The Crystal and Molecular Structure of Isobutyl 4-(4′-phenylbenzylidene-amino)cinnamate (IBPBAC) - and the Crystal Smectic E Transition

Abstract

The crystal and molecular structure of isobutyl 4-(4′-phenyl-benzylidene amino) cinnamate (IBPBAC), C₂₆H₂₅NO₂, has been determined at room temperature by direct methods. The crystals belong to the monoclinic system with space group Ce, a = 20.115(2), b = 5.589(1), C = 37.816(4) Š, β = 97.47 (1)[ddot] with eight molecules per unit cell. The structure was refined by full-matrix least-squares calculation to R = 0.059 for 1791 observed reflections. The structure is a bilayer with the molecules tilted at ∼40[ddot] to the layer normal and packed in each half layer in a distorted hexagonal arrangement. This substance melts to give a smectic Ephase and the relation between the structures of crystal and smectic E phases is described.