On/Off Photoswitching in a Cyanide-Bridged {Fe2Co2} Magnetic Molecular Square

A repeatable bidirectional paramagnetic ↔ diamagnetic photomagnetic effect has been observed in the cyanide-bridged Fe–Co square complex {[Fe{B(pz)4}(CN)3]2[Co(bik)2]2}(ClO4)2·3H2O [B(pz)4 = tetrapyrazolylborate, bik = bis(1-methylimidazol-2-yl)ketone]. Magnetic measurements and low-temperature single-crystal X-ray diffraction experiments have shown that a complete electron transfer from the diamagnetic FeII −Co III state to the paramagnetic FeIII −Co II metastable state is induced by 808 nm laser light irradiation, whereas the diamagnetic state is recovered in an almost quantitative yield under irradiation at 532 nm.