From Bowls to Capsules: Assembly of Hexanuclear Ni II Rings Tailored by Alkali Cations

An anionic hexanuclear Ni II metallamacrocycle with endo and exo linking sites has been employed as a building block to generate a series of capsules and bowls of nanometric size. The supramolecular arrangement of the {Ni 6 } rings was tailored by the size of the alkali cations, showing the transition from {Ni 6 ‐M 2 ‐Ni 6 } capsules (M=Li I and Na I ) to {Ni 6 ‐M} bowls (M=K I and Cs I ). The alkyl co‐cations are determinant to stabilize the assemblies by means of CH⋅⋅⋅π interactions on the exo side of the metallamacrocycles. The effect on the topology of the supramolecular assemblies of the cation size, cation charge, Et 3 NH + or Me 4 N + counter cations has been analyzed. Magnetic measurements reveal the presence of ferromagnetic and antiferromagnetic interactions inside the rings that allow a S= 0 ground state.