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Abstract This work provides a detailed multi‐component analysis of aromaticity in monosubstituted (X = CH₃, C, C, NH₂, NH⁻, NH⁺, OH, O⁻, and O⁺) andpara‐homodisubstituted (X = CH₃, CH₂, NH₂, NH, OH, and O) benzene derivatives. We investigate the effects of substituents using single‐reference (B3LYP/DFT) and multireference (CASSCF/MRCI) methods, focusing on structural (HOMA), vibrational (AI(vib)), topological (ELF_π), electronic (MCI), magnetic (NICS), and stability (S₀–T₁splitting) properties. The findings reveal that appropriateπ‐electron‐donating andπ‐electron‐accepting substituents with suitable size and symmetry can interact with theπ‐system of the ring, significantly influencingπ‐electron delocalization. While the charge factor has a minimal impact onπ‐electron delocalization, the presence of ap_zorbital capable of interacting with theπ‐electron delocalization is the primary factor leading to a deviation from the typical aromaticity characteristics observed in benzene. 

Abstract The chemical stability and the low‐lying singlet and triplet excited states of BN‐n‐acenes (n = 1–7) were studied using single reference and multireference methodologies. From the calculations, descriptors such as the singlet‐triplet splitting, the natural orbital (NO) occupations and aromaticity indexes are used to provide structural and energetic analysis. The boron and nitrogen atoms form an isoelectronic pair of two carbon atoms, which was used for the complete substitution of these units in the acene series. The structural analysis confirms the effects originated from the insertion of a uniform pattern of electronegativity difference within the molecular systems. The covalent bonds tend to be strongly polarized which does not happen in the case of a carbon‐only framework. This effect leads to a charge transfer between neighbor atoms resulting in a more strengthened structure, keeping the aromaticity roughly constant along the chain. The singlet‐triplet splitting also agrees with this stability trend, maintaining a consistent gap value for all molecules. The BN‐n‐acenes molecules possess a ground state with monoconfigurational character indicating their electronic stability. The low‐lying singlet excited states have charge transfer character, which proceeds from nitrogen to boron.