Highly fluorinated liquid crystals with unprecedented polarity were obtained by introducing a tetrahydropyran moiety into their mesogenic core structure. The new materials exhibit an unusually favourable combination of mesophase properties, excellent solubility and low rotational viscosity,

Several examples of highly fluorinated sulfimides and sulfoximides have been synthesized in order to assess their potential usefulness as functional materials, such as liquid crystals or as active components in molecular electronics. The polarity of liquid crystals with these types of functional groups was lower than expected, due to conformational effects. A new synthetic method provides a convenient access to N,S,S‐triaryl sulfimides and sulfoximides, which were characterized by X‐ray crystallography. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

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The cover picture illustrates the conformational equilibrium of highly fluorinated sulfoximides. The conformation of this polar group critically influences the dielectric anisotropy of liquid crystals derived therefrom. The crystal structure of heterostilbene-like fluoroaromatic sulfoximides is dominated by stacking interactions of orthogonal aromatic substructures. Details are discussed in the article by P. Kirsch et al. on p. 797 ff.

Tetrafluoroethylene Substructures. -Aromatic and perfluoroaliphatic dithianylium salts (I) are dimerized in high yields by reduction with tetrakis(dimethylamino)ethylene. A clean conversion of the resulting bis(dithianyls) to the corresponding tetrafluoroethylene derivatives (III) is only achieved if the starting material has relatively electron-rich aromatic substituents. The oxidation of (IId) offers a convenient access to hexafluorodiacetyl (V). -(KIRSCH*, P.; LENGES, M.; RUHL, A.; SEVENARD, D. V.; ROESCHENTHALER, G.-V.; J.