Aromaticity in Polycyclic Aromatic Hydrocarbons (PAHs): A Comparative Analysis Using Magnetic, Geometric, and Electronic Criteria
Year: 2026
Type: preprint
Abstract: An extensive computational investigation has been carried out to determine aromaticity properties in 12 representative polycyclic aromatic hydrocarbon (PAH) compounds of various structural types: reference benzene; linear acenes (naphthalene, anthracene, tetracene); angular (phenanthrene); peri-condensed (pyrene, coronene, perylene, fluoranthene); curved (corannulene); doped by a heteroatom (quinoline, dibenzothiophene). The global and local aromaticity properties of these PAH compounds have been investigated using both local and global aromaticity descriptors calculated at two different theoretical levels, namely B3LYP/def2-SVP and B3LYP/def2-TZVP: geometric (HOMA, mean bond length); magnetic (NICS(0), NICS(1), NICS(1)zz); and electronic (PDI, MCI, FLU) as well as HOMO-LUMO gap and energy. A cross-correlation analysis between all these properties shows that the correlations between geometric and electronic properties are very good (r ≈ 0.8), while there exists an inverse correlation between HOMA and NICS(1)zz values and, finally, that there exist topology-dependent relationships between HOMA and energy gap. As expected, linear acenes present a decrease in HOMA and energy gap values as the number of units of their chains increase. On the other hand, peri-condensed and angular compounds preserve their high local aromaticity because they stabilize through Clar’s sextets. Finally, the analysis of PDI, MCI, and FLU values shows that, in contrast to what occurs in non-fused systems, the local delocalization in fused systems differs from one ring to another depending on whether they belong to the central or to the peripheral region of the compound. This investigation demonstrates that aromaticity in PAHs are a multidimensional property in which geometric and electronic properties show similar behavior while magnetic
Source: ChemRxiv
Author: Mohammad Zain Ansari
Institution: Mahatma Gandhi Kashi Vidyapith
Language: English
Subfield: Organic Chemistry
Field: Chemistry
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7204989360