Crystal and Molecular Structures of Diethyl 6-[4-(4′-Nitrophenylazo)phenoxy]-hexylmalonate and its 2′-Nitrophenyl Isomer

Abstract

The crystal and molecular structures of diethyl 6-[4-(4′-nitrophenylazo)phenoxy]hexylmalonate (1) as a comonomer in the synthesis of liquid-crystalline polymers and its 2′-nitrophenyl isomer (2) have been determined by X-ray analysis. Both compounds crystallize in space group P1 with two molecules per unit cell and the following lattice parameters. 1: a = 7.995(2), b = 10.699(2), c = 15.021(4) Å, a = 95.04(2), β = 96.54(2), γ = 94.72(3)°. 2: a = 8.912(2), b = 9.664(2), c = 16.064(4) Å, α = 98.68(2), β = 97.54(1), γ = 105.11(1)°. The structures were solved by direct methods and refined to R (wR) values of 0.082 (0.068) and 0.071 (0.076), respectively.

The molecules have an optimum stretched shape excepted one of their two ethoxycarbonyl groups which is perpendicularly oriented to the molecular long axis. The molecular packing in the crystal can be described in terms of a sheet structure in which the sheets are penetrated by the laterally branched ethoxycarbonyl groups of neighboring sheets.

Key Words:

• Liquid-crystalline polymers
• side group mesogens
• molecular structure
• crystal packing