Solvent-Induced Sign Inversion of Circularly Polarized Luminescence: Control of Excimer Chirality by Hydrogen Bonding.

A series of pyrenes sandwiched by axially chiral 1,1'-binaphthyls were synthesized. Among them, (R,R)-3 possessing 2-hydroxy-3,3'-dimethylbinaphthyls exhibited solvent-dependent inversion of the sign of circularly polarized luminescence (CPL) without a change in emission wavelength. The (-)- and (+)-CPL were detected in nonpolar and polar solvents, respectively, with glum values of -0.012 and +0.012. This switching property originates from the inversion of excimer chirality caused by the presence or absence of intermolecular hydrogen bonds in the excited state. The CPL intensity was also changed by variation of the temperature and concentration.