Transient absorption spectroscopy of the [Fe(2 CH3-phen)3]2+ complex: Study of the high spin ↔ low spin relaxation of an isolated iron(II) complex

We report on the light induced spin crossover dynamics of [Fe(2 CH3-phen)3]2+ complex in solution. The excitation of the complex by pulses centered at λ = 500 nm along the metal to ligand charge transfer absorption band indicates a selective excitation of the LS state. The excitation of the complex by pulses centered at λ = 330 nm or λ = 335 nm reveals an increase of the LS state population and a photo-bleaching of the HS state population that is associated to a transient photo-dissociation. A method that makes it possible to deduce the kinetics of both the HS → LS state and LS → HS state is proposed.