Decoding Coordination Geometry Enforcement in Metallo-supramolecular Polymer Networks from Macroscopic Rheological Signatures

The control over coordination geometry in metallo-supramolecular polymer networks not only helps developing new polymer structures but also provides new measures of metal complex characteristics. Herein, we compare multiscale characteristics of networks obtained by homo- and heteroleptic association of mono-, bi-, and tridentate ligands, as reflected in rheological measurements and DFT calculations. Accordingly, tetra-arm poly(ethylene glycol) (tetraPEG), functionalized with pyridine, phenanthroline, and terpyridine, form parent homoleptic networks, while their combination with a tetraPEG functionalized by the sterically demanding dimesitylene substituted phenanthroline forms heteroleptic networks. Among all employed transition metal ions, only Cu^+/2+ and Pd²⁺ comply with the coordination geometry necessities of all parent and mixed networks, ranging from trigonal to octahedral, providing good candidates for wide network topology rearrangements. Our rheological measurements and DFT calculations demonstrate that the stability of homoleptic complexes depends primarily on metal identity, whereas that of heteroleptic equivalents increases with increasing the denticity of the slim ligand, being a complex function of steric, electronic, and π–π interactions.