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Fowler PW, Myrvold W, Gibson C, Clarke J, Bird WH. Ring-Current Maps for Benzenoids: Comparisons, Contradictions, and a Versatile Combinatorial Model. J Phys Chem A 2020; 124:4517-4533. [PMID: 32375480 PMCID: PMC7304905 DOI: 10.1021/acs.jpca.0c02748] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2020] [Revised: 05/04/2020] [Indexed: 11/29/2022]
Abstract
As a key diagnostic property of benzenoids and other polycyclic hydrocarbons, induced ring current has inspired diverse approaches for calculation, modeling, and interpretation. Grid-based methods include the ipsocentric ab initio calculation of current maps, and its surrogate, the pseudo-π model. Graph-based models include a family of conjugated-circuit (CC) models and the molecular-orbital Hückel-London (HL) model. To assess competing claims for physical relevance of derived current maps for benzenoids, a protocol for graph-reduction and comparison was devised. Graph reduction of pseudo-π grid maps highlights their overall similarity to HL maps, but also reveals systematic differences. These are ascribed to unavoidable pseudo-π proximity limitations for benzenoids with short nonbonded distances, and to poor continuity of pseudo-π current for classes of benzenoids with fixed bonds, where single-reference methods can be unreliable. Comparison between graph-based approaches shows that the published CC models all shadow HL maps reasonably well for most benzenoids (as judged by L1-, L2-, and L∞-error norms on scaled bond currents), though all exhibit physically implausible currents for systems with fixed bonds. These comparisons inspire a new combinatorial model (Model W) based on cycle decomposition of current, taking into account the two terms of lowest order that occur in the characteristic polynomial. This improves on all pure-CC models within their range of applicability, giving excellent adherence to HL maps for all Kekulean benzenoids, including those with fixed bonds (halving the rms discrepancy against scaled HL bond currents, from 11% in the best CC model, to 5% for the set of 18 360 Kekulean benzenoids on up to 10 hexagonal rings). Model W also has excellent performance for open-shell systems, where currents cannot be described at all by pure CC models (4% rms discrepancy against scaled HL bond currents for the 20112 non-Kekulean benzenoids on up to 10 hexagonal rings). Consideration of largest and next-to-largest matchings is a useful strategy for modeling and interpretation of currents in Kekulean and non-Kekulean benzenoids (nanographenes).
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Affiliation(s)
- Patrick W. Fowler
- Department
of Chemistry, University of Sheffield, Sheffield S3 7HF, United Kingdom
| | - Wendy Myrvold
- Department
of Computer Science, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
| | - Christopher Gibson
- Department
of Chemistry, University of Sheffield, Sheffield S3 7HF, United Kingdom
| | - Joseph Clarke
- Department
of Chemistry, University of Sheffield, Sheffield S3 7HF, United Kingdom
| | - William H. Bird
- Department
of Computer Science, University of Victoria, Victoria, British Columbia V8P 5C2, Canada
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Szczepanik DW, Solà M, Andrzejak M, Pawełek B, Dominikowska J, Kukułka M, Dyduch K, Krygowski TM, Szatylowicz H. The role of the long-range exchange corrections in the description of electron delocalization in aromatic species. J Comput Chem 2017; 38:1640-1654. [PMID: 28436535 DOI: 10.1002/jcc.24805] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2017] [Revised: 03/22/2017] [Accepted: 03/23/2017] [Indexed: 01/07/2023]
Abstract
In this article, we address the role of the long-range exchange corrections in description of the cyclic delocalization of electrons in aromatic systems at the density functional theory level. A test set of diversified monocyclic and polycyclic aromatics is used in benchmark calculations involving various exchange-correlation functionals. A special emphasis is given to the problem of local aromaticity in acenes, which has been a subject of long-standing debate in the literature. The presented results indicate that the noncorrected exchange-correlation functionals significantly overestimate cyclic delocalization of electrons in heteroaromatics and aromatic systems with fused rings, which in the case of acenes leads to conflicting local aromaticity predictions from different criteria. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Dariusz W Szczepanik
- Faculty of Chemistry, K. Gumiński Department of Theoretical Chemistry, Jagiellonian University, Ingardena 3, Cracow, 30-060, Poland
| | - Miquel Solà
- Institut de Química Computational i Catàlisi, Universitat de Girona, Maria Aurèlia Capmany 6, Girona, 17003, Catalonia, Spain
| | - Marcin Andrzejak
- Faculty of Chemistry, K. Gumiński Department of Theoretical Chemistry, Jagiellonian University, Ingardena 3, Cracow, 30-060, Poland
| | - Barbara Pawełek
- Institute of Botany, Department of Plant Cytology and Embryology, Jagiellonian University, Gronostajowa 9, Cracow, 30-387, Poland
| | - Justyna Dominikowska
- Faculty of Chemistry, Department of Theoretical and Structural Chemistry, University of Lodz, Pomorska 163/165, Lodz, 90-236, Poland
| | - Mercedes Kukułka
- Faculty of Chemistry, K. Gumiński Department of Theoretical Chemistry, Jagiellonian University, Ingardena 3, Cracow, 30-060, Poland
| | - Karol Dyduch
- Faculty of Chemistry, K. Gumiński Department of Theoretical Chemistry, Jagiellonian University, Ingardena 3, Cracow, 30-060, Poland
| | - Tadeusz M Krygowski
- Faculty of Chemistry, Department of Theoretical Chemistry and Crystallography, University of Warsaw, Pasteura 1, Warsaw, 02-093, Poland
| | - Halina Szatylowicz
- Faculty of Chemistry, Department of Physical Chemistry, Warsaw University of Technology, Noakowskiego 3, Warsaw, 00-664, Poland
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