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, T-c is 380 K. To our knowledge, the T-c 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 mu(eff)=1.73 to 2.0 mu(B), 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. (C) 2004 Elsevier B.V. All rights reserved.