Imidazo[4,5-f]-1,10-phenanthroline and pyrazino[2,3-f]-1,10-phenanthroline substituted with long alkyl chains are
versatile ligands for the design of metallomesogens because of the ease of ligand substitution. Whereas the ligands
and the corresponding rhenium(I) complexes were not liquid-crystalline, mesomorphism was observed for the corresponding ionic ruthenium(II) complexes with chloride, hexafluorophosphate, and bistriflimide counterions. The
mesophases were identified as smectic A phases by high-temperature small-angle X-ray scattering (SAXS) using
synchrotron radiation. The transition temperatures depend on the anion, the highest temperatures being observed
for the chloride salts and the lowest for the bistriflimide salts. The ruthenium(II) complexes are examples of luminescent ionic liquid crystals.