Photoinduced Ferrimagnetic Systems in Prussian Blue Analogues C^I<i>_x</i>Co₄[Fe(CN)₆]<i>_y</i> (C^I = Alkali Cation). 2. X-ray Absorption Spectroscopy of the Metastable State

A CoFe Prussian blue analogue Rb1.8Co4[Fe(CN)6]3.3·13H2O was synthesized, which presents an important photomagnetic effect. The electronic structure and the local structure of the ground and of the excited states have been investigated. X-ray absorption spectroscopy measurements at the Co and Fe L2,3 edges and cobalt K-edge (XANES and EXAFS) evidence the local electronic transfer and the spin change of the cobalt ions induced by irradiation. We observed a 0.19 Å increase of the Co−N bond length, associated with the transformation of CoIII low spin to CoII high spin. The CoII/CoIII ratio has been evaluated as a function of the irradiation time and revealed as an important parameter to understanding the bulk magnetic properties. The combined role of the diamagnetic FeII−CoIII pairs and hexacyanoferrate(III) vacancies is locally evidenced. This work is a new step in the understanding of the photoinduced electron transfer.