THERMAL AND OPTICAL SWITCHING OF IRON(II) COMPLEXES

The color change dark‐red ⇌ colorless accompanies the transition of [Fe(l‐propyltetrazole)6](BF4)2 from the low‐spin state to the metastable high‐spin state. These states in this complex can be interconverted as often as desired by irradiation with light of the appropriate wavelength or by increasing and decreasing the temperature. Such spin transitions change the properties of the material and can be influenced by many factors like pressure, ligand exchange, or isotopic exchange. If the effect could be controlled, these spin crossover complexes could be potential switches in optical information technology.