Crystal structures of chiral smectogenic 4′-octylbiphenyl-4-yl p-[(S)-1-methylheptyloxy]benzoate and p-octylphenyl 4′-[(S)-1-methylheptyloxy]biphenyl-4-carboxylate

Abstract

Single-crystal X-ray analyses have been carried out for 4′-octylbiphenyl-4-yl p-[(S)-1-methylheptyloxy]benzoate (1), which has a phase sequence of cryst.–s˙_C–chol.–iso., and p-octylphenyl 4′-[(S)-1-methylheptyloxy]biphenyl-4-carboxylate (2), which has a phase sequence of cryst.–s˙_C–s_A–chol.–iso. Each crystal has a smectic-like layer structure, in which the molecular tilt angle is large (65°) in 1, whereas it is small (10°) in 2. These features, which are interpreted to result from the molecular geometry, i.e. the length of the moiety sandwiched by polar groups, are closely related to the structures of the liquid-crystalline phases.