Interconversion between a Vertically Oriented Transition Metal-Complexed Figure-of-Eight and a Horizontally Disposed One

A large ring containing two pairs of transition metal-complexing fragments with alternating bi- and tridentate chelates has been shown to behave as a bimodal figure-of-eight. When coordinated to a preferentially octahedrally coordinated Fe(II) or Cu(II) center, the height of the molecule along the coordinating axis of the tridentate ligands (vertical on the drawing) is only ∼11 Å, whereas the height of the molecule along the same vertical axis is several times as large for the complex of the tetrahedrally coordinated copper(I) center. This new type of molecular machine-prototype could be used as constitutive element in muscle-like dynamic systems.