Dinuclear Triple-Stranded Helicates Comprising Al(III), Ga(III), or In(III) and a Hydrazine-Linked Bisiminopyrrolyl Ligand: Synthesis, Structure, Optical Resolution, and Chiroptical Properties

The synthesis of helical complexes is attracting increased attention because their chiral properties lead to a variety of functional applications. In this work, a series of neutral, dinuclear M(III) (M = Al, Ga, or In) triple-stranded helicates were prepared using a tetradentate bisiminopyrrole ligand (H2L). An X-ray crystallographic analysis revealed that both right-(P) and left-handed (M) helical structures exist in the solid state for Al2L3, Ga2L3, and In2L3. The enantiomers were successfully resolved by chiral column chromatography, and the chiroptical properties of the complexes were characterized by circular dichroism, circularly polarized emission spectroscopy, and time-dependent density functional theory calculations.