand. 1 has been characterized in solution by IR and NMR spectroscopies (1H and 31P), and the solid-state structure has been determined by X-ray diffraction analysis. The electrochemical properties of 1 have been investigated by cyclic voltammetry, and the composition of the DFT-computed HOMO and LUMO levels are discussed relative to the electrochemical data. The thermodynamics for the formation of 1 from the rhenium precursors BrRe(CO)5 and fac-BrRe(CO)3(THF)2 have been evaluated by DFT calculations.

Chemical Clearing and Dehydration of GFP Expressing Mouse Brains

PubMed Central

Saghafi, Saiedeh; Weiler, Reto; Dodt, Hans-Ulrich

2012-01-01

Generally, chemical tissue clearing is performed by a solution consisting of two parts benzyl benzoate and one part benzyl alcohol. However, prolonged exposure to this mixture markedly reduces the fluorescence of GFP expressing specimens, so that one has to compromise between clearing quality and fluorescence preservation. This can be a severe drawback when working with specimens exhibiting low GFP expression rates. Thus, we screened for a substitute and found that dibenzyl ether (phenylmethoxymethylbenzene, CAS 103-50-4) can be applied as a more GFP-friendly clearing medium. Clearing with dibenzyl ether provides improved tissue transparency and strikingly improved fluorescence intensity in GFP expressing mouse brains and other samples as mouse spinal cords, or embryos. Chemical clearing, staining, and embedding of biological samples mostly requires careful foregoing tissue dehydration. The commonly applied tissue dehydration medium is ethanol, which also can markedly impair GFP fluorescence. Screening for a substitute also for ethanol we found that tetrahydrofuran (CAS 109-99-9) is a more GFP-friendly dehydration medium than ethanol, providing better tissue transparency obtained by successive clearing. Combined, tetrahydrofuran and dibenzyl ether allow dehydration and chemical clearing of even delicate samples for UM, confocal microscopy, and other microscopy techniques. PMID:22479475

Chemical clearing and dehydration of GFP expressing mouse brains.

PubMed

Becker, Klaus; Jährling, Nina; Saghafi, Saiedeh; Weiler, Reto; Dodt, Hans-Ulrich

2012-01-01

Generally, chemical tissue clearing is performed by a solution consisting of two parts benzyl benzoate and one part benzyl alcohol. However, prolonged exposure to this mixture markedly reduces the fluorescence of GFP expressing specimens, so that one has to compromise between clearing quality and fluorescence preservation. This can be a severe drawback when working with specimens exhibiting low GFP expression rates. Thus, we screened for a substitute and found that dibenzyl ether (phenylmethoxymethylbenzene, CAS 103-50-4) can be applied as a more GFP-friendly clearing medium. Clearing with dibenzyl ether provides improved tissue transparency and strikingly improved fluorescence intensity in GFP expressing mouse brains and other samples as mouse spinal cords, or embryos. Chemical clearing, staining, and embedding of biological samples mostly requires careful foregoing tissue dehydration. The commonly applied tissue dehydration medium is ethanol, which also can markedly impair GFP fluorescence. Screening for a substitute also for ethanol we found that tetrahydrofuran (CAS 109-99-9) is a more GFP-friendly dehydration medium than ethanol, providing better tissue transparency obtained by successive clearing. Combined, tetrahydrofuran and dibenzyl ether allow dehydration and chemical clearing of even delicate samples for UM, confocal microscopy, and other microscopy techniques.

Photochemistry of Metal-Metal Bonded Transition Element Complexes

DTIC Science & Technology

1980-12-12

longest-lived metal - metal bonded complex in 298 K fluid solution is of tl.e order of _10-6 a in lifetime (7). Thus, excited state reactions of any kind must...may be greater since cage escape of Re(CO)5 radicals may be less thin unity. There is a solvent viscosity effect on the disappearance quantum yield of...M2 (CO) 1 0 in the presence of 12,consistent with a solvent cage effect (11). In polar solvents (pyridine, THF, alcohols, etc.) the photochemistry of

Group 1 and group 2 metal complexes supported by a bidentate bulky iminopyrrolyl ligand: synthesis, structural diversity, and ε-caprolactone polymerization study.

PubMed

Kottalanka, Ravi K; Harinath, A; Rej, Supriya; Panda, Tarun K

2015-12-14

We report here a series of alkali and alkaline earth metal complexes, each with a bulky iminopyrrolyl ligand [2-(Ph3CN=CH)C4H3NH] (1-H) moiety in their coordination sphere, synthesized using either alkane elimination or silylamine elimination methods or the salt metathesis route. The lithium salt of molecular composition [Li(2-(Ph3CN=CH)C4H3N)(THF)2] (2) was prepared using the alkane elimination method, and the silylamine elimination method was used to synthesize the dimeric sodium and tetra-nuclear potassium salts of composition [(2-(Ph3CN=CH)C4H3N)Na(THF)]2 (3) and [(2-(Ph3CN=CH)C4H3N)K(THF)0.5]4 (4) respectively. The magnesium complex of composition [(THF)2Mg(CH2Ph){2-(Ph3CN=CH)C4H3N}] (5) was synthesized through the alkane elimination method, in which [Mg(CH2Ph)2(OEt2)2] was treated with the bulky iminopyrrole ligand 1-H in 1 : 1 molar ratio, whereas the bis(iminopyrrolyl)magnesium complex [(THF)2Mg{2-(Ph3CN=CH)C4H3N}2] (6) was isolated using the salt metathesis route. The heavier alkaline earth metal complexes of the general formula {(THF)nM(2-(Ph3CN=CH)C4H3N)2} [M = Ca (7), Sr (8), and n = 2; M = Ba (9), n = 3] were prepared in pure form using two synthetic methods: in the first method, the bulky iminopyrrole ligand 1-H was directly treated with the alkaline earth metal precursor [M{N(SiMe3)2}2(THF)n] (where M = Ca, Sr and Ba) in 2 : 1 molar ratio in THF solvent at ambient temperature. The complexes 7-9 were also obtained using the salt metathesis reaction, which involves the treatment of the potassium salt (4) with the corresponding metal diiodides MI2 (M = Ca, Sr and Ba) in 2 : 1 molar ratio in THF solvent. The molecular structures of all the metal complexes (1-H, 2-9) in the solid state were established through single-crystal X-ray diffraction analysis. The complexes 5-9 were tested as catalysts for the ring-opening polymerization of ε-caprolactone. High activity was observed in the heavier alkaline earth metal complexes 7-9, with a very narrow polydispersity index in comparison to that of magnesium complexes 5 and 6.

Divergent Synthesis of Multisubstituted Tetrahydrofurans and Pyrrolidines via Intramolecular Aldol-type Trapping of Onium Ylide Intermediates.

PubMed

Jing, Changcheng; Xing, Dong; Gao, Lixin; Li, Jia; Hu, Wenhao

2015-12-21

This paper reports a divergent strategy for the synthesis of multisubstituted tetrahydrofurans and pyrrolidines, starting from easily accessible β-hydroxyketones or β-aminoketones to react with diazo compounds. Under Rh(II) catalysis, this transformation is proposed to proceed through a metal-carbene-induced oxonium ylide or ammonium ylide formation followed by an intramolecular aldol-type trapping of these active intermediates. A series of highly substituted tetrahydrofurans and pyrrolidines are synthesized in high yields with good to excellent diastereoselectivities. Preliminary biological evaluations revealed that both types of heterocycles show good PTP1B inhibitory activities. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Alkyl complexes of strontium and barium: synthesis and structural characterization of [(Me3Si)2(MeOMe2Si)C]2Sr(THF) and [(Me3Si)2(MeOMe2Si)C]2Ba(MeOCH2CH2OMe).

PubMed

Izod, Keith; Liddle, Stephen T; Clegg, William

2003-06-25

Metathesis between either SrI2 or BaI2 and 2 equiv of {(Me3Si)2(MeOMe2Si)C}K in THF yields the novel heavier alkali metal dialkyls {(Me3Si)2(MeOMe2Si)C}2M(L) [M(L) = Sr(THF) (2), Ba(DME) (3) (DME = 1,2-dimethoxyethane)] after recrystallization.

Reduced repair capacity of a DNA clustered damage site comprised of 8-oxo-7,8-dihydro-2'-deoxyguanosine and 2-deoxyribonolactone results in an increased mutagenic potential of these lesions

DOE PAGES

Cunniffe, Siobhan; O’Neill, Peter; Greenberg, Marc M.; ...

2014-04-01

A signature of ionizing radiation is the induction of DNA clustered damaged sites. Non-double strand break (DSB) clustered damage has been shown to compromise the base excision repair pathway, extending the lifetimes of the lesions within the cluster, compared to isolated lesions. This increases the likelihood the lesions persist to replication and thus increasing the mutagenic potential of the lesions within the cluster. Lesions formed by ionizing radiation include 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo) and 2-deoxyribonolactone (dL). dL poses an additional challenge to the cell as it is not repaired by the short-patch base excision repair pathway. Here we show recalcitrant dL repairmore » is reflected in mutations observed when DNA containing it and a proximal 8-oxodGuo is replicated in Escherichia coli. 8-oxodGuo in close proximity to dL on the opposing DNA strand results in an enhanced frequency of mutation of the lesions within the cluster and a 20 base sequence flanking the clustered damage site in an E. coli based plasmid assay. In vitro repair of a dL lesion is reduced when compared to the repair of an abasic (AP) site and a tetrahydrofuran (THF), and this is due mainly to a reduction in the activity of polymerase β, leading to retarded FEN1 and ligase 1 activities. This study has given insights in to the biological effects of clusters containing dL.« less

Thermochemistry of Alane Complexes for Hydrogen Storage: A Theoretical and Experimental Investigation

PubMed Central

2011-01-01

Knowledge of the relative stabilities of alane (AlH3) complexes with electron donors is essential for identifying hydrogen storage materials for vehicular applications that can be regenerated by off-board methods; however, almost no thermodynamic data are available to make this assessment. To fill this gap, we employed the G4(MP2) method to determine heats of formation, entropies, and Gibbs free energies of formation for 38 alane complexes with NH3−nRn (R = Me, Et; n = 0−3), pyridine, pyrazine, triethylenediamine (TEDA), quinuclidine, OH2−nRn (R = Me, Et; n = 0−2), dioxane, and tetrahydrofuran (THF). Monomer, bis, and selected dimer complex geometries were considered. Using these data, we computed the thermodynamics of the key formation and dehydrogenation reactions that would occur during hydrogen delivery and alane regeneration, from which trends in complex stability were identified. These predictions were tested by synthesizing six amine−alane complexes involving trimethylamine, triethylamine, dimethylethylamine, TEDA, quinuclidine, and hexamine and obtaining upper limits of ΔG° for their formation from metallic aluminum. Combining these computational and experimental results, we establish a criterion for complex stability relevant to hydrogen storage that can be used to assess potential ligands prior to attempting synthesis of the alane complex. On the basis of this, we conclude that only a subset of the tertiary amine complexes considered and none of the ether complexes can be successfully formed by direct reaction with aluminum and regenerated in an alane-based hydrogen storage system. PMID:22962624

Relative bioavailability of 13C5-folic acid in pectin-coated folate fortified rice in humans using stable isotope techniques.

PubMed

de Ambrosis, A; Vishnumohan, S; Paterson, J; Haber, P; Arcot, J

2017-01-01

The aim of the study was to measure the relative bioavailability of labeled pteroylglutamic acid (13C5-PteGlu) from a pectin-coated fortified rice in vivo to measure any effect of the edible coating on folic acid bioavailability. Healthy volunteers (N=26) aged 18-39 years received three test meals in three randomized short-term cross-over trials: Trial 1: aqueous 400 μg 13C5-PteGlu, Trial 2: 200 g cooked white rice+400 μg 13C5-PteGlu,Trial 3: 200 g fortified cooked white rice with pectin-coated premix containing 400 μg 13C5-PteGlu. Blood samples were drawn at 0,1,2,5 and 8 h postprandial. The concentration of 13C5-5 methyl-tetrahydrofolate appearing in plasma was quantified using high performance liquid chromatography-mass spectrometry (MS)/MS. For 24 h before baseline estimation and during the area under the curve (AUC) study, the subjects were placed on a low folate diet (∼100 μg/day). The relative bioavailability of the folic acid following Trial 3 was measured by comparing the 13C5-5 methyl-tetrahydrofuran (THF) AUC with Trials 1 and 2. The bioavailability of folic acid in a pectin-coated rice premix was 68.7% (range 47-105) and 86.5% (range 65-115) in uncoated fortified rice relative to aqueous folic acid. This study is the first demonstration of the bioavailability of folate in pectin-coated fortified rice in humans.

[11C]metaraminol, a false neurotransmitter: preparation, metabolite studies and positron emission tomography examination in monkey.

PubMed

Någren, K; Halldin, C; Swahn, C G; Suhara, T; Farde, L

1996-04-01

No-carrier-added racemic [11C]metaraminol was prepared by a selective condensation of [11C]nitroethane with 3-hydroxy-benzaldehyde using tetrabutylammonium fluoride in tetrahydrofuran (THF) as a catalyst, followed by a reduction with Raney nickel in formic acid. [11C]Metaraminol was produced in 30 to 45% decay-corrected yield from [11C]nitroethane (13 to 20% decay corrected from [11C]CO2) within 45 to 55 min total synthesis time. Reversed phase high-performance liquid chromatography (HPLC) was used for the separation of the racemic erythro- and threo-forms of [11C]metaraminol. The radiochemical purity was higher than 98%, and the specific radioactivity at the end of synthesis was 500 to 800 Ci/mmol (18 to 30 GBq/mumol). Positron emission tomography (PET) examination of racemic erythro-[11C]metaraminol in a Cynomolgus monkey showed a high uptake of radioactivity in the heart. Following pretreatment with the selective norepinephrine reuptake inhibitor desipramine, the radioactivity uptake in the myocardium was markedly reduced (80%), demonstrating the specificity of erythro-[11C]metaraminol for the norepinephrine reuptake system of the heart. Pretreatment with desipramine had no effect on radioactivity in lung. The metabolism was rapid for [11C]metaraminol. The amounts of the total radioactivity representing [11C]metaraminol in plasma, determined by HPLC, were 14% at 6 min and 8% at 34 min. The high specific uptake of racemic erythro-[11C]metaraminol indicates that enantiomerically pure (R,S)-[11C]metaraminol has potential for detailed mapping of the sympathetic innervation of the human myocardium.

Novel Method for Quantitative Estimation of Biofilms.

PubMed

Syal, Kirtimaan

2017-10-01

Biofilm protects bacteria from stress and hostile environment. Crystal violet (CV) assay is the most popular method for biofilm determination adopted by different laboratories so far. However, biofilm layer formed at the liquid-air interphase known as pellicle is extremely sensitive to its washing and staining steps. Early phase biofilms are also prone to damage by the latter steps. In bacteria like mycobacteria, biofilm formation occurs largely at the liquid-air interphase which is susceptible to loss. In the proposed protocol, loss of such biofilm layer was prevented. In place of inverting and discarding the media which can lead to the loss of the aerobic biofilm layer in CV assay, media was removed from the formed biofilm with the help of a syringe and biofilm layer was allowed to dry. The staining and washing steps were avoided, and an organic solvent-tetrahydrofuran (THF) was deployed to dissolve the biofilm, and the absorbance was recorded at 595 nm. The protocol was tested for biofilm estimation of E. coli, B. subtilis and M. smegmatis, and compared with the traditional CV assays. Isoniazid drug molecule, a known inhibitor of M. smegmatis biofilm, was tested and its inhibitory effects were quantified by the proposed protocol. For ease in referring, this method has been described as the Syal method for biofilm quantification. This new method was found to be useful for the estimation of early phase biofilm and aerobic biofilm layer formed at the liquid-air interphase. The biofilms formed by all three tested bacteria-B. subtilis, E. coli and M. smegmatis, were precisely quantified.

Manipulation of a Schlenk Line: Preparation of Tetrahydrofuran Complexes of Transition-Metal Chlorides

ERIC Educational Resources Information Center

Davis, Craig M.; Curran, Kelly A.

2007-01-01

Before taking an inorganic laboratory course few students have experience handling air-sensitive materials using Schlenk techniques. This exercise introduces them to techniques they will employ in later syntheses. The procedure involves the formation of anhydrous tetrahydrofuran complexes of transition-metal chlorides from metal-chloride hydrates;…

Dinuclear rare-earth metal alkyl complexes supported by indolyl ligands in μ-η(2) :η(1) :η(1) hapticities and their high catalytic activity for isoprene 1,4-cis-polymerization.

PubMed

Zhang, Guangchao; Wei, Yun; Guo, Liping; Zhu, Xiancui; Wang, Shaowu; Zhou, Shuangliu; Mu, Xiaolong

2015-02-02

Two series of new dinuclear rare-earth metal alkyl complexes supported by indolyl ligands in novel μ-η(2) :η(1) :η(1) hapticities are synthesized and characterized. Treatment of [RE(CH2 SiMe3 )3 (thf)2 ] with 1 equivalent of 3-(tBuN=CH)C8 H5 NH (L1 ) in THF gives the dinuclear rare-earth metal alkyl complexes trans-[(μ-η(2) :η(1) :η(1) -3-{tBuNCH(CH2 SiMe3 )}Ind)RE(thf)(CH2 SiMe3 )]2 (Ind=indolyl, RE=Y, Dy, or Yb) in good yields. In the process, the indole unit of L1 is deprotonated by the metal alkyl species and the imino C=N group is transferred to the amido group by alkyl CH2 SiMe3 insertion, affording a new dianionic ligand that bridges two metal alkyl units in μ-η(2) :η(1) :η(1) bonding modes, forming the dinuclear rare-earth metal alkyl complexes. When L1 is reduced to 3-(tBuNHCH2 )C8 H5 NH (L2 ), the reaction of [Yb(CH2 SiMe3 )3 (thf)2 ] with 1 equivalent of L2 in THF, interestingly, generated the trans-[(μ-η(2) :η(1) :η(1) -3-{tBuNCH2 }Ind)Yb(thf)(CH2 SiMe3 )]2 (major) and cis-[(μ-η(2) :η(1) :η(1) -3-{tBuNCH2 }Ind)Yb(thf)(CH2 SiMe3 )]2 (minor) complexes. The catalytic activities of these dinuclear rare-earth metal alkyl complexes for isoprene polymerization were investigated; the yttrium and dysprosium complexes exhibited high catalytic activities and high regio- and stereoselectivities for isoprene 1,4-cis-polymerization. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Total folate and unmetabolized folic acid in the breast milk of a cross-section of Canadian women.

PubMed

Page, Rachael; Robichaud, André; Arbuckle, Tye E; Fraser, William D; MacFarlane, Amanda J

2017-05-01

Background: Folate requirements increase during pregnancy and lactation. It is recommended that women who could become pregnant, are pregnant, or are lactating consume a folic acid (FA)-containing supplement. Objectives: We sought to determine breast-milk total folate and unmetabolized folic acid (UMFA) contents and their relation with FA-supplement use and doses in a cohort of Canadian mothers who were enrolled in the MIREC (Maternal-Infant Research on Environmental Chemicals) study. Design: Breast-milk tetrahydrofolate (THF), 5-methyl-THF, 5-formyl-THF, 5,10-methenyl-THF, and UMFA were measured with the use of liquid chromatography-tandem mass spectrometry ( n = 561). Total daily supplemental FA intake was based on self-reported FA-supplement use. Results: UMFA was detectable in the milk of 96.1% of the women. Total daily FA intake from supplements was associated with breast folate concentration and species. Breast-milk total folate was 18% higher ( P < 0.001) in supplement users ( n = 401) than in nonusers ( n = 160), a difference driven by women consuming >400 μg FA/d ( P ≤ 0.004). 5-Methyl-THF was 19% lower ( P < 0.001) and UMFA was 126% higher ( P < 0.001) in supplement users than in nonusers. Women who consumed >400 μg FA/d had proportionally lower 5-methyl-THF and higher UMFA than did women who consumed ≤400 μg FA/d. Conclusions: FA-supplement use was associated with modestly higher breast-milk total folate. Detectable breast-milk UMFA was nearly ubiquitous, including in women who did not consume an FA supplement. Breast-milk UMFA was proportionally higher than 5-methyl-THF in women who consumed >400 μg FA/d, thereby suggesting that higher doses exceed the physiologic capacity to metabolize FA and result in the preferential uptake of FA in breast milk. Therefore, FA-supplement doses >400 μg may not be warranted, especially in populations for whom FA fortification is mandatory. © 2017 American Society for Nutrition.

The Redox-Active Chromium Phthalocyanine System: Isolation of Five Oxidation States from Pc4- CrI to Pc2- CrIII.

PubMed

Zhou, Wen; Thompson, John R; Leznoff, Clifford C; Leznoff, Daniel B

2017-02-16

The preparation and structural characterization of a series of chromium phthalocyanine complexes with multiple metal and ring oxidation states were achieved using PcCr II (1) (Pc=phthalocyanine) or PcCr II (THF) 2 (1⋅THF 2 ) as starting materials. The reaction of soluble 1⋅THF 2 with Br 2 or I 2 gave the PcCr III halide complexes PcCrX(THF) (X=I/I 3 , Br; 3, 4, respectively). Treatment of 1 with 0.5 equivalent of PhIO or air generated the dinuclear [PcCr(THF)] 2 (μ-O) (5), whereas the addition of one equivalent of AgSbF 6 to 1 resulted in oxidation to THF-solvated octahedral [PcCr III (THF) 2 ]SbF 6 (6). The reduction of 1 with three sequential equivalents of KEt 3 BH resulted in the isolation of [K(DME) 4 ][Pc 3- Cr II ] (7), [K(DME) 4 ] 2 [Pc 4- Cr II ] (8) and [K 6 (DME) 4 ][Pc 4- Cr I ] 2 (9), respectively. The reduced products are deep purple in colour, with visible absorption maxima between 500-580 nm. The ring-reduced complexes 7 and 8 are monomeric, whereas 9 is a 1D chain of dinuclear [PcCr] 2 units with intercalated K + cations and supported by Cr-Cr interactions of 2.988(2) Å. Addition of four equivalents of KC 8 resulted in the demetallated product PcK 2 (DME) 4 (10), which has a 1D chain structure. The isolation and structural characterization of new PcCr complexes spanning five oxidation states, including rare examples of crystalline reduced Pc-ring species emphasizes the broad redox activity and stability of phthalocyanine-based complexes. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

A Tetrahydrofolate-Dependent Methyltransferase Catalyzing the Demethylation of Dicamba in Sphingomonas sp. Strain Ndbn-20

PubMed Central

Yao, Li; Yu, Lin-Lu; Zhang, Jun-Jie; Xie, Xiang-Ting; Tao, Qing; Yan, Xin; Hong, Qing; Qiu, Ji-Guo

2016-01-01

ABSTRACT Sphingomonas sp. strain Ndbn-20 degrades and utilizes the herbicide dicamba as its sole carbon and energy source. In the present study, a tetrahydrofolate (THF)-dependent dicamba methyltransferase gene, dmt, was cloned from the strain, and three other genes, metF, dhc, and purU, which are involved in THF metabolism, were found to be located downstream of dmt. A transcriptional study revealed that the four genes constituted one transcriptional unit that was constitutively transcribed. Lysates of cells grown with glucose or dicamba exhibited almost the same activities, which further suggested that the dmt gene is constitutively expressed in the strain. Dmt shared 46% and 45% identities with the methyltransferases DesA and LigM from Sphingomonas paucimobilis SYK-6, respectively. The purified Dmt catalyzed the transfer of methyl from dicamba to THF to form the herbicidally inactive metabolite 3,6-dichlorosalicylic acid (DCSA) and 5-methyl-THF. The activity of Dmt was inhibited by 5-methyl-THF but not by DCSA. The introduction of a codon-optimized dmt gene into Arabidopsis thaliana enhanced resistance against dicamba. In conclusion, this study identified a THF-dependent dicamba methyltransferase, Dmt, with potential applications for the genetic engineering of dicamba-resistant crops. IMPORTANCE Dicamba is a very important herbicide that is widely used to control more than 200 types of broadleaf weeds and is a suitable target herbicide for the engineering of herbicide-resistant transgenic crops. A study of the mechanism of dicamba metabolism by soil microorganisms will benefit studies of its dissipation, transformation, and migration in the environment. This study identified a THF-dependent methyltransferase, Dmt, capable of catalyzing dicamba demethylation in Sphingomonas sp. Ndbn-20, and a preliminary study of its enzymatic characteristics was performed. Introduction of a codon-optimized dmt gene into Arabidopsis thaliana enhanced resistance against dicamba, suggesting that the dmt gene has potential applications for the genetic engineering of herbicide-resistant crops. PMID:27422839

Second generation measurement of the electric dipole moment of the electron using trapped ThF+ ions

NASA Astrophysics Data System (ADS)

Ng, Kia Boon; Zhou, Yan; Gresh, Daniel; Cairncross, William; Grau, Matthew; Ni, Yiqi; Ye, Jun; Cornell, Eric

2016-05-01

ThF+ has been chosen as the candidate for a second generation measurement of the electric dipole moment of the electron (eEDM). Compared to the current HfF+ eEDM experiment, ThF+ has several advantages: (i) the eEDM-sensitive state (3Δ1) is the ground state, which facilitates a long coherence time; (ii) its effective electric field (38 GV/cm) is 50% larger than that of HfF+, which promises a direct increase of the eEDM sensitivity; and (iii) the ionization energy of neutral ThF is lower than its dissociation energy, which introduces greater flexibility in rotational state-selective photoionization via core-nonpenetrating Rydberg states. Here, we present progress of our experimental setup, preliminary spectroscopic data of multi-photon ionization, and discussions of new features in ion trapping, state preparation and population readout.

In Situ Observation of Directed Nanoparticle Aggregation During the Synthesis of Ordered Nanoporous Metal in Soft Templates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parent, Lucas R.; Robinson, David B.; Cappillino, Patrick J.

2014-02-11

The prevalent approach to developing new nanomaterials is a trial and error process of iteratively altering synthesis procedures and then characterizing the resulting nanostructures. This is fundamentally limited in that the growth processes that occur during synthesis can only be inferred from the final synthetic structure. Directly observing real-time nanomaterial growth provides unprecedented insight into the relationship between synthesis conditions and product evolution, and facilitates a mechanistic approach to nanomaterial development. Here we use in situ liquid stage scanning transmission electron microscopy to observe the growth of mesoporous palladium in a solvated block copolymer (BCP) template under various synthesis conditions,more » and ultimately determine a refined synthesis procedure that yields ordered pores. We find that at low organic solvent (tetrahydrofuran, THF) content, the BCP assembles into a rigid, cylindrical micelle array with a high degree of short-range order, but poor long-range order. Upon slowing the THF evaporation rate using a solvent-vapor anneal step, the long-range order is greatly improved. The electron beam induces nucleation of small particles in the aqueous phase around the micelles. The small particles then flocculate and grow into denser structures that surround the micelles, forming an ordered mesoporous structure. The microscope observations revealed that template disorder can be addressed prior to reaction, and is not invariably induced by the growth process itself, allowing us to more quickly optimize the synthetic method. This work was conducted in the William R. Wiley Environmental Molecular Sciences Laboratory (EMSL), a national scientific user facility sponsored by DOE’s Office of Biological and Environmental Research and located at Pacific Northwest National Laboratory. The Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy under contract DE-AC05-76RL01830. This research was funded in part by: the Presidential Early Career Award for Scientist and Engineers for I.A., the University of California Academic Senate and the University of California Laboratory fee research grant, the Laboratory-Directed Research and Development program at Sandia National Laboratories, and the Chemical Imaging Initiative at Pacific Northwest National Laboratory. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.« less

Charge-separated and molecular heterobimetallic rare earth-rare earth and alkaline earth-rare earth aryloxo complexes featuring intramolecular metal-pi-arene interactions.

PubMed

Deacon, Glen B; Junk, Peter C; Moxey, Graeme J; Ruhlandt-Senge, Karin; St Prix, Courtney; Zuniga, Maria F

2009-01-01

Treatment of a rare earth metal (Ln) and a potential divalent rare earth metal (Ln') or an alkaline earth metal (Ae) with 2,6-diphenylphenol (HOdpp) at elevated temperatures (200-250 degrees C) afforded heterobimetallic aryloxo complexes, which were structurally characterised. A charge-separated species [(Ln'/Ae)(2)(Odpp)(3)][Ln(Odpp)(4)] was obtained for a range of metals, demonstrating the similarities between the chemistry of the divalent rare earth metals and the alkaline earth metals. The [(Ln'/Ae)(2)(Odpp)(3)](+) cation in the heterobimetallic structures is unusual in that it consists solely of bridging aryloxide ligands. A molecular heterobimetallic species [AeEu(Odpp)(4)] (Ae = Ca, Sr, Ba) was obtained by treating an alkaline earth metal and Eu metal with HOdpp at elevated temperatures. Similarly, [BaSr(Odpp)(4)] was prepared by treating Ba metal and Sr metal with HOdpp. Treatment of [Ba(2)(Odpp)(4)] with [Mg(Odpp)(2)(thf)(2)] in toluene afforded [Ba(2)(Odpp)(3)][Mg(Odpp)(3)(thf)]. Analogous solution-based syntheses were not possible for [(Ln'/Ae)(2)(Odpp)(3)][Ln(Odpp)(4)] complexes, for which the free-metal route was essential. As a result of the absence of additional donor ligands, the crystal structures of the heterobimetallic complexes feature extensive pi-Ph-metal interactions involving the pendant phenyl groups of the Odpp ligands, thus enabling the large electropositive metal atoms to attain coordination saturation. The charge-separated heterobimetallic species were purified by extraction with toluene/thf mixtures at ambient temperature (Ba-containing compounds) or by extraction with toluene under pressure above the boiling point of the solvent (other products). In donor solvents, heterobimetallic complexes other than those containing barium were found to fragment into homometallic species.

Trapping of Li(+) Ions by [ThFn](4-n) Clusters Leading to Oscillating Maxwell-Stefan Diffusivity in the Molten Salt LiF-ThF4.

PubMed

Chakraborty, Brahmananda; Kidwai, Sharif; Ramaniah, Lavanya M

2016-08-18

A molten salt mixture of lithium fluoride and thorium fluoride (LiF-ThF4) serves as a fuel as well as a coolant in the most sophisticated molten salt reactor (MSR). Here, we report for the first time dynamic correlations, Onsager coefficients, Maxwell-Stefan (MS) diffusivities, and the concentration dependence of density and enthalpy of the molten salt mixture LiF-ThF4 at 1200 K in the composition range of 2-45% ThF4 and also at eutectic composition in the temperature range of 1123-1600 K using Green-Kubo formalism and equilibrium molecular dynamics simulations. We have observed an interesting oscillating pattern for the MS diffusivity for the cation-cation pair, in which ĐLi-Th oscillates between positive and negative values with the amplitude of the oscillation reducing as the system becomes rich in ThF4. Through the velocity autocorrelation function, vibrational density of states, radial distribution function analysis, and structural snapshots, we establish an interplay between the local structure and multicomponent dynamics and predict that formation of negatively charged [ThFn](4-n) clusters at a higher ThF4 mole % makes positively charged Li(+) ions oscillate between different clusters, with their range of motion reducing as the number of [ThFn](4-n) clusters increases, and finally Li(+) ions almost get trapped at a higher ThF4% when the electrostatic force on Li(+) exerted by various surrounding clusters gets balanced. Although reports on variations of density and enthalpy with temperature exist in the literature, for the first time we report variations of the density and enthalpy of LiF-ThF4 with the concentration of ThF4 (mole %) and fit them with the square root function of ThF4 concentration, which will be very useful for experimentalists to obtain data over a range of concentrations from fitting the formula for design purposes. The formation of [ThFn](4-n) clusters and the reduction in the diffusivity of the ions at a higher ThF4% may limit the percentage of ThF4 that can be used in the MSR to optimize the neutron economy.

Aldehydes and ketones form intermediate π complexes with the Gilman reagent, Me2CuLi, at low temperatures in tetrahydrofuran.

PubMed

Bertz, Steven H; Hardin, Richard A; Ogle, Craig A

2013-07-03

Typical aldehydes and ketones form π complexes with Me2CuLi at low temperatures in tetrahydrofuran. They range in stability from fleeting intermediates at -100 °C to entities that persist up to -20 °C. Three subsequent reaction pathways have been identified.

Trends and variability of the atmosphere–ocean turbulent heat flux in the extratropical Southern Hemisphere

PubMed Central

Herman, Agnieszka

2015-01-01

Ocean–atmosphere interactions are complex and extend over a wide range of temporal and spatial scales. Among the key components of these interactions is the ocean–atmosphere (latent and sensible) turbulent heat flux (THF). Here, based on daily optimally-interpolated data from the extratropical Southern Hemisphere (south of 30°S) from a period 1985–2013, we analyze short-term variability and trends in THF and variables influencing it. It is shown that, in spite of climate-change-related positive trends in surface wind speeds over large parts of the Southern Ocean, the range of the THF variability has been decreasing due to decreasing air–water temperature and humidity differences. Occurrence frequency of very large heat flux events decreased accordingly. Remarkably, spectral analysis of the THF data reveals, in certain regions, robust periodicity at frequencies 0.03–0.04 day−1, corresponding exactly to frequencies of the baroclinic annular mode (BAM). Finally, it is shown that the THF is correlated with the position of the major fronts in sections of the Antarctic Circumpolar Current where the fronts are not constrained by the bottom topography and can adjust their position to the atmospheric and oceanic forcing, suggesting differential response of various sections of the Southern Ocean to the changing atmospheric forcing. PMID:26449323

Development of a lateral flow dipstick immunoassay for evaluation of folate levels in maize.

PubMed

Liang, Qiuju; Yi, Chen; Jiang, Ling; Tan, Guiyu; Zhang, Chunyi; Wang, Baomin

2017-09-01

Folates (vitamin B9) are essential for all organisms as cofactors for one-carbon metabolism. However, measurement of folates is technically complicated and time-consuming. In this study, we developed a dipstick immunoassay using a folate-specific monoclonal antibody (mAb), allowing rapid and low-cost detection of folates. The indicator range of the dipstick for 5-formylterahydrofolate (5-CHO-THF), 5-methyltetrahydrofolate (5-CH 3 -THF) and their polyglutamyl forms was 100-200 ng mL -1 ; moreover, no cross-reactivity was observed with tetrahydrofolate (THF) or 5,10-methenyltetrahydrofolate (5,10-CH=THF) at 500 ng mL -1 , or with the folate precursors pterin-6-COOH, p-aminobenzoate (pABA), and L-glutamate, or with the folate analogues methotrexate and 10-formyltetrahydrofolate (10-CHO-THF) at up to 1000 ng mL -1 . The dipstick immunoassay was tested in maize seeds; the results classified the seeds into those with low, moderate, and high levels of folates, and were in agreement with those of liquid chromatography-mass spectrometry. Thus, we conclude that the dipstick assay will provide a versatile tool to facilitate large-scale screening of maize rich in folates. Graphical Abstract The dipstick based immunoassay for analyzing folate level in maize.

Environmental analysis of the life cycle emissions of 2-methyl tetrahydrofuran solvent manufactured from renewable resources.

PubMed

Slater, C Stewart; Savelski, Mariano J; Hitchcock, David; Cavanagh, Eduardo J

2016-01-01

An environmental analysis has been conducted to determine the cradle to gate life cycle emissions to manufacture the green solvent, 2-methyl tetrahydrofuran. The solvent is considered a greener chemical since it can be manufactured from renewable resources with a lower life cycle footprint. Analyses have been performed using different methods to show greenness in both its production and industrial use. This solvent can potentially be substituted for other ether and chlorinated solvents commonly used in organometallic and biphasic reactions steps in pharmaceutical and fine chemical syntheses. The 2-methyl tetrahydrofuran made from renewable agricultural by-products is marketed by Penn A Kem under the name ecoMeTHF™. The starting material, 2-furfuraldehyde (furfural), is produced from corn cob waste by converting the available pentosans by acid hydrolysis. An evaluation of each step in the process was necessary to determine the overall life cycle and specific CO2 emissions for each raw material/intermediate produced. Allocation of credits for CO2 from the incineration of solvents made from renewable feedstocks significantly reduced the overall carbon footprint. Using this approach, the overall life cycle emissions for production of 1 kg of ecoMeTHF™ were determined to be 0.191 kg, including 0.150 kg of CO2. Life cycle emissions generated from raw material manufacture represents the majority of the overall environmental impact. Our evaluation shows that using 2-methyl tetrahydrofuran in an industrial scenario results in a 97% reduction in emissions, when compared to typically used solvents such as tetrahydrofuran, made through a conventional chemical route.

Tryptophan 80 and leucine 143 are critical for the hydride transfer step of thymidylate synthase by controlling active site access.

PubMed

Fritz, Timothy A; Liu, Lu; Finer-Moore, Janet S; Stroud, Robert M

2002-06-04

Mutant forms of thymidylate synthase (TS) with substitutions at the conserved active site residue, Trp 80, are deficient in the hydride transfer step of the TS reaction. These mutants produce a beta-mercaptoethanol (beta-ME) adduct of the 2'-deoxyuridine-5'-monophosphate (dUMP) exocyclic methylene intermediate. Trp 80 has been proposed to assist hydride transfer by stabilizing a 5,6,7,8-tetrahydrofolate (THF) radical cation intermediate [Barrett, J. E., Lucero, C. M., and Schultz, P. G. (1999) J. Am. Chem. Soc. 121, 7965-7966.] formed after THF changes its binding from the cofactor pocket to a putative alternate site. To understand the molecular basis of hydride transfer deficiency in a mutant in which Trp 80 was changed to Gly, we determined the X-ray structures of this mutant Escherichia coli TS complexed with dUMP and the folate analogue 10-propargyl-5,8-dideazafolate (CB3717) and of the wild-type enzyme complexed with dUMP and THF. The mutant enzyme has a cavity in the active site continuous with bulk solvent. This cavity, sealed from bulk solvent in wild-type TS by Leu 143, would allow nucleophilic attack of beta-ME on the dUMP C5 exocyclic methylene. The structure of the wild-type enzyme/dUMP/THF complex shows that THF is bound in the cofactor binding pocket and is well positioned to transfer hydride to the dUMP exocyclic methylene. Together, these results suggest that THF does not reorient during hydride transfer and indicate that the role of Trp 80 may be to orient Leu 143 to shield the active site from bulk solvent and to optimally position the cofactor for hydride transfer.

Do Mitochondria Limit Hot Fish Hearts? Understanding the Role of Mitochondrial Function with Heat Stress in Notolabrus celidotus

PubMed Central

Iftikar, Fathima I.; Hickey, Anthony J. R.

2013-01-01

Hearts are the first organs to fail in animals exposed to heat stress. Predictions of climate change mediated increases in ocean temperatures suggest that the ectothermic heart may place tight constraints on the diversity and distribution of marine species with cardiovascular systems. For many such species, their upper temperature limits (Tmax) and respective heart failure (HF) temperature (THF) are only a few degrees from current environmental temperatures. While the ectothermic cardiovascular system acts as an “ecological thermometer,” the exact mechanism that mediates HF remains unresolved. We propose that heat-stressed cardiac mitochondria drive HF. Using a common New Zealand fish, Notolabrus celidotus, we determined the THF (27.5°C). Haemoglobin oxygen saturation appeared to be unaltered in the blood surrounding and within heat stressed hearts. Using high resolution respirometry coupled to fluorimeters, we explored temperature-mediated changes in respiration, ROS and ATP production, and overlaid these changes with THF. Even at saturating oxygen levels several mitochondrial components were compromised before THF. Importantly, the capacity to efficiently produce ATP in the heart is limited at 25°C, and this is prior to the acute THF for N. celidotus. Membrane leakiness increased significantly at 25°C, as did cytochrome c release and permeability to NADH. Maximal flux rates and the capacity for the electron transport system to uncouple were also altered at 25°C. These data indicate that mitochondrial membrane integrity is lost, depressing ATP synthesis capacity and promoting cytochrome c release, prior to THF. Mitochondria can mediate HF in heat stressed hearts in fish and play a significant role in thermal stress tolerance, and perhaps limit species distributions by contributing to HF. PMID:23724026

Do mitochondria limit hot fish hearts? Understanding the role of mitochondrial function with heat stress in Notolabrus celidotus.

PubMed

Iftikar, Fathima I; Hickey, Anthony J R

2013-01-01

Hearts are the first organs to fail in animals exposed to heat stress. Predictions of climate change mediated increases in ocean temperatures suggest that the ectothermic heart may place tight constraints on the diversity and distribution of marine species with cardiovascular systems. For many such species, their upper temperature limits (Tmax) and respective heart failure (HF) temperature (T(HF)) are only a few degrees from current environmental temperatures. While the ectothermic cardiovascular system acts as an "ecological thermometer," the exact mechanism that mediates HF remains unresolved. We propose that heat-stressed cardiac mitochondria drive HF. Using a common New Zealand fish, Notolabrus celidotus, we determined the THF (27.5°C). Haemoglobin oxygen saturation appeared to be unaltered in the blood surrounding and within heat stressed hearts. Using high resolution respirometry coupled to fluorimeters, we explored temperature-mediated changes in respiration, ROS and ATP production, and overlaid these changes with T(HF). Even at saturating oxygen levels several mitochondrial components were compromised before T(HF). Importantly, the capacity to efficiently produce ATP in the heart is limited at 25°C, and this is prior to the acute T(HF) for N. celidotus. Membrane leakiness increased significantly at 25°C, as did cytochrome c release and permeability to NADH. Maximal flux rates and the capacity for the electron transport system to uncouple were also altered at 25°C. These data indicate that mitochondrial membrane integrity is lost, depressing ATP synthesis capacity and promoting cytochrome c release, prior to T(HF). Mitochondria can mediate HF in heat stressed hearts in fish and play a significant role in thermal stress tolerance, and perhaps limit species distributions by contributing to HF.

Four-Wavelength Lidar Evaluation of Particle Characteristics and Aerosol Densities

DTIC Science & Technology

1985-06-01

34 Cure2: 11.4% with/witlhot 0.0 OAS Own 3: 25.9% PONameter .0s _ uve :1 %omu-lmlto x -, 0 2 0.01 Tagt 199% ---- Target solution Curve 1: 11.8% Bt-fit...propagation paths. 2. (U) MULTUVELZNGTI LMIAR SYSTIM (U) The multiwavelength lidar systmn is installed within a 6-meter long van to facilitate opera- ti"ms...the, lidar receivers fog application to the Smoke Week VI/SNOW-TWO exparimenta. New extended-range logarithmic amlif jets were ýý -& led on thfý 0.53

Theoretical and experimental quantification of doubly and singly differential cross sections for electron-induced ionization of isolated tetrahydrofuran molecules

DOE PAGES

Champion, Christophe; Quinto, Michele A.; Bug, Marion U.; ...

2014-07-29

Electron-induced ionization of the commonly used surrogate of the DNA sugar-phosphate backbone, namely, the tetrahydrofuran molecule, is here theoretically described within the 1 st Born approximation by means of quantum-mechanical approach. Comparisons between theory and recent experiments are reported in terms of doubly and singly differential cross sections.

Studies on the acaricidal mechanism of the active components from neem (Azadirachta indica) oil against Sarcoptes scabiei var. cuniculi.

PubMed

Chen, Zhen-zhen; Deng, Yun-xia; Yin, Zhong-qiong; Wei, Qin; Li, Mei; Jia, Ren-yong; Xu, Jiao; Li, Li; Song, Xu; Liang, Xiao-xia; Shu, Gang; He, Chang-liang; Gu, Xiao-bin; Lv, Cheng; Yin, Lizi

2014-08-29

Octadecanoic acid-3,4-tetrahydrofuran diester, isolated from neem (Azadirachta indica) oil, exhibited potent acaricidal activity against Sarcoptes scabiei var. cuniculi. In this paper, the acaricidal mechanism of octadecanoic acid-3,4-tetrahydrofuran diester against Sarcoptes scabiei var. cuniculi was evaluated based on pathologic histology and enzyme activities. The results showed that after compound treatment for 24h at a concentration of 20mg/mL, the lesions of mites were prominent under transmission electron microscopy. The lesions consisted of the lysis of dermis cell membranes and cell nuclear membranes, mitochondrial morphological abnormalities, the drop of spinal disorders, and mitochondrial vacuolization. The activity of superoxide dismutase (SOD), peroxidase (POD), glutathione-s-transferases (GSTs), and Ca(2+)-ATPase of mites significantly changed after treatment with octadecanoic acid-3,4-tetrahydrofuran diester compared with the control group. The activities of SOD, POD, and Ca(2+)-ATPase were significantly suppressed, whereas that of GSTs was activated. These results indicated that the mechanism of the acaricidal activity of octadecanoic acid-3,4-tetrahydrofuran diester was mainly achieved through interference with the energy metabolism of mites, thus resulting in insect death. Copyright © 2014 Elsevier B.V. All rights reserved.

Star-shaped PHB-PLA block copolymers: immortal polymerization with dinuclear indium catalysts.

PubMed

Yu, I; Ebrahimi, T; Hatzikiriakos, S G; Mehrkhodavandi, P

2015-08-28

The first example of a one-component precursor to star-shaped polyesters, and its utilization in the synthesis of previously unknown star-shaped poly(hydroxybutyrate)-poly(lactic acid) block copolymers, is reported. A series of such mono- and bis-benzyl alkoxy-bridged complexes were synthesized, fully characterized, and their solvent dependent solution structures and reactivity were examined. These complexes were highly active catalysts for the controlled polymerization of β-butyrolactone to form poly(hydroxybutyrate) at room temperature. Solution studies indicate that a mononuclear propagating species formed in THF and that the dimer-monomer equilibrium affects the rates of BBL polymerization. In the presence of linear and branched alcohols, these complexes catalyze well-controlled immortal polymerization and copolymerization of β-butyrolactone and lactide.

Synthesis, structure, and reactivity of N-benzoyl iminophosphoranes ortho lithiated at the benzoyl group.

PubMed

Aguilar, David; Fernández, Ignacio; Cuesta, Luciano; Yañez-Rodríguez, Víctor; Soler, Tatiana; Navarro, Rafael; Urriolabeitia, Esteban P; López Ortiz, Fernando

2010-10-01

Ortho lithiation of N-benzamido-P,P,P-triaryliminophosphoranes through deprotonation with alkyllithium bases was achieved with ortho-C═O and ortho-P═N chemoselectivity. However, the synthetic scope of these processes was rather limited. Ortho-lithiated N-benzamido-P,P,P-triphenyliminophosphorane 8 was efficiently prepared via lithium/halogen exchange of the corresponding ortho-brominated precursor with s-BuLi in THF at -90 °C. The reaction of 8 with a variety of electrophiles provides an easy and mild method for the regioselective synthesis of ortho-modified iminophosphoranes via C-C (alkylation and hydroxyalkylation) and C-X (X = I, Si, P, Sn, and Hg) bond-forming reactions. NMR characterization of 8 in THF solution showed that 8 exists as an equilibrium mixture of one monomer and two dimers. The Li atoms of these species become members of five-membered rings through chelation by the ortho-metalated carbon and the carbonyl oxygen. The dimers differ in the relative orientation of the two chelates with respect to the plane defined by the C(2)Li(2) core. The equilibrium between all species is established by splitting the dimers into monomers and subsequent recombination with formation of a different dimer.

Syntheses and structures of alkaline earth metal bis(diphenylamides).

PubMed

Gärtner, Martin; Fischer, Reinald; Langer, Jens; Görls, Helmar; Walther, Dirk; Westerhausen, Matthias

2007-06-11

Various preparative procedures are employed in order to synthesize alkaline earth metal bis(diphenylamides) such as (i) metalation of HNPh2 with the alkaline earth metal M, (ii) metalation of HNPh2 with MPh2, (iii) metathesis reaction of MI2 with KNPh2, (iv) metalation of HNPh2 with PhMI in THF, and (v) metathesis reaction of PhMI with KNPh2 followed by a dismutation reaction yielding MPh2 and M(NPh2)2. The magnesium compounds [(diox)MgPh2]infinity (1) and (thf)2Mg(NPh2)2 (2) show tetracoordinate metal atoms, whereas in (dme)2Ca(NPh2)2 (3), (thf)4Sr(NPh2)2 (4), and (thf)4Ba(NPh2)2 (5) the metals are 6-fold coordinated. Additional agostic interactions between an ipso-carbon of one of the phenyl groups of the amide ligand and the alkaline earth metal atom lead to unsymmetric coordination of the NPh2 anions with two strongly different M-N-C angles in 3-5.

Validation and application of a high-performance liquid chromatography-tandem mass spectrometric method for simultaneous quantification of lopinavir and ritonavir in human plasma using semi-automated 96-well liquid-liquid extraction.

PubMed

Wang, Perry G; Wei, Jack S; Kim, Grace; Chang, Min; El-Shourbagy, Tawakol

2006-10-20

Kaletra is an important antiretroviral drug, which has been developed by Abbott Laboratories. It is composed of lopinavir (low-pin-a-veer) and ritonavir (ri-toe-na-veer). Both have been proved to be human immunodeficiency virus (HIV) protease inhibitors and have substantially reduced the morbidity and mortality associated with HIV-1 infection. We have developed and validated an assay, using liquid chromatography coupled with atmospheric pressure chemical ionization tandem mass spectrometry (LC/MS/MS), for the routine quantification of lopinavir and ritonavir in human plasma, in which lopinavir and ritonavir can be simultaneously analyzed with high throughput. The sample preparation consisted of liquid-liquid extraction with a mixture of hexane: ethyl acetate (1:1, v/v), using 100 microL of plasma. Chromatographic separation was performed on a Waters Symmetry C(18) column (150 mm x 3.9 mm, particle size 5 microm) with reverse-phase isocratic using mobile phase of 70:30 (v/v) acetonitrile: 2 mM ammonium acetate aqueous solution containing 0.01% formic acid (v/v) at a flow rate of 1.0 mL/min. A Waters symmetry C(18) guard column (20 mm x 3.9 mm, particle size 5 microm) was connected prior to the analytical column, and a guard column back wash was performed to reduce the analytical column contamination using a mixture of tetrahydrofuran (THF), methanol and water (45:45:10, v/v/v). The analytical run was 4 min. The use of a 96-well plate autosampler allowed a batch size up to 73 study samples. A triple-quadrupole mass spectrometer was operated in a positive ion mode and multiple reaction monitoring (MRM) was used for drug quantification. The method was validated over the concentration ranges of 19-5,300 ng/mL for lopinavir and 11-3,100 ng/mL for ritonavir. A-86093 was used as an internal standard (I.S.). The relative standard deviation (RSD) were <6% for both lopinavir and ritonavir. Mean accuracies were between the designed limits (+/-15%). The robust and rapid LC/MS/MS assay has been successfully applied for routine assay to support bioavailability, bioequivalence, and pharmacokinetics studies.

Influence of 5,10-methylenetetrahydrofolate reductase polymorphism on whole-blood folate concentrations measured by LC-MS/MS, microbiologic assay, and bio-rad radioassay.

PubMed

Fazili, Zia; Pfeiffer, Christine M; Zhang, Mindy; Jain, Ram B; Koontz, Deborah

2008-01-01

The 5,10-methylenetetrahydrofolate reductase (NADPH) (MTHFR) C677T polymorphism may affect whole-blood folate pattern measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and total folate measured by LC-MS/MS, microbiologic assay, and Bio-Rad radioassay (BR). We analyzed 171 whole blood hemolysates from 2 blood banks for folate pattern and total folate concentrations using these 3 methods and determined MTHFR genotype. The median (range) total folate concentration by LC-MS/MS was higher in the US set [378 (228-820) nmol/L; n = 96] than in the European set [250 (122-582) nmol/L; n = 75]. The whole-blood folate pattern [median (range)] was similar for individuals with C/C (n = 73) and C/T (n = 66) genotype: 88% (71%-91%) and 86% (50%-91%), respectively, for 5-methyltetrahydrofolic acid (5CH(3)THF) vs 12% (9%-29%) and 14% (9%-51%) for forms other than 5-methyltetrahydrofolic acid (non-5CH(3)THF). Individuals with T/T (n = 32) genotype had 58% (22%-87%) 5CH(3)THF vs 42% (13%-78%) non-5CH(3)THF. Compared with microbiologic assay results, LC-MS/MS (r = 0.94) and BR (r = 0.87) results were significantly lower (-10% and -45%, respectively); however, these differences were concentration dependent and also genotype dependent for the BR assay (-48% for C/C+C/T and -31% for T/T). The microbiologic assay completely recovered [mean (SD)] folates added to a whole blood hemolysate, except for tetrahydrofolic acid (THF) [46.4% (8.1%)]. The BR assay under-recovered 5CH(3)THF [51% (4.1%)] and 5-formyltetrahydrofolic acid [18% (0.1%)], and over-recovered THF [152% (19%)]. MTHFR C677T polymorphism influences the folate pattern in whole blood. The agreement between total folate by LC-MS/MS and microbiologic assay, independent of the MTHFR genotype, allows the use of one regression equation. Because BR results are genotype dependent, different regression equations should be used.

Two-Coordinate Magnesium(I) Dimers Stabilized by Super Bulky Amido Ligands.

PubMed

Boutland, Aaron J; Dange, Deepak; Stasch, Andreas; Maron, Laurent; Jones, Cameron

2016-08-01

A variety of very bulky amido magnesium iodide complexes, LMgI(solvent)0/1 and [LMg(μ-I)(solvent)0/1 ]2 (L=-N(Ar)(SiR3 ); Ar=C6 H2 {C(H)Ph2 }2 R'-2,6,4; R=Me, Pr(i) , Ph, or OBu(t) ; R'=Pr(i) or Me) have been prepared by three synthetic routes. Structurally characterized examples of these materials include the first unsolvated amido magnesium halide complexes, such as [LMg(μ-I)]2 (R=Me, R'=Pr(i) ). Reductions of several such complexes with KC8 in the absence of coordinating solvents have afforded the first two-coordinate magnesium(I) dimers, LMg-MgL (R=Me, Pr(i) or Ph; R'=Pr(i) , or Me), in low to good yields. Reductions of two of the precursor complexes in the presence of THF have given the related THF adduct complexes, L(THF)Mg-Mg(THF)L (R=Me; R'=Pr(i) ) and LMg-Mg(THF)L (R=Pr(i) ; R'=Me) in trace yields. The X-ray crystal structures of all magnesium(I) complexes were obtained. DFT calculations on the unsolvated examples reveal their Mg-Mg bonds to be covalent and of high s-character, while Ph⋅⋅⋅Mg bonding interactions in the compounds were found to be weak at best. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Toward Rotational State-Selective Photoionization of ThF+ Ions

NASA Astrophysics Data System (ADS)

Zhou, Yan; Ng, Kia Boon; Gresh, Dan; Cairncross, William; Grau, Matt; Ni, Yiqi; Cornell, Eric; Ye, Jun

2016-06-01

ThF+ has been chosen to replace HfF+ for a second-generation measurement of the electric dipole moment of the electron (eEDM). Compared to the currently running HfF+ eEDM experiment, ThF+ has several advantages: (i) the eEDM-sensitive state (3Δ1) is the ground state, which facilitates a long coherence time [1]; (ii) its effective electric field (35 GV/cm) is 50% larger than that of HfF+, which promises a direct increase of the eEDM sensitivity [2]; and (iii) the ionization energy of neutral ThF is lower than its dissociation energy, which introduces greater flexibility in rotational state-selective photoionization via core-nonpenetrating Rydberg states [3]. In this talk, we first present our strategy of preparing and utilizing core-nonpenetrating Rydberg states for rotational state-selective ionization. Then, we report spectroscopic data of laser-induced fluorescence of neutral ThF, which provides critical information for multi-photon ionization spectroscopy. [1] D. N. Gresh, K. C. Cossel, Y. Zhou, J. Ye, E. A. Cornell, Journal of Molecular Spectroscopy, 319 (2016), 1-9 [2] M. Denis, M. S. Nørby, H. J. A. Jensen, A. S. P. Gomes, M. K. Nayak, S. Knecht, T. Fleig, New Journal of Physics, 17 (2015) 043005. [3] Z. J. Jakubek, R. W. Field, Journal of Molecular Spectroscopy 205 (2001) 197-220.

Exploration on effects of 15 nm SiO2 filler on miscibility, thermal stability and ionic conductivity of PMMA/ENR 50 electrolytes

NASA Astrophysics Data System (ADS)

Zamri, S. F. M.; Latif, F. A.; Ali, A. M. M.; Ibrahim, R.; Azuan, S. I. H. M.; Kamaluddin, N.; Hadip, F.

2017-02-01

The effects of silicon dioxide (SiO2) (15 nm) filler on miscibility, thermal stability and ionic conductivity of polymethyl methacrylate/50% epoxidized narural rubber (PMMA/ENR 50) electrolytes were successfully explored. Samples were prepared by solvent casting method with tetrahydrofuran (THF) as solvent and doped with lithium tetrafluoroborate (LiBF4). Fourier transform infrared spectroscopy (FTIR) confirmed the present of hydrogen bond between PMMA and ENR 50. However, the hydrogen bond was reduced when SiO2 was added. Differential scanning calorimeter (DSC) analysis shows that PMMA/ENR 50 blends exhibit two glass transition temperatures (Tgs) recorded at -35 and 89 °C corresponding to the Tg of ENR 50 rich phase (Tg1) and PMMA rich phase (Tg2), respectively. However, the two Tgs almost merging and reduced when SiO2 was added. Tg1 was found increases as SiO2 weight percent increased. Thermogravimetric analysis (TGA) revealed that thermal degradation temperatures (Tds) of SiO2 filled PMMA/ENR 50 was similar as PMMA/ENR 50. Interestingly, thermal degradation temperatures of the loss of impurities (Td1) and thermal degradation temperatures of PMMA side chain (Td2) were increased when SiO2 was added. Meanwhile thermal degradation temperatures of main PMMA and ENR 50 main chain (Td3) was decreased as SiO2 was added. There was no significant change in Td1, Td2 and Td3 as SiO2 weight percent was varied. Electrochemical impedence spectroscopy (EIS) analysis shows that room temperature ionic conductivity of SiO2 filled PMMA/ENR 50 electrolytes were higher compaed PMMA/ENR 50 electrolyte with two conductivity maxima.

Oxygen sensitive polymeric nanocapsules for optical dissolved oxygen sensors

NASA Astrophysics Data System (ADS)

Sun, Zhijuan; Cai, Chenxin; Guo, Fei; Ye, Changhuai; Luo, Yingwu; Ye, Shuming; Luo, Jianchao; Zhu, Fan; Jiang, Chunyue

2018-04-01

Immobilization of the oxygen-sensitive probes (OSPs) in the host matrix greatly impacts the performance and long-term usage of the optical dissolved oxygen (DO) sensors. In this work, fluorescent dyes, as the OSPs, were encapsulated with a crosslinked fluorinated polymer shell by interfacial confined reversible addition fragmentation chain transfer miniemulsion polymerization to fabricate oxygen sensitive polymeric nanocapsules (NCs). The location of fluorescent dyes and the fluorescent properties of the NCs were fully characterized by fourier transform infrared spectrometer, x-ray photoelectron spectrometer and fluorescent spectrum. Dye-encapsulated capacity can be precisely tuned from 0 to 1.3 wt% without self-quenching of the fluorescent dye. The crosslinked fluorinated polymer shell is not only extremely high gas permeability, but also prevents the fluorescent dyes from leakage in aqueous as well as in various organic solvents, such as ethanol, acetone and tetrahydrofuran (THF). An optical DO sensor based on the oxygen sensitive NCs was fabricated, showing high sensitivity, short response time, full reversibility, and long-term operational stability of online monitoring DO. The sensitivity of the optical DO sensor is 7.02 (the ratio of the response value in fully deoxygenated and saturated oxygenated water) in the range 0.96-14.16 mg l-1 and the response time is about 14.3 s. The sensor’s work curve was fit well using the modified Stern-Volmer equation by two-site model, and its response values are hardly affected by pH ranging from 2 to 12 and keep constant during continuous measurement for 3 months. It is believed that the oxygen sensitive polymeric NCs-based optical DO sensor could be particularly useful in long-term online DO monitoring in both aqueous and organic solvent systems.

Synthesis and biological activities of turkesterone 11α-acyl derivatives

PubMed Central

Dinan, Laurence; Bourne, Pauline; Whiting, Pensri; Tsitsekli, Ada; Saatov, Ziyadilla; Dhadialla, Tarlochan S.; Hormann, Robert E.; Lafont, René; Coll, Josep

2003-01-01

Turkesterone is a phytoecdysteroid possessing an 11α-hydroxyl group. It is an analogue of the insect steroid hormone 20-hydroxyecdysone. Previous ecdysteroid QSAR and molecular modelling studies predicted that the cavity of the ligand binding domain of the ecdysteroid receptor would possess space in the vicinity of C-11/C-12 of the ecdysteroid. We report the regioselective synthesis of a series of turkesterone 11α-acyl derivatives in order to explore this possibility. The structures of the analogues have been unambiguously determined by spectroscopic means (NMR and low-resolution mass spectrometry). Purity was verified by HPLC. Biological activities have been determined in Drosophila melanogaster BII cell-based bioassay for ecdysteroid agonists and in an in vitro radioligand-displacement assay using bacterially-expressed D. melanogaster EcR/USP receptor proteins. The 11α-acyl derivatives do retain a significant amount of biological activity relative to the parent ecdysteroid. Further, although activity initially drops with the extension of the acyl chain length (C2 to C4), it then increases (C6 to C10), before decreasing again (C14 and C20). The implications of these findings for the interaction of ecdysteroids with the ecdysteroid receptor and potential applications in the generation of affinity-labelled and fluorescently-tagged ecdysteroids are discussed. Abbreviation: CoMFA comparative molecular field analysis DCM dichloromethane DMF dimethylformamide DMP 2,2-dimethoxypropane 4D-QSAR 4-dimensional quantitative structure-activity relationship EcR ecdysteroid receptor EcRE ecdysteroid response element HPLC high-performance liquid chromatography LBD ligand-binding domain NMR nuclear magnetic resonance ponA ponasterone A QSAR quantitative structure-activity relationship RXR retinoid X receptor SAR structure-activity relationship SPE solid-phase extraction THF tetrahydrofuran TLC thin-layer chromatography p-TsOH para-toluenesulphonic acid USP ultraspiracle UV-VIS ultraviolet-visible PMID:15841223

PS-b-PMMA/PLA blends for nanoporous templates with hierarchical and tunable pore size

NASA Astrophysics Data System (ADS)

Nguyen, Thi-Hoa; Vayer, Marylène; Sinturel, Christophe

2018-01-01

Blends of poly(styrene)-block-poly(methyl methacrylate) (PS-b-PMMA) and poly(lactide) (PLA) were deposited in the form of thin films on the surface of modified silicon wafers and exposed to tetrahydrofuran (THF) vapor annealing. It was shown that in specific experimental conditions, a core-shell morphology consisting in cylinders with a PMMA shell and a PLA core, within a continuous matrix of PS, was formed. In this case, PLA naturally segregated in the core of the PMMA cylinders, minimizing the PS/PLA interaction, which constitutes the most incompatible pair (the interaction strength between the various components was confirmed in thin films of the corresponding polymer blends). Compared to other block copolymer/homopolymer blends described in the literature, this system exhibits unexpected high increase of the characteristic lengths of the system (center-to-center distance and diameter). This was attributed to a partial solubilization of the PLA in the PMMA corona (the two polymers are highly compatible), inducing an enhanced level of PS and PLA stretching caused by the strong repulsion between these two polymers. The selective extraction of the PLA yielded to porous domains with small dimensions (6 ± 2.5 nm), reaching the performances that are currently attained in highly incompatible block polymers with low molecular weight. Further PMMA removal revealed a second porosity level, with higher pores diameter and center-to-center distance compared to the neat PS-b-PMMA system. This work highlights how PS-b-PMMA, that currently represents one of the industrial standards nanoporous template precursors, can be modified in an easy and costless approach using PLA homopolymer addition.

Novel imino thioether complexes of platinum(II): synthesis, structural investigation, and biological activity.

PubMed

Sgarbossa, Paolo; Sbovata, Silvia Mazzega; Bertani, Roberta; Mozzon, Mirto; Benetollo, Franco; Marzano, Cristina; Gandin, Valentina; Michelin, Rino A

2013-05-20

The reactions of the nitrile complexes cis- and trans-[PtCl2(NCR)2] (R = Me, Et, CH2Ph, Ph) with an excess of ethanethiol, EtSH, in the presence of a catalytic amount of n-BuLi in tetrahydrofuran (THF), afforded in good yield the bis-imino thioether derivatives cis-[PtCl2{E-N(H)═C(SEt)R}2] (R = Me (1), Et (2), CH2Ph (3), Ph (4)) and trans-[PtCl2{E-N(H)═C(SEt)R}2] (R = Me (5), Et (6), CH2Ph (7), Ph (8)). The imino thioether ligands assumed the E configuration corresponding to a cis addition of the thiol to the nitrile triple bond. The spectroscopic properties of these complexes have been reported along with the molecular structures of 1, 2, and 7 as established by X-ray crystallography which indicated that these compounds exhibit square-planar coordination geometry around the platinum center. Four N-H···Cl intermolecular contacts (N-H···Cl ca. 2.5-2.7 Å) between each chlorine atom and the N-H proton of the imino thioether ligand gave rise to "dimers" Pt2Cl4L4 (L = imino thioether) formed by two PtCl2L2 units. The cytotoxic properties of these new platinum(II) complexes were evaluated against various human cancer cell lines. Among all derivatives, trans-[PtCl2{E-N(H)═C(SEt)CH2Ph}2] showed the greatest in vitro cytotoxic activity being able to decrease cancer cell viability roughly 3-fold more effectively than cisplatin.

Carbon and nitrogen co-doped bowl-like Au/TiO2 nanostructures with tunable size for enhanced visible-light-driven photocatalysis

NASA Astrophysics Data System (ADS)

Li, Yayuan; Cao, Shubo; Zhang, Ang; Zhang, Chen; Qu, Ting; Zhao, Yongbin; Chen, Aihua

2018-07-01

It is of great importance to extend the UV response of anatase TiO2 into the visible light range for the practical applications. Here, a facile rout to carbon and nitrogen co-doped, Au loaded bowl-like TiO2 nanostructures with tunable size are proposed by using self-assembled polystyrene-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymer (BCP) spherical micelles as templates. Amphiphilic PS-b-P4VP self-assembles to form PS@P4VP core-shell spherical micelles with P4VP as the out layer in an evaporable mixed solvents of ethanol/tetrahydrofuran (THF). The size of uniform PS@P4VP spherical micelles can be precisely tuned in the range of a few nm to several hundred nm by controlling the molecular composition of the BCPs. Bowl-like TiO2 nanostructures with a replicate size loaded with highly dispersed Au nanoparticles (NPs) of ∼5 nm in diameter are fabricated from these spherical micelles because of strong complex ability of pyridine groups. PS-b-P4VP provides carbon and nitrogen sources to dope the resulting samples simultaneously. The special carbon and nitrogen co-doped bowl-like Au/TiO2 nanostructures exhibit much higher photocatalytic activity in the photodegradation of rhodamine B (RhB) compared to Au/P25 under visible light irradiation. Furthermore, the photocatalytic activity is significantly influenced by the BCP molecular composition due to different surface area and loading capacity of the resulting samples. This study provides a facile way to synthesize multi-element doped hollow or bowl-like nanoparticles with tunable size in the nanometer range which have potential application at photocatalysis, oxygen reduction reaction, etc.

Advanced, Non-Toxic, Anti-Corrosion, Anti-Fouling and Foul-Release Coatings Based on Covalently Attached Monolayers, Multilayers and Polymers

DTIC Science & Technology

2007-08-08

McCarthy Polymer Science and Engineering Department, University of Massachusetts, Amherst, Massachusetts 01003 Electrophilic aromatic substitution reactions...with a fluorinated silane reagent. Reduction of the amide groups with borane-THF (BH 3-THF) complex leads to a 69% conversion of surface amides to the

Preliminary Study on LiF4-ThF4-PuF4 Utilization as Fuel Salt of miniFUJI Molten Salt Reactor

NASA Astrophysics Data System (ADS)

Waris, Abdul; Aji, Indarta K.; Pramuditya, Syeilendra; Widayani; Irwanto, Dwi

2016-08-01

miniFUJI reactor is molten salt reactor (MSR) which is one type of the Generation IV nuclear energy systems. The original miniFUJI reactor design uses LiF-BeF2-ThF4-233UF4 as a fuel salt. In the present study, the use of LiF4-ThF4-PuF4 as fuel salt instead of LiF-BeF2-ThF4-UF4 will be discussed. The neutronics cell calculation has been performed by using PIJ (collision probability method code) routine of SRAC 2006 code, with the nuclear data library is JENDL-4.0. The results reveal that the reactor can attain the criticality condition with the plutonium concentration in the fuel salt is equal to 9.16% or more. The conversion ratio diminishes with the enlarging of plutonium concentration in the fuel. The neutron spectrum of miniFUJI MSR with plutonium fuel becomes harder compared to that of the 233U fuel.

Triblock copolyampholytes from 5-(N,N-dimethyl amino)isoprene styrene, and methacrylic acid: Synthesis and solution properties

NASA Astrophysics Data System (ADS)

Bieringer, R.; Abetz, V.; Müller, A. H. E.

ABC triblock copolymers of the type poly[5-(N,N-dimethyl amino)isoprene]-block-polystyrene-block-poly(tert-butyl methacrylate) (AiST) were synthesized and hydrolyzed to yield poly[5-(N,N-dimethyl amino)isoprene]-block-polystyrene-block-poly(methacrylic acid) (AiSA) triblock copolyampholytes. Due to a complex solubility behavior the solution properties of these materials had to be investigated in THF/water solvent mixtures. Potentiometric titrations of AiSA triblock copolyampholytes showed two inflection points with the A block being deprotonated prior to the Ai hydrochloride block thus forming a polyzwitterion at the isoelectric point (iep). The aggregation behavior was studied by dynamic light scattering (DLS) and freeze-fracture/transmission electron microscopy (TEM). Large vesicular structures with almost pH-independent radii were observed.

Cuscuta europaea plastid apparatus in various developmental stages: localization of THF1 protein.

PubMed

Švubová, Renáta; Ovečka, Miroslav; Pavlovič, Andrej; Slováková, L'udmila; Blehová, Alžbeta

2013-05-01

It was generally accepted that Cuscuta europaea is mostly adapted to a parasitic lifestyle with no detectable levels of chlorophylls. We found out relatively high level of chlorophylls (Chls a+b) in young developmental stages of dodder. Significant lowering of Chls (a+b) content and increase of carotenoid concentration was typical only for ontogenetically more developed stages. Lower content of photosynthesis-related proteins involved in Chls biosynthesis and in photosystem formation as well as low photochemical activity of PSII indicate that photosynthesis is not the main activity of C. europaea plastids. Previously, it has been shown in other species that the Thylakoid Formation Protein 1 (THF1) is involved in thylakoid membrane differentiation, plant-fungal and plant-bacterial interactions and in sugar signaling with its preferential localization to plastids. Our immunofluorescence localization studies and analyses of haustorial plasma membrane fractions revealed that in addition to plastids, the THF1 protein localizes also to the plasma membrane and plasmodesmata in developing C. europaea haustorium, most abundantly in the digitate cells of the endophyte primordium. These results are supported by western blot analysis, documenting the highest levels of the THF1 protein in "get together" tissues of dodder and tobacco. Based on the fact that photosynthesis is not a typical process in the C. europaea haustorium and on the extra-plastidial localization pattern of the THF1, our data support rather other functions of this protein in the complex relationship between C. europaea and its host.

Synthesis and Spectroscopic Properties of Carbazole-Oxadiazoles.

PubMed

Gündoğdu, Leyla; Şen, Nihan; Hızlıateş, Cevher Gündoğdu; Ergün, Mustafa Yavuz

2017-11-01

Four new carbazole-oxadiazole derivatives (3a-b, 6a-b) were prepared from the reaction of aromatic aldehydes and carbohydrazides which were synthesized from carbazole aldehydes namely 9-hexyl-9H-carbazole-3-carbaldehyde 1 and 4-(9H-carbazole-9-yl)benzaldehyde 4 and acid hydrazides. The structures of the new derivatives were confirmed by 1 H-NMR and FT-IR. The optical properties such as maximum absorption and emission wavelengths (λ; nm), molar extinction coefficients (ε; cm -1 M -1 ), Stoke's shifts (ΔλST; nm) and quantum yields (ϕF), of the carbazole-oxadiazole derivatives were declared in dichloromethane, toluene and tetrahydrofuran solutions.

Enthalpy characteristics of L-proline dissolution in certain water-organic mixtures at 298.15 K

NASA Astrophysics Data System (ADS)

Badelin, V. G.; Smirnov, V. I.

2017-01-01

A thermochemical study of the processes of L-proline dissolution in aqueous solutions of acetonitrile, 1,4-dioxane, acetone, dimethyl sulfoxide, nitromethane and tetrahydrofuran at T = 298.15 K in the range of organic solvent concentrations x2 = 0-0.25 mole fractions is performed. Standard values of the enthalpies of solution and transfer of L-proline from water to mixed solvent, and the enthalpy coefficients of pairwise interactions between L-proline and molecules of organic solvents, are calculated. The effect the composition of a water-organic mixture and the structure of organic solvents have on the enthalpy characteristics of L-proline dissolution and transfer is examined. The effect the energy properties of intermolecular interactions between components of a mixed solvent has on the intermolecular interactions between L-proline and molecules of cosolvent is estimated. The correlation between the enthalpy characteristics of L-proline dissolution and electron-donor properties of organic cosolvent in aqueous solutions is determined.

Thermoluminescence of the Films, Nanocomposites, and Solutions of the Silicon Organic Polymer Poly(di- n-hexyl silane)

NASA Astrophysics Data System (ADS)

Ostapenko, N. I.; Kerita, O. A.; Ostapenko, Yu. V.

2018-03-01

A comparative study of low-temperature thermoluminescence (5-120 K) of silicon organic polymer poly(di-n-hexyl silane) films, nanocomposites (when the polymer is introduced into nanopores of silica MCM-41 and SBA-15 with diameter of pores 2.8 and 10 nm) as well as solutions of polymer in tetrahydrofuran with different concentrations from 10-3 to 10-5 mol/L was carried out. It was shown that it is possible to control the number of charge carrier traps, as well as their energy distribution by changing the diameter of silica nanopores. It is established that maxima and FWHMs of the thermoluminescence curves of nanocomposites significantly depend on the pore diameter of the nanoporous silica. This result agrees with the data obtained in the investigation of polymer solutions. In the nanocomposite with a minimum pore diameter (2.8 nm), the number and depth of the traps as well as dispersion of their energy are significantly reduced compared to their values in the polymer film.

Developing Novel Fluorescent Materials with Near Infrared Emission by Using m-Phenylene

NASA Technical Reports Server (NTRS)

Pang, Yi; Liao, Ling; Meador, Michael A.

2003-01-01

Our research focuses on development of novel p-conjugated polymers with desired emission. In the current study, the structure of a highly green-emitting poly[(m-phenylenevinylene)- alt-( p-phenylenevinylene)] has been modified by increasing the content of p-phenylene to achieve red- and infrared-emission. The polymer is synthesized via Wittig-Horner condensation, which is known to lead to trans-olefin linkage. The polymer is soluble in common organic solvents such as toluene, chloroform and THF. The spectroscopic properties of the polymer in both solution and film states will be discussed in comparison with its model compound.

Effect of Concentration on the Electrochemistry and Speciation of the Magnesium Aluminum Chloride Complex Electrolyte Solution.

PubMed

See, Kimberly A; Liu, Yao-Min; Ha, Yeyoung; Barile, Christopher J; Gewirth, Andrew A

2017-10-18

Magnesium batteries offer an opportunity to use naturally abundant Mg and achieve large volumetric capacities reaching over four times that of conventional Li-based intercalation anodes. High volumetric capacity is enabled by the use of a Mg metal anode in which charge is stored via electrodeposition and stripping processes, however, electrolytes that support efficient Mg electrodeposition and stripping are few and are often prepared from highly reactive compounds. One interesting electrolyte solution that supports Mg deposition and stripping without the use of highly reactive reagents is the magnesium aluminum chloride complex (MACC) electrolyte. The MACC exhibits high Coulombic efficiencies and low deposition overpotentials following an electrolytic conditioning protocol that stabilizes species necessary for such behavior. Here, we discuss the effect of the MgCl 2 and AlCl 3 concentrations on the deposition overpotential, current density, and the conditioning process. Higher concentrations of MACC exhibit enhanced Mg electrodeposition current density and much faster conditioning. An increase in the salt concentrations causes a shift in the complex equilibria involving both cations. The conditioning process is strongly dependent on the concentration suggesting that the electrolyte is activated through a change in speciation of electrolyte complexes and is not simply due to the annihilation of electrolyte impurities. Additionally, the presence of the [Mg 2 (μ-Cl) 3 ·6THF] + in the electrolyte solution is again confirmed through careful analysis of experimental Raman spectra coupled with simulation and direct observation of the complex in sonic spray ionization mass spectrometry. Importantly, we suggest that the ∼210 cm -1 mode commonly observed in the Raman spectra of many Mg electrolytes is indicative of the C 3v symmetric [Mg 2 (μ-Cl) 3 ·6THF] + . The 210 cm -1 mode is present in many electrolytes containing MgCl 2 , so its assignment is of broad interest to the Mg electrolyte community.

Photoinduced electron transfer (PET) versus excimer formation in supramolecular p/n-heterojunctions of perylene bisimide dyes and implications for organic photovoltaics.

PubMed

Nowak-Król, Agnieszka; Fimmel, Benjamin; Son, Minjung; Kim, Dongho; Würthner, Frank

2015-01-01

Foldamer systems comprised of two perylene bisimide (PBI) dyes attached to the conjugated backbones of 1,2-bis(phenylethynyl)benzene and phenylethynyl-bis(phenylene)indane, respectively, were synthesized and investigated with regard to their solvent-dependent properties. UV/Vis absorption and steady-state fluorescence spectra show that both foldamers exist predominantly in a folded H-aggregated state consisting of π-π-stacked PBIs in THF and in more random conformations with weaker excitonic coupling between the PBIs in chloroform. Time-resolved fluorescence spectroscopy and transient absorption spectroscopy reveal entirely different relaxation pathways for the photoexcited molecules in the given solvents, i.e. photoinduced electron transfer leading to charge separated states for the open conformations (in chloroform) and relaxation into excimer states with red-shifted emission for the stacked conformations (in THF). Supported by redox data from cyclic voltammetry and Rehm-Weller analysis we could relate the processes occurring in these solution-phase model systems to the elementary processes in organic solar cells. Accordingly, only if relaxation pathways such as excimer formation are strictly avoided in molecular semiconductor materials, excitons may diffuse over larger distances to the heterojunction interface and produce photocurrent via the formation of electron/hole pairs by photoinduced electron transfer.

Mixed ligand coordination polymers with flexible bis-imidazole linker and angular sulfonyldibenzoate: Crystal structure, photoluminescence and photocatalytic activity

NASA Astrophysics Data System (ADS)

Bisht, Kamal Kumar; Rachuri, Yadagiri; Parmar, Bhavesh; Suresh, Eringathodi

2014-05-01

Four ternary coordination polymers (CPs) namely, {[Ni(SDB)(BITMB)(H2O)]·H2O}n (CP1), {[Cd(SDB)(BITMB) (H2O)]·(THF)(H2O)}n (CP2), {[Zn2(SDB)2(BITMB)]·(THF)2}n (CP3) and {[Co2(SDB)2(BITMB)]·(Dioxane)3}n (CP4) composed of angular dicarboxylate SDB (4,4'-sulfonyldibenzoate) and N-donor BITMB (1,3-bis(imidazol-1-ylmethyl)-2,4,6-trimethyl benzene) have been synthesized by solvothermal reactions and characterized by single crystal X-ray diffraction and other physico-chemical techniques. CP1 possesses one-dimensional ribbon type metal-organic motifs glued together by H-bonds and π⋯π interactions, whereas CP2-CP4, exhibit non-interpenetrated sql networks supported by weak supramolecular interactions. Structural diversity of these CPs can be attributed to the coordination geometry adopted by the metal nodes, versatile coordination modes of SDB and conformational flexibility of BITMB. Solid state luminescence properties of CP1-CP4 were explored. Photocatalytic performance of all CPs for the decomposition of metanil yellow by dilute hydrogen peroxide in the presence of visible light was also investigated. 25-83% dye removal from aqueous solutions in the presence of CP1-CP4 was observed.

Effects of electrolytes on redox potentials through ion pairing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bird, Matthew J.; Iyoda, Tomokazu; Bonura, Nicholas

Here, reduction potentials have been determined for two molecules, benzophenone (BzPh) and perylene (Per), effectively in the complete absence of electrolyte as well as in the presence of three different supporting electrolytes in the moderately polar solvent THF. A description of how this can be so, and qualifications, are described in the discussion section. The primary tool in this work, pulse radiolysis, measures electron transfer (ET) equilibria in solution to obtain differences in redox potentials. Voltammetry measures redox potentials by establishing ET equilibria at electrodes, but electrolytes are needed for current flow. Results here show that without electrolyte the redoxmore » potentials were 100–451 mV more negative than those with 100 mM electrolyte. These changes depended both on the molecule and the electrolyte. In THF the dominant contributor to stabilization of radical anions by electrolyte was ion pairing. An equation was derived to give changes in redox potentials when electrolyte is added in terms of ion pair dissociation constants and activity coefficients. Definite values were determined for energetics, ΔG d°, of ion pairing. Values of ΔG d° for pairs with TBA + give some doubt that it is a “weakly-coordinating cation.” Computations with DFT methods were moderately successful at describing the ion paring energies.« less

Effects of electrolytes on redox potentials through ion pairing

DOE PAGES

Bird, Matthew J.; Iyoda, Tomokazu; Bonura, Nicholas; ...

2017-09-21

Here, reduction potentials have been determined for two molecules, benzophenone (BzPh) and perylene (Per), effectively in the complete absence of electrolyte as well as in the presence of three different supporting electrolytes in the moderately polar solvent THF. A description of how this can be so, and qualifications, are described in the discussion section. The primary tool in this work, pulse radiolysis, measures electron transfer (ET) equilibria in solution to obtain differences in redox potentials. Voltammetry measures redox potentials by establishing ET equilibria at electrodes, but electrolytes are needed for current flow. Results here show that without electrolyte the redoxmore » potentials were 100–451 mV more negative than those with 100 mM electrolyte. These changes depended both on the molecule and the electrolyte. In THF the dominant contributor to stabilization of radical anions by electrolyte was ion pairing. An equation was derived to give changes in redox potentials when electrolyte is added in terms of ion pair dissociation constants and activity coefficients. Definite values were determined for energetics, ΔG d°, of ion pairing. Values of ΔG d° for pairs with TBA + give some doubt that it is a “weakly-coordinating cation.” Computations with DFT methods were moderately successful at describing the ion paring energies.« less

U(IV) chalcogenolates synthesized via oxidation of uranium metal by dichalcogenides.

PubMed

Gaunt, Andrew J; Scott, Brian L; Neu, Mary P

2006-09-04

Treatment of uranium metal with dichalcogenides in the presence of a catalytic amount of iodine in pyridine affords molecular U(IV) chalcogenolates that do not require stabilizing ancillary ligands. Oxidation of U(0) by PhEEPh yields monomeric seven-coordinate U(EPh)4(py)3 (E = S(1), Se(2)). The dimeric eight-coordinate complexes [U(EPh)2(mu2-EPh)2(CH3CN)2]2 (E = S(3), Se(4)) are obtained by crystallization from solutions of 1 and 2 dissolved in acetonitrile. Oxidation of U(0) by pySSpy and crystallization from thf yields nine-coordinate U(Spy)4(thf) (5). Incorporation of elemental selenium into the oxidation of U(0) by PhSeSePh results in the isolation of [U(py)2(SePh)(mu3-Se)(mu2-SePh)]4.4py (6), a tetrameric cluster in which each U(IV) ion is eight-coordinate and the U4Se4 core forms a distorted cube. The compounds were analyzed spectroscopically and the single-crystal X-ray structures of 1 and 3-6 were determined. The isolation of 1-6 represents six new examples of actinide chalcogenolates and allows insight into the nature of "hard" actinide ion-"soft" chalcogen donor interactions.

Understanding the directed ortho lithiation of (R)-Ph₂P(=NCO₂Me)NHCH(Me)Ph. NMR spectroscopic and computational study of the structure of the N-lithiated species.

PubMed

Casimiro, M; García-López, J; Iglesias, M J; López-Ortiz, F

2014-10-14

A multinuclear magnetic resonance ((1)H, (7)Li, (13)C, (15)N, (31)P) and DFT computational study at the M06-2X(SMD,THF)/6-311+G(d,p)//B3LYP/6-31G(d) level of the structure of a N-lithiated phosphinimidic amide (R)-Ph2P(=NCO2Me)NHCH(Me)Ph 13 has been performed. In THF solution it exists as an equilibrium mixture of monomers and dimers. The monomers consist of a six-membered ring formed by coordination of the lithium atom with the deprotonated nitrogen and the oxygen atom of the carbonyl group. This coordination mode is in contrast to the standard N,N-chelation observed in N-lithiated N,N'-bis(trimethylsilyl)phosphinimidic amides. The calculations showed that the metallacycle adopts a twist-boat conformation and that the lithium atom is in a tetrahedral environment involving O,N-chelation by the ligand and coordination to two/one THF molecules in the monomer/dimer. Dimerization takes place through O-Li bridges. For all species two series of isomers have been identified, which originated by restricted rotation of the methoxy group and ring inversion. The twist-boat conformational interconversion seems to be operating for explaining the pattern of signals observed in the (7)Li and (31)P NMR spectra. The structure found for the most stable dimer is analogous to the molecular structure reported for a related C(α)-lithiated phosphazene 20. The structural study revealed that the chiral side-arm of the N-lithiated species is oriented to the outer face of the pro-S P-phenyl ring, which shows one ortho-proton very close to the nitrogen atom of the carbamate moiety. In this conformation, proton abstraction by a base is highly favoured, in agreement with the experimental results.

Nylon surface modification: 2. Nylon-supported composite films.

PubMed

Herrera-Alonso, Margarita; McCarthy, Thomas J; Jia, Xinqiao

2006-02-14

We have developed techniques for the introduction of reactive functional groups to nylon surfaces via site-specific reactions targeting at the naturally abundant amide repeating units on the surface. In this report, we describe the fabrication of nylon-supported composite surfaces using the most efficient modification methods we have developed. N-Alkylation with (3-glycidoxypropyl)triethoxysilane (GPTES) in the presence of potassium tert-butoxide (t-BuOK) leads to surfaces with silica-like reactivity. Subsequent chemical vapor deposition using tetrachlorosilane (SiCl4) and water results in composite films with a thin layer of silica, which was made hydrophobic by reaction with a fluorinated silane reagent. Reduction of the amide groups with borane-THF (BH3-THF) complex leads to a 69% conversion of surface amides to the corresponding secondary amine groups. Alginate was chosen as the model polyelectrolyte for the introduction of a hydrated surface layer. Because of the strong electrostatic interaction between alginate and the amine-enriched nylon surfaces, the adsorption is fast and concentration-independent (within the concentration range studied). The polysaccharide coats the surface homogeneously, without the formation of large aggregates. The amine surfaces obtained by reduction with BH3-THF ((BH3-THF)nylon-NH) and by alkylation with 2-bromoethylamine hydrobromide (BEA-HBr, (EBA-HBr)nylon-NH2) were also used to study gold deposition through electroless plating. Immobilization of a negatively charged metal complex (AuCl4(-)) was achieved through electrostatic interaction. Gold particles disperse preferentially in the bulk of (EBA-HBr)nylon-NH2 films, while they remain confined to the outer surface layer of (BH3-THF)nylon-NH films.

[Construction and characterization of a selective membrane electrode for tenoxicam determination].

PubMed

Murăraşu, Andreea Elena; Mândrescu, Mariana; Spac, A F; Dorneanu, V

2010-01-01

This paper describes the construction and characterization of a selective membrane electrode which can be used for determination of tenoxicam. The electroactive compound is a precipitate obtained in 2 N hydrocloric acid solution containing tenoxicam in which a solution of iodine is added. The membrane is made by mixing the electroactive compound with polyethylene using tetrahydrofurane as solvent. The solution is evaporated in order to obtain a thick membrane, which is attached at one end of a PVC tube and is fixed with the same polymeric solution. In this tube an internal Ag/AgCl reference electrode is inserted. The assembly is filled with an internal solution containing tenoxicam. The electrode was characterized (electrode slope, selectivity, optimal pH range, response time, life time). The developed method was validated. The method showed a good liniarity in the range of 10(-6)-10(-1) M (the correlation coefficient r = 0.9999). The detection limit (LD) was 7.347 x 10(-7) M and the quantification limit (LQ) was 1.017 x 10(-6) M. There were established the precision (RSD = 1.79%) and the accuracy (mean recovery is 100.17%) The experimental results demonstrated a good sensibility.

Facile synthesis of bis(dichalcogenophosphinate)s and a remarkable [Li8(OH)6]2+ polyhedron.

PubMed

Davies, Robert P; Martinelli, M Giovanna; Patel, Laura; White, Andrew J P

2010-05-17

The synthesis and characterization of three lithium complexes of novel bis(dichalcogenophosphinate) ligands are reported: (PhP(S)(2)CH(2)CH(2)P(S)(2)Ph)Li(2)(THF)(4) (2), (PhP(Se)(2)CH(2)CH(2)P(Se)(2)Ph)Li(2)(THF)(4).(PhP(Se)(2)CH(2)CH(2)P(Se)(2)Ph)Li(2)(THF)(6) (3), and [PhP(Te)(2)CH(2)CH(2)P(Te)(2)Ph][Li(8)(OH)(6)(THF)(8)] (4). The synthetic route to these complexes proceeds via the insertion reaction of elemental chalcogens into the phosphorus-lithium bonds of 1,2-dilithio-1,2-di(phenylphosphine)ethylene (1). X-ray analysis of 2 revealed isobidentate coordination of the lithiums by the dithiophosphinate groups. In contrast, the diselenophosphinate groups in 3 coordinate the lithium centers in both isobidentate and monodentate modes, and the ditellurophosphinate groups in 4 form non-coordinate separate ion pairs. The countercation in 4 is shown to be a unique [Li(8)(OH)(6)](2+) rhombic dodecahedral polyhedron, putatively formed from the capping of a hexameric [Li(OH)](6) aggregate with lithium cations on its open faces.

Solvent effects on the adsorption and self-organization of Mn12 on Au(111).

PubMed

Pineider, Francesco; Mannini, Matteo; Sessoli, Roberta; Caneschi, Andrea; Barreca, Davide; Armelao, Lidia; Cornia, Andrea; Tondello, Eugenio; Gatteschi, Dante

2007-11-06

A sulfur-containing single molecule magnet, [Mn12O12(O2CC6H4SCH3)16(H2O)4], was assembled from solution on a Au(111) surface affording both submonolayer and monolayer coverages. The adsorbate morphology and the degree of coverage were inspected by scanning tunneling microscopy (STM), while X-ray photoelectron spectroscopy (XPS) allowed the determination of the chemical nature of the adsorbate on a qualitative and quantitative basis. The properties of the adsorbates were found to be strongly dependent on the solvent used to dissolve the magnetic complex. In particular, systems prepared from tetrahydrofuran solutions gave arrays of isolated and partially ordered clusters on the gold substrate, while samples prepared from dichloromethane exhibited a homogeneous monolayer coverage of the whole Au(111) surface. These findings are relevant to the optimization of magnetic addressing of single molecule magnets on surfaces.

Optical signatures of bulk and solutions of KC{sub 8} and KC{sub 24}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tristant, Damien; LPCNO, UMR-5215 CNRS, INSA, Université Fédérale de Toulouse-Midi-Pyrénées, Université de Toulouse, 135 Avenue de Rangueil, 31077 Toulouse; Wang, Yu

2015-07-28

We first performed an analysis of the shape of the Raman features of potassium-intercalated graphite at stage 1 (KC{sub 8} GIC) and 2 (KC{sub 24} GIC), respectively. By varying the excitation energy from ultraviolet to infrared, we observed a sign change of the Fano coupling factor below and above the optical transition related to the shift of the Fermi level which was determined from first principle calculations. This behavior is explained by a sign change in the Raman scattering amplitude of the electronic continuum. The GICs were then dissolved in two different solvents (N-Methyl-2-pyrrolidone and tetrahydrofuran), and the absorbance ofmore » the graphenide solutions obtained was measured in the UV range. Two peaks were observed which correspond to the maximum of the computed imaginary part of the optical index.« less

Tuning of the ionization potential of paddlewheel diruthenium(II, II) complexes with fluorine atoms on the benzoate ligands.

PubMed

Miyasaka, Hitoshi; Motokawa, Natsuko; Atsuumi, Ryo; Kamo, Hiromichi; Asai, Yuichiro; Yamashita, Masahiro

2011-01-21

A series of paddlewheel diruthenium(ii, ii) complexes with various fluorine-substituted benzoate ligands were isolated as THF adducts and structurally characterized: [Ru(2)(F(x)PhCO(2))(4)(THF)(2)] (F(x)PhCO(2)(-) = o-fluorobenzoate, o-F; m-fluorobenzoate, m-F; p-fluorobenzoate, p-F; 2,6-difluorobenzoate, 2,6-F(2); 3,4-difluorobenzoate, 3,4-F(2); 3,5-difluorobenzoate, 3,5-F(2); 2,3,4-trifluorobenzoate, 2,3,4-F(3); 2,3,6-trifluorobenzoate, 2,3,6-F(3); 2,4,5-trifluorobenzoate, 2,4,5-F(3); 2,4,6-trifluorobenzoate, 2,4,6-F(3); 3,4,5-trifluorobenzoate, 3,4,5-F(3); 2,3,4,5-tetrafluorobenzoate, 2,3,4,5-F(4); 2,3,5,6-tetrafluorobenzoate, 2,3,5,6-F(4); pentafluorobenzoate, F(5)). By adding fluorine atoms on the benzoate ligands, it was possible to tune the redox potential (E(1/2)) for [Ru(2)(II,II)]/[Ru(2)(II,III)](+) over a wide range of potentials from -40 mV to 350 mV (vs. Ag/Ag(+) in THF). 2,3,6-F(3), 2,3,4,5-F(4), 2,3,5,6-F(4) and F(5) were relatively air-stable compounds even though they are [Ru(2)(II,II)] species. The redox potential in THF was dependent on an electronic effect rather than on a structural (steric) effect of the o-F atoms, although more than one substituent in the m- and p-positions shifted E(1/2) to higher potentials in relation to the general Hammett equation. A quasi-Hammett parameter for an o-F atom (σ(o)) was estimated to be ∼0.2, and a plot of E(1/2)vs. a sum of Hammett parameters including σ(o) was linear. In addition, the HOMO energy levels, which was calculated based on atomic coordinates of solid-state structures, as well as the redox potential were affected by adding F atoms. Nevertheless, a steric contribution stabilizing their static structures in the solid state was present in addition to the electronic effect. On the basis of the electronic effect, the redox potential of these complexes is correlated to the HOMO energy level, and the electronic effect of F atoms is the main factor controlling the ionization potential of the complexes with ligands free from the rotational constraint, i.e. complexes in solution.

A new selective fluorescent sensor for Fe3+ based on a pyrazoline derivative.

PubMed

Hu, Shengli; Zhang, Shushu; Gao, Chan; Xu, Caihua; Gao, Qing

2013-09-01

A new pyrazoline derivative was designed and synthesized. The structure of the pyrazoline was confirmed by single crystal X-ray diffraction and its photophysical properties were studied by absorption and fluorescence spectra. This compound can be used to determine Fe(3+) ion with high selectivity among a series of cations in tetrahydrofuran and even in aqueous tetrahydrofuran. This sensor forms a 1:1 complex with Fe(3+) and displays fluorescent quenching. Copyright © 2013 Elsevier B.V. All rights reserved.

Phosphoserine Phosphatase Is Required for Serine and One-Carbon Unit Synthesis in Hydrogenobacter thermophilus.

PubMed

Kim, Keugtae; Chiba, Yoko; Kobayashi, Azusa; Arai, Hiroyuki; Ishii, Masaharu

2017-11-01

Hydrogenobacter thermophilus is an obligate chemolithoautotrophic bacterium of the phylum Aquificae and is capable of fixing carbon dioxide through the reductive tricarboxylic acid (TCA) cycle. The recent discovery of two novel-type phosphoserine phosphatases (PSPs) in H. thermophilus suggests the presence of a phosphorylated serine biosynthesis pathway; however, the physiological role of these novel-type metal-independent PSPs (iPSPs) in H. thermophilus has not been confirmed. In the present study, a mutant strain with a deletion of pspA , the catalytic subunit of iPSPs, was constructed and characterized. The generated mutant was a serine auxotroph, suggesting that the novel-type PSPs and phosphorylated serine synthesis pathway are essential for serine anabolism in H. thermophilus. As an autotrophic medium supplemented with glycine did not support the growth of the mutant, the reversible enzyme serine hydroxymethyltransferase does not appear to synthesize serine from glycine and may therefore generate glycine and 5,10-CH 2 -tetrahydrofolate (5,10-CH 2 -THF) from serine. This speculation is supported by the lack of glycine cleavage activity, which is needed to generate 5,10-CH 2 -THF, in H. thermophilus Determining the mechanism of 5,10-CH 2 -THF synthesis is important for understanding the fundamental anabolic pathways of organisms, because 5,10-CH 2 -THF is a major one-carbon donor that is used for the synthesis of various essential compounds, including nucleic and amino acids. The findings from the present experiments using a pspA deletion mutant have confirmed the physiological role of iPSPs as serine producers and show that serine is a major donor of one-carbon units in H. thermophilus IMPORTANCE Serine biosynthesis and catabolism pathways are intimately related to the metabolism of 5,10-CH 2 -THF, a one-carbon donor that is utilized for the biosynthesis of various essential compounds. For this reason, determining the mechanism of serine synthesis is important for understanding the fundamental anabolic pathways of microorganisms. In the present study, we experimentally confirmed that a novel phosphoserine phosphatase in the obligate chemolithoautotrophic bacterium Hydrogenobacter thermophilus is essential for serine biosynthesis. This finding indicates that serine is synthesized from an intermediate of gluconeogenesis in H. thermophilus In addition, because glycine cleavage system activity and genes encoding an enzyme capable of producing 5,10-CH 2 -THF were not detected, serine appears to be the major one-carbon donor to tetrahydrofolate (THF) in H. thermophilus . Copyright © 2017 American Society for Microbiology.

Correlation consistent basis sets for actinides. I. The Th and U atoms.

PubMed

Peterson, Kirk A

2015-02-21

New correlation consistent basis sets based on both pseudopotential (PP) and all-electron Douglas-Kroll-Hess (DKH) Hamiltonians have been developed from double- to quadruple-zeta quality for the actinide atoms thorium and uranium. Sets for valence electron correlation (5f6s6p6d), cc - pV nZ - PP and cc - pV nZ - DK3, as well as outer-core correlation (valence + 5s5p5d), cc - pwCV nZ - PP and cc - pwCV nZ - DK3, are reported (n = D, T, Q). The -PP sets are constructed in conjunction with small-core, 60-electron PPs, while the -DK3 sets utilized the 3rd-order Douglas-Kroll-Hess scalar relativistic Hamiltonian. Both series of basis sets show systematic convergence towards the complete basis set limit, both at the Hartree-Fock and correlated levels of theory, making them amenable to standard basis set extrapolation techniques. To assess the utility of the new basis sets, extensive coupled cluster composite thermochemistry calculations of ThFn (n = 2 - 4), ThO2, and UFn (n = 4 - 6) have been carried out. After accurately accounting for valence and outer-core correlation, spin-orbit coupling, and even Lamb shift effects, the final 298 K atomization enthalpies of ThF4, ThF3, ThF2, and ThO2 are all within their experimental uncertainties. Bond dissociation energies of ThF4 and ThF3, as well as UF6 and UF5, were similarly accurate. The derived enthalpies of formation for these species also showed a very satisfactory agreement with experiment, demonstrating that the new basis sets allow for the use of accurate composite schemes just as in molecular systems composed only of lighter atoms. The differences between the PP and DK3 approaches were found to increase with the change in formal oxidation state on the actinide atom, approaching 5-6 kcal/mol for the atomization enthalpies of ThF4 and ThO2. The DKH3 atomization energy of ThO2 was calculated to be smaller than the DKH2 value by ∼1 kcal/mol.

Potential allelopathic azaphilones produced by the endophytic Chaetomium globosum TY1 inhabited in Ginkgo biloba using the one strain-many compounds method.

PubMed

Wang, Dacheng; Zhang, Yamei; Li, Xiang; Pan, Hongyu; Chang, Mengyuan; Zheng, Tianyu; Sun, Jinzhu; Qiu, Daren; Zhang, Mingzhe; Wei, Dongsheng; Qin, Jianchun

2017-03-01

On the basis of the one strain-many compounds strategy, seven azaphilones, including Chaetomugilin A (1), D (2), S (3), I (4), J (5), Q (6) and O (7), were isolated from the endophytic Chaetomium globosum TY1. Their structures were identified by NMR and HRESIMS spectrometry data. All azaphilones were evaluated for plant growth regulation using eight species of herbaceous plant seeds seedling growth bioassay, which showed the plant growth influence of the seedling. Among these compounds tested, Chaetomugilin O (7) with tetrahydrofuran exhibited higher response index and lower IC 50 values than positive control glyphosate, a broad-spectrum systemic herbicide. 1-3 also showed better or similar inhibit activity to glyphosate. The structure-allelopathic activity relationship analysis of these isolated azaphilones indicates that both tetrahydrofuran and tetrahydrofuran combine with lactones ring groups give potent inhibition of seedling growth. Chaetomugilin O and Chaetomugilin A, D, S could be used to develop natural eco-friendly herbicides.

Raman spectrum of bacteriochlorophyll a in the S1 state

NASA Astrophysics Data System (ADS)

Nishizawa, Ei-ichi; Hashimoto, Hideki; Koyama, Yasushi

1991-07-01

The S 1 Raman spectrum of bacteriochlorophyll a is reported for the first time. A one-color experiment using the 351 nm picosecond pulses (duration 50 ps and repetition 1 kHz) for tetrahydrofuran solution detected a transient species, which showed distinct Raman lines at 1567, 1409 and 1320 cm -1 and weak profiles around 1169, 1092, 1051 and 794 cm -1. The other one-color experiment using the 355 nm nanosecond pulses (duration 12 ns and repetition 10 Hz) detected the T 1 species reported previously showing Raman lines at 1578 and 1330 cm -1. Thus, the newly identified transient species, which was pumped and probed within 50 ps, is assigned to S 1.

Modelling of ceramide interactions with porous graphite carbon in non-aqueous liquid chromatography.

PubMed

West, C; Cilpa, G; Gaudin, K; Chaminade, P; Lesellier, E

2005-09-16

Interactions of solutes on porous graphitic carbon (PGC) with non-aqueous mobile phases are studied by the linear solvation energy relationship (LSER). Studies have been carried out with eight binary mixtures composed of a weak solvent (acetonitrile or methanol) and a strong solvent (tetrahydrofuran, n-butanol, CH2Cl2, 1,1,2-trichloro-2,2,1-trifluoroethane). The systematic analysis of a set of test compounds was performed for each solvent mixture in isocratic mode (50:50). The results were compared to those obtained on PGC with hydro-organic liquids and supercritical fluids. They were then correlated with the observed retention behaviour of lipid compounds, more particularly ceramides.

Two-photon absorption resonance in 3-(1,1-dicyanoethenyl)-1-phenyl-4,5-dihydro-1H-pyrazole (DCNP)

NASA Astrophysics Data System (ADS)

Miniewicz, Andrzej; Delysse, Stéphane; Nunzi, Jean-Michel; Kajzar, François

1998-04-01

A two-photon absorption spectrum of 3-(1,1-dicyanoethenyl)-1-phenyl-4,5-dihydro-1H-pyrazole (DCNP) in tetrahydrofuran solution has been studied by the Kerr ellipsometry technique. The spectral shape and amplitude of the imaginary part of the dominant molecular hyperpolarizability term Im( γXXXX) is compared with the relevant linear absorption spectrum within a simple two-level model. Agreement between the measured γXXXX=2.0×10 -48 m 5 V -2 and calculated γXXXX=(1.2-1.5)×10 -48 m 5 V -2 two-photon absorption molecular hyperpolarizabilties in the vicinity of the two-photon resonance transition is satisfactory.

Using logic programming for modeling the one-carbon metabolism network to study the impact of folate deficiency on methylation processes.

PubMed

Gnimpieba, Etienne Z; Eveillard, Damien; Guéant, Jean-Louis; Chango, Abalo

2011-08-01

Dynamical modeling is an accurate tool for describing the dynamic regulation of one-carbon metabolism (1CM) with emphasis on the alteration of DNA methylation and/or dUMP methylation into dTMP. Using logic programming we present a comprehensive and adaptative mathematical model to study the impact of folate deficiency, including folate transport and enzymes activities. 5-Methyltetrahydrofolate (5mTHF) uptake and DNA and dUMP methylation were studied by simulating nutritional 5mTHF deficiency and methylenetetrahydrofolate reductase (MTHFR) gene defects. Both conditions had distinct effects on 1CM metabolite synthesis. Simulating severe 5mTHF deficiency (25% of normal levels) modulated 11 metabolites. However, simulating a severe decrease in MTHFR activity (25% of normal activity) modulated another set of metabolites. Two oscillations of varying amplitude were observed at the steady state for DNA methylation with severe 5mTHF deficiency, and the dUMP/dTMP ratio reached a steady state after 2 h, compared to 2.5 h for 100% 5mTHF. MTHFR activity with 25% of V(max) resulted in an increased methylated DNA pool after half an hour. We observed a deviation earlier in the profile compared to 50% and 100% V(max). For dUMP methylation, the highest level was observed with 25%, suggesting a low rate of dUMP methylation into dTMP with 25% of MTHFR activity. In conclusion, using logic programming we were able to construct the 1CM for analyzing the dynamic system behavior. This model may be used to refine biological interpretations of data or as a tool that can provide new hypotheses for pathogenesis.

GRL-09510, a Unique P2-Crown-Tetrahydrofuranylurethane -Containing HIV-1 Protease Inhibitor, Maintains Its Favorable Antiviral Activity against Highly-Drug-Resistant HIV-1 Variants in vitro

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amano, Masayuki; Miguel Salcedo-Gómez, Pedro; Yedidi, Ravikiran S.

We report that GRL-09510, a novel HIV-1 protease inhibitor (PI) containing a newly-generated P2-crown-tetrahydrofuranylurethane (Crwn-THF), a P2'-methoxybenzene, and a sulfonamide isostere, is highly active against laboratory and primary clinical HIV-1 isolates (EC50: 0.0014–0.0028 μM) with minimal cytotoxicity (CC50: 39.0 μM). Similarly, GRL-09510 efficiently blocked the replication of HIV-1NL4-3 variants, which were capable of propagating at high-concentrations of atazanavir, lopinavir, and amprenavir (APV). GRL-09510 was also potent against multi-drug-resistant clinical HIV-1 variants and HIV-2ROD. Under the selection condition, where HIV-1NL4-3 rapidly acquired significant resistance to APV, an integrase inhibitor raltegravir, and a GRL-09510 congener (GRL-09610), no variants highly resistant against GRL-09510more » emerged over long-term in vitro passage of the virus. Crystallographic analysis demonstrated that the Crwn-THF moiety of GRL-09510 forms strong hydrogen-bond-interactions with HIV-1 protease (PR) active-site amino acids and is bulkier with a larger contact surface, making greater van der Waals contacts with PR than the bis-THF moiety of darunavir. The present data demonstrate that GRL-09510 has favorable features for treating patients infected with wild-type and/or multi-drug-resistant HIV-1 variants, that the newly generated P2-Crwn-THF moiety confers highly desirable anti-HIV-1 potency. The use of the novel Crwn-THF moiety sheds lights in the design of novel PIs.« less

Evaluation of Particle Size Influence on Proximate Composition, Physicochemical, Techno-Functional and Physio-Functional Properties of Flours Obtained from Persimmon (Diospyros kaki Trumb.) Coproducts.

PubMed

Lucas-González, Raquel; Viuda-Martos, Manuel; Pérez-Álvarez, José Ángel; Fernández-López, Juana

2017-03-01

The aim of the work was to study the influence of particle size in the composition, physicochemical, techno-functional and physio-functional properties of two flours obtained from persimmon (Diospyros kaki Trumb. cvs. 'Rojo Brillante' (RBF) and 'Triump' (THF) coproducts. The cultivar (RBF and THF) and particle size significantly affected all parameters under study, although depending on the evaluated property, only one of these effects predominated. Carbohydrates (38.07-46.98 g/100 g) and total dietary fiber (32.07-43.57 g/100 g) were the main components in both flours (RBF and THF). Furthermore, insoluble dietary fiber represented more than 68% of total dietary fiber content. All color properties studied were influenced by cultivar and particle size. For both cultivars, the lower particle size, the higher lightness and hue values. RBF flours showed high values for emulsifying activity (69.33-74.00 mL/mL), while THF presented high values for water holding capacity (WHC: 9.47-12.19 g water/g sample). The bile holding capacity (BHC) and fat/oil binding values were, in general, higher in RBF (19.61-12.19 g bile/g sample and 11.98-9.07, respectively) than THF (16.12-12.40 g bile/g sample and 9.78-7.96, respectively). The effect of particle size was really evident in both WHC and BHC. Due to their dietary fiber content, techno-functional and physio-functional properties, persimmon flours seem to have a good profile to be used as potential functional ingredient.

Morphometry of human terminal and vellus hair follicles.

PubMed

Vogt, Annika; Hadam, Sabrina; Heiderhoff, Marc; Audring, Heike; Lademann, Juergen; Sterry, Wolfram; Blume-Peytavi, Ulrike

2007-11-01

Previous studies suggest that drug delivery systems based on particles can be used to deposit active compounds in hair follicles and to target hair follicle-associated cell populations. The development of application protocols is complicated by the fact that there is no information available on the size and the position of key target structures in the different hair follicle types and their intra- and interindividual variation. Therefore, we performed morphometric measurements on histological sections of human terminal (THF) and vellus hair follicles (VHF) from the scalp and the retroauricular region. With 3864 +/- 605 microm and 580 +/- 84 microm in THF compared to 646 +/- 140 microm and 225 +/- 34 microm in VHF, the total length and the length of the infundibulum differed significantly as determined by paired t-test (P < 0.0001). The same level of significance was observed for the position and the length of the bulge region. The thickness of the epithelial lining was lowest in VHF (45 +/- 14 microm at 100 microm from skin surface) compared to 65 +/- 20 microm at 150 microm in THF, while the thickness of the interfollicular epidermis ranged between 64 +/- 12 microm and 99 +/- 18 microm in VHF-bearing skin and 72 +/- 16 microm and 136 +/- 37 microm in THF-bearing skin. In addition, the diameter of the hair follicle opening was determined at 50 microm intervals from the skin surface. Our data suggest that hair follicle types in defined body regions represent rather homogenous groups and that particle-based drug delivery may be a feasible approach, also in larger numbers of individuals. We provide precise information on the size and the position of key target structures in VHF and THF.

Synthesis, structure, and catalytic activity of novel trinuclear rare-earth metal amido complexes incorporating μ-η5:η1 bonding indolyl and μ3-oxo groups.

PubMed

Yang, Song; Zhu, Xiancui; Zhou, Shuangliu; Wang, Shaowu; Feng, Zhijun; Wei, Yun; Miao, Hui; Guo, Liping; Wang, Fenhua; Zhang, Guangchao; Gu, Xiaoxia; Mu, Xiaolong

2014-02-14

The reactions of different pyrrolyl-functionalized indoles with rare-earth metal(III) amides [(Me3Si)2N]3RE(III)(μ-Cl)Li(THF)3 (RE = Yb, Er, Dy, Eu, Y) produced different kinds of rare-earth metal amido complexes. Reactions of N-((1H-pyrrol-2-yl)methylene)-2-(1H-indol-3-yl)ethanamine with rare-earth metal amides [(Me3Si)2N]3RE(III)(μ-Cl)Li(THF)3 (RE = Yb, Er, Dy, Eu, Y) in toluene or THF at temperatures of 75-80 °C afforded the novel trinuclear rare-earth metal amido complexes incorporating the indolyl ligand in μ-η(5):η(1) bonding modes and a μ3-O group, which is believed to originate from cleavage of the THF ring based on experimental results. Reactions of 2-(1H-indol-3-yl)-N-((1-methyl-1H-pyrrol-2-yl)methylene)ethanamine with rare-earth metal(III) amides [(Me3Si)2N]3RE(III)(μ-Cl)Li(THF)3 (RE = Yb, Dy) produced mononuclear ytterbium and dysprosium amides having the indolyl ligand in an η(1) bonding fashion. The results indicate that substituents not only have an influence on reactivity, but also have an influence on the bonding of the indolyl ligands with metals. The catalytic activities of the novel lanthanide amido complexes for the hydrophosphonylation of both aromatic and aliphatic aldehydes and ketones were explored. The results indicate that these complexes display a high catalytic activity for the C-P bond formation under mild conditions when using low catalyst loadings (0.1 mol% for aldehydes and ketones). Thus, it provides a potential way to prepare α-hydroxy phosphonates.

A Magnesium-Activated Carbon Hybrid Capacitor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yoo, HD; Shterenberg, I; Gofer, Y

2013-12-11

Prototype cells of hybrid capacitor were developed, comprising activated carbon (AC) cloth and magnesium (Mg) foil as the positive and negative electrodes, respectively. The electrolyte solution included ether solvent (TBF) and a magnesium organo-halo-aluminate complex 0.25 M Mg2Cl3+-Ph2AlCl2-. In this solution Mg can be deposited/dissolved reversibly for thousands of cycles with high reversibility (100% cycling efficiency). The main barrier for integrating porous AC electrodes with this electrolyte solution was the saturation of the pores with the large ions in the AC prior to reaching the potential limit. This is due to the existence of bulky Mg and Al based ionicmore » complexes consisting Cl, alkyl or aryl (R), and THF ligands. This problem was resolved by adding 0.5 M of lithium chloride (LiCl), thus introducing smaller ionic species to the solution. This Mg hybrid capacitor system demonstrated a stable cycle performance for many thousands of cycles with a specific capacitance of 90 Fg(-1) for the AC positive electrodes along a potential range of 2.4 V. (C) 2014 The Electrochemical Society. All rights reserved.« less

First X-ray crystal structure and internal reference diffusion-ordered NMR spectroscopy study of the prototypical Posner reagent, MeCu(SPh)Li(THF)3.

PubMed

Bertz, Steven H; Hardin, Richard A; Heavey, Thomas J; Jones, Daniel S; Monroe, T Blake; Murphy, Michael D; Ogle, Craig A; Whaley, Tara N

2013-07-29

Grow slow: The usual direct treatment of MeLi and CuSPh did not yield X-ray quality crystals of MeCu(SPh)Li. An indirect method starting from Me2CuLi⋅LiSPh and chalcone afforded the desired crystals by the slow reaction of the intermediate π-complex (see scheme). This strategy produced the first X-ray crystal structure of a Posner cuprate. A complementary NMR study showed that the contact ion pair was also the main species in solution. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Liquid Crystals of Dendron-like Pt Complexes Processable into Nanofilms

DTIC Science & Technology

2013-05-01

vermicular dendrimers of the phenyleneethynylene type, which resulted be very soluble in non-polar solvents such as CHCl3, THF, toluene. Their chemical... dendrimers of the phenyleneethynylene type, which resulted be very soluble in non-polar solvents such as CHCl3, THF, toluene. Their chemical...2012 and 2013, to synthesize the same above dendron like oligomers but without the platinum atom in order to give, for example, the dendrimers

The inverse podant [Li3(NBut)3S)]+ stabilises a single ethylene oxide OCH=CH2 anion as a high- and low-temperature polymorph of [(thf)3Li3(OCH=CH2)(NBut)3S)].

PubMed

Walfort, B; Pandey, S K; Stalke, D

2001-09-07

A single ethylene oxide anion derived from the ether cleavage reaction of thf with ButLi is stabilised by the inverse podant [Li3(NBut)3S)]+ to give a high- and a low-temperature polymorph with a considerable difference in conformation and packing.

Complexes of a dianionic bis(diphosphinomethanide) with lithium, sodium, potassium and zirconium. Effect of substitution on the Schlenk dimerisation of vinylidene phosphines.

PubMed

Izod, Keith; McFarlane, William; Tyson, Brent V; Clegg, William; Harrington, Ross W

2004-12-07

The vinylidene phosphine (Pr(n)(2)P)(2)C=CH(2) (1) undergoes Schlenk dimerisation on treatment with an excess of any of the alkali metals Li, Na or K to give the butane-1,4-diide complexes [(L)M{(Pr(n)(2)P)(2)CCH(2)}](2)[(L)M =(THF)(2)Li (6), (THF)(3)Na (7b), (DME)(2)K (8b)], after recrystallisation. Whereas the reaction between the analogous phenyl derivative (Ph(2)P)(2)C=CH(2) and K results in cleavage of a P-C bond, 1 reacts smoothly with K to give 8, with no evidence for P-C cleavage. Compound 6 is an excellent ligand transfer reagent: metathesis reactions between either 6 or its phenyl analogue [(THF)(2)Li{(Ph(2)P)(2)CCH(2)}](2) (2) and two equivalents of Cp(2)ZrCl(2) in THF give the corresponding dinuclear zirconocene derivatives [Cp(2)Zr(Cl){(R(2)P)(2)CCH(2)}](2) in good yields [R = Ph (11), Pr(n)(12)]. Compounds 6, 7b, 8b, 11 and 12 have been characterised by multi-element NMR spectroscopy and, where possible, by elemental analysis; compounds 6, 7b, 11 and 12 have additionally been characterised by X-ray crystallography.

Organosolv-Water Cosolvent Phase Separation on Cellulose and its Influence on the Physical Deconstruction of Cellulose: A Molecular Dynamics Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, Micholas Dean; Cheng, Xiaolin; Petridis, Loukas

Deconstruction of cellulose is crucial for the chemical conversion of lignocellulose into fuel/bioproduct precursors. Recently, a water-organosolv cosolvent system (THF-water) has been shown to both phase-separate on cellulose surfaces and partially deconstruct Avicel (cellulose) in the absence of acid. Here we employ molecular dynamics simulations to determine whether other common water-organosolv cosolvent systems (acetone, ethanol, and γ-valerolactone) exhibit phase separation at cellulose surface and whether this alters a purely physical cellulose dissociation pathway. Despite finding varied degrees of phase-separation of organosolv on cellulose surfaces, physical dissociation is not enhanced. Interestingly, however, the total amount the median water-cellulose contact lifetimes increasesmore » for the cosolvent systems in the order of THF > acetone > ethanol > γ-valerolactone. Together our results indicate two points: a purely physical process for deconstruction of cellulose is unlikely for these cosolvents, and in THF-water, unlike γ-valerolactone- (and some concentrations of acetone and ethanol) water cosolvents, a significant fraction of surface water is slowed. As a result, this slowing may be of importance in enhancing chemical deconstruction of cellulose, as it permits an increase in potential THF-water-cellulose reactions, even while the amount of water near cellulose is decreased.« less

Studies on mimicry of naturally occurring annonaceous acetogenins: non-THF analogues leading to remarkable selective cytotoxicity against human tumor cells.

PubMed

Zeng, Bu-Bing; Wu, Yikang; Jiang, Sheng; Yu, Qian; Yao, Zhu-Jun; Liu, Zhong-Hai; Li, Hong-Yan; Li, Yan; Chen, Xiao-Guang; Wu, Yu-Lin

2003-01-03

A class of structurally simplified analogues of the naturally occurring annonaceous acetogenins were developed, amongst which some non-THF analogues showed remarkable cytotoxicities against tumor cell lines, as well as good selectivity between human tumor cells and normal cells. The synthetic routes were significantly shortened because of the removal of the chiral centers bearing the THF rings on the natural templates. This simplification also provides access to the parallel synthesis of these mimics by a combinatorial strategy. The remaining stereogenic centers at the positions alpha to the ethereal links were introduced by the Chiron approach from the easily accessible chiral building blocks 6a and/or 6b, made in turn from L-ascorbic acid or D-mannitol, while the one in the butenolide segment was taken from L-lactate. All four diastereomeric non-THF analogues 2a-2d showed remarkable activity against the HCT-8 cell line, and better differentiation was found when testing against the HT-29 cell line. It was also discovered that both the butenolide and ethylene glycol subunits play essential roles in the cytotoxicities against tumor cell lines, while the 10-substituted hydroxy group and the absolute configuration of methyl group at the butenolide moiety are less important for their activity.

Insight into Oxide-Bridged Heterobimetallic Al/Zr Olefin Polymerization Catalysts.

PubMed

Boulho, Cédric; Zijlstra, Harmen S; Hofmann, Alexander; Budzelaar, Peter H M; Harder, Sjoerd

2016-11-21

Reaction of (TBBP)AlMe⋅THF with [Cp* 2 Zr(Me)OH] gave [(TBBP)Al(THF)-O-Zr(Me)Cp* 2 ] (TBBP=3,3',5,5'-tetra-tBu-2,2'-biphenolato). Reaction of [DIPPnacnacAl(Me)-O-Zr(Me)Cp 2 ] with [PhMe 2 NH] + [B(C 6 F 5 ) 4 ] - gave a cationic Al/Zr complex that could be structurally characterized as its THF adduct [(DIPPnacnac)Al(Me)-O-Zr(THF)Cp 2 ] + [B(C 6 F 5 ) 4 ] - (DIPPnacnac=HC[(Me)C=N(2,6-iPr 2 -C 6 H 3 )] 2 ). The first complex polymerizes ethene in the presence of an alkylaluminum scavenger but in the absence of methylalumoxane (MAO). The adduct cation is inactive under these conditions. Theoretical calculations show very high energy barriers (ΔG=40-47 kcal mol -1 ) for ethene insertion with a bridged AlOZr catalyst. This is due to an unfavorable six-membered-ring transition state, in which the methyl group bridges the metal and ethene with an obtuse metal-Me-C angle that prevents synchronized bond-breaking and making. A more-likely pathway is dissociation of the Al-O-Zr complex into an aluminate and the active polymerization catalyst [Cp* 2 ZrMe] + . © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Organosolv-Water Cosolvent Phase Separation on Cellulose and its Influence on the Physical Deconstruction of Cellulose: A Molecular Dynamics Analysis

DOE PAGES

Smith, Micholas Dean; Cheng, Xiaolin; Petridis, Loukas; ...

2017-11-03

Deconstruction of cellulose is crucial for the chemical conversion of lignocellulose into fuel/bioproduct precursors. Recently, a water-organosolv cosolvent system (THF-water) has been shown to both phase-separate on cellulose surfaces and partially deconstruct Avicel (cellulose) in the absence of acid. Here we employ molecular dynamics simulations to determine whether other common water-organosolv cosolvent systems (acetone, ethanol, and γ-valerolactone) exhibit phase separation at cellulose surface and whether this alters a purely physical cellulose dissociation pathway. Despite finding varied degrees of phase-separation of organosolv on cellulose surfaces, physical dissociation is not enhanced. Interestingly, however, the total amount the median water-cellulose contact lifetimes increasesmore » for the cosolvent systems in the order of THF > acetone > ethanol > γ-valerolactone. Together our results indicate two points: a purely physical process for deconstruction of cellulose is unlikely for these cosolvents, and in THF-water, unlike γ-valerolactone- (and some concentrations of acetone and ethanol) water cosolvents, a significant fraction of surface water is slowed. As a result, this slowing may be of importance in enhancing chemical deconstruction of cellulose, as it permits an increase in potential THF-water-cellulose reactions, even while the amount of water near cellulose is decreased.« less

Freezing polystyrene-b-poly(2-vinylpyridine) micelle nanoparticles with different nanostructures and sizes.

PubMed

Fan, Hailong; Jin, Zhaoxia

2014-04-28

Herein we report how to control the nanostructures and sizes of polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) nanoparticles via manipulating freezing in solvent-exchange. By characterizing and analyzing the distinct structural features of the obtained nanoparticles, we recognized that micelle self-assembly happens in the precipitation of PS-b-P2VP when water is added into the block copolymer (BCP) solution. Solvent properties significantly influence micelle types that are vesicles in acetone/H2O and spherical micelles in tetrahydrofuran/H2O, respectively, thus further inducing different frozen nanostructures of the obtained nanoparticles, onion-like in acetone/H2O and large compound micelles in tetrahydrofuran/H2O. By changing the concentration of the block copolymers and the Vsolvent/VH2O ratio to modify the freezing stage at which block copolymer micelles are frozen, we can further control the size of the nanoparticles. Moreover, small molecules (phosphotungstic acid, pyrene, 1-pyrenebutyric acid) can be trapped into the block copolymer nanoparticles via the freezing process. Their distribution in the nanoparticles relies not only on the solvent property, but also on their interactions with block copolymers. The hybrid nanoparticles with ordered distribution of small molecules can be further changed to partially-void nanoparticles. Our study demonstrated that manipulating the freezing of block copolymers in the solvent exchange process is a simple and controllable fabrication method to generate BCP nanoparticles with different architectures.

Formation of itraconazole-succinic acid cocrystals by gas antisolvent cocrystallization.

PubMed

Ober, Courtney A; Gupta, Ram B

2012-12-01

Cocrystals of itraconazole, an antifungal drug with poor bioavailability, and succinic acid, a water-soluble dicarboxylic acid, were formed by gas antisolvent (GAS) cocrystallization using pressurized CO(2) to improve itraconazole dissolution. In this study, itraconazole and succinic acid were simultaneously dissolved in a liquid solvent, tetrahydrofuran, at ambient conditions. The solution was then pressurized with CO(2), which decreased the solvating power of tetrahydrofuran and caused crystallization of itraconazole-succinic acid cocrystals. The cocrystals prepared by GAS cocrystallization were compared to those produced using a traditional liquid antisolvent, n-heptane, for crystallinity, chemical structure, thermal behavior, size and surface morphology, potential clinical relevance, and stability. Powder X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetry, and scanning electron microscopy analyses showed that itraconazole-succinic acid cocrystals with physical and chemical properties similar to cocrystals produced using a traditional liquid antisolvent technique can be prepared by CO(2) antisolvent cocrystallization. The dissolution profile of itraconazole was significantly enhanced through GAS cocrystallization with succinic acid, achieving over 90% dissolution in less than 2 h. The cocrystals appeared stable against thermal stress for up to 4 weeks under accelerated stability conditions, showing only moderate decreases in their degree of crystallinity but no change in their crystalline structure. This study shows the utility of an itraconazole-succinic acid cocrystal for improving itraconazole bioavailability while also demonstrating the potential for CO(2) to replace traditional liquid antisolvents in cocrystal preparation, thus making cocrystal production more environmentally benign and scale-up more feasible.

Thermodynamic assessment of the LiF-NaF-BeF2-ThF4-UF4 system

NASA Astrophysics Data System (ADS)

Capelli, E.; Beneš, O.; Konings, R. J. M.

2014-06-01

The present study describes the full thermodynamic assessment of the LiF-NaF-BeF2-ThF4-UF4 system which is one of the key systems considered for a molten salt reactor fuel. The work is an extension of the previously assessed LiF-NaF-ThF4-UF4 system with addition of BeF2 which is characterized by very low neutron capture cross section and a relatively low melting point. To extend the database the binary BeF2-ThF4 and BeF2-UF4 systems were optimized and the novel data were used for the thermodynamic assessment of BeF2 containing ternary systems for which experimental data exist in the literature. The obtained database is used to optimize the molten salt reactor fuel composition and to assess its properties with the emphasis on the melting behaviour.

Group 10 Metal Benzene-1,2-dithiolate Derivatives in the Synthesis of Coordination Polymers Containing Potassium Countercations.

PubMed

Castillo, Oscar; Delgado, Esther; Gómez-García, Carlos J; Hernández, Diego; Hernández, Elisa; Martín, Avelino; Martínez, José I; Zamora, Félix

2017-10-02

The use of theoretical calculations has allowed us to predict the coordination behavior of dithiolene [M(SC 6 H 4 S) 2 ] 2- (M = Ni, Pd, Pt) entities, giving rise to the first organometallic polymers {[K 2 (μ-H 2 O) 2 ][Ni(SC 6 H 4 S) 2 ]} n and {[K 2 (μ-H 2 O) 2 (thf)] 2 [K 2 (μ-H 2 O) 2 (thf) 2 ][Pd 3 (SC 6 H 4 S) 6 ]} n by one-pot reactions of the corresponding d 10 metal salts, 1,2-benzenedithiolene, and KOH. The polymers are based on σ,π interactions between potassium atoms and [M(SC 6 H 4 S) 2 ] 2- (M = Ni, Pd) entities. In contrast, only σ interactions are observed when the analogous platinum derivative is used instead, yielding the coordination polymer {[K 2 (μ-thf) 2 ][Pt(SC 6 H 4 S) 2 ]} n .

Synthesis and reactivity of bis(tetramethylcyclopentadienyl) yttrium metallocenes including the reduction of Me(3)SiN(3) to [(Me(3)Si)(2)N](-) with [(C(5)Me(4)H)(2)Y(THF)](2)(mu-eta(2):eta(2)-N(2)).

PubMed

Lorenz, Sara E; Schmiege, Benjamin M; Lee, David S; Ziller, Joseph W; Evans, William J

2010-07-19

The metallocene precursors needed to provide the tetramethylcyclopentadienyl yttrium complexes (C(5)Me(4)H)(3)Y, [(C(5)Me(4)H)(2)Y(THF)](2)(mu-eta(2):eta(2)-N(2)), and [(C(5)Me(4)H)(2)Y(mu-H)](2) for reactivity studies have been synthesized and fully characterized, and their reaction chemistry has led to an unexpected conversion of an azide to an amide. (C(5)Me(4)H)(2)Y(mu-Cl)(2)K(THF)(x), 1, synthesized from YCl(3) and KC(5)Me(4)H reacts with allylmagnesium chloride to make (C(5)Me(4)H)(2)Y(eta(3)-C(3)H(5)), 2, which is converted to [(C(5)Me(4)H)(2)Y][(mu-Ph)(2)BPh(2)], 3, with [Et(3)NH][BPh(4)]. Complex 3 reacts with KC(5)Me(4)H to form (C(5)Me(4)H)(3)Y, 4. The reduced dinitrogen complex, [(C(5)Me(4)H)(2)Y(THF)](2)(mu-eta(2):eta(2)-N(2)), 5, can be synthesized from either [(C(5)Me(4)H)(2)Y](2)[(mu-Ph)(2)BPh(2)], 3, or (C(5)Me(4)H)(3)Y, 4, with potassium graphite under a dinitrogen atmosphere. The (15)N labeled analogue, [(C(5)Me(4)H)(2)Y(THF)](2)(mu-eta(2):eta(2)-(15)N(2)), 5-(15)N, has also been prepared, and the (15)N NMR data have been compared to previously characterized reduced dinitrogen complexes. Complex 2 reacts with H(2) to form the corresponding hydride, [(C(5)Me(4)H)(2)Y(mu-H)](2), 6. Complex 5 displays similar reactivity to that of the analogous [(C(5)Me(4)H)(2)Ln(THF)](2)(mu-eta(2):eta(2)-N(2)) complexes (Ln = La, Lu), with substrates such as phenazine, anthracene, and CO(2). In addition, 5 reduces Me(3)SiN(3) to form (C(5)Me(4)H)(2)Y[N(SiMe(3))(2)], 7.

Acaricidal activity of four fractions and octadecanoic acid-tetrahydrofuran-3,4-diyl ester isolated from chloroform extracts of neem (Azadirachta indica) oil against Sarcoptes scabiei var. cuniculi larvae in vitro.

PubMed

Du, Yong-Hua; Li, Jin-Liang; Jia, Ren-Yong; Yin, Zhong-Qiong; Li, Xu-Ting; Lv, Cheng; Ye, Gang; Zhang, Li; Zhang, Yu-Qun

2009-07-07

Four fractions obtained from chloroform extracts of neem (Azadirachta indica) oil by column chromatography were investigated for acaricidal activity against Sarcoptes scabiei var. cuniculi larvae in vitro. Octadecanoic acid-tetrahydrofuran-3,4-diyl ester was isolated from an active fraction of the chloroform extract and its toxicity against S. scabiei larvae was tested in vitro. A complementary log-log model was used to analyse the toxicity data. Activity was found in the third fraction, with 100% corrected mortality after 4.5 h of exposure at a concentration of 200 mg ml(-1). This fraction was repeatedly re-crystallised in acetone to yield a white amorphous powder, identified as octadecanoic acid-tetrahydrofuran-3,4-diyl ester, with a median lethal concentration (LC(50)) of 0.1 mg ml(-1) at 24 h post-treatment. The median lethal time (LT(50)) for this compound was 15.3 h at a concentration of 7.5 mg ml(-1).

Decomposition mechanism of an artemisinin-type compound via hemin-electrocatalysis.

PubMed

Chen, H Y; Chen, Y; Zhu, S M; Bian, N S; Shan, F; Li, Y

1999-01-01

The interaction between a typical derivative of artemisinin and hemin was investigated by electrochemical and spectroelectrochemical methods. This derivative can be reduced via hemin-catalysis at the glassy carbon electrode, the cathodic overpotential is decreased by ca. 650 mV. A HPLC method for separating the products of the catalytic reaction was established. They were identified either in H(2)O-CH(3)CN solution or in tetrahydrofuran, respectively. The structures of these products show that the hemin-catalyzed decomposition of an artemisinin-type compound on the glassy carbon or reticulated vitreous carbon electrode can be achieved by both electrochemical reduction and rearrangement. The conclusion that the reaction of artemisinin with hemin is a critical step in the antimalarial mechanism of artemisinin can be drawn.

Hemilability of the 1,2-Bis(dimethylphosphino)ethane (dmpe) Ligand in Cp*Mo(NO)(κ2-dmpe).

PubMed

Holmes, Aaron S; Patrick, Brian O; Levesque, Taleah M; Legzdins, Peter

2017-09-18

Reaction of Cp*Mo(NO)Cl 2 with 1 equiv of 1,2-bis(dimethylphosphino)ethane (dmpe) in THF at ambient temperature forms [Cp*Mo(NO)(Cl)(κ 2 -dmpe)]Cl (1), which is isolable as an analytically pure yellow powder in 65% yield. Further addition of 2 equiv of Cp 2 Co to 1 in CH 2 Cl 2 affords dark red Cp*Mo(NO)(κ 2 -dmpe) (2), which was isolated in 36% yield by recrystallization from Et 2 O at -30 °C. Reaction of a benzene solution of 2 with an equimolar amount of elemental sulfur results in the immediate production of dark blue (μ-S)[Cp*Mo(NO)(κ 1 -dmpeS)] 2 (3), which is a rare example of a bimetallic transition-metal complex bridged by only a single sulfur atom and involving Mo═S═Mo bonding. In contrast, reaction of 2 with an excess of sulfur in benzene results in the formation of Cp*Mo(NO)(η 2 -S 2 )(κ 1 -dmpeS) (4). Complex 4 can also be formed by the addition of elemental sulfur to 3, thereby indicating that 3 is a precursor to 4. Cp*Mo(NO)(κ 2 -dmpe) (2) also undergoes interesting transformations when treated with organic bromides. For instance, reaction of 2 with 5 equiv benzyl bromide in THF produces the bimetallic complex (μ-dmpe)[Cp*Mo(NO)Br 2 ] 2 (5) and bibenzyl after 4 d at 70 °C probably via radical intermediates. In contrast to its reaction with benzyl bromide, complex 2 forms [Mo(NO)Br 2 (κ 2 -dmpe)] 2 (6), olefin, alkane, and Cp*H when treated with 5 equiv of 1-bromopropane or 1-bromooctane in THF at 70 °C for 72 h. Interestingly, complex 2 does not display any reactivity with bromobenzene or 1-bromoadamantane even after being heated for several days at 70 °C. All new complexes were characterized by conventional spectroscopic and analytical methods, and the solid-state molecular structures of most of them were established by single-crystal X-ray crystallographic analyses.

Formate supplementation enhances folate-dependent nucleotide biosynthesis and prevents spina bifida in a mouse model of folic acid-resistant neural tube defects.

PubMed

Sudiwala, Sonia; De Castro, Sandra C P; Leung, Kit-Yi; Brosnan, John T; Brosnan, Margaret E; Mills, Kevin; Copp, Andrew J; Greene, Nicholas D E

2016-07-01

The curly tail mouse provides a model for neural tube defects (spina bifida and exencephaly) that are resistant to prevention by folic acid. The major ct gene, responsible for spina bifida, corresponds to a hypomorphic allele of grainyhead-like 3 (Grhl3) but the frequency of NTDs is strongly influenced by modifiers in the genetic background. Moreover, exencephaly in the curly tail strain is not prevented by reinstatement of Grhl3 expression. In the current study we found that expression of Mthfd1L, encoding a key component of mitochondrial folate one-carbon metabolism (FOCM), is significantly reduced in ct/ct embryos compared to a partially congenic wild-type strain. This expression change is not attributable to regulation by Grhl3 or the genetic background at the Mthfd1L locus. Mitochondrial FOCM provides one-carbon units as formate for FOCM reactions in the cytosol. We found that maternal supplementation with formate prevented NTDs in curly tail embryos and also resulted in increased litter size. Analysis of the folate profile of neurulation-stage embryos showed that formate supplementation resulted in an increased proportion of formyl-THF and THF but a reduction in proportion of 5-methyl THF. In contrast, THF decreased and 5-methyl THF was relatively more abundant in the liver of supplemented dams than in controls. In embryos cultured through the period of spinal neurulation, incorporation of labelled thymidine and adenine into genomic DNA was suppressed by supplemental formate, suggesting that de novo folate-dependent biosynthesis of nucleotides (thymidylate and purines) was enhanced. We hypothesise that reduced Mthfd1L expression may contribute to susceptibility to NTDs in the curly tail strain and that formate acts as a one-carbon donor to prevent NTDs. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

What a difference a 5f element makes: trivalent and tetravalent uranium halide complexes supported by one and two bis[2-(diisopropylphosphino)-4-methylphenyl]amido (PNP) ligands.

PubMed

Cantat, Thibault; Scott, Brian L; Morris, David E; Kiplinger, Jaqueline L

2009-03-02

The coordination behavior of the bis[2-(diisopropylphosphino)-4-methylphenyl]amido ligand (PNP) toward UI3(THF)4 and UCl4 has been investigated to access new uranium(III) and uranium(IV) halide complexes supported by one and two PNP ligands. The reaction between (PNP)K (6) and 1 equiv of UI3(THF)4 afforded the trivalent halide complex (PNP)UI2(4-tBu-pyridine)2 (7) in the presence of 4-tert-butylpyridine. The same reaction carried out with UCl4 and no donor ligand gave [(PNP)UCl3]2 (8), in which the uranium coordination sphere in the (PNP)UCl3 unit is completed by a bridging chloride ligand. When UCl4 is reacted with 1 equiv (PNP)K (6) in the presence of THF, trimethylphosphine oxide (TMPO), or triphenylphosphineoxide (TPPO), the tetravalent halide complexes (PNP)UCl3(THF) (9), (PNP)UCl3(TMPO)2 (10), and (PNP)UCl3(TPPO) (11), respectively, are formed in excellent yields. The bis(PNP) complexes of uranium(III), (PNP)2UI (12), and uranium(IV), (PNP)2UCl2 (13), were easily isolated from the analogous reactions between 2 equiv of 6 and UI3(THF)4 or UCl4, respectively. Complexes 12 and 13 represent the first examples of complexes featuring two PNP ligands coordinated to a single metal center. Complexes 7-13 have been characterized by single-crystal X-ray diffraction and 1H and 31P NMR spectroscopy. The X-ray structures demonstrate the ability of the PNP ligand to adopt new coordination modes upon coordination to uranium. The PNP ligand can adopt both pseudo-meridional and pseudo-facial geometries when it is kappa3-(P,N,P) coordinated, depending on the steric demand at the uranium metal center. Additionally, its hemilabile character was demonstrated with an unusual kappa2-(P,N) coordination mode that is maintained in both the solid-state and in solution. Comparison of the structures of the mono(PNP) and bis(PNP) complexes 7, 9, 11-13 with their respective C5Me5 analogues 1-4 undoubtedly show that a more sterically congested environment is provided by the PNP ligand. The electronic influence of replacing the C5Me5 ligands with PNP was investigated using electronic absorption spectroscopy and electrochemistry. For 12 and 13, a chemically reversible wave corresponding to the UIV/UIII redox transformation comparable to that for 3 and 4 was observed. However, a 350 mV shift of this couple to more negative potentials was observed on substitution of the bis(C5Me5) by the bis(PNP) framework, therefore pointing to a greater electronic density at the metal center in the PNP complexes. The UV-visible region of the electronic spectra for the mono(PNP) and bis(PNP) complexes appear to be dominated by PNP ligand-based transitions that are shifted to higher energy in the uranium complexes than in the simple ligand anion (6) spectrum, for both the UVI and UIII oxidation states. The near IR region in complexes 1-4 and 7, 9, 11-13 is dominated by f-f transitions derived from the 5f3 and 5f2 valence electronic configuration of the metal center. Though complexes of both ligand sets exhibit similar intensities in their f-f bands, a somewhat larger ligand-field splitting was observed for the PNP system, consistent with its higher electron donating ability.

Highly emissive platinum(II) metallacages

NASA Astrophysics Data System (ADS)

Yan, Xuzhou; Cook, Timothy R.; Wang, Pi; Huang, Feihe; Stang, Peter J.

2015-04-01

Light-emitting materials, especially those with tunable wavelengths, attract considerable attention for applications in optoelectronic devices, fluorescent probes, sensors and so on. Many species evaluated for these purposes either emit as a dilute solution or on aggregation, with the former often self-quenching at high concentrations, and the latter falling dark when aggregation is disrupted. Here we preserve emissive behaviour at both low- and high-concentration regimes for two discrete supramolecular coordination complexes (SCCs). These tetragonal prismatic SCCs are self-assembled on mixing a metal acceptor, Pt(PEt3)2(OSO2CF3)2, with two organic donors, a pyridyl-decorated tetraphenylethylene and one of two benzene dicarboxylate species. The rigid organization of these fluorescence-active ligands imparts an emissive behaviour to dilute solutions of the resulting assemblies. Furthermore, on aggregation the prisms exhibit variable-wavelength visible-light emission, including rare white-light emission in tetrahydrofuran. The favourable photophysical properties and solvent-dependent aggregation behaviour provide a means to tune emission wavelengths.

Multimicrometer Noncovalent Monolayer Domains on Layered Materials through Thermally Controlled Langmuir-Schaefer Conversion for Noncovalent 2D Functionalization.

PubMed

Hayes, Tyler R; Bang, Jae Jin; Davis, Tyson C; Peterson, Caroline F; McMillan, David G; Claridge, Shelley A

2017-10-18

As functionalized 2D materials are incorporated into hybrid materials, ensuring large-area structural control in noncovalently adsorbed films becomes increasingly important. Noncovalent functionalization avoids disrupting electronic structure in 2D materials; however, relatively weak molecular interactions in such monolayers typically reduce stability toward solution processing and other common material handling conditions. Here, we find that controlling substrate temperature during Langmuir-Schaefer conversion of a standing phase monolayer of diynoic amphiphiles on water to a horizontally oriented monolayer on a 2D substrate routinely produces multimicrometer domains, at least an order of magnitude larger than those typically achieved through drop-casting. Following polymerization, these highly ordered monolayers retain their structures during vigorous washing with solvents including water, ethanol, tetrahydrofuran, and toluene. These findings point to a convenient and broadly applicable strategy for noncovalent functionalization of 2D materials in applications that require large-area structural control, for instance, to minimize desorption at defects during subsequent solution processing.

Synthesis of Fuels and Value-Added Nitrogen-Containing Compounds from N2

DTIC Science & Technology

2014-11-24

The Haber - Bosch ammonia synthesis is one of the great technological achievements of the 20th century, having revolutionized agriculture and hence the...catalytic synthesis of ammonia or hydrazine compatible with renewable (CO2-free) hydrogen. N Ph N Ph N V Ar iPr iPr N THF N N Ph N Ph N V Ar Ar THF...atom transfer from renewable H2. Concurrent with these efforts, we have also been exploring related molybdenum platforms for ammonia oxidation. The

Salt-Induced Block Copolymer Micelles as Nanoreactors for the Formation of CdS Nanoparticles

DTIC Science & Technology

2001-11-01

or corona of micelles is presented. Poly(styrene-block-2-vinylpyridine) ( PS - b - P2VP ) and cadmium ions form aggregates of single micelles, called...ratio and block copolymer concentration in THF etc. EXPERIMENTAL DETAILS The synthesis of the PS - b - P2VP block copolymer was performed using sequential...nanoparticles: PS - b - P2VP block copolymer was dissolved in THF at different concentrations under vigorous stirring for 1 hour. Cd(Ac)2.2H 20 dissolved in a

Development of taste sensor system for differentiation of Indonesian herbal medicines

NASA Astrophysics Data System (ADS)

Kaltsum, U.; Triyana, K.; Siswanta, D.

2014-09-01

In Indonesia, herbal medicines are usually produced by small and medium enterprises which are relatively low in quality control. The purpose of this paper is to report that we have developed a taste sensor system with global selectivity, i.e., electronic tongue (e-tongue) for differentiation of Indonesian herbal medicines. The e-tongue was composed of five kinds of ion selective electrodes as working electrodes, data acquisition system, and pattern recognition system. Each ion selective electrode (ISE) was built by attaching lipid/polymer membrane. For this purpose, the five kinds of membranes were built by mixing lipid, plasticizer (nitrophenyl octyl ether/NPOE), polyvinyl chloride (PVC), and tetrahydrofuran (THF). In this study, we employed five kinds of lipid, namely oleic acid (OA), dioctyl phosphate (DOP), decyl alcohol (DA), dodecylamine (DDC), and trioctyl methyl ammonium chloride (TOMA). In this case, the membranes transform information of taste substances into electric signal. The five kinds of Indonesian herbal medicine were purchased from local supermarket in Yogyakarta, i.e., kunyit asam (made from turmeric and tamarind), beras kencur (made from rice and kencur), jahe wangi (made from ginger and fragrance), sirih wangi (made from betel leaf), and temulawak (made from Javanese ginger). Prior to detecting the taste from the Indonesian herbal medicine samples, each ion selective electrode was tested with five basic taste samples, i.e., for saltiness, sweetness, umami, bitterness, and sourness. All ISEs showed global selectivity to all samples. Furthermore, the array of ISEs showed specific response pattern to each Indonesian herbal medicine. For pattern recognition system, we employed principle component analysis (PCA). As a result, the e-tongue was able to differentiate five kinds of Indonesian herbal medicines, proven by the total variance of first and second principle components is about 93%. For the future, the e-tongue may be developed for quality control application in herbal medicine industries.

Parametric study of the physical properties of hydrate-bearing sand, silt, and clay sediments: 2. Small-strain mechanical properties

USGS Publications Warehouse

Lee, J.Y.; Francisca, F.M.; Santamarina, J.C.; Ruppel, C.

2010-01-01

The small-strain mechanical properties (e.g., seismic velocities) of hydrate-bearing sediments measured under laboratory conditions provide reference values for calibration of logging and seismic exploration results acquired in hydrate-bearing formations. Instrumented cells were designed for measuring the compressional (P) and shear (S) velocities of sand, silts, and clay with and without hydrate and subject to vertical effective stresses of 0.01 to 2 MPa. Tetrahydrofuran (THF), which is fully miscible in water, was used as the hydrate former to permit close control over the hydrate saturation Shyd and to produce hydrate from dissolved phase, as methane hydrate forms in most natural marine settings. The results demonstrate that laboratory hydrate formation technique controls the pattern of P and S velocity changes with increasing Shyd and that the small-strain properties of hydrate-bearing sediments are governed by effective stress, δ'v and sediment specific surface. The S velocity increases with hydrate saturation owing to an increase in skeletal shear stiffness, particularly when hydrate saturation exceeds Shyd≈ 0.4. At very high hydrate saturations, the small strain shear stiffness is determined by the presence of hydrates and becomes insensitive to changes in effective stress. The P velocity increases with hydrate saturation due to the increases in both the shear modulus of the skeleton and the bulk modulus of pore-filling phases during fluid-to-hydrate conversion. Small-strain Poisson's ratio varies from 0.5 in soft sediments lacking hydrates to 0.25 in stiff sediments (i.e., subject to high vertical effective stress or having high Shyd). At Shyd ≥ 0.5, hydrate hinders expansion and the loss of sediment stiffness during reduction of vertical effective stress, meaning that hydrate-rich natural sediments obtained through pressure coring should retain their in situ fabric for some time after core retrieval if the cores are maintained within the hydrate stability field.

Development of taste sensor system for differentiation of Indonesian herbal medicines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaltsum, U., E-mail: um-mik@yahoo.co.id; Triyana, K., E-mail: triyana@ugm.ac.id; Siswanta, D., E-mail: triyana@ugm.ac.id

In Indonesia, herbal medicines are usually produced by small and medium enterprises which are relatively low in quality control. The purpose of this paper is to report that we have developed a taste sensor system with global selectivity, i.e., electronic tongue (e-tongue) for differentiation of Indonesian herbal medicines. The e-tongue was composed of five kinds of ion selective electrodes as working electrodes, data acquisition system, and pattern recognition system. Each ion selective electrode (ISE) was built by attaching lipid/polymer membrane. For this purpose, the five kinds of membranes were built by mixing lipid, plasticizer (nitrophenyl octyl ether/NPOE), polyvinyl chloride (PVC),more » and tetrahydrofuran (THF). In this study, we employed five kinds of lipid, namely oleic acid (OA), dioctyl phosphate (DOP), decyl alcohol (DA), dodecylamine (DDC), and trioctyl methyl ammonium chloride (TOMA). In this case, the membranes transform information of taste substances into electric signal. The five kinds of Indonesian herbal medicine were purchased from local supermarket in Yogyakarta, i.e., kunyit asam (made from turmeric and tamarind), beras kencur (made from rice and kencur), jahe wangi (made from ginger and fragrance), sirih wangi (made from betel leaf), and temulawak (made from Javanese ginger). Prior to detecting the taste from the Indonesian herbal medicine samples, each ion selective electrode was tested with five basic taste samples, i.e., for saltiness, sweetness, umami, bitterness, and sourness. All ISEs showed global selectivity to all samples. Furthermore, the array of ISEs showed specific response pattern to each Indonesian herbal medicine. For pattern recognition system, we employed principle component analysis (PCA). As a result, the e-tongue was able to differentiate five kinds of Indonesian herbal medicines, proven by the total variance of first and second principle components is about 93%. For the future, the e-tongue may be developed for quality control application in herbal medicine industries.« less

Thermodynamic assessment of the LiF-ThF4-PuF3-UF4 system

NASA Astrophysics Data System (ADS)

Capelli, E.; Beneš, O.; Konings, R. J. M.

2015-07-01

The LiF-ThF4-PuF3-UF4 system is the reference salt mixture considered for the Molten Salt Fast Reactor (MSFR) concept started with PuF3. In order to obtain the complete thermodynamic description of this quaternary system, two binary systems (ThF4-PuF3 and UF4-PuF3) and two ternary systems (LiF-ThF4-PuF3 and LiF-UF4-PuF3) have been assessed for the first time. The similarities between CeF3/PuF3 and ThF4/UF4 compounds have been taken into account for the presented optimization as well as in the experimental measurements performed, which have confirmed the temperatures predicted by the model. Moreover, the experimental results and the thermodynamic database developed have been used to identify potential compositions for the MSFR fuel and to evaluate the influence of partial substitution of ThF4 by UF4 in the salt.

Prediction of Burst Pressure in Multistage Tube Hydroforming of Aerospace Alloys.

PubMed

Saboori, M; Gholipour, J; Champliaud, H; Wanjara, P; Gakwaya, A; Savoie, J

2016-08-01

Bursting, an irreversible failure in tube hydroforming (THF), results mainly from the local plastic instabilities that occur when the biaxial stresses imparted during the process exceed the forming limit strains of the material. To predict the burst pressure, Oyan's and Brozzo's decoupled ductile fracture criteria (DFC) were implemented as user material models in a dynamic nonlinear commercial 3D finite-element (FE) software, ls-dyna. THF of a round to V-shape was selected as a generic representative of an aerospace component for the FE simulations and experimental trials. To validate the simulation results, THF experiments up to bursting were carried out using Inconel 718 (IN 718) tubes with a thickness of 0.9 mm to measure the internal pressures during the process. When comparing the experimental and simulation results, the burst pressure predicated based on Oyane's decoupled damage criterion was found to agree better with the measured data for IN 718 than Brozzo's fracture criterion.

Low severity coal conversion by ionic hydrogenation: Quarterly report, October--December 1988

DOE Office of Scientific and Technical Information (OSTI.GOV)

Maioriello, J.; Larsen, J.W.

1988-12-31

A newly developed reaction system consisting of H/sub 2/O:BF/sub 3//H/sub 2//(CH/sub 3/CN)/sub 2/PtCl/sub 2/ was applied to the ionic hydrogenation of aromatic and functionalized aromatic compounds. Hydrogenations were carried out in this aqueous system at 50/degree/C and 500 psi H/sub 2/. Aryl ethers were hydrogenated and cleaved, yielding deoxygenated, fully saturated compounds as the major products. Reactions of nitrogen-containing aromatic compounds resulted in partial saturation of aromatic rings without cleavage of the C-N bonds. Aromatic and PNA compounds can be fully or partially hydrogenated depending on their structures. Aromatic thiols, sulfides and thiophenes poison the catalyst; the oxidized sulfur formsmore » (sulfonic acids, sulfones) were not reduced and did not poison the catalyst. It was found that certain aromatic compounds were easier to hydrogenate than others. Ionic hydrogenation of Wyodak cola using a H/sub 2/O:BF/sub 3//H/sub 2//(MeCN)/sub 2/PtCl/sub 2/ resulted in no significant increase in THF extractability (5.8--9.6% THF-extractables, wt) over that of the parent coal (4.6--6.7% THF-extractables, wt). Ionic hydrogenation of a demineralized Wyodak coal (1 M aq. citric acid, reflux 1 day) resulted in a slight increase in THF extractability (10.4%) over the untreated parent coal (5.6--5.8%). 4 refs., 1 fig., 1 tab.« less

Experimental and Metabolic Modeling Evidence for a Folate-Cleaving Side-Activity of Ketopantoate Hydroxymethyltransferase (PanB)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thiaville, Jennifer J.; Frelin, Océane; García-Salinas, Carolina

Tetrahydrofolate (THF) and its one-carbon derivatives, collectively termed folates, are essential cofactors, but are inherently unstable. While it is clear that chemical oxidation can cleave folates or damage their pterin precursors, very little is known about enzymatic damage to these molecules or about whether the folate biosynthesis pathway responds adaptively to damage to its end-products. The presence of a duplication of the gene encoding the folate biosynthesis enzyme 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase (FolK) in many sequenced bacterial genomes combined with a strong chromosomal clustering of the folK gene with panB, encoding the 5,10-methylene-THF-dependent enzyme ketopantoate hydroxymethyltransferase, led us to infer that PanBmore » has a side activity that cleaves 5,10-methylene-THF, yielding a pterin product that is recycled by FolK. Genetic and metabolic analyses of Escherichia coli strains showed that overexpression of PanB leads to accumulation of the likely folate cleavage product 6-hydroxymethylpterin and other pterins in cells and medium, and—unexpectedly—to a 46% increase in total folate content. In silico modeling of the folate biosynthesis pathway showed that these observations are consistent with the in vivo cleavage of 5,10-methylene-THF by a side-activity of PanB, with FolK-mediated recycling of the pterin cleavage product, and with regulation of folate biosynthesis by folates or their damage products.« less

Cuscuta europaea plastid apparatus in various developmental stages

PubMed Central

Švubová, Renáta; Ovečka, Miroslav; Pavlovič, Andrej; Slováková, Ľudmila; Blehová, Alžbeta

2013-01-01

It was generally accepted that Cuscuta europaea is mostly adapted to a parasitic lifestyle with no detectable levels of chlorophylls. We found out relatively high level of chlorophylls (Chls a+b) in young developmental stages of dodder. Significant lowering of Chls (a+b) content and increase of carotenoid concentration was typical only for ontogenetically more developed stages. Lower content of photosynthesis-related proteins involved in Chls biosynthesis and in photosystem formation as well as low photochemical activity of PSII indicate that photosynthesis is not the main activity of C. europaea plastids. Previously, it has been shown in other species that the Thylakoid Formation Protein 1 (THF1) is involved in thylakoid membrane differentiation, plant-fungal and plant-bacterial interactions and in sugar signaling with its preferential localization to plastids. Our immunofluorescence localization studies and analyses of haustorial plasma membrane fractions revealed that in addition to plastids, the THF1 protein localizes also to the plasma membrane and plasmodesmata in developing C. europaea haustorium, most abundantly in the digitate cells of the endophyte primordium. These results are supported by western blot analysis, documenting the highest levels of the THF1 protein in “get together” tissues of dodder and tobacco. Based on the fact that photosynthesis is not a typical process in the C. europaea haustorium and on the extra-plastidial localization pattern of the THF1, our data support rather other functions of this protein in the complex relationship between C. europaea and its host. PMID:23438585

Liquid chromatographic-tandem mass spectrometric method for the simultaneous determination of alkylphenols polyethoxylates, alkylphenoxy carboxylates and alkylphenols in wastewater and surface-water.

PubMed

Ciofi, L; Ancillotti, C; Chiuminatto, U; Fibbi, D; Checchini, L; Orlandini, S; Del Bubba, M

2014-10-03

Four different pellicular stationary phases (i.e. octadecylsilane, octasilane, Phenyl-Hexyl and pentafluorophenyl) were investigated for the chromatographic resolution of alkylphenols (APs), alkylphenols polyethoxylates (APnEOs) and alkylphenoxy carboxylates (APECs) using mixtures of water and organic solvents (i.e. methanol, acetonitrile and tetrahydrofuran) as eluents, in order to obtain their determination by a single LC-MS/MS run. In fact, alkylphenols and alkylphenoxy carboxylates must be analysed in negative ion mode, whereas alkylphenols polyethoxylates undergo ionisation only in positive ion mode, and therefore, two distinct LC-MS/MS analysis are commonly adopted. The best resolution among the aforementioned target analytes was achieved on the pentafluorophenyl column, eluting with an acidified water-acetonitrile-tetrahydrofuran mixture and using the post column addition of an ammonia solution in methanol for the detection of positively ionisable compounds. Under these optimized chromatographic conditions the investigated compounds were determined via a single chromatographic run, with only one polarity switch, in 15min, achieving the following instrumental detection limits: 600pg for AP1EOs, 0.8-14pg for AP2EOs, 10.4-150pg for APs and 4.4-4.8pg for APECs. The chromatographic method was coupled with solid-phase extraction and clean-up procedures and successfully applied to the analysis of wastewater and surface water samples, highlighting mean concentration ranging from 6ng/L for 4-t-OP1EC to 1434ng/L for 4-NP1121EC, depending on the sample analysed. Copyright © 2014 Elsevier B.V. All rights reserved.

Exploring Trends in Metal-Metal Bonding, Spectroscopic Properties, and Conformational Flexibility in a Series of Heterobimetallic Ti/M and V/M Complexes (M = Fe, Co, Ni, and Cu).

PubMed

Wu, Bing; Wilding, Matthew J T; Kuppuswamy, Subramaniam; Bezpalko, Mark W; Foxman, Bruce M; Thomas, Christine M

2016-12-05

To understand the metal-metal bonding and conformational flexibility of first-row transition metal heterobimetallic complexes, a series of heterobimetallic Ti/M and V/M complexes (M = Fe, Co, Ni, and Cu) have been investigated. The titanium tris(phosphinoamide) precursors ClTi(XylNP i Pr 2 ) 3 (1) and Ti(XylNP i Pr 2 ) 3 (2) have been used to synthesize Ti/Fe (3), Ti/Ni (4, 4 THF ), and Ti/Cu (5) heterobimetallic complexes. A series of V/M (M = Fe (7), Co (8), Ni (9), and Cu (10)) complexes have been generated starting from the vanadium tris(phosphinoamide) precursor V(XylNP i Pr 2 ) 3 (6). The new heterobimetallic complexes were characterized and studied by NMR spectroscopy, X-ray crystallography, electron paramagnetic resonance, and Mössbauer spectroscopy, where applicable, and computational methods (DFT). Compounds 3, 4 THF , 7, and 8 are C 3 -symmetric with three bridging phosphinoamide ligands, while compounds 9 and 10 adopt an asymmetric geometry with two bridging phosphinoamides and one phosphinoamide ligand bound η 2 to vanadium. Compounds 4 and 5, on the other hand, are asymmetric in the solid state but show evidence for fluxional behavior in solution. A correlation is established between conformational flexibility and metal-metal bond order, which has important implications for the future reactivity of these and other heterobimetallic molecules.

Synergistic Diazo-OH Insertion/Conia-Ene Cascade Catalysis for the Stereoselective Synthesis of γ-Butyrolactones and Tetrahydrofurans.

PubMed

Hunter, Arianne C; Schlitzer, Steven C; Sharma, Indrajeet

2016-11-02

A novel and highly efficient diazo-OH insertion/Conia-ene cascade reaction of readily available homopropargylic acids and alcohols with diazo carbonyl compounds is described. The cascade reaction involves a synergistic Rh/Ag/Au catalyst cocktail and proceeds instantly with a variety of substituted diazo compounds and acids/alcohols to provide functionalized γ-butyrolactones and tetrahydrofurans with complete regio- and stereoselectivity. The unprecedented rate-enhancement, complete stereoselectivity, and the enabling of new Conia-ene cyclizations suggest a concerted [4+1]-cycloaddition reaction pathway under synergistic (Rh/Ag/Au)-catalysis conditions. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

2,3,5-Substituted tetrahydrofurans: COX-2 inhibitory activities of 5-hydroxymethyl-/carboxyl-2,3-diaryl-tetrahydro-furan-3-ols.

PubMed

Singh, Palwinder; Mittal, Anu; Kaur, Satwinderjeet; Kumar, Subodh

2008-12-01

5-Hydroxymethyl-/carboxyl-2,3-diaryl-tetrahydro-furan-3-ols have been investigated for their COX-1 and COX-2 inhibitory activities. Compounds 17, 18 and 20 have been identified as showing appreciable COX-2 inhibition and selectivity. The group present at C-5 of tetrahydrofuran and the substituents at the two phenyl rings, through their interactions with active site amino acid residues, significantly affect the activities of these molecules. The quantitative structure-activity relationship studies indicate the role of logP, TPSA, molecular connectivity and valence connectivity towards the activities of these molecules.

An efficient system for the asymmetric acylation of (R,S)-3-n-butylphthalide catalyzed by novozyme 435.

PubMed

Li, Cuiqin; He, Laping; Qiu, Baoquan; Gao, Bing

2010-01-01

Novozyme 435 could be a highly efficient catalyst in the asymmetric acylation of (R,S)-3-n-butylphthalide in tetrahydrofuran-hexane solvents. The effect of various reaction parameters such as agitation velocity, water content, mixed media, temperature, concentration of Novozyme 435, molar ratio of acetic anhydride to (R,S)-3-n-butylphthalide, reaction time, enantiomeric excess of substrate (ee(S)), enantiomeric excess of product (ee(P)), and enantioselective ratio (E) were studied. Tetrahydrofuran markedly improved (R,S)-3-n-butylphthalide conversion, enantiomeric excess of remaining 3-n-butylphthalide, and enantiomeric ratio. The optimum media were 50% (v/v) tetrahydrofuran and 50% (v/v) hexane. Other ideal reaction conditions were an agitation velocity of 150 rpm, 0.4% (v/v) water content, temperature of 30 °C, 8 mg/mL dosage of Novozyme 435, 8:1 (0.4 mmol: 0.05 mmol) molar ratio of acetic anhydride to (R,S)-3-n-butylphthalide, and a reaction time of 48 hr. Under the optimum conditions, 96.4% ee(S) and 49.3% conversion of (R,S)-3-n-butylphthalide were achieved. In addition, enantiomeric excess of the product was above 98.0%.

Investigation of Different Colloidal Porous Silicon Solutions and Their Composite Solid Matrix Rods by Optical Techniques

NASA Astrophysics Data System (ADS)

Khan, M. Naziruddin; Aldalbahi, Ali; Almohammedi, Abdullah

2018-03-01

Colloidal porous silicon (PSi) in different solvents was synthesized by simple chemical etching. Colloidal solutions were then prepared using different quantities of silicon wafer pieces (Pcs) and chloroplatinic (Pt) acid in catalyst solution. The effect on the properties of the colloidal solutions and composite rods were investigated using various optical characterization techniques. Absorption and photoluminescence (PL) intensity of the colloidal PSi solutions are observed to depend on the quantity of wafer Pcs, the Pt-solution, and the porosity formation on the wafer surface. The morphological structure of the PSi in a solvent and the solid-rod environments were studied using field-emission scanning electron microscopy (FE-SEM) and were observed to have different structures. A mono-oriented structure of PSi exists in tetrahydrofuran, which has stereo orientation in dioxane and dimethylsulfoxide (approximately 5-8 nm as confirmed using high resolution transmission electron microscopy). Subsequently, some colloidal PSi solutions were directly embedded in three types of sol-gel-based matrices, silica, ormosils (or organically modified silica) and polymer, which easily generated solid rods. Spontaneous emission (SE) of the PSi solutions and their composite rods were examined using a high power picosecond 355 nm laser source. The emitted PL and SE signals of the colloidal PSi solutions were dependent on the Pt volume, nature of the solvent, quantity of Si wafer piece, and pumping energy. The response of SE signals from the PSi composites rods is an interesting phenomenon, and such nanocomposites may be used for future research on light amplification.

Investigation of Different Colloidal Porous Silicon Solutions and Their Composite Solid Matrix Rods by Optical Techniques

NASA Astrophysics Data System (ADS)

Khan, M. Naziruddin; Aldalbahi, Ali; Almohammedi, Abdullah

2018-07-01

Colloidal porous silicon (PSi) in different solvents was synthesized by simple chemical etching. Colloidal solutions were then prepared using different quantities of silicon wafer pieces (Pcs) and chloroplatinic (Pt) acid in catalyst solution. The effect on the properties of the colloidal solutions and composite rods were investigated using various optical characterization techniques. Absorption and photoluminescence (PL) intensity of the colloidal PSi solutions are observed to depend on the quantity of wafer Pcs, the Pt-solution, and the porosity formation on the wafer surface. The morphological structure of the PSi in a solvent and the solid-rod environments were studied using field-emission scanning electron microscopy (FE-SEM) and were observed to have different structures. A mono-oriented structure of PSi exists in tetrahydrofuran, which has stereo orientation in dioxane and dimethylsulfoxide (approximately 5-8 nm as confirmed using high resolution transmission electron microscopy). Subsequently, some colloidal PSi solutions were directly embedded in three types of sol-gel-based matrices, silica, ormosils (or organically modified silica) and polymer, which easily generated solid rods. Spontaneous emission (SE) of the PSi solutions and their composite rods were examined using a high power picosecond 355 nm laser source. The emitted PL and SE signals of the colloidal PSi solutions were dependent on the Pt volume, nature of the solvent, quantity of Si wafer piece, and pumping energy. The response of SE signals from the PSi composites rods is an interesting phenomenon, and such nanocomposites may be used for future research on light amplification.

Solvent effects on the properties of hyperbranched polythiophenes.

PubMed

Torras, Juan; Zanuy, David; Aradilla, David; Alemán, Carlos

2016-09-21

The structural and electronic properties of all-thiophene dendrimers and dendrons in solution have been evaluated using very different theoretical approaches based on quantum mechanical (QM) and hybrid QM/molecular mechanics (MM) methodologies: (i) calculations on minimum energy conformations using an implicit solvation model in combination with density functional theory (DFT) or time-dependent DFT (TD-DFT) methods; (ii) hybrid QM/MM calculations, in which the solute and solvent molecules are represented at the DFT level as point charges, respectively, on snapshots extracted from classical molecular dynamics (MD) simulations using explicit solvent molecules, and (iii) QM/MM-MD trajectories in which the solute is described at the DFT or TD-DFT level and the explicit solvent molecules are represented using classical force-fields. Calculations have been performed in dichloromethane, tetrahydrofuran and dimethylformamide. A comparison of the results obtained using the different approaches with the available experimental data indicates that the incorporation of effects associated with both the conformational dynamics of the dendrimer and the explicit solvent molecules is strictly necessary to satisfactorily reproduce the properties of the investigated systems. Accordingly, QM/MM-MD simulations are able to capture such effects providing a reliable description of electronic properties-conformational flexibility relationships in all-Th dendrimers.

[Preparation and evaluation of stationary phase of high performance liquid chromatography for the separation of basic solutes].

PubMed

Wang, P; Wang, J; Cong, R; Dong, B

1997-05-01

A bonded phase for high performance liquid chromatography (HPLC) has been prepared by the new reaction between silica and silicon ether. The ether was synthesized from alkylchlorosilane and pentane-2,4-dione in the presence of imidazole under inert conditions by using anhydrous tetrahydrofuran as solvent. The bonded phase thus obtained was characterized by elemental analysis, diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and HPLC evaluation. The carbon content was 9.4% and the surface coverage almost attained 3.0micromol/m2 without end-capping. The silanol absorption peaks of the product cannot be observed from the DRIFT spectrum, which revealed that the silanization reaction proceeded thoroughly. The basic solutes, such as aniline, o-toluidine, p-toluidine, N,N-dimethylaniline and pyridine were used as the probe solutes to examine their interaction with the residual silanols on the surface of the products. No buffer or salt was used in the mobile phase for these experiments. In comparison with an acidic solute, such as, phenol, basic aniline eluted in front of phenol, and the ratio of asymmetry of aniline peak to that of the phenol peak was 1.1. Furthermore the relative k' value of p-toluidine to that of o-toluidine was also 1.1. All the results showed that the stationary phase has better quality and reproducibility and can be used for the separation of basic solutes efficiently.

Synthesis of styrene/isoprene/butadiene integrated rubber with wide glass transition temperature by reactive extrusion

NASA Astrophysics Data System (ADS)

Huang, Tianhua; Zheng, Anna; Zhan, Pengfei; Shi, Han; Li, Xiang; Guan, Yong; Wei, Dafu

2018-05-01

In this work, styrene/isoprene/butadiene integrated rubber (SIBR) was synthesized with n-butyllithium as the initiator and tetrahydrofuran as structure modifier in a co-rotating intermeshing twin-screw extruder. The content of diene in these terpolymers reached a surprising 70 wt% by feeding the monomers in two different sites of the twin-screw extruder. 1H-NMR, GPC and TEM results showed that the molecular structures of terpolymers changed with the variation of feeding site. Dynamic mechanical analysis of the vulcanized SIBR showed that the terpolymer had a wide glass transition region, which assured an excellent combination of high antiskid properties and low rolling resistance. Different from traditional solution polymerization, the present work provides a green approach to prepare the SIBR via bulk polymerization without solvent.

Color-tunable, aggregation-induced emission of a butterfly-shaped molecule comprising a pyran skeleton and two cholesteryl wings.

PubMed

Tong, Hui; Hong, Yuning; Dong, Yongqiang; Ren, Yan; Häussler, Matthias; Lam, Jacky W Y; Wong, Kam Sing; Tang, Ben Zhong

2007-03-01

A chiral pyran derivative containing two cholesteryl groups (1) is synthesized, and its optical properties are investigated. Whereas the isolated molecule of 1 is virtually nonluminescent in dilute solutions, it becomes highly emissive with a 2 orders of magnitude increase in fluorescence quantum yield upon aggregation in poor solvents or in solid state, showing a novel phenomenon of aggregation-induced emission (AIE). The color and efficiency of the AIE of 1 can be tuned by varying the morphology of its aggregates: photoluminescence of its aggregates formed in a tetrahydrofuran/water mixture progressively red-shifts (green --> yellow --> red) with increasing water content of the mixture, with the crystalline aggregates emitting bluer lights in higher efficiencies than their amorphous counterparts.

Fundamental Investigations of the Tribological Properties of Biological Interfaces

DTIC Science & Technology

2007-11-01

flat at the bottom of a septum-sealed vial that was purged with nitrogen gas. Into this vial, dry, distilled toluene, and 0.1 mL each of...allowed to polymerize with o-Si " 0’r +N .N+-- O ___0 stirring at 60-75 C for 43 hours. The 0 CN 2. Soxhlet extraction reaction was terminated by exposure 3...with THF to air. The PS-modified silicon wafer CN - 4 was washed by Soxhlet extraction 4- in THF for 44 hours to remove any 0 free polymer. Scheme 1

Protonation of a lanthanum phosphide-alkyl occurs at the P-La not the C-La bond: isolation of a cationic lanthanum alkyl complex.

PubMed

Izod, Keith; Liddle, Stephen T; Clegg, William

2004-08-07

Protonation of the heteroleptic, cyclometalated lanthanum phosphide complex [((Me3Si)2CH)(C6H4-2-CH2NMe2)P]La(THF)[P(C6H4-2-CH2NMe2)(CH(SiMe3)(SiMe2CH2))] with [Et3NH][BPh4] yields the cationic alkyllanthanum complex [(THF)4La[P(C6H4-2-CH2NMe2)(CH(SiMe3)(SiMe2CH2))

Alteration of Folic Metabolism in Breast Cancer

DTIC Science & Technology

2014-08-01

folates  into  5-­‐ methyl -­‐THF.           As  shown  in  Fig.  5  ,  upon  methionine  deprivation...for  1hr,  5-­‐ methyl -­‐THF  accounts  for  >90%  of  all   folates  in  MDA-­‐MB-­‐468  triple  negative  breast...Annual 3. DATES COVERED 01Aug2013 – 31July2014 4. TITLE AND SUBTITLE Alteration of Folate Metabolism in Breast Cancer

Ge(14)[Ge(SiMe(3))(3)](5)Li(3)(THF)(6): the largest metalloid cluster compound of germanium: on the way to fullerene-like compounds?

PubMed

Schenk, Christian; Schnepf, Andreas

2008-10-14

The reaction of GeBr with LiGe(SiMe(3))(3) yields the largest metalloid cluster compound of germanium Ge(14)[Ge(SiMe(3))(3)](5)Li(3)(THF)(6), in which 14 germanium atoms are arranged as a hollow sphere in the cluster core, showing that in the case of germanium also fullerene-like compounds might be present in the borderland between the molecular and solid states.

Double addition of diethylamine to biacetylene (in Russian)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Trofimov, B.A.; Vavilova, A.N.

1986-03-01

Biacetylene reacts with an excess of diethylamine in dilute solutions of anhydrous acetonitrile, methanol, ethanol, and THF to form the diadduct 1,3-bis(diethyl-amino)-1,3-butadiene (lambda/sub max/ 325 nm). During concentration of the reaction mixture the latter undergoes hydration by the residual amounts of water in the 3-(diethylamino)-2-butenal. The spectral characteristics (UV, IR, PMR) of the intermediate reaction products are given. The kinetics of the stage of addition of the diethylamine and water to the monoadduct, 1-(diethylamino)-1-buten-3-yne, were studied. It was concluded that the addition of the nucleophile to the triple bond during its secondary amination and hydration is facilitated by the concertedmore » transfer of a proton.« less

Synthesis and reactivity of ultra-fine coal liquefaction catalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Linehan, J.C.; Matson, D.W.; Fulton, J.L.

1992-10-01

The Pacific Northwest Laboratory is currently developing ultra-fine iron-based coal liquefaction catalysts using two new particle production technologies: (1) modified reverse micelles (MRM) and (2) rapid thermal decomposition of solutes (RTDS). These methodologies have been shown to allow control over both particle size (from 1 nm to 60 nm) and composition when used to produce ultra-fine iron-based materials. Powders produced using these methods are found to be selective catalysts for carbon-carbon bond scission using the naphthyl bibenzylmethane model compound, and to promote the production of THF soluble coal products during liquefaction studies. This report describes the materials produced by bothmore » MRM and the RTDS methods and summarizes the results of preliminary catalysis studies using these materials.« less

Photochemical grafting of methyl groups on a Si(111) surface using a Grignard reagent.

PubMed

Herrera, Marvin Ustaris; Ichii, Takashi; Murase, Kuniaki; Sugimura, Hiroyuki

2013-12-01

The photochemical grafting of methyl groups onto an n-type Si(111) substrate was successfully achieved using a Grignard reagent. The preparation involved illuminating a hydrogen-terminated Si(111) that was immersed in a CH3MgBr-THF solution. The success was attributed to the ability of the n-type hydrogenated substrate to produce holes on its surface when illuminated. The rate of grafting methyl groups onto the silicon surface was higher when a larger illumination intensity or when a substrate with lower dopant concentration was used. In addition, the methylated layer has an atomically flat structure, has a hydrophobic surface, and has electron affinity that was lower than the bulk Si. Copyright © 2013 Elsevier Inc. All rights reserved.

Multi-electron oxygen reduction by a hybrid visible-light-photocatalyst consisting of metal-oxide semiconductor and self-assembled biomimetic complex.

PubMed

Naya, Shin-ichi; Niwa, Tadahiro; Negishi, Ryo; Kobayashi, Hisayoshi; Tada, Hiroaki

2014-12-08

Adsorption experiments and density functional theory (DFT) simulations indicated that Cu(acac)2 is chemisorbed on the monoclinic sheelite (ms)-BiVO4 surface to form an O2-bridged binuclear complex (OBBC/BiVO4) like hemocyanin. Multi-electron reduction of O2 is induced by the visible-light irradiation of the OBBC/BiVO4 in the same manner as a blue Cu enzyme. The drastic enhancement of the O2 reduction renders ms-BiVO4 to work as a good visible-light photocatalyst without any sacrificial reagents. As a model reaction, we show that this biomimetic hybrid photocatalyst exhibits a high level of activity for the aerobic oxidation of amines to aldehydes in aqueous solution and imines in THF solution at 25 °C giving selectivities above 99% under visible-light irradiation. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Conformational Transformation of Five-Membered Rings: the Gas Phase Structure of 2-METHYLTETRAHYDROFURAN

NASA Astrophysics Data System (ADS)

Van, Vinh; Nguyen, Ha Vinh Lam; Stahl, Wolfgang

2015-06-01

2-Methyltetrahydrofuran (2-MeTHF) is a promising environmentally friendly solvent and biofuel component which is derived from renewable resources. Following the principles of Green Chemistry, 2-MeTHF has been evaluated in various fields like organometallics, metathesis, and biosynthesis on the way to more eco-friendly syntheses. Cyclopentane as the prototype of five-membered rings is well-known to exist as twist or envelope structures. However, the conformational analysis of its heterocyclic derivative 2-methyl-tetrahydrothiophene (MTTP) yielded two stable twist conformers and two envelope transition states. Here, we report on the heavy atom r_s structure of the oxygen-analog of MTTP, 2-MeTHF, studied by a combination of molecular beam Fourier transform microwave spectroscopy and quantum chemistry. One conformer of 2-MeTHF was observed and highly accurate molecular parameters were determined using the XIAM program. In addition, all 13C-isotopologues were assigned in natural abundance of 1%. A structural determination based on the r_s positions of all carbon atoms was achieved via Kraitchman's equations. The methyl group in 2-MeTHF undergoes internal rotation and causes A-E splittings of the rotational lines. The barrier was calculated to be 1142 wn at the MP2/6-311++G(d,p) level of theory, which is rather high. Accordingly, narrow A-E splittings could be observed for only a few transitions. However, the barrier height could be fitted while the angles between the internal rotor axis and the principal axes of inertia were taken from the experimental geometry. V. Pace, P. Hoyos, L. Castoldi, P. Domínguez de María, A. R. Alcántara, ChemSusChem 5 (2012), 1369-1379. a) D. F. Aycock, Org. Process Res. Dev. 11 (2007),156-159. b) M. Smoleń, M. Kȩdziorek, K. Grela, Catal. Commun. 44 (2014), 80-84. V. Van, C. Dindic, H.V.L. Nguyen, W. Stahl, ChemPhysChem 16 (2015), 291-294. H. Hartwig, H. Dreizler, Z. Naturforsch. A 51 (1996), 923-932. J. Kraitchman, Am. J. Phys. 21 (1953), 17-24.

Solvent effect on the synthesis of clarithromycin: A molecular dynamics study

NASA Astrophysics Data System (ADS)

Duran, Dilek; Aviyente, Viktorya; Baysal, Canan

2004-02-01

Clarithromycin (6- O-methylerythromycin A) is a 14-membered macrolide antibiotic which is active in vitro against clinically important gram-positive and gram-negative bacteria. The selectivity of the methylation of the C-6 OH group is studied on erythromycin A derivatives. To understand the effect of the solvent on the methylation process, detailed molecular dynamics (MD) simulations are performed in pure DMSO, pure THF and DMSO:THF (1:1) mixture by using the anions at the C-6, C-11 and C-12 positions of 2',4''-[ O-bis(TMS)]erythromycin A 9-[ O-(dimethylthexylsilyl)oxime] under the assumption that the anions are stable on the sub-nanosecond time scale. The conformations of the anions are not affected by the presence of the solvent mixture. The radial distribution functions are computed for the distribution of different solvent molecules around the `O-' of the anions. At distances shorter than 5 Å, DMSO molecules are found to cluster around the C-11 anion, whereas the anion at the C-12 position is surrounded by the THF molecules. The anion at the C-6 position is not blocked by the solvent molecules. The results are consistent with the experimental finding that the methylation yield at the latter position is increased in the presence of a DMSO:THF (1:1) solvent mixture. Thus, the effect of the solvent in enhancing the yield during the synthesis is not by changing the conformational properties of the anions, but rather by creating a suitable environment for methylation at the C-6 position.

Cation Dependence of the Dimerization Enthalpy for A2 [tetracyanoethylene]2 (A=NMe4 , Mepy, NEt4 ) Possessing a Long, Multicenter Bond.

PubMed

Graham, Adora G; Fedin, Matvey V; Miller, Joel S

2017-09-12

[TCNE] .- (TCNE=tetracyanoethylene) has been isolated as D 2h π-[TCNE] 2 2- possessing a long, 2.9 Å multicenter 2-electron-4-center (2e - /4c) C-C bond, and as C 2 π-[TCNE] 2 2- possessing a longer, 3.04 Å multicenter 2e - /6c (4 C+2 N atoms) bond. Temperature-dependent UV/Vis spectroscopic measurements in 2-methyltetrahydrofuran (MeTHF) has led to the determination of the dimerization, 2[TCNE] .- ⇌π-[TCNE] 2 2- , equilibrium constants, K eq (T), [[TCNE] 2 2- ]/[[TCNE] .- ] 2 , enthalpy, ΔH, and entropy, ΔS, of dimerization for [Mepy] 2 [TCNE] 2 (Mepy=N-methylpyridinium, H 3 CNC 5 H 5 + ) possessing D 2h π-[TCNE] 2 2- and [NMe 4 ] 2 [TCNE] 2 possessing C 2 π-[TCNE] 2 2- conformations in the solid state; however, both form D 2h π-[TCNE] 2 2- in MeTHF solution. Based on ΔH=-3.6±0.1 kcal mol -1 (-15.2 kJ mol -1 ), and ΔS=-11±1 eu (-47 J mol -1  K -1 ) and ΔH=-2.4±0.2 kcal mol -1 (-10.2 kJ mol -1 ), and ΔS=-8±1 eu (-32 J mol -1  K -1 ) in MeTHF for [NMe 4 ] 2 [TCNE] 2 and [Mepy] 2 [TCNE] 2 , respectively, the calculated K eq (298 K) are 1.6 and 1.3 m -1 , respectively. The observed K eq (145 K) are 3 and 2 orders of magnitude greater for [NMe 4 ] 2 [TCNE] 2 and [Mepy] 2 [TCNE] 2 , respectively. The K eq (130 K) is 4470, 257, ≈0.8, and ≪0.1 m -1 for [NMe 4 ] 2 [TCNE] 2 , [Mepy] 2 [TCNE] 2 , [NEt 4 ] 2 [TCNE] 2 , and [N(nBu) 4 ] 2 [TCNE] 2 , respectively, decreasing with increasing cation size. At standard conditions and below ambient temperature the equilibrium favors the dimer for the NMe 4 + and Mepy + cations. From the decreasing enthalpy, NMe 4 + >Mepy + , along with the decrease in dimer formation K eq (T) as NMe 4 + >Mepy + >NEt 4 + >N(nBu) 4 + , the dimer bond energy decreases with increasing cation size in MeTHF. This is attributed to a decrease in the [A] + ⋅⋅⋅[TCNE] - attractive interactions with increasing cation size. Solid state UV/Vis spectroscopic determinations of [NMe 4 ] 2 [TCNE] 2 are reported and compared to D 2h π-[TCNE] 2 2- conformers. The feasibility and limitations of temperature-dependent electron paramagnetic resonance (EPR) measurements for the determination of K eq (T) are also discussed. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

[Na5(THF)10Ce(mnt)4]infinity: a honeycomb network polymer that yields homoleptic cerium(III) tetrakis(dithiolene) complexes in donor solvents.

PubMed

Weis, Eric M; Barnes, Charles L; Duval, Paul B

2006-12-11

The first example of a lanthanide tetrakis(dithiolene) complex, [Na5(THF)10Ce(mnt)4] (1) (mnt = 1,2-maleonitrile-1,2-dithiolate), has been synthesized and characterized by X-ray crystallography and spectroscopic methods. In the solid state, 1 exists as a 2-D corrugated honeycomb network polymer in which the monomeric units comprising the trigonal nodes are knitted together by interlocking dative Na-N bonds extended from nitrile groups of bifunctional mnt ligands coordinated through the sulfur atoms to adjacent cerium centers. Individual honeycomb sheets are separated by 14.8 A. Compound 1 dissolves in donor solvents such as THF and acetonitrile to give soluble [Ce(mnt)4]5- units that exhibit spectroscopic features (i.e., NMR, luminescence, UV-vis) that are consistent with the 4f1 Ce(III) ion. In the first examination of the redox chemistry of a lanthanide dithiolene complex, cyclic voltammetry measurements conducted on 1 reveal a single irreversible oxidation wave that is likely attributable to ligand-centered oxidation.

Dynamic torsional motion of a diruthenium complex with four homo-catecholates and first synthesis of a diruthenium complex with mixed-catecholates

NASA Astrophysics Data System (ADS)

Chang, Ho-Chol; Mochizuki, Katsunori; Kitagawa, Susumu

2008-11-01

Dynamic properties of a diruthenium complex with ligand-unsupported Ru-Ru triple bonds, Na 2[Ru 2(3,6-DTBCat) 4] ( 1), were studied using variable-temperature 1H NMR. Structural freedom derived from the ligand-unsupported structure leads to torsional motion about the Ru-Ru bonds in THF and in DMF. The observed solvent dependency corresponds to the electrostatic interactions between the diruthenium complex and Na + counter cations, which are sensitive to the polarity of solvents. In addition, a new diruthenium complex, [{Na(THF) 2(H 2O)}{Na(THF) 0.5(H 2O)}{Ru 2(3,6-DTBCat) 2(H 4Cat) 2}] ( 2·2.5THF·2H 2O), with a ligand-unsupported Ru-Ru bond surrounded by two different kinds of catecholate derivatives, has been synthesized and crystallographically characterized. The complex, which was characterized by single-crystal structural analysis, will provide an opportunity to investigate not only static molecular structures but also dynamic physicochemical properties in comparison with analogues containing four identical catecholate derivatives.

Dimensional control of block copolymer nanofibers with a π-conjugated core: crystallization-driven solution self-assembly of amphiphilic poly(3-hexylthiophene)-b-poly(2-vinylpyridine).

PubMed

Gwyther, Jessica; Gilroy, Joe B; Rupar, Paul A; Lunn, David J; Kynaston, Emily; Patra, Sanjib K; Whittell, George R; Winnik, Mitchell A; Manners, Ian

2013-07-08

With the aim of accessing colloidally stable, fiberlike, π-conjugated nanostructures of controlled length, we have studied the solution self-assembly of two asymmetric crystalline-coil, regioregular poly(3-hexylthiophene)-b-poly(2-vinylpyridine) (P3HT-b-P2VP) diblock copolymers, P3HT23-b-P2VP115 (block ratio=1:5) and P3HT44-b-P2VP115 (block ratio=ca. 1:3). The self-assembly studies were performed under a variety of solvent conditions that were selective for the P2VP block. The block copolymers were prepared by using Cu-catalyzed azide-alkyne cycloaddition reactions of azide-terminated P2VP and alkyne end-functionalized P3HT homopolymers. When the block copolymers were self-assembled in a solution of a 50% (v/v) mixture of THF (a good solvent for both blocks) and an alcohol (a selective solvent for the P2VP block) by means of the slow evaporation of the common solvent; fiberlike micelles with a P3HT core and a P2VP corona were observed by transmission electron microscopy (TEM). The average lengths of the micelles were found to increase as the length of the hydrocarbon chain increased in the P2VP-selective alcoholic solvent (MeOH3 μm) fiberlike micelles were prepared by the dialysis of solutions of the block copolymers in THF against iPrOH. Furthermore the widths of the fibers were dependent on the degree of polymerization of the chain-extended P3HT blocks. The crystallinity and π-conjugated nature of the P3HT core in the fiberlike micelles was confirmed by a combination of UV/Vis spectroscopy, photoluminescence (PL) measurements, and wide-angle X-ray scattering (WAXS). Intense sonication (iPrOH, 1 h, 0 °C) of the fiberlike micelles formed by P3HT23-b-P2VP115 resulted in small (ca. 25 nm long) stublike fragments that were subsequently used as initiators in seeded growth experiments. Addition of P3HT23-b-P2VP115 unimers to the seeds allowed the preparation of fiberlike micelles with narrow length distributions (L(w)/L(n) < 1.11) and lengths from about 100-300 nm, that were dependent on the unimer-to-seed micelle ratio. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Evaluation of mixed solvent electrolytes for ambient temperature secondary lithium cells

NASA Technical Reports Server (NTRS)

Shen, D. H.; Subbarao, S.; Deligiannis, F.; Dawson, S.; Halpert, G.

1988-01-01

The ethylene carbonate/2-methyltetrahydrofuran (EC/2-MeTHF) mixed-solvent electrolyte has been experimentally found to possess many desirable electrolyte characteristics for ambient-temperature secondary Li-TiS2 cell applications. As many as 300 cycles have been demonstrated, and a cycling efficiency figure-of-merit of 38.5 percent, for 10-percent EC/90-percent MeTHF mixed-solvent electrolyte in experimental Li-TiS2 cells. The improved performance of this electrolyte is attributable to the formation of a beneficial passivating film on the Li electrode by interaction with the EC.

Solid State Synthesis Under Supramolecular Control of a 2D Heterotetratopic Self-complementary Tecton Tailored to Halogen Bonding

DTIC Science & Technology

2006-07-31

BuLi . A 96 : 4 mixture of trans : cis isomers was obtained in 84% overall yield; stereoisomers were easily separated by chroma- tography. Iodination of...the tetrafluorobenzene group12 was carried out with n- BuLi –I2 in THF affording 4 in 85% yield (Scheme 1). Orange-yellow prismatic crystals have been...mmol) of phosphonium salt 1 were suspended in 1 mL of THF at 70 1C. 0.7 mmol of n- BuLi (1.6 M) were added and the mixture was warmed up to room