Synthesis and Thermal Properties of Some Ferrocene Containing Liquid Crystals

The synthesis and mesophase characterization of some monosubstituted ferrocene-containing liquid crystals were reported. For a better understanding of the thermal behavior, the LC properties were compared with a series of pattern compounds, possessing similar structures, but without the ferrocenyl unit. The liquid crystalline compounds without ferrocene group presented a very short stability of the mesophase on heating, while all of them exhibit an enantiotropic behavior. The introduction of the ferrocenyl unit in the rigid core induced a monotropic or enantiotropic behavior. Although the appearance of a monotropic behavior is a little surprising, the bulkiness ferrocenyl unit is asymmetrically connected in respect of the rigid core axis. These behaviors were explained by the change of the dipolmoment in the rigid core, when one or two esteric groups are present.