Taking a last look at lanthanidomesogens? The use of basic thermodynamics for programming the temperature domains of existence of luminescent liquid crystals

As for any thermotropic liquid crystals (often referred to as mesogens), those containing transition metals (metallomesogens), and more specifically lanthanides (lanthanidomesogens) would benefit from rational correlations between the microscopic variations introduced by chemists in their molecular structures and some planned macroscopic properties such as temperature domain of existence, viscosity and supramolecular organization. The novel concept of cohesive free energy density (CFED) allows the building of pseudo-phase boundaries, which connect chemical perturbations, usually measured with the help of arbitrary structural parameters, into quantitative pressure increments relevant to those found in pressure-temperature phase diagrams. With the help of this novel toolkit, cyanobiphenyl-based dendrimeric tridentate ligands have been used as a proof-of-concept for exploring the consequences of (i) the successive methylation of polyaromatic termini, (ii) the complexation to luminescent europium carriers and (iii) the statistical doping with structural defects on the thermodynamic parameters which control the phase transitions.