Periphery Engineering and Heteroatom Incorporation of Polycyclic Aromatic Hydrocarbons

Abstract

Nanographenes(NGs) and polycyclic aromatic hydrocarbons(PAHs), both finite forms of graphene, are promising organic semiconducting materials because their optoelectronic and magnetic properties can be modulated through periphery engineering or heteroatom incorporation. Several atomically precise edge modification or heteroatom incorporation have been explored by bottom-up synthesis; however, no systematic elucidation of these modulations at the molecular level has been reported. Herein, we present rationally designed modular syntheses of isomeric dibenzoixenes with diverse molecular peripheries and boron-nitrogen(BN) embedded contorted hexabenzocoronene (c-HBC). The single-crystal structures of dibenzo[a,p]ixene and dibenzo[j,y]ixene reveal enantiomeric pairs with helically twisted cove edges and packing structures. The molecular edge structures are identified from the C–H bonds of the dibenzoixenes using Fourier transform infrared (FTIR) spectroscopy with different vibrational modes, which were further explained using density functional theory (DFT) calculations. Electron spin resonance (ESR) spectroscopy indicates that the zigzag-edged molecular periphery significantly affects the magnetic properties of the material. Furthermore, the electrochemical characteristics, examined using dibenzoixenes as anode materials in lithium-ion batteries (LIBs), reveal that the dibenzo[a,p]ixene exhibits promising lithium (Li) intercalation behavior, achieving a specific capacity of 120 mAh g–1. The findings of this study could facilitate the synthesis of larger 𝜋-extended systems with engineered molecular peripheries or incorporated heteroatoms, and potential application in organic electronics.