Novel Co complex with high transformation temperature of valence tautomerism

The preparation and characterization of [CoII-HS(dpa)(3,5-DBSQ)2] are presented first time. From the magnetic curve, the phase transition temperatures, Tc is 380 K. To our knowledge, the Tc value is the highest among the species exhibiting thermal valence tautomerism. After illumination with 532 nm light at 5 K, the magnetization values increase from μeff=1.73 to 2.0μB, showing valence tautomerism. The metastable state will recover to the original state with the increase of temperature. The alternate illumination with 532 and 830 nm light at 5 K can induce a reversible change in magnetization. The quick response to light means that this compound can be used for the development of optical–magnetic switch.