Decoupled Associative and Dissociative Processes in Strong yet Highly Dynamic Host-Guest Complexes.
Del Barrio, Jesús
Driscoll, Max D
Journal of the American Chemical Society
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Appel, E. A., Biedermann, F., Hoogland, D., Del Barrio, J., Driscoll, M. D., Hay, S., Wales, D., & et al. (2017). Decoupled Associative and Dissociative Processes in Strong yet Highly Dynamic Host-Guest Complexes.. Journal of the American Chemical Society, 139 (37), 12985-12993. https://doi.org/10.1021/jacs.7b04821
Kinetics and thermodynamics in supramolecular systems are intimately linked, yet both are independently important for application in sensing assays and stimuli-responsive switching/self-healing of materials. Host-guest interactions are of particular interest in many water-based materials, sensing and drug delivery applications. Herein we investigate the binding dynamics of a variety of electron-rich aromatic moieties forming hetero-ternary complexes with the macrocycle cucurbituril (CB) and an auxiliary guest, dimethyl viologen, with high selectivity and equilibrium binding constants (Keq up to 10(14)M(-2)). Using stopped-flow spectrofluorimetry, association rate constants were observed to approach the diffusion limit, and were found to be insensitive to the structure of the guest. Conversely, the dissociation rate constants of the ternary complexes varied dramatically with the guest structure and were correlated with the thermodynamic binding selectivity. Hence differing molecular features were found to contribute to the associative and dissociative processes, mimicking naturally occurring reactions and giving rise to a decoupling of these kinetic parameters. Moreover, we demonstrate the ability to exploit the phenomena and selectively perturb the associative process with external stimuli (e.g.viscosity and pressure). Significantly, these complexes exhibit increased binding equilibria with increasing pressure, carrying important implications in the application of theCB ternary complex for the formation of hydrogels, as these gels exhibit unprecedented pressure-insensitive rheological properties. A high degree of flexibility therefore exists in the design of host-guest systems with tunable kinetic and thermodynamic parameters for tailor-made applications across a broad range of fields.
European Research Council (240629)
External DOI: https://doi.org/10.1021/jacs.7b04821
This record's URL: https://www.repository.cam.ac.uk/handle/1810/269777