Synthesis and Characterization of a β‐Thio‐δ‐Diimine (BTDDI) and the Related Bimetallic Dimethylaluminium(III) Compound

Thionation of the β‐oxo‐δ‐diimine (BODDI) 3 with P 2 S 5 ·2Py affords the ditopic β‐thio‐δ‐diimine (BTDDI) 4 . Based on 1 H NMR spectroscopy and single‐crystal X‐ray diffraction, 4 is best described as a bis(β‐enamine)‐thione in both solution and the solid state. Furthermore, 4 features a thermochromic behavior in solution ( c > 2 mmol l −1 ) and as a solid. Reaction with trimethyl aluminium readily affords the bimetallic dimethylaluminium BTDDI complex 5 . In contrast to its oxygen relative, 5 is only weakly emissive and the emission is significantly red‐shifted. Scalar‐relativistic time‐dependent density functional theory calculations suggest that introduction of the sulfur atom promotes an intersystem crossing pathway (∼1 ns) to low‐lying and non‐emissive triplet states, which competes with fluorescence (∼5 ns).