Zinc(ii) coordination polymers, metallohexacycles and metallocapsules—do we understand self-assembly in metallosupramolecular chemistry: algorithms or serendipity?

Using a strategy of layering solvents and solutions of ligands and metal salts under ambient conditions, we observe the assembly of a discrete molecular metallohexacycle from ZnCl2 and 4′-(4-ethynylphenyl)-4,2′:6′,4′′-terpyridine, polycatenated, triply interlocked metallocapsules from ZnI2 and 4′-(4-pyridyl)-4,2′:6′,4′′-terpyridine, and 1-dimensional coordination polymers from either ZnCl2 or ZnI2 with 4′-{4-(3-chloropyridyl)}-4,2′:6′,4′′-terpyridine. On the basis of these studies and a comparison with related structures in the literature, we urge crystal engineers to be wary of drawing conclusions about self-assembly algorithms in solution using data from single crystal determinations.