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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:mrow><mml:mi>I</mml:mi> <mml:mi>m</mml:mi> <mml:mover><mml:mn>3</mml:mn> <mml:mo>¯</mml:mo></mml:mover> <mml:mi>m</mml:mi></mml:mrow> <mml:annotation>$Im\bar{3}m$</mml:annotation></mml:semantics> </mml:math> , 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.