Materials Literature
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B-trichloroborazene reacts with bis(trimethylsilyl)carbodiimide to form non-oxide gels (see scheme). The xerogels consist of a polymeric network of borazine rings linked by carbodiimide groups. Pyrolysis at 1200°C provides amorphous ceramics with the composition BC0.23N1.1Si0.05H0.09 ≈ B4CN4. At 2000°C pure B4C is for…
Eine prismenartige Hohlraumstruktur baut sich aus drei pyridylsubstituierten Porphyrin-„Platten“ auf, die durch sechs PdII-Ionen verknüpft werden. Eine drastische Strukturänderung (Symmetrieänderung von D3h nach C2) wird durch die Aufnahme von Pyren ausgelöst.
Esterified B12 icosahedra with totally organoderivatized surfaces are obtained from the reaction of [closo-B12(OH)12]2− with acetic anhydride or benzoyl chloride. The resulting “closomers”, in which each cluster vertex is substituted with an organic ester moiety, can provide camouflaged modules of variable size, shape…
The transient thermoreflectance (TTR) method consists of measuring changes in the reflectivity of a material (thin film) under pulsed laser heating, and relating these changes to the corresponding surface temperature variations. Analytical solutions of the diffusion problem are then used to determine the thermal condu…
The 18 and 19 valence electron (VE) nitrosyl complexes [Fe(NO)('pyS4')]BF4 ([1]BF4) and [Fe(NO)('pyS4')] (2) have been synthesized from [Fe('pyS4')]x ('pyS4'(2-) = 2,6-bis(2-mercaptophenylthiomethyl)pyridine(2-)) and either NOBF4 or NO gas. Complex [1]BF4 was also obtained from [Fe(CO)('pyS4')] and NOBF4. The cation […
The water-exchange reactions of three modified iron(III) porphyrins were studied in acidic medium as a function of temperature and pressure using 17O NMR spectroscopic techniques. The positive activation entropies and activation volumes support a dissociative mechanism (see scheme showing the transition state; L=nucle…
By analyzing the point groups of the (nonsymmorphic) rod-groups of carbon nanotubes we show, for the first time, to the best of our knowledge, that all achiral carbon nanotubes possess only 8 Raman-active and 3 infrared-active phonon modes. This is in contrast to previously predicted 15--16 and 7-8 active modes, respe…
The description of molecular motion by macroscopic hydrodynamics has a long and continuing history. The Stokes−Einstein relation between the diffusion coefficient of a solute and the solvent viscosity predicted using macroscopic continuum hydrodynamics is well satisfied for liquids under ordinary to high-temperature c…
The planar aromatic tridentate ligand 2,6-bis(1-S-neopentylbenzimidazol-2-yl)pyridine (L(11)) reacts with Ln(III) (Ln = La-Lu) in acetonitrile to give the successive complexes [Ln(L(11))(n)](3+) (n = 1-3). However, stability constants determined by spectrophotometry and NMR titrations show that formation of the tris c…
In this work we present a prospective study on the potential capabilities of optical devices based on Fibonacci dielectric multilayers. We perform a detailed analytical comparison of the linear optical response of periodic versus quasiperiodic multilayers. Based on this study we will suggest the use of hybrid-order de…
Sozusagen superamphiphob wurden extrem hydrophobe ausgerichtete Filme aus Kohlenstoffnanoröhren (siehe Elektronenmikroskopiebild), die durch Pyrolyse von Metallophthalocyaninen erhalten wurden, durch Modifizierung mit Fluoralkylsilangruppen. Dadurch erhielten die Filmoberflächen sowohl superhydrophobe als auch superli…
The synthesis of nitronyl and imino nitroxides has been reexamined with the aim of both increasing yields and of offering opportunities for new structures. The conditions for the formation of 2,3-bis(hydroxyamino)-2,3-dimethylbutane, the key intermediate of Ullman's route, have been carefully studied, and a new proced…
Ein enger elektrischer Kontakt besteht zwischen einem substituierten Polymetaphenylenvinylen (PmPV) und einem Bündel von Einzelwand-Nanoröhren (SWNT), wie durch kraftmikroskopische, optische und elektronische Messungen an isolierten SWNT/PmPV-Strukturen (siehe Bild) gezeigt wurde. Mithilfe von PmPV könnten SWNTs mögli…
This paper describes the chemical modification of high surface area, photoluminescent porous silicon (PSi) by reaction at a moderately elevated temperature (<115 °C) with alkenes (RCH CH 2 ) and aldehydes (RCHO) to give organic monolayers covalently bonded to the surface through Si−C and Si−O−C linkages, respectively.…
A prismlike hollow structure was assembled when three pyridyl-substituted porphyrin panels were linked by six PdII ions. A dramatic D3h→C2 structural change of the prism (see scheme) was triggered by complexation of pyrene.
We report the magnetic susceptibility, specific heat and dielectric constant for high-purity polycrystalline samples of three hexagonal manganites: YMnO 3 , LuMnO 3 and ScMnO 3 . These materials can exhibit a ferroelectric transition at very high temperatures ( T FE >700 K). At lower temperatures there is magnetic ord…
Diastereoselectivities as high as 98 % were the result of the photochemical ring-closure of stereochemically pure copper(I) helicates of a chiral oxazoline-substituted 1,2-dithienylethene photochrome (see scheme). The variations in optical rotation that accompany the photochromic event provide a means to read stored i…
Weak localization has a strong influence on both the normal and superconducting properties of metals. In particular, since weak localization leads to the decoupling of electrons and phonons, the temperature dependence of resistance (i.e., $λ_{tr}$) is decreasing with increasing disorder, as manifested by Mooij's empir…
Informationsspeicherung in einzelnen magnetischen Nanodrähten? Die Grundlage hierfür könnten erste Hinweise auf die langsame Dynamik liefern, welche für eindimensionale magnetische Systeme mit Ising-Anisotropie vorhergesagt wurde: Langsame magnetische Relaxation und Hystereseeffekte dynamischen Ursprungs wurden oberha…
The phase diagram and stability limits of diatomic solid nitrogen have been explored in a wide pressure--temperature range by several optical spectroscopic techniques. A newly characterized narrow-gap semiconducting phase $η$ has been found to exist in a range of 80--270 GPa and 10--510 K. The vibrational and optical…