Superior Circularly Polarized Luminescence Brightness Achieved with Chiral Heteroleptic Nine-Coordinate Coumarin-Based Tb3+ Complexes

In order to facilitate the practical application of circularly polarized luminescence (CPL) active molecules, the CPL brightness (B_CPL) must be optimized. We have applied a binary modular strategy to synthesize two chiral organo-Tb³⁺ complexes, [Tb(Coum)₃(1R,2R-Ph-PyBox)] (2) and [Tb(Coum)₃(1S,2S-Ph-PyBox)] (5), combining 3-acetyl-4-hydroxy-coumarin (Coum) and enantiopure 2,6-bis(4-phenyl-2-oxazolin-2-yl) pyridine (1R,2R/1S,2S-Ph-PyBox). The photophysical properties of these novel complexes have been fully characterized. The combined point-chiral induction capability of chiral bis(oxazoline) derivatives and the outstanding photophysical properties of the coumarin-derived ligand have resulted in an intense excited-state chiroptical activity (|g_lum| = 0.097-0.103) for both Tb³⁺ enantiomers, with a bright Tb³⁺-centered high-purity green emission (Φ_PL = 74%) and enhanced antenna-centered absorption behavior (ε_{320 nm} = 47820-47940 M^-1 cm^-1). A superior B_CPL (1132.7-1205.8 M^-1 cm^-1 at ⁵D₄ → ⁷F₅) has been established for complexes 2 and 5. The strategy adopted in this work provides a new route to chiroptical organo-Tb³⁺ luminophores with outstanding comprehensive performance.