New molecular systems for functional dye-based molecular switching of luminescence
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Liquid Crystal Formation Coupled with the Coil−Helix Transition in the Ternary System Poly(γ-benzyll-glutamate)/Dichloroacetic Acid/Dichloroethane
Phase behavior and ordering characteristics were reported for poly(γ-benzyl l -glutamate) (PBLG) in a mixed solvent containing a denaturant acid, dichloroacetic acid (DCA), + dichloroethane (DCE). The solutions of PBLG prepared so as to be liquid crystal at room temperature were observed to undergo a reentrant isotrop…
Computer Simulations of Polyisoprene Local Dynamics in Vacuum, Solution, and the Melt: Are Conformational Transitions Always Important?
Molecular dynamics computer simulations have been performed on an isolated polyisoprene chain at 298 K. Simulations of polyisoprene in the melt (413 K) and in solution (298 K) have been previously reported. The local dynamics of polyisoprene chains in these three environments are compared. While conformational transit…
Active Site Structure of Rieske-Type Proteins: Electron Nuclear Double Resonance Studies of Isotopically Labeled Phthalate Dioxygenase from Pseudomonas cepacia and Rieske Protein from Rhodobacter capsulatus and Molecular Modeling Studies of a Rieske Center,
Continuous wave electron nuclear double resonance (CW ENDOR) spectra of [delta-15N,epsilon(-14)N]histidine-labeled phthalate dioxygenase (PDO) from Pseudomonas cepacia were recorded and found to be virtually identical to those previously recorded from [delta,epsilon-15N2]histidine-labeled protein [Gurbiel, R. J., Bati…
Thermochemistry of Iron Chlorides and Their Positive and Negative Ions
The iron chlorides FeCl, FeCl 2, and FeCl 3 and their ions FeCl +, FeCl 2 +, FeCl -, FeCl 2 -, and FeCl 3 - were investigated using MP2 and QCISD(T) calculations with double- and triple-ζ basis sets augmented with multiple sets of diffuse and polarization functions. The dissociation enthalpies for FeCl → Fe + Cl, FeCl…
A fast double-stage convergent synthesis of dendritc polyethers
Two tert-butyldiphenylsilyl-protected synthons 7 and 9 are prepared in excellent yields and used in a one-pot synthesis of higher generation polyether dendrons.
Redox Chemistry of CoZSM-5 Zeolite
The redox chemistry and the changes that occurred within the solids were studied for an excessively exchanged and a nearly stoichiometric CoZSM-5 zeolite as a function of pretreatment, reduction, and reoxidation conditions. Both gravimetric and volumetric techniques were used to determine this chemistry and the stoich…
New Aspects Concerning the Structure and Degree of Crystallinity in High-Pressure-Crystallized Poly(ethylene terephthalate)
The crystallinity ( x c ) of high-pressure-crystallized poly(ethylene terephthalate) (PET), which shows values of x c ≅ 0.90 when measured by differential scanning calorimetry (DSC), was examined by means of wide-angle X-ray scattering (WAXS). PET samples crystallized under normal conditions were also investigated by…
Spectroscopy of Hydrothermal Reactions. 4. Kinetics of Urea and Guanidinium Nitrate at 200−300 °C in a Diamond Cell, Infrared Spectroscopy Flow Reactor
Infrared spectroscopy measurements of the kinetics and decomposition pathways of aqueous urea ((NH 2 ) 2 CO, 200−300 °C, 275 bar) and guanidinium nitrate ([(NH 2 ) 3 C]NO 3, 240−300 °C, 275 bar) are described. A Pt/Ir alloy flow cell with diamond wafer windows was used, and heat and fluid transport models show that is…
Light-Directed Generation of the Actin-Activated ATPase Activity of Caged Heavy Meromyosin
An understanding of the molecular mechanism of muscle contraction will require a complete description of the kinetics of the myosin motor in vitro and in vivo. To this end chemical relaxation studies employing light-directed generation of ATP from caged ATP have provided detailed kinetic information in muscle fibers.…
Alternating Donor−Acceptor Substitutions in Conjugated Polythiophenes
A series of bithiophenes, disubstituted with electron donor and electron acceptor groups, have been synthesized. The electronic effects exerted by these groups, on the electrochemical oxidation potential of bithiophenes, are additive, which allows us to control the overall substituent effect and make it compatible wit…
Structure Evolution of a Polymer Solution at High Shear Rates
We utilized large angle light scattering to study the structure of a sheared semidilute polymer solution. Below a critical shear rate γ̇ c we observe an enhancement of concentration fluctuations in accordance with previous experimental and theoretical work. Above γ̇ c we find dramatic changes in the transient and stea…
Iodine as a Visible Probe for the Evaluation of Zeolite Donor Strength
The visible absorption band of iodine adsorbed on zeolite blue-shifted with increasing the electropositivity of the countercation and the aluminum content in the framework. This phenomenon was attributed to the increase in the donor strength of the zeolite framework based on the analogous spectral shift of iodine in s…
Effects of Silver and Palladium Doping on the Dielectric Properties of 0.9Pb(Mg 1/3 Nb 2/3 )O 3 –0.1 PbTiO 3 Ceramic
The doping of silver and palladium into a 0.9Pb‐(Mg 1/3 Nb 2/3 )O 3 –0.1PbTiO 3 (PMN–PT) ceramic has been investigated. It was found that Ag could be incorporated into the PMN–PT lattice, though this was almost impossible with Pd. Doping at up to 0.2 mol% of Ag and Pd reduced the maximum dielectric constant ( K max )…
Structural and Morphological Characterization of PbS Nanocrystallites Synthesized in the Bicontinuous Cubic Phase of a Lipid
We report the synthesis and characterization of monodispersed lead sulfide (PbS) particles with diameters in the range 4−14 nm, using bicontinuous cubic phase as a matrix. It was found, through polarized optical microscopy and small-angle X-ray scattering studies, that the viscous isotropic bicontinuous cubic phase co…
(1-Ferrocenyl-η6-borabenzene)(η5-cyclopentadienyl)cobalt(1+): A New Heterobimetallic Basic NLO Chromophore,
The heterobimetallic cationic NLO chromophore (1-ferrocenyl-η 6 -borabenzene)(η 5 -cyclopentadienyl)cobalt(1+) ([{1-((η 5 -C 5 H 5 )Fe(η 5 -C 5 H 4 ))-η 6 -BC 5 H 5 }Co(η 5 -C 5 H 5 )] +, 1 + ) has been synthesized by reaction of FcBBr 2 and cobaltocene and subsequent oxidation with FeCl 3 . The neutral bimetallic com…
Rheological and Dielectric Behavior of a Styrene−Isoprene−Styrene Triblock Copolymer in n-Tetradecane. 1. Rubbery−Plastic−Viscous Transition
Rheological and dielectric behavior was examined for a 50 wt % solution of a symmetric styrene−isoprene−styrene (SIS) triblock copolymer ( M = 60.2K, S content = 28%) dissolved in an I-selective solvent, n -tetradecane (C14). Dynamic mechanical tests with various strain amplitudes, γ 0 = 0.03−0.8, were performed at va…
Thermo-oxidative erosion of amorphous hydrogenated carbon films
Amorphous C:D (or C:H) films were deposited on the inner surface of a spherical ultrahigh vacuum chamber by means of a direct current glow discharge in a ∼75% D2 (or H2) and ∼25% CD4 (CH4) gas mixture. Laser Raman spectroscopy analysis of the film exhibited the absence of a diamond peak at 1334.3 cm−1. The general app…
Synthesis, Molecular Structure, and Physical Properties of [tetrakis((methylthio)methyl)borate]2M (M = Fe, Co, Ni)
The synthesis and characterization of a series of [RTt] 2 M (RTt - = tetrakis((methylthio)methyl)borate; M = Fe, Co, Ni) complexes are reported. Isostructural derivatives of the newly synthesized phenyltris((methylthio)methyl)borate (PhTt - ) also have been prepared and characterized. In each case, the ligand provides…
Spectroscopic study of oxygen adsorption on CeO 2 /γ-Al 2 O 3 catalyst supports
EPR and FTIR have been used to obtain information on the oxygen adsorption sites generated on CeO2/γ-Al2O3 samples by outgassing treatments at different temperatures. Several types of O2– species, showing EPR signals with different line shapes, have been detected depending on the type of surface sites where the radica…