Crystal structures of chiral mesogenic 4-hexylphenyl 4′-[(S)-2-methylbutyl]biphenyl-4-carboxylate and 4-[(S)-2-methylbutyl]phenyl 4′hexylbiphenyl-4-carboxylate

Abstract

Single crystal X-ray analysis has been carried out for 4-hexylphenyl 4′-[(S)-2-methylbutyl]biphenyl-4-carboxylate (1), which has a phase sequence of crystal-cholesteric-isotropic, and 4-[(S)-2-methylbutyl]phenyl 4′-hexylbiphenyl-4-carboxylate (2), which has a phase sequence of crystal-S_A-cholesteric-isotropic. Crystal data:

M _r = 428·61, C₃₀H₃₆O₂, monoclinic, P₂, T=298K, a = 25·697(3), b = 5·7055(4), c=18·718(1)Å, β=110·124(7)°, V= 2576·8(4) ų, Z=4, d_x =1·105 g cm⁻³, F(000)=928·00, μ 928·00, μ= 4·49 cm⁻¹;

M _r=428·61, C₃₀H₃₆O₂, monoclinic, P2₁, T=239 K, a = 25·631(2), b=10·019(1), c= 10·081(1) Å, B=94·67(1), V= 2580·1(5) Å₃, Z=4, d _x=1·103 g cm₋₃, F(000)=928·00, μ=4·48 cm₋₁.

Each crystal has a smectic-like layer structure, in which the molecular tilt angle is 50° in 1, and 30° in 2. Chiral groups are disordered in both crystals. Normal alkyl chains are also highly disordered in 2. The features correspond to the different mesophase sequences. The layer thickness of S_A was measured for 2 by X-ray diffraction.