Photoinduced phase transition and relaxation behavior in a spin-crossover Fe (II) complex Nafion-[Fe(Htrz)(3)] film

We have observed a photoinduced phase transition (PIPT) in a spin-crossover Fe (II) complex Nafion [Fe(Htrz)(3)] film (Nafion is an ion exchange polym er film, and Htrz = 1, 2, 4-1H-triazole) from a low-spin (LS) state (S = 0) to a high-spin (HS) state (S = 2) below 150 K. The phototransferred HS sta te relaxes to the initial LS state, exhibiting a nonexponential time behavi or, which has been interpreted in terms of the critical nucleation and subs equent growth of the LS clusters. We have also observed that the decay time tau (c) is approximately temperature-independent in the low temperature ra nge of 4.2-20 K, and then decreases exponentially with temperature.