Circularly Polarized Luminescence of Chiral Perylene Diimide Based Enantiomers Triggered by Supramolecular Self-Assembly

Two perylene diimide (PDI) enantiomers (D/L-PDI) incorporating the D/L-alanine moiety have been designed and synthesized. D/L-PDI in chloroform displays bright-yellow fluorescence that is redshifted to orange-red when the solvent contains a methanol fraction of 99 vol %. No circular dichroism (CD) or circularly polarized luminescence (CPL) signals were observed for D/L-PDI enantiomers in CHCl3. Interestingly, the D/L-PDI enantiomers exhibit clear mirror-image Cotton effects and CPL emission in the aggregate state. The optical anisotropy factor (g(lum)) is as high as 0.02 at f(m)= 99%, which can be attributed to self-assembly through intermolecular pi-pi interactions in the aggregate state.