Ultrafast spectroscopy of the uranium(IV) and thorium(IV) bis(ketimide) complexes (C₅Me₅)₂An[-N=C(Ph)(CH ₂Ph)]₂ (An = Th, U)

Ultrafast pump-probe spectroscopic studies have been performed on (C ₅Me₅)₂U[ - N=C(Ph)(CH₂Ph)] ₂ and (C₅Me₅)₂Th[ - N=C(Ph)(CH ₂Ph)]₂ including, for the uranium complex, the first direct measurement of dynamics of electronic deactivation within a 5f-electron manifold. Evidence has been found for strong coupling between the electronic ground state and the f-electron manifold which dominates the dynamics of the excited states of the bis(ketimide) uranium complex. These also demonstrate strong singlet - f manifold coupling, which assists in the deactivation of the photoexcited state of the uranium complex, and provide information on intersystem crossing and internal conversion processes in both complexes.