The synthesis and properties of fluorinated quinoline liquid crystals

The synthesis and transition temperatures of a series of novel liquid cryst alline quinolines is described. Palladium-catalysed coupling of arylboronic acids to 6-bromoquinolines is used to create 6-alkyl-2-arylquinolines in w hich the phenyl ring is fluorinated at the 2' and 2',3'-position. The fluor o-substituents give rise to low melting liquid crystals with a wide-rang Sm A phase. The Chichibabin reaction is employed to synthesise 6-alkyl-2-arylq uinolines but fluoro-substitution is limited to the 3'-position. These comp ounds are low melting with broad SmC temperature ranges and SmA and N phase s. When a fluoro substituent is attached directly to the quinoline nucleus and on the same side as the nitrogen atom the dielectric bioaxiality will b e increased and the smectic phase range is greater than for those in which the aryl substituents are fluorinated.