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.