New Insights into Nickel(II), Iron(II), and Cobalt(II) Bis‐Complex‐Based Metallo‐Supramolecular Polymers

Abstract

One of the most important characterization methods for macromolecules is SEC. The main difficulty for this type of measurements concerning metallo‐supramolecular polymers based on terpyridines is related to the interaction between the charged supramolecular species and the SEC column material. In this paper, we report new studies on the characterization and the stability of supramolecular polymers based on terpyridine metal complexes utilizing SEC. The main aspects concerning the equilibrium between complexed and uncomplexed species are discussed in detail. The present study reveals a strong relationship between the binding strength of the metal ion used and the stability of the terpyridine metal complex during the SEC measurements, which is in agreement with previously published results regarding the stability of small terpyridine metal complexes in solution. These results can lead to improved analytic possibilities and to a better fundamental understanding of the mentioned metallo‐supramolecular polymers. Furthermore, the prepared chain‐extended supramolecular‐polymer was analyzed by depth‐sensing indentation proving an increase in elastic modulus in comparison with the starting material.magnified image

Self‐Assembly Behavior of Bis(terpyridine) and Metallo‐bis(terpyridine) Pluronics in Dilute Aqueous Solutions

“…The addition of metal ions into a solution containing bis(terpyridine) Pluronics would lead to a rearrangement of the pre‐existing micelles that could be most likely followed by the variation (increase or decrease in R h,app ) of the micelles. The selected metal ion for our studies was nickel(II) which offers a good stability and low exchange rate when complexed by terpyridine ligands compared to other metal ions 8, 18, 19…”

Thermosensitive and Switchable Terpyridine‐Functionalized Metallo‐Supramolecular Poly(N‐isopropylacrylamide)

“…It is known that terpyridine ligands are capable of chelating a large variety of transitional metal ions in low oxidation states to form metal‐bis(terpyridine) complexes characterized by various stabilities 7. We have selected Fe II and Zn II metal ions as indicative examples with different relative binding strength towards the terpyridine moiety 23, 41. Prior knowledge shows that LCST transitions can be influenced by several variables, such as electrolyte concentration, incorporation of co‐monomers, or molecular weight.…”

Precise Control over the Rheological Behavior of Associating Stimuli-Responsive Block Copolymer Gels

“…This consideration was addressed in our previous study, where the effect of different transition metal ions was tested on the rheological properties of metallo-supramolecular micellar hydrogels [36]. In this study, nickel(II) ions are selected, since they afford one of the more stable bis -complexes in combination with the terpyridine ligand [63], thereby providing efficient bridges towards the formation of a supramolecular network. In practice, the establishment of a percolated network structure is evidenced by the tube inversion test at room temperature.…”

“…In this regard, Ni(II) ions are expected to form long-lifetime complexes in combination with the terpyridine ligand. This particular stability has been used in the strategic formation of metallo-supramolecular polymers with high structural integrity [34,63,70,71] or metallo-supramolecular networks with a delayed terminal relaxation [36,40].…”