Unsymmetrically disubstituted mesogens with a phenyl ring containing lateral branch. Crystal and molecular structure of smectogenic 4-nitrobenzyl 2-(3-chloro-4-n-octyloxybenzoyloxy)-5-(4-n-octyloxybenzoyloxy)benzoate

Abstract

The synthesis of unsymmetrically disubstituted mesogens bearing a cyclic unit within the bulky lateral branch is described. The three-ring basic mesogenic unit of the laterally 4-nitrobenzyloxy-carbonyl substituted molecules has been additionally provided with chlorine atoms in one or two positions, thus influencing the stability of the smectic A phases.

The crystal and molecular structure of the smectogenic 4-nitrobenzyl 2-(3-chloro-4-n-octyloxybenzoyloxy)-5-(4-n-octyloxybenzoyloxy)benzoate (NCOOB) has been determined by X-ray analysis. NCOOB crystallizes in the triclinic space group P1 with 4 molecules per unit cell and the following lattice parameters: a = 13.201(2) Å, b = 16.473(3) Å, c = 19.746(3) Å, α = 96.11(2)°, β = 95.34(2)°, γ = 99.92(1)°, V = 4178.4(1) Å3.

The phenylene bis(n-octyloxybenzoate) mesogenic basic fragment of the NCOOB molecule has a non-planar, but optimally stretched shape, with a perfect all-trans-conformation of the alkyloxy chains and the lateral benzene ring-containing branch is oriented parallel to it. The molecules are arranged in lamellar sheets which are characterized by a parallel molecular alignment with an interlocking of neighbouring molecules by their bulky branches and intercalation of the alkyl chains.