Iron(II) Spin‐Crossover Complexes in Ultrathin Films: Electronic Structure and Spin‐State Switching by Visible and Vacuum‐UV Light

The electronic structure of the iron(II) spin crossover complex [Fe(H2bpz)2(phen)] deposited as an ultrathin film on Au(111) is determined by means of UV-photoelectron spectroscopy (UPS) in the high-spin and in the low-spin state. This also allows monitoring the thermal as well as photoinduced spin transition in this system. Moreover, the complex is excited to the metastable high-spin state by irradiation with vacuum-UV light. Relaxation rates after photoexcitation are determined as a function of temperature. They exhibit a transition from thermally activated to tunneling behavior and are two orders of magnitude higher than in the bulk material.