Reversible valence tautomerism induced by a single-shot laser pulse in a cobalt-iron Prussian blue analog.

Reversible valence tautomeric conversion induced by a single-shot laser pulse (8 ns duration) with a photon excitation energy of 2.38 eV has been observed in Na 0 . 3 6 Co 1 . 3 2 Fe(CN) 6 .5.6H 2 O. A photoswitching process with accompanying magnetization and color changes was successfully achieved within the pulse duration at high temperature (above 200 K) in a thermal hysteresis loop. This unusual photoeffect originates from an optical charge transfer between Fe and Co atoms and evolves due to a cooperative interaction among the local photoexcited sites.