Circularly Polarized Luminescence Liquids Based on Siloxybinaphthyls: Best Binaphthyl Dihedral Angle in the Excited State

A series of axially chiral 1,1′‐binaphthyls with trialkylsiloxy (OSiR 3 ) groups were synthesized. Among them, 1 a – c possessing OSiR 3 groups at the 7,7′‐positions and methyl groups at the 2,2′‐positions were liquids at room temperature, and the neat liquids showed circularly polarized luminescence (CPL) (R=Bu; Φ fl,liquid =0.21, | g lum,liquid |=1.6×10 −3 ). The | g lum,liquid | value is the highest of pure liquids. These compounds remained liquid over a broad range of temperatures, down to −50 °C. Time‐dependent DFT calculations indicated that in the excited state, the binaphthyls adopt a transoid conformation with a small angle between the electric and magnetic transition dipole moments ( θ μ , m =77°), which is a key factor in their CPL activity. The best binaphthyl dihedral angle in the excited state is approximately 110°.