The Interplay of Weakly Coordinating Anions and the Mechanical Bond: A Systematic Study of the Explicit Influence of Counterions on the Properties of (Pseudo)rotaxanes

Weakly coordinating anions (WCAs) have attracted much attention in recent years due to their ability to stabilise highly reactive cations. It may well be argued, however, that a profound understanding of what truly defines a WCA is still lacking, and systematic studies to unravel counterion effects...

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Bibliographic Details
Published in:Molecules (Basel, Switzerland) Switzerland), 2023-03, Vol.28 (7), p.3077
Main Authors: Witte, J Felix, Wasternack, Janos, Wei, Shenquan, Schalley, Christoph A, Paulus, Beate
Format: Article
Language:English
Subjects:
Anions
Calorimetry
Cations
Charge transfer
Chemical compounds
Chemical effects
Chemical properties
Chemical reactions
Chemistry
computational chemistry
energy decomposition analysis
Experiments
isothermal calorimetry
Mechanical properties
Physiological aspects
Rotaxanes
Solvation
Solvents
supramolecular chemistry
thermodynamics
weakly coordinating anions
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Summary:Weakly coordinating anions (WCAs) have attracted much attention in recent years due to their ability to stabilise highly reactive cations. It may well be argued, however, that a profound understanding of what truly defines a WCA is still lacking, and systematic studies to unravel counterion effects are scarce. In this work, we investigate a supramolecular pseudorotaxane formation reaction, subject to a selection of anions, ranging from strongly to weakly coordinating, which not only aids in fostering our knowledge about anion coordination properties, but also provides valuable theoretical insight into the nature of the mechanical bond. We employ state-of-the-art DFT-based methods and tools, combined with isothermal calorimetry and 1H NMR experiments, to compute anion-dependent Gibbs free association energies ΔGa, as well as to evaluate intermolecular interactions. We find correlations between ΔGa and the anions' solvation energies, which are exploited to calculate physico-chemical reaction parameters in the context of coordinating anions. Furthermore, we show that the binding situation within the (pseudo)rotaxanes can be mostly understood by straight-forward electrostatic considerations. However, quantum-chemical effects such as dispersion and charge-transfer interactions become more and more relevant when WCAs are employed.
ISSN:1420-3049
1420-3049
DOI:10.3390/molecules28073077