One synthesis: two redox states. Temperature-oriented crystallization of a charge transfer {Fe2Co2} square complex in a {FeLSIICoLSIII}2 diamagnetic or {FeLSIIICoHSII}2 paramagnetic state

The reaction of [Fe-III(Tp)(CN)(3)](-) with [Co-II(vbik)(2)(S)(2)](2+) leads selectively to the crystallization of cyanide-bridged diamagnetic {(FeLSCoLSIII)-Co-II}(2)-squares at 5 degrees C or paramagnetic {(FeLSCoHSII)-Co-III}(2) ones at 35 degrees C. The diamagnetic crystal phase can be converted to a paramagnetic one upon heating and it shows photomagnetic effects at low temperature.