Multifunctional Supramolecular Gels with Strong Mechanical Properties Formed by Self-Assembly of Polyoxometalate-Based Coordination Polymers

Metallogels built
in a bottom-up approach by metal coordination
and supramolecular interactions have important potential for the elaboration
of smart materials. In this context, we present here the formation
of supramolecular coordination polymers driven by the complexation
of cobalt(II) or zinc(II) ions with polyoxometalate-based hybrids
displaying two terpyridine ligands in a linear arrangement. Thanks
to the electrostatic interactions between the polyoxometalate cores
and metal nodes, the polymer chains self-assemble into fibers that
physically cross-link to form gels above a critical concentration.
Using spectroscopy, microscopy, X-ray scattering, and rheometry, complemented
by molecular dynamics simulations, we investigated the supramolecular
organization of the chains in the fibers and the resulting processes
leading to gelation. Compared to previously reported systems, these
gels have improved rheological features and appealing properties,
such as birefringence, luminescence, and spin crossover, paving the
way for their use as building blocks for multifunctional smart materials.