Structural and Magnetic Study of New LIESST and reverse-LIESST Fe(trz)1.5[Au(CN)2]2 Complex

Department of Chemistry, National Taiwan University
○Lai-Chin Wu Yu Wang

The spin transition between high spin (HS) and low spin (LS) state of metal with d4-d7 electronic configuration has been studied for several dozen years. Spin transition phenomenon can be induced by temperature, pressure and even light. Light induced spin change was called light-induced excited state spin trapping (LIESST). Cooperative effect is an important effect. Usually, abrupt spin transition and spin transition with hysteresis loop happened with strong cooperative effect. Holfmann-like structure is always with relative strong such effect.
A new spin transition complex Fe(trz)1.5[Au(CN)2]2 was synthesized. The magnetic property was studied by SQUID magnetometer. The magnetic property shows half and gradual spin transition which was found between 200K to 80K with Tc around 155K, followed with anti-ferromagnetic interaction until the temperature down to 1.8K. This phenomenon is also reflected on C≡N stretching of IR spectrum. Two peaks can be assigned for LS and HS at wave number, 2135 and 2167 cm-1, respectively. Interestingly, the strength of two C≡N stretching is changed when we light the sample with 532 and 808 nm laser at about 10K. It shows LIESST and reverse-LIESST properties, respectively.