How Aromatic Are Molecular Nanorings? The Case of a Six-Porphyrin Nanoring**
Fecha
2021-11-02Autor
Casademont i Reig, Irene
Guerrero Avilés, Raúl Ignacio
Ramos Córdoba, Eloy
Torrent Sucarrat, Miquel
Matito Gras, Eduard
Metadatos
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Angewandte Chemie International Edition 60(45) : 24080-24088 (2021)
Resumen
Large conjugated rings with persistent currents are novel promising structures in molecular-scale electronics. A six-porphyrin nanoring structure that allegedly sustained an aromatic ring current involving 78 pi electrons was recently synthesized. We provide here compelling evidence that this molecule is not aromatic, contrary to what was inferred from the analysis of H-1-NMR data and computational calculations that suffer from large delocalization errors. The main reason behind the absence of an aromatic ring current in these nanorings is the low delocalization in the transition from the porphyrins to the bridging butadiyne linkers, which disrupts the overall conjugated circuit. These results highlight the importance of choosing a suitable computational method to study large conjugated molecules and the appropriate aromaticity descriptors to identify the part of the molecule responsible for the loss of aromaticity.