Control of Circularly Polarized Luminescence by Orientation of Stacked π-Electron Systems

Planar chiral building blocks based on 4,7,12,15-tetrasubstituted [2.2]paracyclophanes were obtained via a synthetic route involving an optical resolution step. Planar chiral enantiomers, comprising two fluorophores that were stacked to form a V-shaped higher-ordered structure, were synthesized from these building blocks. The V-shaped molecules emitted intense circularly polarized luminescence (CPL). Their chiroptical properties were compared with those of X-shaped molecules bearing the same two fluorophores stacked together. The CPL sign of the X-shaped molecule was opposite to that of the V-shaped molecule, which is supported by the theoretical results, indicating that the CPL sign can be controlled by the orientation of the stacked fluorophores.