A macrocyclic receptor containing two viologen species connected by conjugated terphenyl groups

Long Chen, Kate J.C. Lim, Tahkur S. Babra, James O. Taylor, Martin Pižl, Robert D Evans, Ann M. Chippindale, František Hartl, Howard M. Colquhoun, Barnaby W. Greenland

Research output: Contribution to journalArticle

Abstract

A macrocyclic receptor molecule containing two viologen species connected by conjugated terphenyl groups has been designed and synthesised. The single-crystal X-ray structure shows that the two viologen residues have a transannular N…N separation of ca. 7.4 Å. Thus, the internal cavity dimensions are suitable for the inclusion of π-electron-rich species. The macrocycle is redox active, and can accept electrons from suitable donor species including triethylamine, resulting in a dramatic colour change from pale yellow to dark green as a consequence of the formation of a paramagnetic bis(radical cationic) species. Cyclic voltammetry shows that the macrocycle can undergo two sequential and reversible reduction processes (E1/2 = -0.65 and -0.97 V vs Fc/Fc+). DFT and TD-DFT studies accurately replicate the structure of the tetracationic macrocycle and the electronic absorption spectra the three major redox states of the system. These calculations also showed that during electrochemical reduction, the unpaired electron density of the radical cations remains relatively localised within the heterocyclic rings. The ability of the macrocycle to form supramolecular complexes was confirmed by the formation of a pseudorotaxane with a guest molecule containing a π-electron-rich 1,5-dihydroxynaphthalene derivative. Threading and dethreading of the pseudorotaxane was fast on the NMR timescale, and the complex exhibited an association constant of 150 M-1 (± 30 M-1) as calculated from 1H NMR titration studies.
Original languageEnglish
JournalOrganic and Biomolecular Chemistry
Early online date19 Jun 2018
DOIs
Publication statusE-pub ahead of print - 19 Jun 2018

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Viologens
terphenyls
Rotaxanes
Electrons
Discrete Fourier transforms
Nuclear magnetic resonance
Oxidation-Reduction
nuclear magnetic resonance
Molecules
electrons
Titration
electronic spectra
titration
Cyclic voltammetry
Carrier concentration
Cations
molecules
Absorption spectra
Association reactions
Single crystals

Bibliographical note

© The Royal Society of Chemistry 2018

Cite this

Chen, Long ; Lim, Kate J.C. ; Babra, Tahkur S. ; Taylor, James O. ; Pižl, Martin ; Evans, Robert D ; Chippindale, Ann M. ; Hartl, František ; Colquhoun, Howard M. ; Greenland, Barnaby W. / A macrocyclic receptor containing two viologen species connected by conjugated terphenyl groups. In: Organic and Biomolecular Chemistry . 2018.
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abstract = "A macrocyclic receptor molecule containing two viologen species connected by conjugated terphenyl groups has been designed and synthesised. The single-crystal X-ray structure shows that the two viologen residues have a transannular N…N separation of ca. 7.4 {\AA}. Thus, the internal cavity dimensions are suitable for the inclusion of π-electron-rich species. The macrocycle is redox active, and can accept electrons from suitable donor species including triethylamine, resulting in a dramatic colour change from pale yellow to dark green as a consequence of the formation of a paramagnetic bis(radical cationic) species. Cyclic voltammetry shows that the macrocycle can undergo two sequential and reversible reduction processes (E1/2 = -0.65 and -0.97 V vs Fc/Fc+). DFT and TD-DFT studies accurately replicate the structure of the tetracationic macrocycle and the electronic absorption spectra the three major redox states of the system. These calculations also showed that during electrochemical reduction, the unpaired electron density of the radical cations remains relatively localised within the heterocyclic rings. The ability of the macrocycle to form supramolecular complexes was confirmed by the formation of a pseudorotaxane with a guest molecule containing a π-electron-rich 1,5-dihydroxynaphthalene derivative. Threading and dethreading of the pseudorotaxane was fast on the NMR timescale, and the complex exhibited an association constant of 150 M-1 (± 30 M-1) as calculated from 1H NMR titration studies.",
author = "Long Chen and Lim, {Kate J.C.} and Babra, {Tahkur S.} and Taylor, {James O.} and Martin Pižl and Evans, {Robert D} and Chippindale, {Ann M.} and František Hartl and Colquhoun, {Howard M.} and Greenland, {Barnaby W.}",
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Chen, L, Lim, KJC, Babra, TS, Taylor, JO, Pižl, M, Evans, RD, Chippindale, AM, Hartl, F, Colquhoun, HM & Greenland, BW 2018, 'A macrocyclic receptor containing two viologen species connected by conjugated terphenyl groups', Organic and Biomolecular Chemistry . https://doi.org/10.1039/C8OB00919H

A macrocyclic receptor containing two viologen species connected by conjugated terphenyl groups. / Chen, Long; Lim, Kate J.C. ; Babra, Tahkur S.; Taylor, James O.; Pižl, Martin; Evans, Robert D; Chippindale, Ann M.; Hartl, František ; Colquhoun, Howard M.; Greenland, Barnaby W.

In: Organic and Biomolecular Chemistry , 19.06.2018.

Research output: Contribution to journalArticle

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AU - Chen, Long

AU - Lim, Kate J.C.

AU - Babra, Tahkur S.

AU - Taylor, James O.

AU - Pižl, Martin

AU - Evans, Robert D

AU - Chippindale, Ann M.

AU - Hartl, František

AU - Colquhoun, Howard M.

AU - Greenland, Barnaby W.

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AB - A macrocyclic receptor molecule containing two viologen species connected by conjugated terphenyl groups has been designed and synthesised. The single-crystal X-ray structure shows that the two viologen residues have a transannular N…N separation of ca. 7.4 Å. Thus, the internal cavity dimensions are suitable for the inclusion of π-electron-rich species. The macrocycle is redox active, and can accept electrons from suitable donor species including triethylamine, resulting in a dramatic colour change from pale yellow to dark green as a consequence of the formation of a paramagnetic bis(radical cationic) species. Cyclic voltammetry shows that the macrocycle can undergo two sequential and reversible reduction processes (E1/2 = -0.65 and -0.97 V vs Fc/Fc+). DFT and TD-DFT studies accurately replicate the structure of the tetracationic macrocycle and the electronic absorption spectra the three major redox states of the system. These calculations also showed that during electrochemical reduction, the unpaired electron density of the radical cations remains relatively localised within the heterocyclic rings. The ability of the macrocycle to form supramolecular complexes was confirmed by the formation of a pseudorotaxane with a guest molecule containing a π-electron-rich 1,5-dihydroxynaphthalene derivative. Threading and dethreading of the pseudorotaxane was fast on the NMR timescale, and the complex exhibited an association constant of 150 M-1 (± 30 M-1) as calculated from 1H NMR titration studies.

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DO - 10.1039/C8OB00919H

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