Influence of Dimerization on Aromaticity in Benzene and Heteroaromatic Rings.

Noncovalent interactions are known to affect a variety of physicochemical properties. In this study, the effect of their formation between simple aromatic rings such as benzene, pyridine, furan, and pyrrole is analyzed by combining high-level wave functions with energy decomposition analysis and complementary aromaticity metrics. All binding patterns were characterized using the SAPT method, whereas CCSD(T)-quality wave functions were used for the assessment of most aromaticity indices. Across 13 dimers, dispersion is the most important contributor to the total interaction energy for most motifs. Aromaticity indices based on electron density and geometry change only slightly upon dimerization, indicating that π-delocalization within each monomeric ring is largely preserved. In contrast, NICS(0) values indicate a strong response, especially for π-π bonded systems. These results combine the lack of structural and electronic interference with strong magnetic signatures and provide a reference point for the interpretation of aromaticity descriptors in noncovalent assemblies.