BN- and B2N2-coronenes: Singlet and triplet state aromaticity, HOMO-LUMO and S0-T1 energy gap

Abstract

BN/CC isosterism has emerged as a useful strategy for modulating chemical and physical properties of PAHs, which find applications in organic electronics. For such applications, it is important to predict and understand fundamental properties, such as HOMO-LUMO and S₀-T₁ energy gaps, influenced by the ground and triplet state aromaticity. The subject of this work is the influence of BN unit(s) on the aforementioned properties of coronene, studied using DFT. Structures include positional isomers with one BN unit in the central ring and orientational isomers with two BN units in the spoke bonds. Calculations show that the positional isomers have different HOMO-LUMO and S₀-T₁ gaps, smaller than coronene. They have different aromaticity topologies in both electronic states. Orientational isomers have the same aromaticity topology in both electronic states, similar HOMO-LUMO and S₀-T₁ gaps, also similar to those of coronene. All molecules contain Hückel aromatic carbocyclic subunits in their triplet state.