Electron paramagnetic resonance and LIESST effect in spin-crossover cis-bis(thiocyanato)bis[N-(2-pyridyl-methylene)aminobiphenyl]iron(II) compound

Two different phases of spin-crossover cis-bis(thiocyanato)-bis(N-2'-pyridy lmethylene)-4-(aminobiphenyl) iron(II), Fe(PM-BiA)(2)(NCS)(2) have been inv estigated by EPR in X- and Q-bands. The EPR parameters for Mn2+ show that t he phase II has similar behavior to intentionally doped compound. EPR spect ra as function of the temperature reveal that the spin transition of the ir on(II) centers induced some modifications on the whole structure and then o n the environment of the manganese ions. The LIESST effect is reported for the two phases and for Fe0.216Mn0.784(PM-BiA)(2)(NCS)(2). The magnetic prop erties under irradiation of the phase II and of Fe0.216Mn0.784(PM-BiA)(2)(N CS)(2) are very similar and the limit temperature of the HS metastable stat e is around T-liesst = 50 K, as compared to 80 K for the phase I. The new k ind of bistability called LITH (Light Induced Thermal Hysteresis) has been observed for the three derivatives. The HS --> LS relaxation is higher for the phase II and Fe0.216Mn0.784(PM-BiA)(2)(NCS)(2) than for the phase I.