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Spatiotemporal control over the co-conformational switching in pH-responsive flavylium-based multistate pseudorotaxanes

2015-06Journal article Restricted access
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dc.contributor.authorDiniz, Ana Marta
dc.contributor.authorBasílio, Nuno
dc.contributor.authorCruz, Hugo
dc.contributor.authorPina, Fernando
dc.contributor.authorParola, A Jorge
dc.date.accessioned2016-08-23T12:41:45Z
dc.date.available2016-08-23T12:41:45Z
dc.date.issued2015-06
dc.description.abstractA multistate molecular dyad containing flavylium and viologen units was synthesized and the pH dependent thermodynamics of the network completely characterized by a variety of spectroscopic techniques such as NMR, UV-vis and stopped-flow. The flavylium cation is only stable at acidic pH values. Above pH ≈ 5 the hydration of the flavylium leads to the formation of the hemiketal followed by ring-opening tautomerization to give the cis-chalcone. Finally, this last species isomerizes to give the trans-chalcone. For the present system only the flavylium cation and the trans-chalcone species could be detected as being thermodynamically stable. The hemiketal and the cis-chalcone are kinetic intermediates with negligible concentrations at the equilibrium. All stable species of the network were found to form 1 : 1 and 2 : 1 host : guest complexes with cucurbit[7]uril (CB7) with association constants in the ranges 10(5)-10(8) M(-1) and 10(3)-10(4) M(-1), respectively. The 1 : 1 complexes were particularly interesting to devise pH responsive bistable pseudorotaxanes: at basic pH values (≈12) the flavylium cation interconverts into the deprotonated trans-chalcone in a few minutes and under these conditions the CB7 wheel was found to be located around the viologen unit. A decrease in pH to values around 1 regenerates the flavylium cation in seconds and the macrocycle is translocated to the middle of the axle. On the other hand, if the pH is decreased to 6, the deprotonated trans-chalcone is neutralized to give a metastable species that evolves to the thermodynamically stable flavylium cation in ca. 20 hours. By taking advantage of the pH-dependent kinetics of the trans-chalcone/flavylium interconversion, spatiotemporal control of the molecular organization in pseudorotaxane systems can be achieved.pt_PT
dc.identifier.citationDiniz AM, Basílio N, Cruz H, Pina F, Parola AJ. Spatiotemporal control over the co-conformational switching in pH-responsive flavylium-based multistate pseudorotaxanes. Faraday Discuss. 2015;185:361-79.pt_PT
dc.identifier.doi10.1039/c5fd00078ept_PT
dc.identifier.urihttp://hdl.handle.net/10400.21/6395
dc.language.isoengpt_PT
dc.peerreviewedyespt_PT
dc.publisherRoyal Society of Chemistrypt_PT
dc.relation.publisherversionhttp://pubs.rsc.org/en/Content/ArticleLanding/2015/FD/C5FD00078E#!divAbstractpt_PT
dc.rights.urihttp://creativecommons.org/licenses/by-nc/4.0/pt_PT
dc.subjectChemistrypt_PT
dc.subjectFlavylium cationpt_PT
dc.titleSpatiotemporal control over the co-conformational switching in pH-responsive flavylium-based multistate pseudorotaxanespt_PT
dc.typejournal article
dspace.entity.typePublication
oaire.citation.endPage379pt_PT
oaire.citation.startPage361pt_PT
oaire.citation.titleFaray Discussionspt_PT
oaire.citation.volume185pt_PT
rcaap.rightsrestrictedAccesspt_PT
rcaap.typearticlept_PT

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