Premium
Aromaticity of Giant Polycyclic Aromatic Hydrocarbons with Hollow Sites: Super Ring Currents in Super‐Rings
Author(s) -
Hajgató Balázs,
Deleuze Michael S.,
Ohno Koichi
Publication year - 2006
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200501321
Subject(s) - aromaticity , annulene , ring (chemistry) , chemical shift , density functional theory , chemistry , antiaromaticity , excitation , homo/lumo , computational chemistry , chemical physics , molecular physics , molecule , physics , organic chemistry , quantum mechanics
We present a systematic theoretical study based on semi‐empirical, Hartree–Fock (HF), and density functional theory (DFT) models of a series of polycyclic aromatic hydrocarbons (PAHs) that exhibit hollow sites. In this study we focus particularly on the magnetic criteria of aromaticity, namely 1 H NMR and nucleus‐independent chemical shifts (NICS), and on their relationships with other electronic properties. The computed shifts and NICS indices indicate that an external magnetic field induces exceptionally strong ring currents in even‐layered PAH doughnuts, in particular in the layer directly adjacent to the central hole of double‐layered compounds. These exceptionally strong ring currents also correlate with particularly small HOMO–LUMO gaps and electronic excitation energies and to abnormally high polarizabilities, indicating in turn that these compounds have a more pronounced metallic character. Comparison is made with further depictions of aromaticity in these systems and in [18]–[66]annulene rings by employing topological, structural, and energetic criteria.