Phosphorescent ligand-to-metal charge-transfer excited states in the group IVB metallocene triad

Long-lived ligand-to-metal charge transfer (LMCT) excited states based on a zirconium complex (ca. 2000 μs) and a hafnium complex (ca. 300 μs) are first characterised with use of the Cp2Zr(IV)Cl2 and Cp2Hf(IV)Cl2. The tendency in the observed photophysics (absorption and phosphorescence spectra, lifetimes, and quantum yields) in the homologous group IVB metallocenes Cp2M(IV)Cl2 is discussed in view of the nature of the unique metal (Ti, Zr or Hf)–ligand π-bonding character.