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 (OSiR3) groups were synthesized. Among them, 1 a-c possessing OSiR3 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; phi(fl,liquid)=0.21, |g(lum,liquid)|=1.6x10(-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 degrees 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 (theta(mu,m)=77 degrees), which is a key factor in their CPL activity. The best binaphthyl dihedral angle in the excited state is approximately 110 degrees.

Automated summary

A series of axially chiral 1,1'-binaphthyls with trialkylsiloxy (OSiR3) groups have been synthesized, with some showing circularly polarized luminescence (CPL) in liquid state at room temperature. Time-dependent DFT calculations revealed a transoid conformation in the excited state is essential for the CPL activity, with a dihedral angle of approximately 110 degrees.