Optically Active Micellar-Cubic Liquid Crystals from Quasi-Racemic Octahedral Metallomesogens

Racemic octahedral metal complexes with Δ and Λ chirality and terminal C9 or C10 alkyl chains (M-Cn, n = 9 or 10, M = Ru or Ir) are reported as the first octahedral metallomesogens that exhibit a micellar cubic (Cub_M) liquid-crystal phase. The space group of the Cub_M phase in rac-M-Cn is $Im\overline{3}m$ , and each micelle comprises eight molecules in a J-type aggregate structure. In contrast, enantiopure Δ- and Λ-M-Cn exhibit a hexagonal-columnar phase with helical stacking. To confirm that the Δ-Λ chiral interaction acts as a driving force for the supramolecular assembly, quasi-racemic mixtures of Δ-Ru-C9 and Λ-Ir-C9 as well as Λ-Ru-C9 and Δ-Ir-C9 were prepared in a 1:1 molar ratio. The quasi-racemates exhibit a Cub_M phase with a J-type aggregate structure similar to that of pure rac-M-Cn. They also exhibit novel vibrational circular dichroism signals that are not observed in the enantiopure compounds, which are attributed to the close Δ and Λ packing. The obtained results suggest that mixing enantiomers in a quasi-mirror image relationship could be a new approach for producing novel chiroptical materials.