It was found that FeD adopted a stable syn conformation as a result of the inclusion of atomic oxygen in a mu-oxo fashion, but on exposure to acidic conditions converted into the extended anti form. When this was subsequently made basic the syn conformation was re-adopted, simply due to re-inclusion of atomic oxygen forming the mu-oxo species. It was found that the combination of these affects allowed FeD to undergo repeated conformational switching cycles that were reproducible and robust.