Phase collapse caused by blue-light irradiation in a cyanobridged coordination polymer

In this work, we report a photoinduced phase transition, light-induced phase collapse, using rubidium manganese hexacyanoferrate, (Rb0.43MnII)-Mn-I[Fe-III(CN)(6)](0.81)center dot 3H(2)O, which does not exhibit a phase transition upon changing the temperature. However, when this material is irradiated with blue light at temperature around 100-200 K, the Mn-II-Fe-III phase collapses and the valence isomer Mn-III-Fe-II phase appears. The Mn-II-Fe-III phase is perfectly recovered as the temperature increased. Theoretical analysis suggests that the initial Mn-II-Fe-III phase is a thermodynamically metastable phase, trapped at a local free-energy minimum, while the photogenerated Mn-III-Fe-II phase is the true thermodynamically stable phase below 230 K. (C) 2008 American Institute of Physics.