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Dishi O, Rahav Y, Gidron O. π-Conjugated oligofuran macrocycles. Chem Commun (Camb) 2024; 60:522-529. [PMID: 38109063 DOI: 10.1039/d3cc05225g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
This Feature Article overviews a new class of π-conjugated materials - macrocyclic furans. Starting from their synthesis, we review their unique structural, optical and electronic properties, chemical reactivity, and potential application as synthons. Finally, we discuss the study of oligofuran macrocycles as a model system for exploring the concept of global aromaticity and the size limitation of Hückel's rule in neutral macrocycles.
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Affiliation(s)
- Or Dishi
- The Hebrew University of Jerusalem, Edmond J. Safra Campus, 9190401, Jerusalem, Israel.
| | - Yuval Rahav
- The Hebrew University of Jerusalem, Edmond J. Safra Campus, 9190401, Jerusalem, Israel.
| | - Ori Gidron
- The Hebrew University of Jerusalem, Edmond J. Safra Campus, 9190401, Jerusalem, Israel.
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Rahav Y, Rajagopal SK, Dishi O, Bogoslavsky B, Gidron O. Alternating behavior in furan-acetylene macrocycles reveals the size-dependency of Hückel's rule in neutral molecules. Commun Chem 2023; 6:100. [PMID: 37244950 DOI: 10.1038/s42004-023-00902-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Accepted: 05/15/2023] [Indexed: 05/29/2023] Open
Abstract
Aromaticity can be assigned by Hückel's rule, which predicts that planar rings with delocalized (4n + 2) π-electrons are aromatic, whereas those with 4n π-electrons are antiaromatic. However, for neutral rings, the maximal value of "n" to which Hückel's rule applies remains unknown. Large macrocycles exhibiting global ring current can serve as models for addressing this question, but the global ring current are often overshadowed in these molecules by the local ring current of the constituent units. Here, we present a series of furan-acetylene macrocycles, ranging from the pentamer to octamer, whose neutral states display alternating contributions from global aromatic and antiaromatic ring currents. We find that the odd-membered macrocycles display global aromatic characteristics, whereas the even-membered macrocycles display contributions from globally antiaromatic ring current. These factors are expressed electronically (oxidation potentials), optically (emission spectra), and magnetically (chemical shifts), and DFT calculations predict global ring current alternations up to 54 π-electrons.
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Affiliation(s)
- Yuval Rahav
- Institute of Chemistry, The Center for Nanoscience and Nanotechnology, Casali Center for Applied Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, 9190401, Israel
| | - Shinaj K Rajagopal
- Institute of Chemistry, The Center for Nanoscience and Nanotechnology, Casali Center for Applied Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, 9190401, Israel
| | - Or Dishi
- Institute of Chemistry, The Center for Nanoscience and Nanotechnology, Casali Center for Applied Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, 9190401, Israel
| | - Benny Bogoslavsky
- Institute of Chemistry, The Center for Nanoscience and Nanotechnology, Casali Center for Applied Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, 9190401, Israel
| | - Ori Gidron
- Institute of Chemistry, The Center for Nanoscience and Nanotechnology, Casali Center for Applied Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, 9190401, Israel.
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Rajagopal SK, Dishi O, Bogoslavsky B, Gidron O. Transformation of π-conjugated macrocycles: from furanophanes to napthalenophanes. Chem Commun (Camb) 2022; 58:13652-13655. [PMID: 36412186 DOI: 10.1039/d2cc05434e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Applying sequential Diels-Alder cycloaddition and deoxygenation to small π-conjugated furan macrocycles fully converts them to 1,4-naphthalophanes with either ethylene or acetylene spacers, depending on the reaction conditions. 1,4-Napthalenophane tetraene exhibits a 1,3-alternating conformation in the solid state, inclusion of solvent molecules within the macrocycle, and low reduction potentials.
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Affiliation(s)
- Shinaj K Rajagopal
- Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel.
| | - Or Dishi
- Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel.
| | - Benny Bogoslavsky
- Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel.
| | - Ori Gidron
- Institute of Chemistry and The Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel.
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Dishi O, Rahav Y, Carmieli R, Gidron O. A Macrocyclic Furan with Accessible Oxidation States: Switching Between Aromatic and Antiaromatic Global Ring Currents. Chemistry 2022; 28:e202202082. [PMID: 35932151 PMCID: PMC9826138 DOI: 10.1002/chem.202202082] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2022] [Indexed: 01/11/2023]
Abstract
Macrocyclic furans are predicted to switch between global aromaticity and antiaromaticity, depending on their oxidation states. However, the macrocyclic furans reported to date are stabilized by electron withdrawing groups, which result in inaccessible oxidation states. To circumvent this problem, a post-macrocyclization approach was applied to introduce methylene-substituted macrocyclic furans, which display an extremely low oxidation potential of -0.23 vs. Fc/Fc+ , and are partially oxidized in ambient conditions. Additional oxidation to the dication results in aromaticity switching to a global 30πe- aromatic state, as indicated by the formation of a strong diatropic current observed in the 1 H NMR spectrum. NICS and ACID calculations support this trend and provide evidence for a different pathway for the global current in the neutral and dicationic states. According to these findings, macrocyclic furans can be rendered as promising p-type materials with stable oxidation states.
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Affiliation(s)
- Or Dishi
- Institute of ChemistryThe Hebrew University of JerusalemEdmond J. Safra CampusJerusalem9190401Israel
| | - Yuval Rahav
- Institute of ChemistryThe Hebrew University of JerusalemEdmond J. Safra CampusJerusalem9190401Israel
| | - Raanan Carmieli
- Chemical Research Support UnitWeizmann Institute of ScienceRehovot7610001Israel
| | - Ori Gidron
- Institute of ChemistryThe Hebrew University of JerusalemEdmond J. Safra CampusJerusalem9190401Israel
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Dishi O, Malakar P, Shimon LJW, Ruhman S, Gidron O. Cover Feature: Ring Size Determines the Conformation, Global Aromaticity and Photophysical Properties of Macrocyclic Oligofurans (Chem. Eur. J. 71/2021). Chemistry 2021. [DOI: 10.1002/chem.202104303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Or Dishi
- Institute of Chemistry The Hebrew University of Jerusalem Edmond J. Safra Campus Jerusalem 9190401 Israel
| | - Partha Malakar
- Institute of Chemistry The Hebrew University of Jerusalem Edmond J. Safra Campus Jerusalem 9190401 Israel
| | - Linda J. W. Shimon
- Chemical Research Support Unit Weizmann Institute of Science Rehovot 7610001 Israel
| | - Sanford Ruhman
- Institute of Chemistry The Hebrew University of Jerusalem Edmond J. Safra Campus Jerusalem 9190401 Israel
| | - Ori Gidron
- Institute of Chemistry The Hebrew University of Jerusalem Edmond J. Safra Campus Jerusalem 9190401 Israel
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Dishi O, Malakar P, Shimon LJW, Ruhman S, Gidron O. Ring Size Determines the Conformation, Global Aromaticity and Photophysical Properties of Macrocyclic Oligofurans. Chemistry 2021; 27:17794-17801. [PMID: 34747542 DOI: 10.1002/chem.202103536] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2021] [Indexed: 11/09/2022]
Abstract
In π-conjugated macrocycles, there is a trade-off between the global and local expression of effects such as aromaticity, with the outcome of the trade-off determined by the geometry and aromaticity of the constituent units. Compared with other aromatic rings, the aromatic character of furan is relatively small, and therefore global effects in macrocyclic furans are expected to be more pronounced. Following our introduction of macrocyclic oligofuran, we present the first synthesis of a series of π-conjugated bifuran macrocycles of various ring sizes, from trimer to hexamer, and characterize them using both computational and experimental methods. The properties of macrocyclic oligofurans change considerably with size: The smaller trimer is rigid, weakly emissive and planar as revealed by its single crystal structure, and displays global antiaromaticity. In contrast, the larger pentamer and hexamer are flexible, emissive, have non-planar structures, and exhibit local aromaticity. The results are supported by NICS and ACID calculations that indicate the global antiaromaticity of planar furan macrocycles, and by transient absorption measurements showing sharp absorption band for the trimer and only the internal conversion decay pathway.
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Affiliation(s)
- Or Dishi
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, 9190401, Israel
| | - Partha Malakar
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, 9190401, Israel
| | - Linda J W Shimon
- Chemical Research Support Unit, Weizmann Institute of Science, Rehovot, 7610001, Israel
| | - Sanford Ruhman
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, 9190401, Israel
| | - Ori Gidron
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, 9190401, Israel
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Mulay SV, Dishi O, Fang Y, Niazi MR, Shimon LJW, Perepichka DF, Gidron O. A macrocyclic oligofuran: synthesis, solid state structure and electronic properties. Chem Sci 2019; 10:8527-8532. [PMID: 32055302 PMCID: PMC7003964 DOI: 10.1039/c9sc03247a] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2019] [Accepted: 08/19/2019] [Indexed: 11/27/2022] Open
Abstract
The first π-conjugated macrocyclic system with an oligofuran backbone display planar conformation and forms large π-aggregates, in contrast to the twisted conformation of small macrocyclic oligothiophenes.
We report the first π-conjugated macrocyclic system with an oligofuran backbone. The calculated HOMO–LUMO gap is similar to that of the corresponding linear polymer, indicating a remarkable electron delocalization. The X-ray structure reveals a planar conformation, in contrast to the twisted conformation of macrocyclic oligothiophenes. The intermolecular π–π stacking distance is extremely small (3.17 Å), indicating very strong interactions. The macrocycle forms large π-aggregates in solution and shows a tendency toward highly ordered multilayer adsorption at the solid–liquid interface. The face-on orientation of molecules explains the higher hole mobility observed in the out-of-plane direction.
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Affiliation(s)
- Sandip V Mulay
- Institute of Chemistry , The Hebrew University of Jerusalem , Edmond J. Safra Campus , Jerusalem , Israel .
| | - Or Dishi
- Institute of Chemistry , The Hebrew University of Jerusalem , Edmond J. Safra Campus , Jerusalem , Israel .
| | - Yuan Fang
- Department of Chemistry , McGill University , Montreal , QC H3A 0B8 , Canada .
| | - Muhammad R Niazi
- Department of Chemistry , McGill University , Montreal , QC H3A 0B8 , Canada .
| | - Linda J W Shimon
- Chemical Research Support Unit , Weizmann Institute of Science , Rehovot , Israel
| | | | - Ori Gidron
- Institute of Chemistry , The Hebrew University of Jerusalem , Edmond J. Safra Campus , Jerusalem , Israel .
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Affiliation(s)
- Or Dishi
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904, Israel
| | - Ori Gidron
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Givat Ram, Jerusalem 91904, Israel
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