Synthesis and mesomorphic properties of a new chiral series with anticlinic and TGB phases

A series of difluoro substituted benzoate derivatives: (R)-1-methylheptyl 4-[4-(3-fluoro-4-alkyloxybenzoyloxy)-3 -fluorobenzoyloxy]benzoates is reported. The short chain members (n=8 to 10) display a very rich polymesomorphic sequence with anticlinic properties: Cr-SmCA*-SmCFI*-SmC*-SmCalpha*-SmA-I; the longer chain members exhibit only TGB and SmC* phases. The mesomorphic properties were studied by optical microscopy, DSC, X-ray diffraction, electro-optical and helical pitch measurements, and optical rotatory power studies. The effect of the number and position of fluorines on the mesomorphic sequence is discussed.