Utilizing Secondary Bonds Formed by Halogen Substituents: Achieving the Dynamic Transition of Low-Bandgap Semiconductor Polymers from Macromolecules to Small Molecules

Utilizing supramolecular assembly frameworks as soft materials to investigate the dissolution-recrystallization dynamics presents a viable approach for converting Cu(II) coordination polymer macromolecules into dimeric small molecules. We have designed and synthesized four Cu(II) coordination polymers and four coordination dimers, representing macromolecular polymers and oligomeric small molecules, respectively. Interestingly, the introduction of nitrate anions into the macromolecular polymer system can facilitate the conversion to oligomeric small molecules. This process involves dissolution-recrystallization structural transformation, altering the coordination mode of Cu(II) in the primary building units during the transformation. Moreover, this process entails the disassembly and reformation of the soft supramolecular framework, driven by the dynamic bond exchange of secondary bonds formed by halogen substituents X (F, Cl, Br, and I). These secondary bonds undergo dynamic exchange during the reformation of the supramolecular framework after disassembly. Based on the semiconductor properties of Cu(II) coordination polymers, we compared the electronic properties to evaluate the impact of halogen-substituted secondary bonds on the low-bandgap polymeric semiconductor macromolecules and small molecules of Cu(II).