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Abstract Macroion‐counterion interaction is essential for regulating the solution behaviors of hydrophilic macroions, as simple models for polyelectrolytes. Here, we explore the interaction between uranyl peroxide molecular cluster Li68K12(OH)20[UO2(O2)OH]60(U60) and multivalent counterions. Different from interaction with monovalent counterions that shows a simple one‐step process, isothermal titration calorimetry, combined with light/X‐ray scattering measurements and electron microscopy, confirm a two‐step process for their interaction with multivalent counterions: an ion‐pairing betweenU60and the counterion with partial breakage of hydration shells followed by strongU60‐U60attraction, leading to the formation of large nanosheets with severe breakage and reconstruction of hydration shells. The detailed studies on macroion‐counterion interaction can be nicely correlated to the microscopic (self‐assembly) and macroscopic (gelation or phase separation) phase transitions in the diluteU60aqueous solutions induced by multivalent counterions.
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Abnormal Association between Metal−Organic Cages and Counterions Regulated by the Hydration Shells
Abstract A unique trend in the binding affinity between cationic metal−organic cages (MOCs) and external counteranions in aqueous media was observed. Similar to many macroions, two MOCs, sharing similar structures but carrying different number of charges, self‐assembled into hollow spherical single‐layered blackberry‐type structures through counterion‐mediated attraction. Dynamic and static light scattering and isothermal titration calorimetry measurements confirm the stronger interactions among less charged MOCs and counteranions than that of highly charged MOCs, leading to larger assembly sizes. DOSY NMR measurements suggest the significance of thick hydration shells of highly charged MOCs, inhibiting the MOC‐counterion binding and weakening the interaction between them. This study demonstrates that the greater role played by hydration shell on ion‐pair formation comparing with charge density of MOCs.
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- Award ID(s):
- 1904397
- PAR ID:
- 10446029
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Chemistry – A European Journal
- Volume:
- 28
- Issue:
- 10
- ISSN:
- 0947-6539
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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