Luminescent Zirconocene Complexes with Pendant Phosphine Chalcogenide Donor Groups

Neutral zirconocene complexes of the type [(η5-C5Me5){η5-C5H4CMe2P(E)Ph2}ZrCl2] (E = not present, O, S, or Se) with a cyclopentadienyl-attached phosphine and related phosphine oxide, sulfide, or selenide moiety were prepared and converted to their cationic counterparts by chloride abstraction with K[B(C6F5)4] to give compounds of the general formula [(η5-C5Me5){η5-C5H4CMe2P(E)Ph2-κE}ZrCl]+[B(C6F5)4]−. Alternatively, the chloride abstraction was accomplished by the reaction with ZnCl2 to give the same cationic species with a [Zn2Cl6]2– counteranion. The ionic complexes, unlike the neutral counterparts, exhibited strongly enhanced luminescence properties originating in triplet ligand-to-metal (3LMCT) excited states. Luminescence quantum yields up to 0.95 were determined in the solid state with luminescence lifetimes up to 50.6 μs. In addition to structural characterization of the prepared complexes by X-ray diffraction methods, their electrochemistry was investigated by cyclic voltammetry, and their photophysical properties were studied with quantum-chemical calculations.