Amplified Circularly Polarized and X-ray-Excited Luminescence of Easily Separated Chiral Donor–Acceptor Binaphthalene Imides through a Conformation Locking Strategy

Here, we report a feasibly prepared chiral donor–acceptor (D–A) binaphthalene imide scaffold with locked conformation, exhibiting significantly improved luminescent performance compared with its open conformation species. The C1-symmetrical chiral imide based on a 1,1′-binaphthol (BINOL) backbone could be synthesized on the gram scale with only silica column chromatography resolution, which gave a photoluminescence quantum yield (PLQY) of about 6%. Further configuration rigidification by etherification of the BINOL backbone with a series of alkane linkers showed enhanced PLQY of up to 37% and turned on circularly polarized luminescence (CPL). Moreover, the photophysical data and theoretical calculations revealed that the enhanced molecular orbital overlap and spin–orbital coupling of these locked chiral imides led to the activation of the X-ray excited luminescence (XEL) property, which was successfully applied in an X-ray radiography model. This work not only provides a methodology for synthesizing novel chiral D–A scaffolds but also highlights the potential of conformation locking strategy in achieving multifunction luminescence for axially chiral π-conjugated molecules.