Regioisomeric Dipyridinium-Incorporated [10]Cycloparaphenylenes: Synthesis, Electronic Properties, and Host-Guest Chemistry.

Two regioisomeric dipyridinium-incorporated [10]CPPs, Dipy[10]CPP-1 and Dipy[10]CPP-2, were synthesized, featuring two pyridinium units separated by three and four benzene rings, respectively. Single-crystal X-ray diffraction confirmed the structures of both macrocycles and their corresponding C60 inclusion complexes. Photophysical studies and DFT calculations reveal that the relative positioning of the pyridinium units influences the optical properties and HOMO-LUMO gaps of these donor-acceptor nanohoops. This work demonstrates that positional isomerism on the nanohoop framework is an effective strategy for tuning electronic properties and expands the design space for functionalized carbon nanohoops.