Gold Liquid Crystals in the XXI Century

Since the first gold liquid crystal was described in 1986, much effort has been done to prepare new compounds bearing this property. The review deals with the last results obtained in this new century. Gold(I) has a strong affinity to give linear co-ordination and metal-metal interactions, which produce a rich supramolecular chemistry, and can promote the behavior as liquid crystal. Therefore, most liquid crystals are based on rod-like gold(I) compounds, while gold(III) liquid crystals are scarce. Calamitic and discotic mesogens have been reported, as well as chiral liquid crystals. Weak interactions such as H-bonds have also been used to obtain gold mesogens. Some of them exhibit additional properties, such as color, luminescence, and chirality. Luminescence has been reported, not only in the solid state or in solution, but also in the mesophase. This is relevant for applications in LEDs (Light Emitting Diodes), information storage, and sensors.