Variable-Temperature and Variable-Magnetic Field Relaxation Dynamics of the LIESST State of a Spin-Crossover Complex*

Due to increased interest in understanding the mechanisms of intersystem crossing and controlling the switching of spin-crossover (SCO) complexes [1], the magnetic field effects on the temperature dependent relaxation rates of the metastable LIESST (light-induced electron spin-state trapping) state were studied in [Fe(ptz)₆](BF₄)₂, where ptz = 1-propyltetrazole, an Fe(II) SCO complex [2] with a
light-actuated tristability [3]. The magnet field effects on the relaxation of the photoinduced LIESST state have been studied for a different SCO complex [4]. Using a SQUID magnetometer and a homemade optical sample rod, the relaxation rates from the photoinduced high-spin (S = 2) LIESST state to its low-spin (S = 0) state were studied from 5 K to 45 K and in 100 G to 70 kG. Using MatLab and Origin programs, the data analysis suggests the relaxation is not well fit by a single exponential decay. These results and future directions will be presented.

[1] N.J. Higdon et al., J. Chem. Phys. 152 (2020) 204306.
[2] S. Decurtins et al., Chem. Phys. Lett. 105 (1984) 1.
[3] X. Feng et al., J. Am. Chem. Soc. 135 (2013) 15880.
[4] Y. Ogawa et al., Phys. Rev. B 66 (2002) 073104.