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 3LC 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.