THE MOLECULAR AND CRYSTAL-STRUCTURE OF N-(4-N-BUTYLOXYBENZYLIDENE)-4'-ETHYLANILINE (4O.2) AND N-(4-N-HEPTYLOXYBENZYLIDENE)-4'-HEXYLANINE (7O.6)

The crystal and molecular structure of N-(4-n-butyloxybenzylidene)-4'- ethylaniline (40.2) and the homologue N-(4-n-heptyloxybenzylidene)-4'- hexylaniline (70.6) have been solved (at room temperature) by direct m ethods. The crystals of both compounds belong to the triclinic system with space group P1BAR with two molecules per unit cell. 40.2: a = 5.5 31(2), b = 7.592(3), c = 19.746(7) angstrom, alpha = 86.66(2), beta = 88.15(2), gamma = 90.29(2)-degrees; 70.6: a = 5.420(2), b = 8.307(3), c = 28.057(7) angstrom, alpha = 91.69(2), 89.76(2), gamma = 108.02(2)- degrees. The structures were refined by full-matrix least-squares calc ulations to R = 0.036 for 2297 observed reflections for 40.2 and to R = 0.037 for 2150 reflections for 70.6. The conformations in the asymme tric units of the two compounds differ considerably: The planes of the two phenyl rings of 40.2, forming the mesogenic core of the molecule, are twisted at 61.2-degrees to each other and the butoxy group contai ns a gauche conformation. In contrast the heptoxy chain of 70.6 forms an all trans-conformation which lies almost in one plane with the two coplanar phenyl rings. The hexyl group also exists in an extended form , in a plane which is rotated against the plane of the mesogenic unit. The packing in the crystalline state of the two homologues exhibits a layered structure along c; in 40.2 these layers are separated, but i n 70.6 they are interdigitated. The compensation of the dipole moments of the C-O-C and C=N-C bonds occurs similarly in both structures: mol ecular orientations parallel to the a,c-plane in which the long axes o f the molecules points in the same direction are packed in antiparalle l fashion along b.