Optically active micellar-cubic liquid crystals from quasi-racemic octahedral metallomesogens

Racemic octahedral metal complexes with and 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 (CubM) liquid-crystal phase. The space group of the CubM phase in rac-M-Cn is Im-3m, and each micelle comprises eight molecules in a J-aggregate structure. In contrast, enantiopure delta- and lambda-M-Cn exhibit a hexagonal-columnar phase with helical stacking, similar to that of enantiopure M-C8. To confirm that the delta–lambda chiral interaction acts as a driving force for the supramolecular assembly, quasi-racemic mixtures of delta-Ru-C9 and lambda-Ir-C9 as well as lambda-Ru-C9 and delta-Ir-C9 were prepared in a 1:1 molar ratio. The quasi-racemates exhibit a CubM phase with a J-aggregate structure similar to that of pure rac-M-Cn and novel vibrational circular dichroism signals that are not observed in the enantiopure compounds and can be attributed to the supramolecular J-aggregate structure. The obtained results suggest that mixing enantiomers in a quasi-mirror image relationship could be a new approach for producing novel chiroptical materials.