Enhanced Circularly Polarised Luminescence via Intramolecular Excimers in Chiral Bis‐Naphthalene‐1,8:4,5‐Tetracarboxydiimide Derivatives

When a fluorescent molecule bearing a planar polycyclic aromatic hydrocarbon chromophore is placed in a chiral environment, it is expected to exhibit chiroptical properties such as circular dichroism and circularly polarised luminescence (CPL). Previously, we comparatively studied the fluorescence properties of the chiral bis‐1,8‐naphthalimide derivatives D ‐LyMebNI and L ‐LyMebNI in various solvents and successfully observed CPL originating from intramolecular excimer formation. This study aimed to develop compounds that form intramolecular excimers and exhibit higher CPL brightness ( B CPL ). To this end, we synthesised new chiral bis(1,8:4,5‐naphthalene tetracarboxy)imide derivatives, D ‐LyMebNDI and L‐ LyMebNDI, and investigated their photophysical properties. These molecules exhibited intramolecular excimer fluorescence in polar organic solvents. Mirror‐image circular dichroism and CPL spectra were obtained. In acetonitrile, D ‐ and L ‐LyMebNDI exhibited relatively large luminescence dissymmetry factors (| g lum |) of 2.2 × 10 −3 and 2.8 × 10 −3 , respectively. The B CPL of LyMebNDI was 12 M −1 cm −1 , representing a five‐fold increase relative to LyMebNI (2.5 M −1 cm −1 ). These findings provide insights into the development of practical CPL emitters and the modulation of CPL performance.