Induced Circularly Polarized Luminescence of Dynamically Racemic Luminophores Assisted by Formation of Helical Phase via Self-Assembly of Chiral Block Copolymers

This work aims to suggest a facile approach for induced circular dichroism (ICD) and induced circularly polarized luminescence (iCPL) of the optically inactive, dynamically racemic luminophore tris(1,1,1,2,2,3,3-heptafluoro-7,7-dimethyl-4,6-octanedionato)europium(III) (rac-Eu(fod)₃), through deracemization by interaction with chiral block copolymers (BCPs*), polystyrene-b-poly(l-lactide) (PS-b-PLLA), and polystyrene-b-poly(d-lactide) (PS-b-PDLA)). In a dilute solution, rac-Eu(fod)₃ exhibits no circular dichroism (CD) and a negligibly weak CPL in the presence of PS-b-PLLA and PS-b-PDLA. By contrast, significantly strong CD and CPL of the rac-Eu(fod)₃ chromophore can be induced by the mesochiral self-assembly of BCPs* with the formation of a helical phase (H*) that mostly relies on a highly enantiomer-selective deracemization of the rac-Eu(fod)₃ with propeller chirality (Δ or Λ form) upon complexation with the BCPs*, resulting in a high-luminescence dissymmetry factor up to approximately 10^–2. The vibrational circular dichroism (VCD) results reveal that the VCD signals of the chiral polylactide chains in H* can be remarkably enhanced upon complexation with the deracemized Eu(fod)₃. The enhanced twisting of the packing of polylactide chains via interchain chiral interaction due to the presence of the nonracemic (deracemized) Eu(fod)₃ provides a unique platform for the design of chiroptical devices in various applications.