Circularly Polarized Phosphorescence Properties of Binuclear Cyclometalated Platinum(II) Complexes Bearing Axially Chiral Schiff-Base Ligands

The synthesis, structure, and circularly polarized phosphorescence (CPP) properties of axially chiral cyclometalated binuclear platinum(II) complexes were described. A series of optically pure binuclear platinum(II) complexes were synthesized in five steps from commercially available (<i>R</i>)- or (<i>S</i>)-1,1'-bi-2-naphthol (BINOL) as starting materials. Their three-dimensional molecular structures and square-planar coordination geometries were elucidated from X-ray diffraction and 2D NMR analysis. The complexes were found to exhibit red- to near-infrared photoluminescence in solution and in the solid state. Furthermore, dilute DMSO solutions of the enantiopure samples showed red CPP with relatively high luminescence dissymmetry factor (<i>g</i>_lum) values. Density functional theory (DFT) calculations were conducted to examine their three-dimensional molecular conformations and photophysical properties.