Ferroelectric metallomesogens are a new type of ferroelectric liquid crystal which have unique properties arising from the presence of metal atoms. Here we report an overview of results based on the wide range of structural changes, either in the metallic centre or in the organic part, that these compounds offer.
Ferroelectric salicylaldiminate derivatives, imine ortho-palladated dinuclear complexes and ortho-metallated imine-β-diketone mononuclear compounds give rise to chiral smectic C ordered materials with macroscopic polarizations up to 200 nC.cm-2 while their response times are in the range of ms.
Depending on the metal and the structure of the metallomesogens, additional properties such as paramagnetic behavior as well as non-linear optical reponses are described for these new materials. Thus, imine-β-diketone compounds of Pd(II) and Pt(II) are the first metallomesogens ever reported which show second harmonic generation. deff values in the range of 0.03 to 0.06 pm.V-1 at 10 °C below the transition to the SmC* phase have been measured for these materials under phase matching conditions.