Enhanced Circularly Polarized Green Luminescence Metrics from New Enantiopure Binary Tris-Pyrazolonate-Tb3+ Complexes

Achieving superior circularly polarized luminescence brightness (<i>B</i>_CPL) is an important subject and continuous challenge for chiroptical materials. Herein, by applying a binary molecular design for the synthesis of chiral organo-Tb³⁺ molecules, a novel pair of mononuclear chiral <i>tris</i>-pyrazolate-Tb³⁺ enantiomers, [Tb(PMIP)₃(<i>R</i>,<i>R</i>-Ph-PyBox)] (<b>2</b>) and [Tb(PMIP)₃(<i>S</i>,<i>S</i>-Ph-PyBox)] (<b>5</b>), have been synthesized and characterized. The three 1-phenyl-3-methyl-4-(isobutyryl)-5-pyrazolone (<b>HPMIP</b>) ligands play the role of efficient luminescence sensitizers and strong light-harvesting antennas, while the enantiopure 2,6-bis(4-phenyl-2-oxazolin-2-yl) pyridine ligand (<b><i>R</i>,<i>R</i></b>/<b><i>S</i>,<i>S</i>-Ph-PyBox</b>) is employed as the strong point-chiral inducer. With the proper combination of the <b>HPMIP</b> and <b>Chiral-Ph-PyBox</b> within the Tb³⁺ enantiomers, strong (<b>PMIP</b>)<b>^-</b>-centered π-π^* electronic absorption (<i>ε</i>_{263 nm} = 38,400-39,500 M^-1 cm^-1) and brilliant high-purity ligand-sensitized Tb³⁺-centered green luminescence (<i>Φ</i>_PL = 47-48%) were observed. In addition, a clear circularly polarized luminescence (CPL) activity (|<i>g</i>_lum| = 0.096-0.103) was also observed, resulting in a strong <i>B</i>_CPL (610-623 M^-1 cm^-1) for the two Tb³⁺ enantiomers from the hypersensitive transitions. Our results offer an effective path to develop high-performance chiroptical organo-Tb³⁺ luminophores.