A computational insight to an old concept: The Mills–Nixon effect

[Display omitted] •The Mills-Nixon (MN) effect in some trisannelated benzenes (1–10) is evaluated.•WBO, ΔBL, NICS, HOMA, and LOL analyses are performed at B3LYP/6–311++G (d,p) level.•Structure 4 represents the highest MN effect among the studied structures. The Mills-Nixon (MN) effect in trisannelated benzenes (1–10) is analyzed by Wiberg bond order (WBO), bond lengths alteration (ΔBL), Nucleus Independent Chemical (NICS), Harmonic Oscillator Model of Aromaticity (HOMA), and Localized orbital locator (LOL) analyses in B3LYP/6–311++G (d,p) level of theory. Coulomb repulsion, antiaromatic instability, angle strain and ring strain were the significant factors in the MN effect creation in the studied structures. The obtained results showed that the aromaticity is decreased in the benzene ring is in the 8 > 9 > 3 > 1 > 7 > 2 > 6 > 5 > 10 > 4 order and the strongest MN effect is seen in structure 4.