Thermotropic properties of monosubstituted ferrocene derivatives bearing bidentateN-benzoyl-N′-arylthiourea ligands—novel building blocks for heterometallic liquid crystal systems

Abstract

Ferrocene-based derivatives such as 4-{3-[4-(octyloxy)benzoyl]thioureido}phenyl 4-ferrocenylbenzoate and other higher homologues (n=12,16 and 18; n=length of alkoxy chain) were prepared by reacting 4-alkoxybenzoyl isothiocyanates with the corresponding amines containing the ferrocenyl moiety. Their mesomorphic properties were investigated by means of polarized optical microscopy and differential scanning calorimetry. All the compounds exhibit enantiotropic nematic phases and the nematic range increases with increasing terminal alkyl chain length. On cooling, the nematic phase persists below 0 °C in the first three compounds and in the case of n=18, a phase transformation, possibly to the S_Cphase, around 72 °C during cooling was observed. In all cases, a glass transition was observed around T_g=18–35 °C, which is remarkable for low molecular mass calamitic metallomesogen systems.