Superior Circularly Polarized Luminescence Brightness Achieved with Chiral Heteroleptic Nine-Coordinate Coumarin-Based Tb<sup>3+</sup> Complexes
Jiaxiang Liu, Wenqi Song, Huizhe Niu, Ying Lü, Haiyan Yang, Wentao Li, Yuzhen Zhao, Zongcheng Miao
Abstract
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-Tb 3+ complexes, [Tb(Coum) 3 (1 R,2 R -Ph-PyBox)] ( 2 ) and [Tb(Coum) 3 (1 S,2 S -Ph-PyBox)] ( 5 ), combining 3-acetyl-4-hydroxy-coumarin ( Coum ) and enantiopure 2,6-bis(4-phenyl-2-oxazolin-2-yl) pyridine ( 1 R, 2 R / 1 S, 2 S -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 Tb 3+ enantiomers, with a bright Tb 3+ -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 5 D 4 → 7 F 5 ) has been established for complexes 2 and 5 . The strategy adopted in this work provides a new route to chiroptical organo-Tb 3+ luminophores with outstanding comprehensive performance.