A multi‐descriptor analysis of substituent effects on the structure and aromaticity of benzene derivatives: π‐Conjugation versus charge effects

Abstract This work provides a detailed multi‐component analysis of aromaticity in monosubstituted (X = CH 3 , C, C, NH 2 , NH − , NH + , OH, O − , and O + ) and para ‐homodisubstituted (X = CH 3 , CH 2 , NH 2 , 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 (S 0 –T 1 splitting) properties. The findings reveal that appropriate π ‐electron‐donating and π ‐electron‐accepting substituents with suitable size and symmetry can interact with the π ‐system of the ring, significantly influencing π ‐electron delocalization. While the charge factor has a minimal impact on π ‐electron delocalization, the presence of a p z orbital capable of interacting with the π ‐electron delocalization is the primary factor leading to a deviation from the typical aromaticity characteristics observed in benzene.