Heteroatom-Doping Engineering of Fused Olympic Cations: Metal-Free Modular Syntheses and NIR-II Radicals with Mixed Aromatic/Antiaromatic Characters.

Heteroatom-doping polycyclic aromatic hydrocarbons have attracted immense attention owing to their fascinating optoelectrical properties. However, precise heteroatom-doping engineering and fabricating charged polycyclic aromatic scaffolds remain challenging and far from satisfactory. Herein, a new family of nitrogen and sulfur/oxygen dual-doping fused Olympic heterocyclic cations (FPT/FPOs) are modularly synthesized employing an efficient and convenient metal-free protocol. Tunable optical and redox properties can be achieved by rational structural editing. Compared with their half-fused counterparts, FPTs and FPOs hold higher redox stability and can undergo single-electron reduction to form delocalized neutral radicals, exhibiting NIR-II absorptions around 1300-1400 nm and unexpected mixed aromatic/antiaromatic characters. It is anticipated that this line of research provides a new approach for heteroatom-doping engineering and constructing novel charged π-molecules, with deeper insights into their redox-amphoteric features and aromaticity manipulation.