Strongly emitting Ge(ii) imide complexes

Abstract

The first Ge(II) imide dimers [^R1,R2ArNGe]₂ (^R1,R2Ar = 2,6-((4-R¹-C₆H₄)₂CH)₂-4-R²-C₆H₂) (R¹ = Me, R² = Me, 1 and R¹ = H, R² = Cl, 2) are shown to exhibit mixed metal-centered/ligand-to-metal charge-transfer (MC/LMCT) phosphorescence in the solid state and in solution. Absolute photoluminescence quantum yields reach Φ_p = 76.0% (crystals) and 8.5% (solution), surpassing those of previously reported molecular Ge emitters. Cooling enhances the emission, as the phosphorescence intensity and lifetime increase steadily from τ = 4.3 μs at 480 K to τ = 103.6 μs at 100 K, highlighting potential for luminescent thermometry and OLED-relevant materials. Computational analysis supports an HT-assisted phosphorescence mechanism with limited intrinsic SOC. Halogenation in [^H,ClArNGe]₂ (2) leaves solution photophysics largely unchanged but promotes a distinct packing motif that markedly amplifies solid-state emission.