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Agrawal AR, Shiouki I, Deree Y, Bogoslavsky B, Gidron O. Controlling helicene's pitch by molecular tethering. Org Biomol Chem 2024; 22:1365-1368. [PMID: 38258458 DOI: 10.1039/d3ob02075d] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
We applied post-cyclization annulation to introduce a series of tethered S-shaped double [4]helicenes in which the intramolecular tether imposes a specific helical handedness. Introducing a tether and then shortening the tether length incrementally increase the pitch angle of [4]helicene, thus enabling a quantitative study of the effects of helicene's pitch on its electronic and (chiro)optical properties.
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Affiliation(s)
- Abhijeet R Agrawal
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, Israel.
| | - Israa Shiouki
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, Israel.
| | - Yinon Deree
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, Israel.
| | - Benny Bogoslavsky
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, Israel.
| | - Ori Gidron
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem, Israel.
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2
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Biswas S, Tabasi ZA, Dawe LN, Zhao Y, Bodwell GJ. Synthesis of anti-[1](1,6)Naphthaleno[1](1,6)naphthalenophane by Double Contractive Annulation of [2.2]Paracyclophane. Org Lett 2022; 24:5009-5013. [DOI: 10.1021/acs.orglett.2c01602] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sourav Biswas
- Department of Chemistry, Memorial University of Newfoundland, 45 Arctic Avenue, St. John’s, NL Canada, A1C 5S7
| | - Zahra A. Tabasi
- Department of Chemistry, Memorial University of Newfoundland, 45 Arctic Avenue, St. John’s, NL Canada, A1C 5S7
| | - Louise N. Dawe
- Department of Chemistry and Biochemistry, Wilfrid Laurier University, 75 University Avenue West, Waterloo, ON Canada, N2L 3C5
| | - Yuming Zhao
- Department of Chemistry, Memorial University of Newfoundland, 45 Arctic Avenue, St. John’s, NL Canada, A1C 5S7
| | - Graham J. Bodwell
- Department of Chemistry, Memorial University of Newfoundland, 45 Arctic Avenue, St. John’s, NL Canada, A1C 5S7
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Armon AM, Bedi A, Borin V, Schapiro I, Gidron O. Bending versus Twisting Acenes - A Computational Study. European J Org Chem 2021; 2021:5424-5429. [PMID: 34819798 PMCID: PMC8597036 DOI: 10.1002/ejoc.202100865] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2021] [Revised: 09/23/2021] [Indexed: 01/07/2023]
Abstract
Polycyclic aromatic hydrocarbons (PAHs) are widely used in organic electronic devices. The electronic, magnetic, and optical properties of PAHs can be tuned by structural modifications to the aromatic backbone to introduce an inherent distortion from planarity, such as bending or twisting. However, it remains difficult to isolate and control the effects of such distortions. Here, we sought to understand how backbone twisting and bending affect the electronic properties of acenes, as models for larger PAHs. We found that, even when highly distorted from planarity (30° per ring), acenes maintain their aromatic character and π orbital delocalization with minor mixing of the σ and π orbitals. In addition, the energy gap between the HOMO and LUMO decreases with increasing twist, while the gap is hardly affected by bending, since the energy of both orbitals increase to a similar extent. For bent acenes in the triplet state, the spin becomes more localized with increasing bend, whereas twisting produces an evenly distributed spin delocalization. These findings can guide the synthesis of PAHs with tailored properties.
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Affiliation(s)
- Amit Manor Armon
- Institute of ChemistryThe Hebrew University of JerusalemJerusalem9190401Israel
| | - Anjan Bedi
- Institute of ChemistryThe Hebrew University of JerusalemJerusalem9190401Israel
- Department of ChemistrySRM Institute of Science and TechnologyKattankulathur603203Tamil NaduIndia
| | - Veniamin Borin
- Fritz Haber Center for Molecular Dynamics ResearchInstitute of ChemistryThe Hebrew University of JerusalemJerusalem9190401Israel
| | - Igor Schapiro
- Fritz Haber Center for Molecular Dynamics ResearchInstitute of ChemistryThe Hebrew University of JerusalemJerusalem9190401Israel
| | - Ori Gidron
- Institute of ChemistryThe Hebrew University of JerusalemJerusalem9190401Israel
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Biswas S, Tabasi ZA, Lin JB, Zhao Y, Bodwell GJ. Synthesis of [2.2]Paracyclophane/9-Alkylfluorene Hybrids and the Discovery of a Solvent-assisted Rearrangement. Org Lett 2021; 23:5461-5465. [PMID: 34228471 DOI: 10.1021/acs.orglett.1c01791] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Work on the synthesis of [2.2]paracyclophane/9-alkylfluorene hybrids led to the discovery of the rearrangement of cyclopentadienone 7 to cyclophane 6. A DFT computational study revealed that this formal 1,3-alkyl shift occurs in two steps, but requires the participation of a solvent molecule (ethanol). The rearrangement could be avoided by generating 7 under mild conditions and using benzynes as dienophiles to afford the targeted cyclophanes 14 and 16, the latter of which exhibits dual fluorescence emission.
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Affiliation(s)
- Sourav Biswas
- Chemistry Department, Memorial University of Newfoundland, St. John's, Newfoundland Canada, A1B3X7
| | - Zahra A Tabasi
- Chemistry Department, Memorial University of Newfoundland, St. John's, Newfoundland Canada, A1B3X7
| | - Jian-Bin Lin
- Chemistry Department, Memorial University of Newfoundland, St. John's, Newfoundland Canada, A1B3X7
| | - Yuming Zhao
- Chemistry Department, Memorial University of Newfoundland, St. John's, Newfoundland Canada, A1B3X7
| | - Graham J Bodwell
- Chemistry Department, Memorial University of Newfoundland, St. John's, Newfoundland Canada, A1B3X7
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Unikela KS, Tabasi ZA, Dawe LN, Zhao Y, Bodwell GJ. "Shadow" Synthesis, Structure, and Electronic Properties of [2.2](1,6)(1,8)Pyrenophane-1-monoene. J Org Chem 2021; 86:4405-4412. [PMID: 33656886 DOI: 10.1021/acs.joc.0c02579] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
An unexpected side product of a McMurry reaction was found to be a new [2.2]pyrenophane consisting of two pyrene units with different substitution patterns as well as different types and degrees of distortion from planarity. The new pyrenophane exhibits both monomer and intramolecular excimer fluorescence. Natural bond orbital (NBO) analysis revealed that there is an intramolecular charge-transfer interaction from the more distorted pyrene system to the less distorted one. The origin of the new pyrenophane was traced back to an impurity that was present a full five steps prior to the McMurry reaction from which it was isolated. The pathway to the pyrenophane shadowed that of the main synthetic route.
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Affiliation(s)
- Kiran Sagar Unikela
- Department of Chemistry, Memorial University of Newfoundland, 283 Prince Philip Drive, St. John's, NL Canada, A1B 3X7
| | - Zahra A Tabasi
- Department of Chemistry, Memorial University of Newfoundland, 283 Prince Philip Drive, St. John's, NL Canada, A1B 3X7
| | - Louise N Dawe
- Department of Chemistry and Biochemistry, Wilfrid Laurier University, 75 University Avenue West, Waterloo, ON Canada, N2L 3C5
| | - Yuming Zhao
- Department of Chemistry, Memorial University of Newfoundland, 283 Prince Philip Drive, St. John's, NL Canada, A1B 3X7
| | - Graham J Bodwell
- Department of Chemistry, Memorial University of Newfoundland, 283 Prince Philip Drive, St. John's, NL Canada, A1B 3X7
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Wang Y, Joullié MM. Approaches to Cyclophane-Types of Cyclopeptide Alkaloids. CHEM REC 2021; 21:906-923. [PMID: 33656243 DOI: 10.1002/tcr.202100017] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 02/15/2021] [Indexed: 11/09/2022]
Abstract
The cyclopeptide alkaloids are cyclic depsipeptides incorporating cyclophanes with polyamide units 13-, 14- and 15-membered macrocyclic systems. Although various pharmacological activities have been ascribed to cyclopeptide alkaloids from plants of the Rhamnacea family, these studies have been hampered by their low availability due to the lack of reasonable amounts distributed in nature. Therefore, novel and efficient synthetic approaches should be an important aim, which inspired us to examine how to diversely construct the unique structures of this type of natural products. In this account, several typical strategies are presented in terms of efficient, stereocontrolled and regioselective synthesis of cyclopeptide alkaloids.
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Affiliation(s)
- Yuanhao Wang
- Department of Chemistry, University of Pennsylvania, 231 S. 34th St., Philadelphia, PA 19104, USA
| | - Madeleine M Joullié
- Department of Chemistry, University of Pennsylvania, 231 S. 34th St., Philadelphia, PA 19104, USA
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Colwell CE, Price TW, Stauch T, Jasti R. Strain visualization for strained macrocycles. Chem Sci 2020; 11:3923-3930. [PMID: 34122862 PMCID: PMC8152662 DOI: 10.1039/d0sc00629g] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2020] [Accepted: 03/22/2020] [Indexed: 11/28/2022] Open
Abstract
Strain has a unique and sometimes unpredictable impact on the properties and reactivity of molecules. To thoroughly describe strain in molecules, a computational tool that relates strain energy to reactivity by localizing and quantifying strain was developed. Strain energy is calculated local to every coordinate in the molecule and areas of higher strain are shown experimentally to be more reactive. Not only does this tool directly compare strain energy in parts of the same molecule, but it also computes total strain to give a full picture of molecular strain energy. It is freely available to the public on GitHub under the name StrainViz and much of the workflow is automated to simplify use for non-experts. Unique insight into the reactivity of curved aromatic molecules and strained alkyne bioorthogonal reagents is described within.
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Affiliation(s)
- Curtis E Colwell
- Department of Chemistry & Biochemistry, Materials Science Institute, Knight Campus for Accelerating Scientific Impact, University of Oregon Eugene Oregon 97403 USA
| | - Tavis W Price
- Department of Chemistry & Biochemistry, Materials Science Institute, Knight Campus for Accelerating Scientific Impact, University of Oregon Eugene Oregon 97403 USA
| | - Tim Stauch
- University of Bremen, Institute for Physical and Theoretical Chemistry Leobener Str. NW2 D-28359 Bremen Germany
- MAPEX Center for Materials and Processes, University of Bremen Bibliothekstraße 1 D-28359 Bremen Germany
| | - Ramesh Jasti
- Department of Chemistry & Biochemistry, Materials Science Institute, Knight Campus for Accelerating Scientific Impact, University of Oregon Eugene Oregon 97403 USA
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Bedi A, Gidron O. The Consequences of Twisting Nanocarbons: Lessons from Tethered Twisted Acenes. Acc Chem Res 2019; 52:2482-2490. [PMID: 31453688 DOI: 10.1021/acs.accounts.9b00271] [Citation(s) in RCA: 71] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The properties of polycyclic aromatic hydrocarbons are determined by their size, shape, and functional groups. Equally important is their curvature, since deviation from planarity can affect their optical, electronic, and magnetic properties and also induce chirality. Acenes, which can be viewed as one-dimensional nanocarbons, are often twisted out of planarity. Although twisting is expected to affect the above-mentioned properties, it is often overlooked. This Account focuses on helically locked twistacenes (twisted acenes) having different twist angles and the effect of twisting on their electronic and optical properties. Various synthetic approaches to inducing backbone twist in acenes are discussed, with a focus on the introduction of a diagonal tether across the core, as this minimizes confounding substituent effects. Using such tethered acenes as our model, we then discuss the effects of twisting the aromatic core on twistacene properties. Electronic properties. Increasing the degree of twist only slightly affects the HOMO and LUMO energy levels. Twisting leads to a small increase in the HOMO level and a decrease in the LUMO level, which produces an overall decrease in the HOMO-LUMO gap. Optical properties. As the degree of twist increases, a slight bathochromic shift is observed in the absorption spectra, in accordance with the decrease in the HOMO-LUMO gap. The fluorescence quantum efficiency and the fluorescence lifetime also decrease. This is likely to be related to an increasing rate of intersystem crossing, which arises from increased spin-orbit coupling. In addition, computational studies indicate that the S0-T1 energy gap decreases with increasing twist. Chiroptical properties. Increased twisting results in a larger Cotton effect and anisotropy factor, with the anisotropy factors of Ant-Cn being higher than those of longer helicenes. The parallel orientation of electric and magnetic transition dipole moments in twistacenes underlies this behavior and renders them as excellent chiroptical materials. The same trend is observed for the radical cations of twistacenes, which absorb in the NIR spectral region. Conjugation and delocalization. Twisting the anthracene radical cation up to 40° (13° per benzene ring) does not significantly affect spin delocalization, with the EPR spectra of twistacene radical cations showing that only slight localization occurs. This is in line with computational studies, which show only a small decrease in π-overlap for large acene twist. Overall, modifying the length of the tether in diagonally tethered acenes allows chemists to control core twist and to induce chirality. Twisting affects key optical, electronic, and chiroptical properties of acenes. Consequently, controlling the twist angle can improve the future design of nanocarbons with desired properties.
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Affiliation(s)
- Anjan Bedi
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem 91904, Israel
| | - Ori Gidron
- Institute of Chemistry, The Hebrew University of Jerusalem, Edmond J. Safra Campus, Jerusalem 91904, Israel
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