STRUCTURES OF 2 CRYSTAL FORMS OF CHIRAL SMECTOGENIC 4'-HEXYLOXY-4-BIPHENYLYL P-((S)-2-METHYLBUTYL)BENZOATE

Three crystal forms were found for the title compound. The relationship of the polymorphs was elucidated by DSC and powder X-ray diffraction methods. Two crystal structures, stable at room temperature, have been determined by single crystal X-ray analysis. Crystal data: 4'-hexyloxy-4-biphenylyl p-[(S)-2-methylbutyl]benzoate, [GRAPHICS] M(r) = 444.6, C30H36O3, 1, triclinic, P1, T = 298 K, a = 11.550(2), b = 22.940(3), c = 11.810(3) angstrom, alpha = 104.08(2), beta = 112.87(2), gamma = 99.49(2)-degrees, V = 2676(1) angstrom-3, d(x) = 1.110 g cm-3, mu = 4.74 cm-1, F(000) = 960; 2, monoclinic, P2(1), T = 298 K, a = 23.304(2), b = 5.6080(5), c = 20.451(4) angstrom, beta = 98.39(1)-degrees, V = 2644.1(6) angstrom-3, Z = 4, d(x) = 1.117 g cm-3, mu = 4.80 cm-1, F(000) = 960. Each crystal is composed of a smectic-like layer structure with a large molecular tilt angle (45-degrees and 60-degrees, respectively). The molecules in 1 have largely twisted paraffin chains and the twisted biphenyl moieties, while those in 2 have all-trans zigzag paraffin chains and coplanar biphenyl moieties. Packing modes of the core moieties are also largely different: some of the mutual arrangements of the phenyl rings are nearly parallel (approximately 20-degrees) in 1, while the contact angle of the phenyl rings between the neighbouring molecules is 60-degrees on average in 2.