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Decoupled Associative and Dissociative Processes in Strong yet Highly Dynamic Host-Guest Complexes.

Accepted version
Peer-reviewed

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Authors

Biedermann, Frank 
Hoogland, Dominique 
Del Barrio, Jesús 
Driscoll, Max D 

Abstract

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 cucurbit[8]uril (CB[8]) and an auxiliary guest, dimethyl viologen, with high selectivity and equilibrium binding constants (Keq up to 1014 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 these 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, with important implications for the application of the CB[8] 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.

Description

Keywords

0303 Macromolecular and Materials Chemistry, 0302 Inorganic Chemistry

Journal Title

J Am Chem Soc

Conference Name

Journal ISSN

0002-7863
1520-5126

Volume Title

139

Publisher

American Chemical Society (ACS)
Sponsorship
European Research Council (240629)
Engineering and Physical Sciences Research Council (EP/K028510/1)
Engineering and Physical Sciences Research Council (EP/L027151/1)
Engineering and Physical Sciences Research Council (EP/N035003/1)