Materials Literature
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We demonstrate optical storage by means of trans−cis isomerization within melamine monomers as well as within the corresponding cross-linked melamine resins using holographic grating experiments. The melamine monomer is chemically linked with a photoaddressable azobenzene group. By thermal treatment the semicrystallin…
ADVERTISEMENT RETURN TO ISSUEPREVNotePreparation of Nanocomposite Poly(allylamine)−Poly(ethylene glycol) Thin Films Using Michael AdditionRyan J. Russell, Kaushik Sirkar, and Michael V. PishkoView Author Information Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843-3122 Cite this:…
Eine generell anwendbare Suzuki-Srategie für die Synthese von β-funktionalisierten Porphyrinen geht vom Bromporphyrin 1 aus, das zunächst in ein luft- und wasserstabiles Boronat überführt wird. Die metallvermittelte Kreuzkupplung dieser Verbindung mit Arylbromiden liefert β-Arylporphyrine 2 in ähnlich hohen Ausbeuten…
The new selenogermanates Sr2Ge2Se5 and Ba2Ge2Se5 were synthesized by heating stoichiometric mixtures of binary selenides and the corresponding elements to 750 degrees C. The crystal structures were determined by single-crystal X-ray methods. Both compounds adopt previously unknown structure types. Sr2Ge2Se5 (P2(1)/n,…
Monomolecular films of a poly(vinyl alcohol) derivative having an azobenzene (Az) side chain (6Az10-PVA) transferred onto mica by the Langmuir−Blodgett technique were observed by atomic force microscopy in the noncontact mode. Multifarious features of the film morphology after the thermal and photostimulated processes…
A new class of calix[4]arene crown ethers with one or two bipyridines appended to the polyether ring (lariat calixcrowns) have been designed and synthesized; the luminescence properties of their Eu3+ and Tb3+ complexes have been studied in acetonitrile. In this solvent, long lifetimes for the metal emitting states and…
A reference example for the significance of molecular symmetry in UV/Vis spectroscopy is shown by the spectra of the three planar octaethyltetraoxa[4n+2]porphyrin dications 1 – 3 (n=4 – 6). Whereas the D4h-symmetric 18π and 26π dications 1 and 3 (the symmetry refers to the ring framework) exhibit very sharp Soret band…
Mechanical alloying is performed at cryogenic temperatures to incorporate polyisoprene (PI) or its hydrogenated analogue poly(ethylene- alt -propylene) (PEP) into poly(methyl methacrylate) (PMMA) as an example of high-energy solid-state blending. Morphological characterization of the blends by X-ray and electron micro…
Macrocyclization due to the m-phenylene tether is responsible for the stabilization of the azacyclophane-based dication 12+. EPR (see picture) and quantum-chemical studies indicate that 12+, which can be regarded as two m-phenylenediamines linked by two p-phenylenes, is a triplet diradical. Its properties differ from…
The introduction of a thioxo peptide bond in agonists of the opioid μ-receptor lead to bioactive derivatives. The backbone conformation of these compounds can be specifically modulated by photoinduction of the cis/trans prolyl bond isomerization [Eq. (1)].
The novel microporous germanate (NH4)4[(GeO2)3(GeO1.5F3)2].0.67H2O was prepared from an aqueous solution containing germanium dioxide, pyridine, hydrofluoric acid, and 2,6-diaminopyridine as a template. The solution was kept at 165 degrees C in a Teflon-lined autoclave for 4 days. Large crystals were produced and stud…
The effect of thermal history on the melt drawing of ultrahigh molecular weight polyethylene (UHMWPE) reactor powder was studied. The samples for drawing were prepared by compression-molding of reactor powder at various temperatures above the melting point ( T m ). The drawing temperature ( T d ) was 150 °C. It was fo…
The oxidative dehydrogenation of phenol compounds, as well as polymer formation from these monomers, was studied by UV−vis and Mössbauer spectroscopy using a novel biological catalyst hematin. The mechanism of the polymerization reaction was also followed in various pH environments. Phenol radicals were formed by a tw…
A generally applicable Suzuki methodology for the synthesis of β-derivatized porphyrins has been developed starting from bromoporphyrin 1, which is converted into an air- and water-stable boronate derivative. Metal-mediated cross-coupling of the latter compound with various aryl bromides furnishes β-arylporphyrins 2 w…
Protected from dimerization by incarceration, the highly strained 1,2,4,6-cycloheptatetraene was prepared by photochemical phenylcarbene rearrangement inside the hemicarcerand host 1 and characterized spectroscopically in solution. Unexpected results were obtained from the investigation of the guest reactivity in the…
Blending porphyrins and calixpyrroles, the calix[n]phyrins 1 (n=4, 6, 8; x=1, 2, 3; Ar=C6H2(CH3)3) are easily prepared by condensing an appropriately functionalized dipyrromethane with acetone followed by oxidation with 4,5-dichloro-3,6-dioxo-1,2-benzenedinitrile. The structure of these molecules show a competition be…
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTDendritic Physical Gel: Hierarchical Self-Organization of a Peptide-Core Dendrimer to Form a Micrometer-Scale Fibrous AssemblyWoo-Dong Jang, Dong-Lin Jiang, and Takuzo AidaView Author Information Department of Chemistry and Biotechnology Graduate School of Engineering…
ADVERTISEMENT RETURN TO ISSUEPREVNoteNEXTSynthesis of Nanocrystalline CuMS2 (M = In or Ga) through a Solvothermal ProcessQingyi Lu, Junqing Hu, Kaibin Tang, Yitai Qian, Guien Zhou, and Xianming LiuView Author Information Structure Research Laboratory and Department of Chemistry, University of Science and Technology of…
We employ a new method for studying compositionally disordered ferroelectric oxides. This method is based on the virtual crystal approximation (VCA), in which two or more component potentials are averaged into a composite atomic potential. In our method, we construct a virtual atom with the correctly averaged atomic s…
We describe the introduction of titanium centers to cubic MCM-48 and SBA-15 mesoporous silica by hydrothermal and postsynthetic grafting techniques. MCM-48 was hydrothermally prepared with a gemini surfactant that favors the cubic phase and leads to a high degree of long-range pore ordering. This phase was chosen due…