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.