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 (<i>B</i>_CPL) must be optimized. We have applied a binary modular strategy to synthesize two chiral organo-Tb³⁺ complexes, [Tb(Coum)₃(1<i>R</i>,2<i>R</i>-Ph-PyBox)] (<b>2</b>) and [Tb(Coum)₃(1<i>S</i>,2<i>S</i>-Ph-PyBox)] (<b>5</b>), combining 3-acetyl-4-hydroxy-coumarin (<b>Coum</b>) and enantiopure 2,6-bis(4-phenyl-2-oxazolin-2-yl) pyridine (<b>1</b><i><b>R</b></i>,<b>2</b><i><b>R</b></i>/<b>1</b><i><b>S</b></i>,<b>2</b><i><b>S</b></i><b>-Ph-PyBox</b>). 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 (|<i>g</i>_lum| = 0.097-0.103) for both Tb³⁺ enantiomers, with a bright Tb³⁺-centered high-purity green emission (<i>Φ</i>_PL = 74%) and enhanced antenna-centered absorption behavior (<i>ε</i>_{320 nm} = 47820-47940 M^-1 cm^-1). A superior <i>B</i>_CPL (1132.7-1205.8 M^-1 cm^-1 at ⁵D₄ → ⁷F₅) has been established for complexes <b>2</b> and <b>5</b>. The strategy adopted in this work provides a new route to chiroptical organo-Tb³⁺ luminophores with outstanding comprehensive performance.