Triple Helicate—Tetrahedral Cluster Interconversion Controlled by Host-Guest Interactions

A unique ligand design allows the formation of both an M2L3 triple helicate and an M4L6 tetrahedron (M=Ti, Ga; L=ligand based on 2,6-diaminoanthracene). Although the tetrahedron is entropically disfavored, a strong host–guest interaction with Me4N+ is enough to drive the equilibrium towards the tetrahedron. Remarkably, the helicate can be quantitatively converted into the tetrahedron simply by addition of Me4N+ (shown schematically).