Aromaticity in isoelectronic analogues of benzene, carborazine and borazine: Perspective from electronic structure and magnetic property

Carborazine (B2C2N2H6) and borazine (B3N3H6) are isoelectronic analogues of benzene (C6H6). The aromatic character of borazine remains a controversial issue, and the related properties of carborazine are even rarely reported. In this work, we systematically investigated the geometric structure, charge distribution, frontier molecular orbital characteristics, magnetic shielding effect, and induced ring current of carborazine and borazine, and compared the studied characteristics with those of benzene to determine the aromatic character of two analogues. The combination of multiple properties shown that although they are isoelectronic, carborazine, like benzene, is strongly aromatic, while borazine only exhibits rather weak aromaticity. The C atom acting as a connecting bridge between B and N atoms reduces the electronegativity difference on the molecular backbone and enhances the electron delocalization over the conjugated path, which is the essence of the distinct disparity of aromaticity between carborazine and borazine.