Luminescent d⁰ Scandocene Complexes: Photophysical Studies and Electronic Structure Calculations on Cp*₂ScX (X = Cl, I, Me)

The room-temperature luminescence and photophysics of a series of early transition metal, first-row organometallic complexes with the general formula Cp*₂ScX (where Cp* is η₅-C₅(CH₃)₅⁻ and X represents a σ-donating ligand) are reported. Semiempirical molecular orbital calculations using the INDO/S method (ZINDO) have been performed. The calculations were carried out using full C₅(CH₃)5⁻ ligands for Cp*₂ScX, X = Cl, I, CH₃. The calculations indicate a large amount of metal and ligand orbital mixing in these d⁰ complexes, with the lowest unoccupied molecular orbitals consisting principally of Sc d-orbitals admixing with the Cp* π-orbitals. The highest-occupied molecular orbital for the chloride derivative contains primarily Cp* character, while that of the iodide species is mostly halogen in nature. The presence of a lone pair on X is requisite for room-temperature emission to occur, as evidenced by the observation of luminescence for X = Cl⁻, I⁻, and NHPh and by the lack of luminescence from Cp*₂ScCH₃ or Cp*₂ScCH₂Ph, under identifical conditions.