Enhanced Near-infrared Circularly Polarized Luminescence Activity in Fluorinated Binolate Ytterbium Complexes.

Abstract

Chiral lanthanide complexes hold great potential in developing advanced circularly polarized luminescence (CPL) materials in the near-infrared (NIR) wavelength range. While various ligands, such as β-diketonates and biphenols, have been successfully used to sensitize NIR emission of lanthanide ions, little attention has been paid to regulating CPL behaviors via ligand modification. In this study, we report the synthesis, structure, luminescence, and chiroptical properties of a pair of novel air-stable Shibasaki-type Yb(III) enantiomers supported by 3,3'-fluorinated binaphthol (F₂BINOL). Compared to their nonfluorinated counterparts, these fluorinated complexes exhibit larger dihedral angles between the two naphthyl moieties and more distorted octahedral coordination environments around the Yb(III) ion, leading to increased overall crystal field splitting. These structural modifications result in enhanced photophysical properties: the luminescence lifetime (τ_obs), sensitization efficiency (η_sens), and quantum yield (QY) improve from 2.1 µs, 38%, and 0.7% to 2.7 µs, 63%, and 1.8%, respectively. Additionally, the dissymmetry factor (g_lum) and CPL brightness (B_CPL) at 963 nm increase by 32% and one order of magnitude, respectively. The scope of such chemical modification is broad, potentially encompassing a variety of BINOL derivatives, offering a unique platform to further elucidate the relationship between structural and electronic properties and CPL activity in lanthanide systems.