Pyridone‐Fused Aromatic Belts: Synthesis and Properties of Amide‐Bridged [6]Cycloparaphenylenes

Abstract

ABSTRACT Pyridone‐fused aromatic belts, namely amide‐bridged [6]cycloparaphenylenes, were successfully synthesized to investigate how polar amide groups govern symmetry and electronic structure in π‐conjugated nanobelt molecules. The polar orientations of the six amide bonds give rise to two discrete structural isomers: S 6 ‐ and D 3 ‐symmetric aromatic belts. These compounds were obtained through an efficient macrocyclization directed by the cis ‐preference of tertiary aromatic amides, followed by Ni‐mediated intramolecular aryl–aryl coupling. Single‐crystal x‐ray diffraction analyses revealed that both isomers adopt rigid belt‐shaped architectures with enhanced π‐conjugation along the framework. The D 3 ‐symmetric isomer was successfully resolved into ( M,M )‐ and ( P,P )‐enantiomers using chiral HPLC and the isomer exhibited a distinct chiroptical response in electronic circular dichroism spectroscopy (| g abs | = 2.7 × 10 −3 ). Notably, cyclic voltammetry was used to demonstrate that the D 3 ‐symmetric isomer possesses a narrow HOMO–LUMO energy gap of 2.35 eV together with considerably stabilized frontier molecular orbitals. This work establishes a versatile molecular design concept for constructing aromatic belts with well‐defined chiroptical properties and high oxidative robustness, expanding opportunities in nanobelt science and chiral functional materials.