Cycloparaazine, a full-azine carbon nanoring.

Abstract

Cycloparaphenylenes (CPPs) and related carbon nanorings (CNRs) represent iconic molecular entities in molecular nanocarbon science. While theoretical studies predict that the introduction of nitrogen atoms (N-doping) onto CPP frameworks would add a number of fascinating properties, only a handful of partially N-doped carbon nanorings have been synthesized. We herein report the synthesis of a long-awaited cycloparaazine (CPA), where every para-connected aromatic moiety consists of a N-heterocycle, and two other highly N-doped CNRs. The evaluation of optoelectronic and structural properties coupled with theoretical studies uncovered the impact of both the amount and positioning of N-doping onto the nanorings properties; far less ring strain, red-shifted UV-vis absorption and fluorescence, smaller HOMO-LUMO gaps and both higher reduction and oxidation potentials than pristine CPPs. Ultimately, new potential applications of highly N-doped nanorings were examined in non-covalent supramolecular property engineering with Lewis acids and as energy storage materials.