Metal-Induced Distally Axial Chirality of Vertical Binuclear Platinum(II) Complexes: Chirality Self-Sorting and Chiral Stability/Phosphorescence Enhancement.

Chirality is a fundamental property of nature. Herein, we demonstrate a straightforward strategy to build a new kind of metal-induced distally axial chirality based on vertical binuclear platinum(II) complexes. The strong and balanced steric hindrance between the four methyl substituents of sym-tetraacetylethane bridging ligand causes the two Pt-containing hexatomic rings in these binuclear Pt(II) complexes to be vertically linked by a C-C single bond. Although the two heterobidentate 2-phenylpyridine (C^N) ligands are spatially distant from the C-C single bond, they are strictly orthogonal to each other, resulting in metal-induced distally axial chirality. Moreover, such distally axial chirality can reduce the synthesis difficulty of asymmetric bridging ligands, extend axially chiral plane without distorting the coordination configuration, and enhance rotational barriers for high phosphorescent quantum yield and racemization energy barrier. The enantiomers of complexes can be separated by chiral high-performance liquid chromatography (HPLC) and their absolute configurations were confirmed by X-ray diffraction, circular dichroism, and density functional theory calculation. Furthermore, without the use of chiral HPLC, enantiopure complexes can be prepared using chiral binaphthalene- and estrone-based C^N ligands through chirality self-sorting. The estrone groups can also facilitate the formation of supramolecular gels by self-assembly.