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Browsing by Author "Basílio, Nuno"

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  • 2-Hydroxychalcone−β-Cyclodextrin Conjugate with pH-Modulated Photoresponsive Binding Properties
    Publication . Paulino, Micael; Pérez-Juste, Ignacio; Cid, María Magdalena; Da Silva, José Paulo; Pereira, M. Manuela A.; Basílio, Nuno
    Stimuli-responsive supramolecular receptors are important building blocks for the construction of self-assembled functional materials. We report the design and synthesis of a pH and light-responsive 2-hydroxychalcone-beta-cyclodextrin conjugate (1-Ct) and its characterization by spectroscopic and computational methods. 1-Ct follows the typical reaction network of trans-chalcone-flavylium photoswitches. Upon light irradiation, 1-Ct can be photochemically converted into the cis-chalcone/hemiketal forms (1-Cc/1-B) under neutral pH conditions or to the flavylium cation (1-AH+) at acidic pH values. This stimuli-responsive beta-cyclodextrin host, 1Ct, was found to form stronger intramolecular self-inclusion complexes (Kintra = 14) than 1-AH+ (Kintra = 3) and weaker than 1-Cc/1-B (overall Kintra = 179), allowing control over their stability and binding properties by combinations of pH and light stimuli.
    2022Journal article Restricted access Show more
  • Cooperative assembly of discrete stacked aggregates driven by supramolecular host-guest complexation
    Publication . Basílio, Nuno; Piñeiro, Ángel; Silva, José P. da; García-Río, Luís
    p-Sulfonatocalix[4]arene (SC4) interacts with the aromatic dye crystal violet (CV) to form complexes with stoichiometries ranging from SC4:CV = 1:1 up to 1:5 both in solution and in the gas phase. While the 1:1 complex is of the inclusion type, as frequently observed for other guests, in the higher-order complexes the CV molecules interact with SC4 in a peripheral manner. The formation of such complexes is driven by ionic interactions established between the dye and the calixarene and by CV-CV stacking interactions. The application of an advanced fitting procedure made possible a quantitative analysis of the UV-vis data and allowed the determination of the stepwise binding constants. This unprecedented approach provides evidence that the formation of the highest-order complexes occurs through a cooperative mechanism. Moreover, the development of a quantitative analytical model enables the possibility of using this type of system for water-soluble sensing assays, as is also exemplified in the present work. © 2013 American Chemical Society.
    2013Journal article Restricted access Show more