Metal Dilution of Cooperative Spin-Crossover Compounds: When Stable and Metastable High-Spin States Meet

The photomagnetic properties of a series of metal-diluted spin-crossover complexes, [FexMn1-x(bpp)(2)](BF4)(2) [bpp = 2,6-bis(pyrazol-3-yl)pyridine], have been investigated and compared to the previously reported properties of the thermally quenched state. We observed clear evidence of an overlap between the stable high-temperature high-spin (HS) phase and the metastable low-temperature HS state. A detailed investigation of the evolution of the metastable HS state lifetimes has been performed and suggested a stabilization of the HS state when the overlap is efficient. The deduced thermodynamic parameters governing the relaxation process have been satisfactorily used to simulate the thermal and temporal evolution of the HS state.