The metal-driven self-assembly processes of a covalent polyoxometalate (POM)-based hybrid bearing remote terpyridine binding sites have been investigated. In a strongly dissociating solvent, a discrete metallomacrocycle, described as a molecular triangle, is formed and characterized by 2D diffusion NMR spectroscopy (DOSY), small-angle X-ray scattering (SAXS), and molecular modeling. In a less dissociating solvent, the primary supramolecular structure, combining negatively charged POMs and cationic metal linkers, further self-assemble through intermolecular electrostatic interactions in a reversible process. The resulting hierarchical assemblies are dense monodisperse nanoparticles composed of ca. 50 POMs that were characterized by SAXS and transmission electron microscopy (TEM). This multiscale organized system directed by metal coordination and electrostatic interactions constitutes a promising step for the future design of POM self-assemblies with controllable structure-directing factors.

SignificanceHierarchical self-assembly is a powerful route allowing the elaboration of complex supramolecular architectures with emergent structuration or properties. Starting from well-defined molecular building units, this synthetic strategy relies on the construction of a preassembled structural motif that can further self-assemble through additional noncovalent interactions. In this context, we developed a system based on a covalent organic–inorganic polyoxometalate hybrid building block combining metal-driven self-assembly and electrostatic interactions. We herein show that in this system, the supramolecular organization can be controlled by a redox stimulus and/or the solvent composition giving rise to various types of nanoarchitectures from discrete metallomacrocycles to 1D worm-like nanoobjects.