Fluorescent and Electrochemical Supramolecular Coordination Polymer Hydrogels Formed from Ion-Tuned Self-Assembly of Small Bis-Terpyridine Monomer

Herein, ditopic ligand DTA comprised of terpyridine and acetylene segments with only one aromatic pi-conjugated building block was designed and synthesized. Driven by metal-ligand coordination interactions, we presented that the use of metal salts can direct the self-assembly of DTA in the generation of fluorescent and electrochemical polymers that entrapped water to form ambidextrous hydrogels. These were characterized by several approaches including fluorescent titrations, UV-vis, circular dichroism, and X-ray diffraction spectra as well as scanning electron microscopy and transmission electron microscopy experiments. DTA can selectively recognize Zn2+ ions and gelate water in the presence of ZnC6H10O6 (zinc lactate), giving Zn2+-specific fluorescent metallogels. Otherwise, DTA/Cu(OAc)(2) forms nonfluorescent, electrochemical, and chiral hydrogel that responds to multiple stimuli such as heat, light, shearing, electrolysis, and reducer. The ion-controlled gelation approach, morphology, rheology, as well as fluorescent and chiroptical properties of DTA was studied in detail. Hence, our work demonstrated for the first time the crucial role of metal salts in the supramolecular polymerization and corresponding properties, in which symmetry breaking played an important role for the dynamic assembly difference.