Introducing bulky functional lanthanide cores into thermotropic metallomesogens: a bottom-up approach

Basic thermodynamic considerations are used to rationalize the formation of thermotropic mesophases incorporating aromatic ligands for trivalent lanthanide metal ions (Ln). Standard flat and bent molecular interfaces, separating the central binding unit from the lateral, flexible alkoxy chains, provide programmed lamellar and columnar organization in the mesophases, which are removed upon complexation to Ln(NO3)3 and Ln(CF3CO2)3. Only significantly curved aromatic/aliphatic interfaces, found in polycatenar ligands, are able to overcome the considerable perturbations of the intermolecular interactions produced by the introduction of the bulky metallic core. A rich mesomorphism results, which can be tuned by a judicious control of the metallic coordination sphere. The exploitation of specific, metal-centered luminescence for probing phase transitions and microscopic environments in mesophases is also discussed, as is the use of ionic liquids for producing tunable luminescent mesophases.