Spinolate Lanthanide Complexes for High Circularly Polarized Luminescence Metrics in the Visible and Near-Infrared.

Abstract

Analogues of Shibasaki's complexes supported by enantiopure Spinol are synthesized and characterized. The tris(Spinol) LnIII complexes are generated either by ligand deprotonation followed by complexation with lanthanide triflate salts or by in situ deprotonation by Ln(N(SiMe3)2)3 salts in the presence of additional base. The resulting complexes are found to be luminescent and chiroptically active for both circular dichroism and circularly polarized luminescence (CPL), notably producing strong CPL with dissymmetry factors (glum) of up to 0.50, 0.53, and 0.53 for Sm, Tb, and Dy, respectively. The Sm complex is found to be CPL-active in the near-infrared (NIR) region at 980 nm, representing the first report of NIR CPL from Sm. Additionally, the Tb complex, due to efficient sensitization (Φ = 0.846 in tetrahydrofuran) coupled with strong dissymmetry factors, achieves a CPL brightness (BCPL) of 3760 M-1 cm-1, the highest reported for any CPL-active compound to date. These are rare examples of compounds that show simultaneous improvement of both CPL metrics (glum and BCPL). Solid-state structural analysis of the Spinolate complexes and comparisons to other CPL-active analogues of Shibasaki's complexes also suggest that nondistorted geometries should generate even stronger metrics.