Aromatic Rules of C22H122+/2•/2-: Flexibility in Electronic Structures of 2D Superatomic Molecules

Triangulene (C22H122•), a nonclassic non-Kekulé polycyclic aromatic hydrocarbon, is identified to be aromatic by structural and magnetic criteria. However, its aromatic origin remains confusing. Herein, the aromatic rules of C22H122• and its two charged counterparts C22H122+/2- were investigated on the basis of a recently developed two-dimensional (2D) superatomic-molecule theory. [C22H12]2+/2•/2- exhibit obvious local aromatic characters and can be regarded as [◊N3◊O3]+, [◊N3◊O3]-, and ◊N3◊F3 superatomic molecules, respectively, where ◊N, ◊O, and ◊F denote 2D superatoms bearing 3π, 4π, and 5π electrons. [C22H12]2+/2- realize electronic shell closure via superatomic lone pairs and covalent bonds, mimicking simple molecules, whereas the α-π and β-π electrons in C22H122• follow the superatomic bonding patterns of C22H122- and C22H122+, respectively. Furthermore, based on the local character in 2D superatomic molecules, a doped nanoporous graphene, namely, C9N12B monolayer, was predicted. The material possesses excellent dynamical and thermodynamical stability, as well as a wide band gap of 2.77 eV, positioning it as a promising 2D material for future electronic applications.