Searching for double σ- and π-aromaticity in borazine derivatives

Inspired by the double-aromatic (σ and π) C(6)H(3)(+), C(6)I(6)(2+), and C(6)(SePh)(6)(2+) ring-shaped compounds, herein we theoretically study their borazine derivative analogues. The systems studied are the cation and dications with formulas B(3)N(3)H(3)(+), B(3)N(3)Br(6)(2+), B(3)N(3)I(6)(2+), B(3)N(3)(SeH)(6)(2+), and B(3)N(3)(TeH)(6)(2+). Our DFT calculations indicate that the ring-shaped planar structures of B(3)N(3)H(3)(+), B(3)N(3)I(6)(2+), and B(3)N(3)(TeH)(6)(2+) are more stable in the singlet state, while those of B(3)N(3)Br(6)(2+) and B(3)N(3)(SeH)(6)(2+) prefer the triplet state. Besides, exploration of the potential energy surface shows that the ring-shaped structure is the putative global minimum only for B(3)N(3)I(6)(2+). According to chemical bonding analysis, B(3)N(3)H(3)(+), B(3)N(3)I(6)(2+), and B(3)N(3)(TeH)(6)(2+) have σ and π delocalized bonds. The number of delocalized σ/π electrons is 2/6 for the first, and 10/6 for the second and third, similar to what their carbon analogs exhibit. Finally, the analysis of the magnetically induced current density allows B(3)N(3)H(3)(+), B(3)N(3)I(6)(2+), and B(3)N(3)(TeH)(6)(2+) to be classified as strongly σ aromatic, and poorly π aromatic compounds.