Homoleptic tris-cyclometalated platinum(IV) complexes: a new class of long-lived, highly efficient 3LC emitters

The synthesis of meridional and facial isomers of tris-cyclometalated Pt(IV) complexes, [Pt(C<^>N)(3)] OTf, where C<^>N is a C-deprotonated 2-phenylpyridine-based ligand or 1-phenylpyrazole, is reported for the first time. The facial isomers exhibit high-energy emissions from essentially (LC)-L-3 excited states, characterized by lifetimes of hundreds of microseconds and quantum yields up to 0.49 at room temperature in fluid solution, the highest ever found for Pt(IV) complexes. Stern-Volmer studies demonstrate the high sensitivity of the facial isomers toward oxygen and their electrochemical characterization reveals large redox gaps and a strong oxidizing character in the excited state.