TY - JOUR
T1 - Aromaticity of Even-Number Cyclo[ n]carbons (n = 6-100)
AU - Baryshnikov, Glib V.
AU - Valiev, Rashid R.
AU - Nasibullin, Rinat T.
AU - Sundholm, Dage
AU - Kurten, Theo
AU - Ågren, Hans
N1 - Funding Information:
This work has been supported by the Olle Engkvist Byggmästare foundation (contract no. 189-0223) and the Ministry of Education and Science of Ukraine (project no. 0117U003908). The calculations were performed with computational resources provided by the High-Performance Computing Center North (HPC2N) in Umeå, Sweden, through the project “Multiphysics Modeling of Molecular Materials” SNIC 2019-2-41. The GIMIC calculations were carried out using the SKIF supercomputer at Tomsk State University. This project has also been funded by the Academy of Finland (projects 315600 and 314821). R.R.V. thanks the Tomsk Polytechnic University Competitiveness Enhancement Program (VIU-RSCABS-142/2019) for support.
Publisher Copyright:
© 2020 American Chemical Society.
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2021
Y1 - 2021
N2 - The recently synthesized cyclo[18]carbon molecule has been characterized in a number of studies by calculating electronic, spectroscopic, and mechanical properties. However, cyclo[18]carbon is only one member of the class of cyclo[n]carbons - standalone carbon allotrope representatives. Many of the larger members of this class of molecules have not been thoroughly investigated. In this work, we calculate the magnetically induced current density of cyclo[n]carbons in order to elucidate how electron delocalization and aromatic properties change with the size of the molecular ring (n), where n is an even number between 6 and 100. We find that the Hückel rules for aromaticity (4k + 2) and antiaromaticity (4k) become degenerate for large Cn rings (n > 50), which can be understood as a transition from a delocalized electronic structure to a nonaromatic structure with localized current density fluxes in the triple bonds. Actually, the calculations suggest that cyclo[n]carbons with n > 50 are nonaromatic cyclic polyalkynes. The influence of the amount of nonlocal exchange and the asymptotic behavior of the exchange-correlation potential of the employed density functionals on the strength of the magnetically induced ring current and the aromatic character of the large cyclo[n]carbons is also discussed.
AB - The recently synthesized cyclo[18]carbon molecule has been characterized in a number of studies by calculating electronic, spectroscopic, and mechanical properties. However, cyclo[18]carbon is only one member of the class of cyclo[n]carbons - standalone carbon allotrope representatives. Many of the larger members of this class of molecules have not been thoroughly investigated. In this work, we calculate the magnetically induced current density of cyclo[n]carbons in order to elucidate how electron delocalization and aromatic properties change with the size of the molecular ring (n), where n is an even number between 6 and 100. We find that the Hückel rules for aromaticity (4k + 2) and antiaromaticity (4k) become degenerate for large Cn rings (n > 50), which can be understood as a transition from a delocalized electronic structure to a nonaromatic structure with localized current density fluxes in the triple bonds. Actually, the calculations suggest that cyclo[n]carbons with n > 50 are nonaromatic cyclic polyalkynes. The influence of the amount of nonlocal exchange and the asymptotic behavior of the exchange-correlation potential of the employed density functionals on the strength of the magnetically induced ring current and the aromatic character of the large cyclo[n]carbons is also discussed.
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U2 - 10.1021/acs.jpca.0c09692
DO - 10.1021/acs.jpca.0c09692
M3 - Article
C2 - 33301674
AN - SCOPUS:85098774442
JO - Journal of Physical Chemistry A
JF - Journal of Physical Chemistry A
SN - 1089-5639
ER -