Metal-Induced “Line-Plane-Helix” Mononuclear Platinum(II) Complexes: Stereochemical Configuration Control, Aggregation-Induced Phosphorescence, and Chiroptical Properties

Square-planar Pt(II) complexes are highly phosphorescent but suffer from a lack of metal-induced chirality and aggregation-caused quenching. Herein, a series of mononuclear Pt(II) complexes bearing simple Schiff base and 2-phenylpyridine ligands were synthesized. Tuning ligand steric hindrance enabled precise stereochemical control, inducing a planar-to-"line-plane-helix" transformation and affording axial, planar, and helical chirality. Combined density functional theory calculations and experiments show that racemization barriers range from 4.0 to 40.8 kcal/mol, governed primarily by steric effects. All complexes exhibit aggregation-induced phosphorescence with quantum yields up to 41.2%. One pair of racemic complexes was successfully resolved by chiral high-performance liquid chromatography, and their chiroptical properties were confirmed via circular dichroism and circularly polarized luminescence spectroscopy. This work establishes a comprehensive correlation between stereochemical configuration and chirality stability, providing definitive guidance for designing chiral-at-metal molecules.