Abstract: A new compound Co[HN(C₅H₄N)₂](3,5-DBSQ)₂ with LIESST(Light-induced excited spin state trapping) and LIVT(Light-induced Valence Tautomeric) was synthesized. The magnetic property and relaxation kinetics of valence tautomerism were investigated. The starting temperature of valence tautomerism is about 300 K. After illumination with 532 nm light at 5 K, Co(Ⅱ)(low spin) obtained an electron from ligand 3,5-DBCAT and became Co(Ⅲ)(high spin) while 3,5-DBCAT changed to 3,5-DBSQ. The LIVT increased the effective magnetic moment of the complex. At the temperatures ranging from 5-30 K, the k VT values are independent of temperature, which means that the tunneling is the predominant mechanism for the relaxation behavior. At the temperatures from 30-70 K, the activation energy of relaxation after illumination is 252 cm^-1. When the complex is heated after illumination, the magnetization returns to the original state before irradiation. This means the relaxation temperature, T_R, is 70 K.

Key words: Light-induction, Magnetization, Valence tautomerism, Relaxation kineticst