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Stawski W, Zhu Y, Rončević I, Wei Z, Petrukhina MA, Anderson HL. The anti-aromatic dianion and aromatic tetraanion of [18]annulene. Nat Chem 2024; 16:998-1002. [PMID: 38448656 PMCID: PMC11164681 DOI: 10.1038/s41557-024-01469-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2023] [Accepted: 02/02/2024] [Indexed: 03/08/2024]
Abstract
π-Conjugated macrocycles behave differently from analogous linear chains because their electronic wavefunctions resemble a quantum particle on a ring, leading to aromaticity or anti-aromaticity. [18]Annulene, (CH)18, is the archetypal non-benzenoid aromatic hydrocarbon. Molecules with circuits of 4n + 2 π electrons, such as [18]annulene (n = 4), are aromatic, with enhanced stability and diatropic ring currents (magnetic shielding inside the ring), whereas those with 4n π electrons, such as the dianion of [18]annulene, are expected to be anti-aromatic and exhibit the opposite behaviour. Here we use 1H NMR spectroscopy to re-evaluate the structure of the [18]annulene dianion. We also show that it can be reduced further to an aromatic tetraanion, which has the same shape as the dianion. The crystal structure of the tetraanion lithium salt confirms its geometry and reveals a metallocene-like sandwich, with five Li+ cations intercalated between two [18]annulene tetraanions. We also report a heteroleptic sandwich, with [18]annulene and corannulene tetraanion decks.
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Affiliation(s)
- Wojciech Stawski
- Department of Chemistry, University at Albany, State University of New York, Albany, NY, USA
- Department of Chemistry, Oxford University, Chemistry Research Laboratory, Oxford, UK
| | - Yikun Zhu
- Department of Chemistry, University at Albany, State University of New York, Albany, NY, USA
| | - Igor Rončević
- Department of Chemistry, Oxford University, Chemistry Research Laboratory, Oxford, UK
| | - Zheng Wei
- Department of Chemistry, University at Albany, State University of New York, Albany, NY, USA
| | - Marina A Petrukhina
- Department of Chemistry, University at Albany, State University of New York, Albany, NY, USA.
| | - Harry L Anderson
- Department of Chemistry, Oxford University, Chemistry Research Laboratory, Oxford, UK.
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King RA, Schreiner PR, Crawford TD. Structure of [18]Annulene Revisited: Challenges for Computing Benzenoid Systems. J Phys Chem A 2024; 128:1098-1108. [PMID: 38306465 PMCID: PMC10875677 DOI: 10.1021/acs.jpca.3c07797] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 01/10/2024] [Accepted: 01/15/2024] [Indexed: 02/04/2024]
Abstract
For cyclic conjugated structures, erratic computational results have been obtained with Hartree-Fock (HF) molecular orbital (MO) methods as well as density functional theory (DFT) with large HF-exchange contributions. In this work, the reasons for this unreliability are explored. Extensive computations on [18]annulene and related compounds highlight the pitfalls to be avoided and the due diligence required for such computational investigations. In particular, a careful examination of the MO singlet-stability eigenvalues is recommended. The appearance of negative eigenvalues is not (necessarily) problematic, but near-zero (positive or negative) eigenvalues can lead to dramatic errors in vibrational frequencies and related properties. DFT approaches with a lower HF admixture generally appear more robust in this regard for the description of benzenoid structures, although they may exaggerate the tendency toward planarity and C-C bond-equalization. For the iconic [18]annulene, the results support a nonplanar equilibrium structure. The density-fitted frozen natural orbital coupled-cluster singles and doubles with perturbative triples [DF-FNO CCSD(T)] method of electron correlation with an aug-pVQZ/aug-pVTZ basis set places the C2 global minimum 1.1 kcal mol-1 below the D6h stationary point.
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Affiliation(s)
- Rollin A. King
- Department
of Chemistry, Bethel University, St. Paul, Minnesota 55112, United States
| | - Peter R. Schreiner
- Institute
of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, Giessen 35392, Germany
| | - T. Daniel Crawford
- Department
of Chemistry, Virginia Tech, Blacksburg, Virginia 24061, United States
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4
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Scriven LM, Kaiser K, Schulz F, Sterling AJ, Woltering SL, Gawel P, Christensen KE, Anderson HL, Gross L. Synthesis of Cyclo[18]carbon via Debromination of C 18Br 6. J Am Chem Soc 2020; 142:12921-12924. [PMID: 32646214 PMCID: PMC7393637 DOI: 10.1021/jacs.0c05033] [Citation(s) in RCA: 42] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
![]()
Cyclo[18]carbon (C18, a molecular carbon allotrope)
can be synthesized by dehalogenation of a bromocyclocarbon precursor,
C18Br6, in 64% yield, by atomic manipulation
on a sodium chloride bilayer on Cu(111) at 5 K, and imaged by high-resolution
atomic force microscopy. This method of generating C18 gives
a higher yield than that reported previously from the cyclocarbon
oxide C24O6. The experimental images of C18 were compared with simulated images for four theoretical
model geometries, including possible bond-angle alternation: D18h cumulene, D9h polyyne, D9h cumulene, and C9h polyyne. Cumulenic structures, with (D9h) and without (D18h) bond-angle alternation, can be excluded. Polyynic
structures, with (C9h) and without (D9h)
bond-angle alternation, both show a good agreement with the experiment
and are challenging to differentiate.
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Affiliation(s)
- Lorel M Scriven
- Department of Chemistry, Oxford University, Chemistry Research Laboratory, Oxford, OX1 3TA, U.K
| | - Katharina Kaiser
- IBM Research-Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - Fabian Schulz
- IBM Research-Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
| | - Alistair J Sterling
- Department of Chemistry, Oxford University, Chemistry Research Laboratory, Oxford, OX1 3TA, U.K
| | - Steffen L Woltering
- Department of Chemistry, Oxford University, Chemistry Research Laboratory, Oxford, OX1 3TA, U.K
| | - Przemyslaw Gawel
- Department of Chemistry, Oxford University, Chemistry Research Laboratory, Oxford, OX1 3TA, U.K
| | - Kirsten E Christensen
- Department of Chemistry, Oxford University, Chemistry Research Laboratory, Oxford, OX1 3TA, U.K
| | - Harry L Anderson
- Department of Chemistry, Oxford University, Chemistry Research Laboratory, Oxford, OX1 3TA, U.K
| | - Leo Gross
- IBM Research-Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
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Pacholska-Dudziak E, Hojniak-Thyssen S, Latos-Grażyński L. Expanded Porphyrin Contraction: From [22]Triphyrin(6.6.0) to [22]Triphyrin(6.5.0). Chemistry 2019; 25:11859-11863. [PMID: 31368597 DOI: 10.1002/chem.201903181] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Revised: 07/30/2019] [Indexed: 12/15/2022]
Abstract
An expanded triphyrin containing a bipyrrole moiety and annulene links, namely tetraphenyl-[22]triphyrin(6.5.0), 2, has been synthesized. The synthesis proceeded by a postsynthetic transformation of tetraphenyl-[22]triphyrin(6.6.0), 1, in a metal-free unexpected and unprecedented ring contraction during column chromatography on alumina. The observed transformation, located at the hydrocarbon chain linking the pyrrole units, formally corresponds to a subtraction of one carbon atom from an annulene circuit. In contrast to the flexible substrate 1, the product 2 is conformationally rigid, and capable of chloride anion binding in its protonated form.
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Affiliation(s)
- Ewa Pacholska-Dudziak
- Department of Chemistry, University of Wrocław, ul. Joliot-Curie 14, 50-383, Wrocław, Poland
| | - Sandra Hojniak-Thyssen
- Department of Chemistry, University of Wrocław, ul. Joliot-Curie 14, 50-383, Wrocław, Poland
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Pacholska‐Dudziak E, Latos‐Grażyński L, Białońska A. Shaping a Porphyrinoid Frame by Heteroatoms Extrusion: Formation of an Expanded [22]Triphyrin(6.6.0). Chemistry 2019; 25:10088-10097. [DOI: 10.1002/chem.201901571] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Indexed: 12/15/2022]
Affiliation(s)
- Ewa Pacholska‐Dudziak
- Department of ChemistryUniversity of Wroclaw ul. Joliot-Curie 14 50-383 Wroclaw Poland
| | | | - Agata Białońska
- Department of ChemistryUniversity of Wroclaw ul. Joliot-Curie 14 50-383 Wroclaw Poland
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Robert A, Dechambenoit P, Hillard EA, Bock H, Durola F. Non-planar oligoarylene macrocycles from biphenyl. Chem Commun (Camb) 2017; 53:11540-11543. [DOI: 10.1039/c7cc06798d] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Saddle- and propeller-shaped, partially condensed conjugated macrocycles are synthesized by fourfold Perkin condensation plus fourfold photocyclizations. Their macrocyclic loops are pronouncedly non-planar.
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Affiliation(s)
- Antoine Robert
- Centre de Recherche Paul Pascal
- Université de Bordeaux
- 33600 Pessac
- France
| | | | | | - Harald Bock
- Centre de Recherche Paul Pascal
- CNRS
- 33600 Pessac
- France
| | - Fabien Durola
- Centre de Recherche Paul Pascal
- CNRS
- 33600 Pessac
- France
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Setiawan D, Kraka E, Cremer D. Quantitative Assessment of Aromaticity and Antiaromaticity Utilizing Vibrational Spectroscopy. J Org Chem 2016; 81:9669-9686. [DOI: 10.1021/acs.joc.6b01761] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Dani Setiawan
- Computational and Theoretical
Chemistry Group (CATCO), Department of Chemistry, Southern Methodist University, 3215 Daniel Ave., Dallas, Texas 75275-0314, United States
| | - Elfi Kraka
- Computational and Theoretical
Chemistry Group (CATCO), Department of Chemistry, Southern Methodist University, 3215 Daniel Ave., Dallas, Texas 75275-0314, United States
| | - Dieter Cremer
- Computational and Theoretical
Chemistry Group (CATCO), Department of Chemistry, Southern Methodist University, 3215 Daniel Ave., Dallas, Texas 75275-0314, United States
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