Circularly polarized yellow luminescence using novel chiral binary coumarin-based Dy3+ complexes

Circularly polarized luminescence (CPL) in weakly emissive organo-Dy 3+ complexes has been largely unexplored. The energy gap between the Dy 3+ excited 4 F 9/2 -emitting state and adjacent 6 F 1/2 state is extremely narrow. In order to address this challenge, we have adopted a heteroleptic molecular strategy to construct a pair of novel chiral binary coumarin-based Dy 3+ enantiomers: [Dy(Coum) 3 ( R , R - i pr-PyBox)] ( 2 ) and [Dy(Coum) 3 ( S , S - i pr-PyBox)] ( 5 ), where Coum  = 3-acetyl-4-hydroxy-coumarin and R , R / S , S - i pr-PyBox  = 2,6-bis(( R / S )-4-isopropyl-4,5-dihydrooxazol-2-yl)pyridine. A synergistic integration of the coumarin-derived Coum ligand with high-efficiency sensitization and light-harvesting capabilities and the CPL-induced bis(oxazoline) Chiral- i pr-PyBox derivatives resulted in complexes 2 and 5 exhibiting intense high-purity yellow light ( Φ PL  = 18–19 %) with intense CPL signals (| g lum | = 0.017–0.090). This approach has enabled an effective trade-off with respect to quantum efficiency and degree of polarization. An integrated superior CPL brightness ( B CPL ; 22.2–46.9 M −1  cm −1 ) has been established for the two Dy 3+ enantiomers across multiple 4 F 9/2 → 6 H J/2 transitions (J = 15, 13 and 11). The findings of this study have demonstrated the viability of the binary molecular design strategy in developing high-performance chiroptical organo-Dy 3+ luminophores.