Photoinduced Ferrimagnetic Systems in Prussian Blue Analogues CIxCo₄[Fe(CN)₆]y (CI = Alkali Cation). 2. X-ray Absorption Spectroscopy of the Metastable State

A CoFe Prussian blue analogue Rb 1.8 Co 4 [Fe(CN) 6 ] 3.3 ·13H 2 O 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 L 2,3 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 Co III low spin to Co II high spin. The Co II /Co III 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 Fe II −Co III pairs and hexacyanoferrate(III) vacancies is locally evidenced. This work is a new step in the understanding of the photoinduced electron transfer.