Photochemistry of (M = Zn, Cd, Hg) induced by metal to metal charge transfer excitation

Article abstract of DOI:10.1016/0022-328X(88)89005-3

The electronic absorption spectra of the complexes <(OC)4Co^-1M^IICo^-1(CO)4> with M = Zn, Cd, and Hg display an intense long-wavelength band which is assignated to the allowed Σu⁺ -> Σg⁺ transition from a non-bonding ? to an antibonding ? orbital of the Co-M-Co moiety.This transition is shifted to higher energies and gains an increasing charge transfer (CT) contribution in changing M in the order M = Hg, Cd, and Zn.In a limiting description the ?ⁿ -> ?^* transition can be regarded as a metal to metal (MM) CT transition from Co^-1 to M^II.MMCT excitation induced a photoredox reaction: <(OC)4Co^-1-M^II-Co^-1(CO)4> -> M⁰ + 02(CO)8>.The quantum yields are Φ = 0.45 (λ_irr = 333 nm) for M = Hg and Φ = 0.03 (λ_irr = 313 nm) for Cd.