Magnetic and Optical Bistability Driven by Thermally and Photoinduced Intramolecular Electron Transfer in a Molecular Cobalt−Iron Prussian Blue Analogue

A soluble molecular analogue of photoresponsive Co/Fe Prussian blues is described within this
report. As judged via a variety of spectroscopic, magnetic, and crystallographic methods, electron transfer
within the octanuclear complex (below 250 K) converts paramagnetic red crystals into green diamagnetic
ones. The color and magnetic changes are associated with the transformation of FeIIILS-CN-CoIIHS units
into FeIILS-CN-CoIIILS fragments in manner that is identical to that found for the An[Co(OH2)(6-6m)][Fe(CN)6]m·xH2O
(An = alkali metal cation) family of three-dimensional Prussian blues. Moreover, this intramolecular electron
transfer can be quantitatively circumvented via rapid thermal quenching and reversed via simple white
light irradiation at low temperatures. Remarkably the data suggests that thermally or photoinduced
paramagnetic metastable phases are identical and exhibit long relaxation times that approach 10 years at
120 K.