Electronic communication and switching between two iron atoms across the phenanthrene–dihydrophenanthrene bridging ligands

The complexes [{Fe(η5-C5Me5)}2(µ2,η12-phenanthrene)]n+ have been synthesized for n= 0–2; the green 37-electron mixed-valence FeIFeII monocation is delocalized on the Mössbauer time-scale at 4 K and the bireduced neutral complex has a triplet FeIFeI state for phenanthrene in contrast with the singlet FeIIFeII state for the dihydrophenanthrene complex; interconversion between the phenanthrene and dihydrophenanthrene series by contact with O2and H2O makes this system a switchable molecular-electronic device.