A carregar...
Publicação
Light- and pH-regulated Water-soluble Pseudorotaxanes Comprising a Cucurbit[7]uril and a Flavylium-based Axle
| Nome: | Descrição: | Tamanho: | Formato: | |
|---|---|---|---|---|
| 1.38 MB | Adobe PDF |
Orientador(es)
Resumo(s)
A linear double pyridinium-terminated thread comprising a central chalcone moiety is shown to provide two independent binding sites with similar affinity for cucurbit[7]uril (CB7) macrocycles in water as judged from NMR, UV-Visible and fluorescence spectroscopies. Association results in [2] and [3]pseudorotaxanes, which are both pH and photosensitive. Switching from the neutral chalcone to the cationic flavylium form upon irradiation at 365 nm under acidic conditions provided an enhanced CB7 association (K1:1 increases from 1.2×105 M−1 to 1.5×108 M−1), limiting spontaneous on-thread cucurbituril shuttling. This co-conformational change in the [2]pseudorotaxane is reversible in the dark with kobs=4.1×10−4 s−1. Threading the flavylium moiety into CB7 leads to a dramatic increase in the fluorescence quantum yield, from 0.29 in the free axle to 0.97 in the [2]pseudorotaxane and 1.0 in the [3]pseudorotaxane.
Descrição
Funding Information: This work was supported by the Associate Laboratory for Green Chemistry‐LAQV which is financed by national funds from FCT/MCTES (UIDB/50006/2020). FCT/MCTES is also acknowledged for supporting the National Portuguese NMR Network (ROTEIRO/0031/2013‐PINFRA/22161/2016, cofinanced by FEDER through COMPETE 2020, POCI, PORL, and FCT through PIDDAC) and for grants PTDC/QUI‐QFI/30951/2017 and 2020.07313.BD (A.S.). China Scholarship Council (S.Y.) is acknowledged.
Palavras-chave
Chalcones flavylium photochemistry rotaxanes supramolecular chemistry Catalysis Organic Chemistry