Assessing the Aromaticity of Fluorinated Benzene Derivatives Using New Descriptors Based on the Distributed Multipole Analysis (DMA) Partition of the Electron Density

Abstract

We investigated the impact of fluorination on the aromaticity of 12 benzene-based compounds using a recently proposed new set of six descriptors (ACS Omega 2025, 10, 14, 14157–1417) based on the distributed multipole analysis (DMA) partition of the electron density. These descriptors allow the quantification of electron delocalization, an observable property related to aromaticity, and were defined from the components of the DMA quadrupole moment tensor $Q_2$, the first electric multipole moment with out-of-plane contributions. We found a decrease in aromaticity that is related to the electron-withdrawing inductive effects of fluorine substituents, which modify the electron density distribution on the ring, particularly in regions adjacent to the substituents. The analysis by the $Q_2$-based aromaticity descriptors revealed a strong correlation between electron distribution and electronic delocalization in fluorinated systems, confirming that fluorine substituents directly affect the symmetry and uniformity of electronic delocalization. A linear relationship between the $Q_2$ descriptors $Q_{2\mathrm{zz},\text{origin}}$ and the $\text{NICS}\left(1\right)\mathrm{zz}$ and ring current strength ($\mathrm{RCS}$) descriptors was found, suggesting that these descriptors capture similar aspects of aromaticity. These findings highlight the effectiveness and robustness of the new aromaticity descriptors for rationalizing the aromaticity of fluorinated compounds.