Columnar mesophases from half-discoid platinum cyclometalated metallomesogens

A series of liquid crystals have been synthesized and studied based upon mononuclear ortho-platinated rod-like heteroaromatic and 1,3-diketonate ligands. The liquid crystalline properties of these molecules were investigated using polarized light optical microscopy, differential scanning calorimetry, single crystal X-ray diffraction, and powder X-ray diffraction. Increasing the number of alkyl chains attached to the 1,3-diketonate units resulted in a transition from lamellar (SmA) to hexagonal columnar phases (Colh). The 2-thienylpyridine units were previously unexplored in metallomesogenic complexes and these studies extend the utility of ortho-platinated 2-phenylpyridines and 2-thienylpyridines to produce columnar liquid crystalline phases. The platinum complexes all display photoluminescence and are of interest for electrooptical applications.