One-Pot Transition-Metal-Free Synthesis of π-Extended Bipolar Polyaromatic Hydrocarbons

Abstract

The development of straightforward synthetic methods for photoactive polycyclic aromatic hydrocarbons (PAHs) that avoid Pd-catalyzed or radical-based processes remains a challenge. Such methods are essential to reducing the cost and environmental impact of organic photodevices. In this work, we present a one-pot synthetic approach for creating novel bipolar PAHs with extended π-conjugation, which are not accessible via conventional Pd-catalyzed routes. Our cascade process operates exclusively under basic conditions, utilizing cesium carbonate and molecular sieves to facilitate the coupling of electron-deficient 4-fluoronaphthalene-1,8-dicarboximide with halogenated electron-rich moieties. This results in the regio- and chemoselective formation of new 6- and/or 5-membered conjugated rings via consecutive SN_Ar reactions, as confirmed through experimental and computational studies. The resulting PAHs exhibit strong emissive properties, with quantum yields ranging from 34 % to 99 %. This work provides a simple and efficient synthetic strategy for producing novel semiconducting materials, offering a new framework for designing bipolar PAHs with distinct optical characteristics.