Controlling aromaticity across electronic states is crucial for designing novel species. While aromaticity typically could be achieved in either the lowest singlet state (S0) or the lowest triplet state (T₁), dual-state aromaticity or antiaromaticity remains less developed. Herein, we demonstrate that NO-substitution uniquely induces antiaromaticity in both S0 and T1 states of 1,2-BN-doped cyclobutadiene (1,2-BN-CBD), initially nonaromatic in S0 and weakly aromatic in T1.

Recent research has sparked significant interest in exploring the effects of BN unit doping on the electronic structure of isoelectronic and isostructural benzene analogs, driven by their promising applications in pharmaceuticals and material sciences. In this study, we provide the first comprehensive investigation of BN/CC isosterism in 2,5-dihydro-1,4,2,5-diazadiborinine and its isomers (1−13) through density functional theory (DFT) calculations and machine learning-based analysis.