Photoinduced phase transition to a new macroscopic phase in the spin-crossover complex

We have investigated infrared absorption spectra of the spin-crossover complex, [FeII(2-pic)3]Cl2EtOH in the high-, low-temperature phase (HTP and LTP) and in the photoinduced phase (PIP). It is confirmed that PIP has vibrational modes different from HTP and LTP, especially in the region from 400 to 750 cm−1. These vibrational modes also appear in the Raman spectrum only in PIP. This result indicates that PIP is a new spin-crossover-complex phase different from HTP and LTP.