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

Achieving superior circularly polarized luminescence brightness (B_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 tris-pyrazolate-Tb³⁺ enantiomers, [Tb(PMIP)₃(R,R-Ph-PyBox)] (2) and [Tb(PMIP)₃(S,S-Ph-PyBox)] (5), have been synthesized and characterized. The three 1-phenyl-3-methyl-4-(isobutyryl)-5-pyrazolone (HPMIP) 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 (R,R/S,S-Ph-PyBox) is employed as the strong point-chiral inducer. With the proper combination of the HPMIP and Chiral-Ph-PyBox within the Tb³⁺ enantiomers, strong (PMIP)^--centered π-π^* electronic absorption (ε_{263 nm} = 38,400-39,500 M^-1 cm^-1) and brilliant high-purity ligand-sensitized Tb³⁺-centered green luminescence (Φ_PL = 47-48%) were observed. In addition, a clear circularly polarized luminescence (CPL) activity (|g_lum| = 0.096-0.103) was also observed, resulting in a strong B_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.