Facilely controllable synthesis of copper-benzothiadiazole complexes via solvothermal reactions: exploring the customized synthetic approach by experiments.

It is very challenging to transform small organic molecules into customized coordination polymer (CP) because the functionalities with desired properties are greatly influenced by several elements, including the assembly modes of the organic linkers and metal nodes, organic linker functionalization, and defects. Therefore, deep cognition for the molecular-level engineering of CP chemistry is very important. Herein, we obtained five new copper-benzothiadiazole complexes via a controllable synthesis approach: [CuII(L1)(CH3CN)]2 (C1), [CuIBr(L1)]n (C2), [CuI3Br3(L2)2]n (C3), [CuICl(L3)]2 (C4), and [CuIICl2(L3)2] (C5). In the exploration, we successfully modulated the structure of the organic linker and the valence state of the metal nodes as well as the assembly modes of the organic linkers and metal nodes through the facilely controllable solvothermal reaction. The results from our experiments also indicated that the fusing process was driven by a CuII/CuI catalytic cycle. In this pathway, oxygen is the final electron acceptor and the solvent DMSO acts as a co-oxidant. In C2 and C3, the ever-expanding macrocycles were constructed from CuX clusters and organic chromophore linkers, forming interesting 1D chain structures, while the supramolecular macrocycles were assembled through hydrogen bonding expanding to a 3D network of C5. Interestingly, C1–C4 exhibit chromophore-based fluorescence, but are not phosphorescence.