Metallacrowns are metallamacrocycles characterized by the (M-N-O)nconnectivity and originated by self-assembly of bischelating ligands (e.g. hydroxamic acids) and metal ions. Properties and structure of this class of compounds are tunable through a wise choice of the building blocks set.  Moreover a relatively large amount of metal ions are confined in a small molecular volume, resulting in peculiar chemical physical features, such as luminescence or single-molecule magnets behavior. 
We present here three new metallacrowns-based materials, that were prepared using salicylhydroxamic acid derivatives as ligands and Mn(II/III) as metal ion.
The salicyhydroxamic acid (H3Shi) react with Mn, forming a tightly packed, not porous coordination polymer. The nodes are endeca-manganese clusters, resembling a 3-blade propeller, where each blade is a half of a 16-metallacrown-6. Both the amino (H3p-aShi) and the pyridyl (H3p-pyShi) derivatives result in a novel porous arrays having the same Mn11cluster node. The amino function of H3p-aShi drives the propellers to interact through sodium ions and supramolecular interactions (i.e. hydrogen bonds). The resulting architecture shows hexagonal channels, which correspond to 39 % of the unit cell volume. The pyridyl function of H3p-pyShi coordinates one Mn of the neighboring propeller. As a result H3p-pyShi originates a metallacrown-based network, which shows channels in all the three dimensions and has cavities corresponding to 55% of the unit cell volume. The array, shown in the Figure, can be considered a novel metal-organic-framework with an endeca-Mn node.References: