The Radical Anion,Dianion and Electron Transport Properties of Tetraiodotetraazapentacene

Tetraiodotetraazapentacene I₄TAP , the last missing derivative in the series of halogenated silylated tetraazapentacenes, was synthesized via condensation chemistry from a TIPS-ethynylated diaminobenzothiadiazol in three steps. Single and double reduction furnished its air-stable monoanion and relatively air-stable dianion, both of which were characterized by crystallography. All three species are structurally and spectroscopically compared to non-halogenated TAP and Br₄TAP . I₄TAP is an n-channel material in thin-film transistors with average electron mobilities exceeding 1 cm² (Vs)⁻¹.     

An improved procedure for the preparation of very pure ethanol-OD

Changed molar ratio of starting materials and prolonged reaction times in the deuterolysis of tetraethylorthosilicate gave yields of pure (>99.5%) ethanol-OD (relative to starting D₂O) nearly twice of that of a literature procedure.

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Eine verbesserte Vorschrift zur Herstellung von hochreinem Ethanol-OD (Kurze Mitteilung)

Zusammenfassung Verändertes molares Verhältnis der Ausgangsverbindungen und längere Reaktionszeit bei der Deuterolyse von Orthokieselsäuretetraethylester führt zur nahezu zweifachen Ausbeute einer Literaturmethode an reinem (>99.5%) Ethanol-OD (relativ zu eingesetztem D₂O).

     

Bis (2,4,6,8-cyclononatetraen-1-yl)methane

Bis (2,4,6,8-cyclononatetraen-1-yl)methanes Bis (2,4,6,8-cyclononatetraen-1-yl)methanes ( 2a–c ) have been prepared by reaction of all-cis-cyclononatetraenide with 1,1-dichlorodimethyl ether as well as with carbenium ion precursors 9b and 9c . The title compounds 2 are attractive precursors of highly delocalised nonafulvenes of type 3 ; however, elimination experiments 2→3 failed so far.     

HPLC fractionation and structural dynamics of humic acids

Different soil extracted humic acids as well as a commercial humic acid sodium salt were fractionated by HPLC. An almost complete recovery could be achieved for the dissolved material. All humic samples show a typical chromatogram of at least five fractions. The separation of humic substances is influenced by an altered hydrophobicity due to changes in the tertiary structure. Three fractions were further investigated by Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy and by HPLC/HPLC separation. DRIFT spectroscopy provided data on the primary structure, whereas HPLC/HPLC results gave insight into the secondary and tertiary structure and their changes. Received: 18 June 1996 / Revised: 9 October 1996 / Accepted: 12 October 1996     

Polymer-bound osmium oxide catalysts

Polymer-supported oxidic osmium catalysts based on cross-linked poly(4-vinyl pyridine) were synthesized by various routes and characterized by a number of physical techniques (Raman, IR, XPS, ¹³C and ¹⁵N solid-state NMR spectroscopy). Model compounds of type Os₂O₆L₄ (L = pyridine, 4-iso-propyl pyridine, and 4-tert-butyl pyridine) were obtained under the conditions of the catalyst synthesis. The catalytic systems were successful in the dihydroxylation of alkenes.     

Tricyclic Pyrazole-Based Compounds as Useful Scaffolds for Cannabinoid CB1/CB2 Receptor Interaction

Cannabinoids comprise different classes of compounds, which aroused interest in recent years because of their several pharmacological properties. Such properties include analgesic activity, bodyweight reduction, the antiemetic effect, the reduction of intraocular pressure and many others, which appear correlated to the affinity of cannabinoids towards CB₁ and/or CB₂ receptors. Within the search aiming to identify novel chemical scaffolds for cannabinoid receptor interaction, the CB₁ antagonist/inverse agonist pyrazole-based derivative rimonabant has been modified, giving rise to several tricyclic pyrazole-based compounds, most of which endowed of high affinity and selectivity for CB₁ or CB₂ receptors. The aim of this review is to present the synthesis and summarize the SAR study of such tricyclic pyrazole-based compounds, evidencing, for some derivatives, their potential in the treatment of neuropathic pain, obesity or in the management of glaucoma.     

2- and 2,7-Substituted para-N-Methylpyridinium Pyrenes: Syntheses,Molecular and Electronic Structures,Photophysical, Electrochemical,and Spectroelectrochemical Properties and Binding to Double-Stranded (ds) DNA

Two N-methylpyridinium compounds and analogous N-protonated salts of 2- and 2,7-substituted 4-pyridyl-pyrene compounds were synthesised and their crystal structures, photophysical properties both in solution and in the solid state, electrochemical and spectroelectrochemical properties were studied. Upon methylation or protonation, the emission maxima are significantly bathochromically shifted compared to the neutral compounds, although the absorption maxima remain almost unchanged. As a result, the cationic compounds show very large apparent Stokes shifts of up to 7200 cm⁻¹. The N-methylpyridinium compounds have a single reduction at ca. −1.5 V vs. Fc/Fc⁺ in MeCN. While the reduction process was reversible for the 2,7-disubstituted compound, it was irreversible for the mono-substituted one. Experimental findings are complemented by DFT and TD-DFT calculations. Furthermore, the N-methylpyridinium compounds show strong interactions with calf thymus (ct)-DNA, presumably by intercalation, which paves the way for further applications of these multi-functional compounds as potential DNA-bioactive agents.     

Highly Emissive 9-Borafluorene Derivatives: Synthesis,Photophysical Properties and Device Fabrication

A series of 9-borafluorene derivatives, functionalised with electron-donating groups, have been prepared. Some of these 9-borafluorene compounds exhibit strong yellowish emission in solution and in the solid state with relatively high quantum yields (up to 73.6 % for FMesB-Cz as a neat film). The results suggest that the highly twisted donor groups suppress charge transfer, but the intrinsic photophysical properties of the 9-borafluorene systems remain. The new compounds showed enhanced stability towards the atmosphere, and exhibited excellent thermal stability, revealing their potential for application in materials science. Organic light-emitting diode (OLED) devices were fabricated with two of the highly emissive compounds, and they exhibited strong yellow-greenish electroluminescence, with a maximum luminance intensity of >22 000 cd m⁻². These are the first two examples of 9-borafluorene derivatives being used as light-emitting materials in OLED devices, and they have enabled us to achieve a balance between maintaining their intrinsic properties while improving their stability.     

Untersuchungen an Natriumtrifluormethylsulfonat – Kristallstruktur und Phasenumwandlung des Monohydrats und Natriumionenleitfähigkeit des wasserfreien Salzes

Studies on Sodium Trifluormethanesulfonate – Crystal Structure and Phase Transition of Sodium Trifluormethanesulfonate Monohydrate and Sodium Ion Conductivity of Anhydrous Sodium Trifluormethanesulfonate According to the results of temperature dependent powder diffractometry (Guinier-Simon-technique) sodium trifluormethanesulfonate monohydrate is dimorphous. The phase transition occurs at ?35°C. The room-temperature modification crystallizes monoclinic in space group P2₁/c with the lattice parameters a = 941.6(5) pm, b = 654.3(2) pm, c = 1062.4(5) pm and β = 107.73(2)°. The crystal structure consists of double layers of trifluormethanesulfonate anions, the lipophilic CF₃-groups pointing at each other. Sodium is coordinated by four oxygen atoms from four different anions and by two molecules of crystal water. The resulting polyhedron may be addressed as a distorted octahedron. The low-temperature modification crystallizes orthorhombic in space group Pnma with the lattice parameters a = 645.31(9) pm, b = 538.03(9) pm, c = 1745.3(3) pm. The loss of crystal water occurs at 136°C. Anhydrous sodium trifluormethanesulfonate shows a phase transition at 252°C. The high-temperature modification is a good sodium ionic conductor (σ = 4.1 · 10^?1 Ω^?1 cm^?1 at 250°C).