Switchable columnar metallomesogens

Chiral columnar liquid crystals have recently appeared as a promising new t ype of ferroelectric materials. To date, all the columnar liquid crystals t hat have been reported to show ferroelectric switching consist of organic c ompounds. However, metal-containing liquid crystals open this field to a si gnificant number of new structures and offer the possibility of adding to t he ferroelectric behavior other properties inherent to the presence of meta ls in the structure, such as magnetism, as well as the use of new methods o f characterization (EPR, synchrotron radiation, etc.). The potential of col umnar metal-containing liquid crystals as ferroelectric materials has been demonstrated even though only a few organic columnar ferroelectric liquid c rystals have been described. As a first approach to this type of material, this concepts article describes the results obtained with chiral metal P-di ketonates that show ferroelectric switching in the columnar mesophase. It h as been shown that these materials have a helical columnar arrangement in t he mesomorphic state, and a chiral superstructure has been proposed from ci rcular dichroism studies. This type of supramolecular structure plays a fun damental role in the ferroelectric properties of these compounds. The discu ssion is mainly focused on the strategy employed for the molecular design, and on the interpretation of the mesophase structure and the electrooptic e ffect. The use of a diverse range of techniques, both those commonly used i n the field of liquid crystals and those that are more specific will be hig hlighted, and the principles of these specific techniques are summarized to gether with a justification of their applicability to this study.