The molecular and crystal structure of alpha,omega-bis[4-(4 '-hexyloxybenzylidene-iminophenyl)]octane (6O.8.O6) and alpha,omega-bis [4-(4 '-heptyloxybenzylideneiminophenyl)]octane (7O.8.O7)

The crystal and molecular structures of alpha,omega-bis [4-(4'-hexyloxybenz ylideneiminophenyl)]octane (6O.8.O6) and the homologue alpha,omega-bis [4-( 4'-heptyloxybenzylideneiminophenyl)]octane (7O.8.O7) have been determined b y direct methods at room temperature. The crystals of both compounds belong to the monoclinic system with space group P 2(1)/a and two molecules per u nit cell which are placed on centers of symmetry. For 6O.8.O6: a = 10.613(4 ), b = 8.7596(10), c = 22.149(7) Angstrom, beta = 100.02(2)degrees; for 7O. 8.O7: a = 5.909(4), b = 7.412(3), c = 47.174(27) Angstrom, beta = 91.15(3)d egrees. The structures were refined by full-matrix least-squares calculatio ns against F to R = 0.078 for 4993/(3596 unique) collected reflections for 6O.8.O6 and to R = 0.077 for 1772/(1548 unique) reflections for 7O.8.O7. Both molecules as a whole exhibit a rod-like form although the conformation s in the spacer and wing groups differ considerably. For both compounds the molecular packing consists of layers parallel to the a,b-plane, piled up i n c*-direction with minimal interdigitation of the wing groups. In 6O.8.O6 the layers are strongly tilted br an angle of about 60 degrees, in 7O.8.O7 they are tilted by a smaller angle of about 25 degrees towards the c*-direc tion.