Unusual Spin Transition Behavior in 2,6-Bis((pyrazol-3-yl)-pyridine) Iron(II)-bis-oxalato-platinate(II)

[Fe(bpp)2][Pt(ox)2]·H2O (with bpp = 2,6-bis(pyrazol-3-yl)-pyridine and ox = oxalate) was prepared, and its spin crossover behavior was characterized. The two-step spin transition behavior changes over several cycles. The original behavior is restored when the sample is allowed to relax for a week. Furthermore, the ST exhibits a strong dependence on the heating and cooling rate. Heating the compound at 1 K/min leads to a spin transition with a third step and a second plateau at γHS ≈ 0.8. Quenching the sample to 77 K also affects the spin transition behavior. The kinetic relaxation is followed after quenching and after light-induced excited spin state trapping experiments.