Functionalization of Pentacene: A Facile and Versatile Approach to Contorted Polycyclic Aromatic Hydrocarbons

Abstract

Herein, a facile and versatile strategy for the synthesis of contorted polycyclic aromatic hydrocarbons (PAHs) starting from the functionalized pentacene was established. A series of novel PAHs 1‐4 were synthesized through a simple two‐step synthesis protocol involving an intramolecular reductive Friedel‐Crafts cyclization of four newly synthesized pentacene aldehydes 5‐8 as a key step. All the molecules were confirmed by single‐crystal X‐ray diffraction and their photophysical and electrochemical properties were studied in detail. Interestingly, the most striking feature of 1‐4 is their highly contorted carbon structures and the accompanying helical chirality. In particular, the optical resolution of 2 was successfully achieved by chiral‐phase HPLC, and the enantiomers were characterized by CD and CPL spectroscopy. Despite the highly non‐planar conformations, these contorted PAHs also exhibited intrinsically emissive properties with moderate‐to‐good fluorescence quantum yields, implying the potential utility of this series PAHs as possible high‐quality organic laser dyes. Together with epoxy resin by a self‐assembly method, a bottle microlaser based on 3a was successfully illustrated with a lasing wavelength of 567.8 nm at a threshold of 0.3 mJ/cm2. We believe that this work will shed light on the chemical versatility of pentacene and its derivatives in the construction of novel functionalized PAHs.