Analysis of Stability and (Anti)aromaticity of BN-Dibenzo[a,e]pentalenes

Abstract

Relatively scarce literature data on BN/CC isosterism in 4nπ-electronic systems have prompted us to investigate theoretically the influence of BN pair position within the central butadiene fragment of dibenzo[a,e]pentalene on two fundamental molecular properties: stability and (anti)aromaticity. It was found that stability and aromaticity follow the same trend only for BN-orientational isomers. The source of different stability of other isomers was examined first by an analysis of bond types and their dissociation energies and then by isomerization energy decomposition analysis and was explained in terms of classical electrostatic interactions, quantum-mechanical orbital interactions, structural changes and electronic changes (transition from charge-separated π-system to the neutral one). (Anti)aromaticity was investigated by using three kinds of indices, HOMA, FLUπ, and NICS(1)zz, which indicated that delocalization at the central pentalene motif is almost unaffected by various BN arrangements, molecular perimeter is slightly affected, while the most affected subunits are five-membered rings and benzene-fused five-membered rings containing only one heteroatom.