CRYSTAL AND MOLECULAR-STRUCTURES OF DIETHYL 6-[4-(4'-NITROPHENYLAZO)PHENOXY]-HEXYLMALONATE AND ITS 2'-NITROPHENYL ISOMER

The crystal and molecular structures of diethyl 6-[4-(4'-nitrophenylaz o)phenoxy]hexylmalonate (1) as a comonomer in the synthesis of liquid- crystalline polymers and its 2'-nitrophenyl isomer (2) have been deter mined by X-ray analysis. Both compounds crystallize in space group PT with two molecules per unit cell and the following lattice parameters. 1: a = 7.995(2), b = 10.699(2), c = 15.021(4) Angstrom, alpha = 95.04 (2), beta = 96.54(2), gamma = 94.72(3)degrees. 2: a = 8.912(2), b = 9. 664(2), c = 16.064(4) Angstrom, alpha = 98.68(2), beta = 97.54(1), gam ma = 105.11(1)degrees. The structures were solved by direct methods an d refined to R (wR) values of 0.082 (0.068) and 0.071 (0.076), respect ively. The molecules have an optimum stretched shape excepted one of t heir two ethoxycarbonyl groups which is perpendicularly oriented to th e molecular long axis. The molecular packing in the crystal can be des cribed in terms of a sheet structure in which the sheets are penetrate d by the laterally branched ethoxycarbonyl groups of neighboring sheet s.