From bowls to capsules: assembly of hexanuclear NiII rings tailored by alkaline cations.

Abstract

An anionic hexanuclear NiII 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 {Ni6} rings was tailored by the size of the alkali cations, showing the transition from {Ni6-M2-Ni6} capsules (M = LiI and NaI) to {Ni6-M} bowls (M = KI and CsI). The alkyl co-cations are determinant to stabilize the assemblies by means of CHꞏꞏꞏ interactions on the exo side of the metallamacrocycles. The effect on the topology of the supramolecular assemblies of the cation size, cation charge, Et3NH+ or Me4N+ countercations has been analysed. Magnetic mesurements reveal the presence of ferromagnetic and antiferromagnetic interactions inside the rings that allow a S = 0 ground state.