Materials Literature
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Base-catalyzed cross condensation of dipropylmaleonitrile 1 with bis(dimethylamino)maleonitrile 2 in an equimolar ratio afforded the porphyrazines 3a, 4a, 5a, 6a and 7a. Subsequent demetalation of 5a with TFA followed by remetalation with Zn(OAc)(2) gave ligand 5c in good yield. Compound 5c was, in turn, selectively o…
The electropolymerization and optical properties of poly(3,4-ethylenedioxythiophene) (PEDOT) was investigated in detail by a combined electrochemistry and surface plasmon spectroscopy setup. The simultaneous electrochemical−surface plasmon spectroscopy (EC-SPS) technique allowed for characterization of the changing di…
The influence of macromolecular architecture on the physical properties of polymeric materials has been studied by comparing poly(benzyl ether) dendrons with their exact linear analogues. The results clearly confirm the anticipation that dendrimers are unique when compared to other architectures. Physical properties,…
NMR studies on a series of poly(lactic acid)−poly(ethylene oxide) (PLA−PEG) diblock copolymers have been carried out in d 6 -acetone and in D 2 O. Nanoparticles of the PLA−PEG copolymers were obtained using a modified interfacial polymer deposition−solvent evaporation technique (Fessi, H.; Devissaguet, J. P.; Puisieux…
Epimerases and racemases are enzymes that catalyze the inversion of stereochemistry in biological molecules. In this article, three distinct examples are used to illustrate the wide range of chemical strategies employed during catalysis, and the diverse set of ancestors from which these enzymes have evolved. Glutamate…
The complexes Fe2(OCHPh2)6 and L2FeOR (R = Et or CHPh2, L = N,N'-bis(trimethylsilyl)benzamidinate) were structurally characterized, and comparative studies of the behavior of those compounds comprising the same alkoxide (Ph2HCO-) in polymerizations of -caprolactone (CL) and D,L-lactide (LA) were performed. Both Fe2(OC…
Electron-donating π-conjugated polymers with dithiafulvene moiety ( 4 ) or with diselenafulvene moiety ( 5 ) were prepared by cycloaddition polymerization of chalcogenoketenes derived from aromatic diynes ( 3 ). The solubilities of the polymers strongly depended on the structures. The diselenafulvene polymers ( 5 ) sh…
As part of a high-throughput, structural proteomic project we have used NMR spectroscopy to determine the solution structure and ascertain the function of a previously unknown, conserved protein (MtH895) from the thermophilic archeon Methanobacterium thermoautotrophicum. Our findings indicate that MtH895 contains a ce…
The crystal structure of rimkorolgite, ideally Ba[Mg 5 (H 2 O) 7 (PO 4 ) 4 ](H 2 O), (monoclinic, P 2 1 / c, a = 8.3354(9), b = 12.8304(13), c = 18.313(2) A, β = 90.025(2)°, V = 1958.5(4) A 3 , Z = 4) has been solved by direct methods and refined to R 1 = 0.052 using X-ray diffraction data collected from a crystal twi…
Self-assembled monolayers of 1-(10-mercaptodecyl)imidazole on Au electrodes were used to bind cobalt “picket fence” porphyrin (cobalt 5,10,15,20-tetrakis(α,α,α,α-2-pivalamidophenyl)porphyrin) to the electrode surface. The binding involved coordination of the cobalt center of the porphyrin to the pendant imidazole grou…
The dynamics of propylene glycol (PG) and its 7-mer have been investigated by quasielastic neutron scattering (QENS). In the case of PG we used two techniques; ordinary QENS and neutron spin-echo (NSE). The QENS and NSE experiments were carried out at the temperature ranges 300–420 K and 260–340 K, respectively. The Q…
Texture is defined as preferred crystallographic orientation in a polycrystalline aggregate. The main mechanisms of geological texture formation are crystallization, sedimentation, plastic deformation, recrystallization and metamorphism. Textures of geomaterials are fingerprints of the earth's history. The complexity…
Using the technique of electron momentum spectroscopy (EMS) we have measured the oxygen 2p- and 2s-derived valence bands and lithium 1s-derived core level in lithium oxide. All three sets of bands have been measured in a single experiment allowing the energy gap between the bands to be determined. At the Γ point the O…
This paper presents a new method of synthesis, mechanochemical activation, for the preparation of the Sr 3 Ti 2 O 7 Ruddlesden−Popper (RP) phase. The results obtained from different starting reagents (SrO, SrCO 3, or Sr(OH) 2 ·8H 2 O and TiO 2 anatase) and mechanical activation systems (vibrating and planetary mills)…
Tetra(alkoxybenzoato)dirhodium(II) complexes of the formula Rh 2 ( x, y, z -B m OC n ) 4 (where B is the benzoate group; m is the number of alkoxy chains on the aromatic ring; x, y, and z are their positions of anchoring; and n is the number of carbon atoms in each alkoxy chain) and the corresponding pyrazine adducts…
Ab initio pseudopotential total energy calculations of MoSe nanowires were performed within the local density approximation. The ${\mathrm{Li}}_{2}{\mathrm{Mo}}_{6}{\mathrm{Se}}_{6}$ crystal is composed of molecular chains, which can be separated from one another to form individual nanowires approximately $3 \mathrm{\…
A model is developed to account for the viscous flow of glass-forming liquids. We consider that a supercooled glass-forming liquid is composed of a liquid phase and some solidlike clusters which have a higher activation energy for viscous flow than the liquid regions. This approach yields a fitting equation for viscos…
Strain–size evaluations from diffraction line broadening for MgO ceramic materials have been compared using single-line integral-breadth and Rietveld procedures with the Voigt function. Diffraction data were measured by Bragg–Brentano X-ray diffractometry (XRD), without incident beam monochromatization, and neutron di…
Crystallographic texture (or preferred orientation) characterization of uniaxially pressed molybdite (MoO 3 ) and calcite (CaCO 3 ) powders has been carried out using the BT-1 high-resolution fixed-wavelength 32-detector powder diffractometer at the NIST Center for Neutron Research. Initially, each pattern was analyse…
The crystal structure of the glass-forming molecular liquid triphenyl phosphite [TPP, P(OC 6 H 5 ) 3 , six torsional degrees of freedom] has been solved ab initio at 110 K from powder synchrotron X-ray diffraction data by real-space methods (simulated annealing) followed by rigid-body Rietveld refinements. The symmetr…