[(FeLSCoLSIII)-Co-II](2) <-> [(FeLSCoHSII)-Co-III](2) photoinduced conversion in a cyanide-bridged heterobimetallic molecular square

The self-assembly of [Fe-III{B(pz)(4)}(CN)(3)](-) and [Co-II(bik)(2)(S)(2)](2+) affords the diamagnetic cyanide-bridged [(FeLSCoLSIII)-Co-II](2) molecular square which is converted into the corresponding magnetic [(FeLSCoHSII)-Co-III](2) species under light irradiation at relatively low temperatures.