Achieving Precise Control Over the Molecular Periphery of Dibenzoixenes Through Modular Synthesis

Nanographenes and polycyclic aromatic hydrocarbons, both finite forms of graphene, are promising organic semiconducting materials because their optoelectronic and magnetic properties can be modulated through precise control of their molecular peripheries. Several atomically precise edge structures have been prepared by bottom-up synthesis; however, no systematic elucidation of these edge topologies at the molecular level has been reported. Herein, we describe rationally designed modular syntheses of isomeric dibenzoixenes with diverse molecular peripheries, including cove, zigzag, bay, fjord, and gulf structured. 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 spectroscopy with different vibrational modes, which were further explained using density functional theory calculations. Electron spin resonance 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 Li-ion batteries, reveal that the dibenzo[a,p]ixene exhibits promising Li intercalation behaviors with a specific capacity of ~120 mAh g^-1. The findings of this study could facilitate the synthesis of larger <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:semantics><mml:mi>π</mml:mi> <mml:annotation>${\pi }$</mml:annotation> </mml:semantics> </mml:math> -extended systems with engineered molecular peripheries and potential application in organic electronics.