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Article: Controlling switching in bistable [2]catenanes by combining donor-acceptor and radical-radical interactions

TitleControlling switching in bistable [2]catenanes by combining donor-acceptor and radical-radical interactions
Authors
Issue Date2012
Citation
Journal of the American Chemical Society, 2012, v. 134, n. 28, p. 11709-11720 How to Cite?
AbstractTwo redox-active bistable [2]catenanes composed of macrocyclic polyethers of different sizes incorporating both electron-rich 1,5-dioxynaphthalene (DNP) and electron-deficient 4,4′-bipyridinium (BIPY 2+) units, interlocked mechanically with the tetracationic cyclophane cyclobis(paraquat-p- phenylene) (CBPQT 4+), were obtained by donor-acceptor template-directed syntheses in a threading-followed-by-cyclization protocol employing Cu(I)-catalyzed azide-alkyne 1,3-dipolar cycloadditions in the final mechanical-bond forming steps. These bistable [2]catenanes exemplify a design strategy for achieving redox-active switching between two translational isomers, which are driven (i) by donor-acceptor interactions between the CBPQT 4+ ring and DNP, or (ii) radical-radical interactions between CBPQT 2(•+) and BIPY •+, respectively. The switching processes, as well as the nature of the donor-acceptor interactions in the ground states and the radical-radical interactions in the reduced states, were investigated by single-crystal X-ray crystallography, dynamic 1H NMR spectroscopy, cyclic voltammetry, UV/vis spectroelectrochemistry, and electron paramagnetic resonance (EPR) spectroscopy. The crystal structure of one of the [2]catenanes in its trisradical tricationic redox state provides direct evidence for the radical-radical interactions which drive the switching processes for these types of mechanically interlocked molecules (MIMs). Variable-temperature 1H NMR spectroscopy reveals a degenerate rotational motion of the BIPY 2+ units in the CBPQT 4+ ring for both of the two [2]catenanes, that is governed by a free energy barrier of 14.4 kcal mol -1 for the larger catenane and 17.0 kcal mol -1 for the smaller one. Cyclic voltammetry provides evidence for the reversibility of the switching processes which occurs following a three-electron reduction of the three BIPY 2+ units to their radical cationic forms. UV/vis spectroscopy confirms that the processes driving the switching are (i) of the donor-acceptor type, by the observation of a 530 nm charge-transfer band in the ground state, and (ii) of the radical-radical ilk in the switched state as indicated by an intense visible absorption (ca. 530 nm) and near-infrared (ca. 1100 nm) bands. EPR spectroscopic data reveal that, in the switched state, the interacting BIPY •+ radical cations are in a fast exchange regime. In general, the findings lay the foundations for future investigations where this radical-radical recognition motif is harnessed in bistable redox-active MIMs in order to achieve close to homogeneous populations of co-conformations in both the ground and switched states. © 2012 American Chemical Society.
Persistent Identifierhttp://hdl.handle.net/10722/332995
ISSN
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DC FieldValueLanguage
dc.contributor.authorZhu, Zhixue-
dc.contributor.authorFahrenbach, Albert C.-
dc.contributor.authorLi, Hao-
dc.contributor.authorBarnes, Jonathan C.-
dc.contributor.authorLiu, Zhichang-
dc.contributor.authorDyar, Scott M.-
dc.contributor.authorZhang, Huacheng-
dc.contributor.authorLei, Juying-
dc.contributor.authorCarmieli, Raanan-
dc.contributor.authorSarjeant, Amy A.-
dc.contributor.authorStern, Charlotte L.-
dc.contributor.authorWasielewski, Michael R.-
dc.contributor.authorStoddart, J. Fraser-
dc.date.accessioned2023-10-06T05:15:57Z-
dc.date.available2023-10-06T05:15:57Z-
dc.date.issued2012-
dc.identifier.citationJournal of the American Chemical Society, 2012, v. 134, n. 28, p. 11709-11720-
dc.identifier.issn0002-7863-
dc.identifier.urihttp://hdl.handle.net/10722/332995-
dc.description.abstractTwo redox-active bistable [2]catenanes composed of macrocyclic polyethers of different sizes incorporating both electron-rich 1,5-dioxynaphthalene (DNP) and electron-deficient 4,4′-bipyridinium (BIPY 2+) units, interlocked mechanically with the tetracationic cyclophane cyclobis(paraquat-p- phenylene) (CBPQT 4+), were obtained by donor-acceptor template-directed syntheses in a threading-followed-by-cyclization protocol employing Cu(I)-catalyzed azide-alkyne 1,3-dipolar cycloadditions in the final mechanical-bond forming steps. These bistable [2]catenanes exemplify a design strategy for achieving redox-active switching between two translational isomers, which are driven (i) by donor-acceptor interactions between the CBPQT 4+ ring and DNP, or (ii) radical-radical interactions between CBPQT 2(•+) and BIPY •+, respectively. The switching processes, as well as the nature of the donor-acceptor interactions in the ground states and the radical-radical interactions in the reduced states, were investigated by single-crystal X-ray crystallography, dynamic 1H NMR spectroscopy, cyclic voltammetry, UV/vis spectroelectrochemistry, and electron paramagnetic resonance (EPR) spectroscopy. The crystal structure of one of the [2]catenanes in its trisradical tricationic redox state provides direct evidence for the radical-radical interactions which drive the switching processes for these types of mechanically interlocked molecules (MIMs). Variable-temperature 1H NMR spectroscopy reveals a degenerate rotational motion of the BIPY 2+ units in the CBPQT 4+ ring for both of the two [2]catenanes, that is governed by a free energy barrier of 14.4 kcal mol -1 for the larger catenane and 17.0 kcal mol -1 for the smaller one. Cyclic voltammetry provides evidence for the reversibility of the switching processes which occurs following a three-electron reduction of the three BIPY 2+ units to their radical cationic forms. UV/vis spectroscopy confirms that the processes driving the switching are (i) of the donor-acceptor type, by the observation of a 530 nm charge-transfer band in the ground state, and (ii) of the radical-radical ilk in the switched state as indicated by an intense visible absorption (ca. 530 nm) and near-infrared (ca. 1100 nm) bands. EPR spectroscopic data reveal that, in the switched state, the interacting BIPY •+ radical cations are in a fast exchange regime. In general, the findings lay the foundations for future investigations where this radical-radical recognition motif is harnessed in bistable redox-active MIMs in order to achieve close to homogeneous populations of co-conformations in both the ground and switched states. © 2012 American Chemical Society.-
dc.languageeng-
dc.relation.ispartofJournal of the American Chemical Society-
dc.titleControlling switching in bistable [2]catenanes by combining donor-acceptor and radical-radical interactions-
dc.typeArticle-
dc.description.naturelink_to_subscribed_fulltext-
dc.identifier.doi10.1021/ja3037355-
dc.identifier.scopuseid_2-s2.0-84863946995-
dc.identifier.volume134-
dc.identifier.issue28-
dc.identifier.spage11709-
dc.identifier.epage11720-
dc.identifier.eissn1520-5126-
dc.identifier.isiWOS:000306457900062-

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