Materials Literature
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The addition of [N(CH(3))(4)]OH to a methanolic solution of FeCl(3) and thme (thme = 1,1,1-tris(hydroxymethyl)ethane) yielded [N(CH(3))(4)](2)[OFe(6)(H(-)(3)thme)(3)(OCH(3))(3)Cl(6)].2H(2)O (1). Crystal data: C(26)H(64)Cl(6)Fe(6)N(2)O(15), trigonal space group P31c, a = 12.459(2) Å, c = 18.077(4) Å, Z = 2. The complex…
The first example of a dimer of corner sharing BO3 and PO4 units, BPO64-, occurs in the title compound. The structure is built of layers of such dimers separated by double layers of isolated PO4 tetrahedra. The cobalt atoms are 6-, 5-, and 4-coordinated by the oxygen.
In ${\mathrm{BaTiO}}_{3}$ the alkali ions Na and K, replacing Ba, lead to acceptor levels about 50 meV above the valence band edge. The structure of these defects can be studied by electron spin resonance, after light induced valence-band holes have been captured at neighboring ${\mathrm{O}}^{2\mathrm{\ensuremath{-}}}…
High-resolution crystallographic data show that Glu 168 and Glu 211 lie on opposite surfaces of the active site from Lys 345. Two different proposals for general base catalysis have emerged from these structural studies. In one scheme, the carboxylate side chains of Glu 168 and Glu 211 are proposed to ionize a trapped…
The structural and dynamic properties of a styrene−isoprene−styrene (SIS) triblock copolymer, with block molecular weights of 10 4, 10 5, and 10 4, respectively, and the matching styrene−isoprene (SI) diblock, with block molecular weights of 10 4 and 5 × 10 4, respectively, are examined in the selective solvent di- n…
A new high-performance device for Raman/absorption simultaneous determination was developed. This was combined with a newly designed microcirculating system and was successfully applied to study intermediates in the reaction of bovine oxidized cytochrome c oxidase (CcO) with hydrogen peroxide under steady state condit…
Peripherally-functionalized porphyrazines of the form M[pz(A n:B 4- n )] (inset 1), where A and B symbolize functional moieties (e.g., a−d in Table 1) fused directly to the β-positions of the pyrroles, have the potential to serve in a wide range of applications. Previously, we reported the synthesis of porphyrazinedi-…
Infiltration of alumina powder compacts by molten copper‐oxygen alloys under controlled oxygen partial pressures has been studied. Spontaneous infiltration occurred for copper alloys containing more than approximately 5 at.% oxygen. Despite supersaturation of the copper with oxygen, no Cu 2 O or interfacial reaction l…
Very low concentrations of D-galactose and D-fructose are bound to a dendrimer containing eight boronic acids and eight anthracene units; the binding events are sensitively monitored by changes in the fluorescence intensity.
Two new nickel(II) trans -monodimensional end-to-end azide-bridged complexes were synthesized and characterized: [Ni(1,3-diamino-2,2-dimethylpropane) 2 (μ-N 3 )] n (PF 6 ) n ( 1 ) and [Ni(1,3-diaminopropane) 2 (μ-N 3 )] n (PF 6 ) n ( 2 ). The crystal structures of 1 and 2 were solved. Complex 1 crystallizes in the ort…
High-resolution 29 Si NMR was used to investigate the acid-catalyzed hydrolysis and esterification reactions of methyltrimethoxysilane (MTMS) in methanol. The INEPT experiment, adapted for spin systems with multiple heteronuclear coupling constants, was used to assign the closely spaced resonances of the MTMS hydrolys…
Transmission electron micrographic images of platinum wires, incorporated into the channels of mesoporous molecular sieves, show that one-dimensional channels are arranged parallel in MCM-41 while the channels are three-dimensionally interconnected in other types of mesoporous molecular sieves constructed with silica…
The association behavior of a triblock ethylene oxide (E) and butylene oxide (B) copolymer with a very long middle E block (B 12 E 260 B 12 ) in aqueous solution has been investigated by means of laser light scattering. The flower-like closed association behavior of BEB−type triblock copolymers in aqueous solution can…
ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTTemperature Dependence of Relaxation in Polypropylene and Poly(ethylene-co-propylene)P. G. Santangelo, K. L. Ngai, and C. M. RolandView Author Information Chemistry Division, Code 6120, Naval Research Laboratory, Washington, D.C. 20375-5342Cite this: Macromolecules 1996, 29, 10…
Four block copolymer melts two poly(isoprene- block -dimethylsiloxane) (PI−PDMS) and two poly(ethylene- alt -propylene- block -dimethylsiloxane) (PEP−PDMS) have been investigated through rheological measurements, SANS, and SAXS. In both systems, lamellar to disorder and Ia 3̄ d bicontinuous to disorder transitions hav…
The rate of charge separation in a series of cyclophane-bridged Zn−porphyrin−quinone systems has been investigated in nonpolar and polar solvents by means of fluorescence upconversion. In all systems with driving forces in the range 0.3−1.3 eV, ultrafast charge separation occurs with a rate constant of (2−5) × 10 12 s…
Condensation of a tetraalkyl-α, α-dipyrromethane dialdehyde in a MacDonald-type [2 + 2]-condensation with a trialkyl-α,β-dipyrromethane gives a heptaalkyl N-confused porphyrin.
The one-dimensional arrays {(DMF)10Yb2[Ni(CN)4]3}∞ (1) and {(DMF)10Yb2[Pt(CN)4]3}∞ (2) were prepared from the metathesis reactions of YbCl3 and K2Ni(CN)4 or K2Pt(CN)4 in DMF (DMF = N,N-dimethylformamide). Unlike other one-dimensional structures adopted by complexes of M(CN)42- anions, two unusual array structures were…
Molecular dynamics (MD) simulations for a NiZr model adapted to Hausleitner-Hafner interatomic potentials are analyzed within the mode coupling theory (MCT). Fitting numerical solutions of the (modified) schematic MCT equation with the self-intermediate scattering function of the MD system demonstrates unambiguously t…
Low-temperature MCD spectra were recorded for the bis 4-(dimethylamino)pyridine ( 1 ), bis(1-methylimidazole) ( 2 ), and bis(4-cyanopyridine) ( 3 ) complexes of ferric tetramesitylporphyrinate. The ground state electronic configuration is formally (d xy ) 2 (d xz,d yz ) 3 for both 1 and 2, but these two complexes give…