Effect of the proximal secondary sphere on the self-assembly of tetrahedral zinc-oxo clusters

Metal-oxo clusters are useful building units of supramolecular assemblies. Here the authors explore the influence of NH moieties in the proximal secondary coordination sphere on the self-assembly of tetrahedral zinc-oxo clusters. Metal-oxo clusters can serve as directional and rigid building units of coordination and noncovalent supramolecular assemblies. Therefore, an in-depth understanding of their multi-faceted chemistry is vital for the development of self-assembled solid-state structures of desired properties. Here we present a comprehensive comparative structural analysis of isostructural benzoate, benzamidate, and new benzamidinate zinc-oxo clusters incorporating the [O,O]-, [O,NH]- and [NH,NH]-anchoring donor centers, respectively. We demonstrated that the NH groups in the proximal secondary coordination sphere are prone to the formation of intermolecular hydrogen bonds, which affects the packing of clusters in the crystal structure. Coordination sphere engineering can lead to the rational design of new catalytic sites and novel molecular building units of supramolecular assemblies.