Strongly emitting Ge(II) imide complexes.

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 Φp = 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.