Cycloaddition between nitrogen-doped graphene (6π-component) and benzene (4π-component): a theoretical approach using density functional theory with vdW-DF correction

Abstract

The interaction between nitrogen-doped graphene defects (N₃V₁ and N₄V₂ pyridinic, and N₃V₁ and N₃V₃ pyrrolic) and benzene have been investigated by applying density functional theory (DFT), together with the vdW-DF correction. We discovered that only the N₃V₃ pyrrolic defect is a reactive site (6π-component), forming a cycloadduct with benzene (4π-component) that has energy barriers below 154.38 kJ mol⁻¹ (1.60 eV). The conduction and valence bands (HOMO and LUMO) for N₃V₃ form a degenerate pair of orbitals at the gamma point, with the same ionization potential (IP) and electron affinity (EA). Likewise, inspection of the orbital symmetries for both systems confirms that these must undergo concerted reactions based on the Woodward and Hoffmann principles of orbital symmetry, with the appropriate orbital occupancies. This is the first time that substitutionally doped graphene has been demonstrated to participate as a 6π-component for cycloaddition reactions with benzene.