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

The phosphonium-decorated phenanthro-imidazolyl pyridine ligand, LP + Br, readily reacts with zinc(II) and cadmium(II) bromides to give inorganic-organic zero-dimensional compounds [ LP + ZnBr 2 ] 2 [ZnBr 4 ] ( 1 ) and [( LP + ) 2 Cd 2 Br 4 ][CdBr 4 ] ( 2 ), respectively, upon crystallization. These salts are moderately fluorescent in the solid state under ambient conditions (λ em = 458 nm, Φ em = 0.11 for 1 ; λ em = 460 nm, Φ em = 0.13 for 2 ). Their emission results from spin-allowed electronic transitions localized on the organic component with the negligible effect of [MBr 4 ] 2- and MBr 2 units. Contrary to ionic species 1 and 2 , lead(II) bromide affords a neutral and water-stable complex [( LP + ) 2 Pb 3 Br 8 ] ( 3 ), 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 3 (λ em = 575 nm, Φ em = 0.06), is assigned to the intraligand triplet excited state, which is a rare phenomenon among Pb(II) molecular materials.