Hybrid Inorganic-Organic Complexes of Zn, Cd, and Pb with a Cationic Phenanthro-diimine Ligand.

The phosphonium-decorated phenanthro-imidazolyl pyridine ligand, Br, readily reacts with zinc(II) and cadmium(II) bromides to give inorganic-organic zero-dimensional compounds [ZnBr][ZnBr] () and [()CdBr][CdBr] (), respectively, upon crystallization. These salts are moderately fluorescent in the solid state under ambient conditions (λ = 458 nm, Φ = 0.11 for ; λ = 460 nm, Φ = 0.13 for ). Their emission results from spin-allowed electronic transitions localized on the organic component with the negligible effect of [MBr] and MBr units. Contrary to ionic species and , lead(II) bromide affords a neutral and water-stable complex [()PbBr] (), showing weak room-temperature phosphorescence arising from spin-orbit coupling due to the heavy atom effect. The emission, which is substantially enhanced for the amorphous sample of (λ = 575 nm, Φ = 0.06), is assigned to the intraligand triplet excited state, which is a rare phenomenon among Pb(II) molecular materials.