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Tribute to Josef Michl
 
 
Article

Exploitation of Baird Aromaticity and Clar’s Rule for Tuning the Triplet Energies of Polycyclic Aromatic Hydrocarbons

Department of Chemistry, Loughborough University, Loughborough LE11 3TU, UK
Academic Editors: Igor Alabugin and Petr Klán
Chemistry 2021, 3(2), 532-549; https://doi.org/10.3390/chemistry3020038
Received: 3 March 2021 / Revised: 7 April 2021 / Accepted: 9 April 2021 / Published: 14 April 2021
(This article belongs to the Special Issue A Special Issue in Honor of Professor Josef Michl)
Polycyclic aromatic hydrocarbons (PAH) are a prominent substance class with a variety of applications in molecular materials science. Their electronic properties crucially depend on the bond topology in ways that are often highly non-intuitive. Here, we study, using density functional theory, the triplet states of four biphenylene-derived PAHs finding dramatically different triplet excitation energies for closely related isomeric structures. These differences are rationalised using a qualitative description of Clar sextets and Baird quartets, quantified in terms of nucleus independent chemical shifts, and represented graphically through a recently developed method for visualising chemical shielding tensors (VIST). The results are further interpreted in terms of a 2D rigid rotor model of aromaticity and through an analysis of the natural transition orbitals involved in the triplet excited states showing good consistency between the different viewpoints. We believe that this work constitutes an important step in consolidating these varying viewpoints of electronically excited states. View Full-Text
Keywords: aromaticity; antiaromaticity; chemical shift; hydrocarbons, benzene; π-conjugated systems aromaticity; antiaromaticity; chemical shift; hydrocarbons, benzene; π-conjugated systems
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MDPI and ACS Style

Plasser, F. Exploitation of Baird Aromaticity and Clar’s Rule for Tuning the Triplet Energies of Polycyclic Aromatic Hydrocarbons. Chemistry 2021, 3, 532-549. https://doi.org/10.3390/chemistry3020038

AMA Style

Plasser F. Exploitation of Baird Aromaticity and Clar’s Rule for Tuning the Triplet Energies of Polycyclic Aromatic Hydrocarbons. Chemistry. 2021; 3(2):532-549. https://doi.org/10.3390/chemistry3020038

Chicago/Turabian Style

Plasser, Felix. 2021. "Exploitation of Baird Aromaticity and Clar’s Rule for Tuning the Triplet Energies of Polycyclic Aromatic Hydrocarbons" Chemistry 3, no. 2: 532-549. https://doi.org/10.3390/chemistry3020038

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