Metal Dilution Effects on the Thermal and Light-Induced Spin Transition of Iron(II) in the Three-Dimensional Coordination Polymer [Fe^sub x^Zn^sub 1-x^(pyrazine)(Pt(CN)^sub 4^)]

The effects of metal dilution on the spin-crossover behavior on the three-dimensional coordination polymer [Fe(pyrazine)(Pt(CN)4)] have been studied in the mixed-crystal series [FexZn1-x(pyrazine)(Pt(CN)4)] (0 ≤ x ≤ 1), using magnetic and photomagnetic measurements. For all the materials investigated, the thermal spin-crossover properties, T1/2, were measured and the stability of the photoinduced high-spin states was probed through determination of the T(LIESST) values associated with the light-induced excited spin-state trapping (LIESST) effect. Whereas the neat polymeric [FeII(pz)(Pt(CN)4)] (pz = pyrazine) compound shows an abrupt spin transition centered at room temperature, it has been found that T1/2 decreases with the metal dilution. Similarly, dilution tends to decrease the hysteresis width and smoothen the transition curves: when x changes from 1 to 0.27, the transition temperature varies from 282 to 237 K in the cooling mode and from 308 to 237 K in the heating mode. The hysteresis, which is 26 K for x = 1.00, vanishes for x = 0.27. All the mixed-compounds exhibit LIESST effect. These results were discussed taking into account the relative sizes of Zn(II), high-spin Fe(II), and low-spin Fe(II) ions and compared with previous results.