Synthesis of Fluorocycloparaphenylenes via Macrocyclic Pd Complexes

Fluorocycloparaphenylenes (F-CPPs) are strained, cyclic, π-conjugated molecules with unique electronic and supramolecular properties. Here, we report a novel synthetic approach to create F-CPPs via the formation of macrocyclic palladium complexes that contain covalent Pd-C bonds. The thermal stability of the fluorinated biaryl Pd motifs and the reversibility of the formation of Pd-C bonds enable the self-assembly of macrocyclic Pd complexes. Subsequent ligand exchange with Xantphos facilitates reductive elimination, yielding various F-CPPs that incorporate tetrafluorophenylene, phenylene, or thienylene units. A structural analysis revealed that the thienylene-based F-CPPs adopt tubular packing structures due to their high fluorine content. Optical measurements and time-dependent density-functional-theory (TD-DFT) calculations demonstrated size- and structure-dependent absorption and emission behavior. This Pd-mediated synthetic strategy provides a new platform for the synthesis of functionalized CPPs with tailored properties for potential applications in nanomaterials and supramolecular chemistry.