Photoexcitation and relaxation properties of a spin-crossover solid in the case of a stable high-spin state.
The molecular solid [Fe(II)L(2)](ClO(4))(2).CH(3)CN where L is 2,6-bis(3,5-dimethylpyrazol-1-ylmethyl)pyridine provides a stable high-spin (HS) state at low temperature. Photoexcitation and subsequent relaxation have been studied using light-induced excited state spin trapping [LIESST(H --> L)] in the 700-850 nm range, determination of T(LIESST), relaxation curves at different temperatures, and temperature dependence of the light-induced spin equilibrium under constant irradiation. The measured photoinduced population of the metastable low-spin (LS) state (<30%) was drastically limited by the concomitant L --> H photoprocess. The absence of static light-induced thermal hysteresis and the stretched exponential shape of the relaxation curves respectively revealed the absence of sizable interactions and a large spreading of the activation energies attributed to the ligand flexibility. The whole data set has been simulated using a linear rate equation, with a simplified correction for the bulk extinction of light in the powder sample.
Laboratoire de Magnétisme et d'Optique, CNRS-Université de Versailles, 78035 Versailles, France.
Cristian
C
Enachescu
François
F
Varret
Epiphane
E
Codjovi
Jorge
J
Linarès
Sébastien
S
Floquet
Palanichamy
P
Manikandan
Periakaruppan T
PT
Manoharan