Photoresponsive Binding Dynamics in High-Affinity Cucurbit[8]uril-Dithienylethene Host-Guest Complexes

Colaço, Miriam; Máximo, Patrícia; Jorge Parola, A.; Basílio, Nuno

http://hdl.handle.net/10362/127174

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The use of external stimuli to control the binding kinetics in supramolecular systems is of critical importance for the development of advanced molecular machines and devices. In this work, a study focused on the kinetics of a water-soluble host-guest system based on cucurbit[8]uril and two dithienylethene (DTE) photoswitches is reported. It is shown that for the DTE guest comprising two anionic sulfonate side arms appended to pyridinium moieties, the formation/dissociation of the pseudorotaxane structures is slowed down by more than 100000-fold with respect to its bipyridinium analogue. The decrease in ingression rate leads to the emergence of a competitive metastable product with the open DTE isomer that has an important influence in the overall binding kinetics. Moreover, the host-guest dissociation kinetics is demonstrated to be approximately 100-fold slower for the closed DTE isomer (t1/2=107 h vs. t1/2=1.2 h for the open isomer) allowing control over the dissociation rate with light.

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This work was supported by the Associate Laboratory for Green Chemistry-LAQV which is financed by national funds from FCT/MCTES (UIDB/50006/2020 and UIDP/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 the grants PTDC/QUI-COL/32351/2017, PTDC/QUI-QFI/30951/2017 and CEECIND/00466/2017.