Co-ion Effects in the Self-Assembly of Macroions: From Co-ions to Co-macroions and to the Unique Feature of Self-Recognition

Abstract

Macroions, as soluble ions with a size on the nanometer scale, show unique solution behavior different from those of simple ions and large colloidal suspensions. In macroionic solutions, the counterions are known to be important and well-explored. However, the role of co-ions (ions carrying the same type of charge as the macroions) is often ignored. Here, through experimental and simulation studies, we demonstrate the role of co-ions as a function of co-ion size on their interaction with the macroions (using {Mo72Fe30} and {SrPd12} as models) and the related self-assembly into blackberry-type structures in dilute solutions. Several regimes of unique co-ion effects are clearly identified: small ions (halides, oxoacid ions), subnanometer-scaled bulky ions (lacunary Keggin and dodecaborate ions), and those with sizes comparable to the macroions. Small co-ions have no observable effect on the self-assembly of fully hydrophilic {Mo72Fe30}, while due to hydrophobic interaction and intermolecular hydrogen bonds, the small co-ions show influences on the self-assembly of hydrophobic {SrPd12}. Subnanometer ions, a.k.a. “superchaotropic ions”, are still too small to assemble into a blackberry by themselves, but they can coassemble with the macroions, showing a strong interaction with the macroionic system. When the co-ion size is comparable to that of the macroions, they assemble independently instead of assembling with the macroions, leading to the previously reported unique self-recognition phenomenon for macroions.

“Host in Host” Supramolecular Core–Shell Type Systems Based on Giant Ring‐Shaped Polyoxometalates

“…[22] More recently, the chaotropic effect has been pinpointed out within the formation of POM-based globular assemblies or blackberry-like structures. [23], [24] Here we report on the aqueous solution behaviour of the giant Mo-blue ring-shaped polyoxometalate [Mo154O462H14(H2O)70] 14-(abbreviated {Mo154} 14-and shown in Fig. 1a) [25], [26] in the presence of g-cyclodextrin (noted g-CD), a highly popular macrocycle for its remarkable hosting properties and related applications.…”

Polynorbornene-Based Polyelectrolytes with Covalently Attached Metallacarboranes: Synthesis, Characterization, and Lithium-Ion Mobility

“…The term “nano-ion” has been used for nanometer-sized ions of diverse structure, shape, and charge in recent literature. − The term was coined for distinguishing unusual ions such as anionic boron cluster compounds (ABCCs) , and polyoxometalates (POMs) − from the family of classical inorganic and organic ions. Despite their different chemical nature, there is a strong evidence that such large ions have many features in common.…”

“…In the current study, we took advantage from the up-to-date knowledge on norbornene chemistry − , and the theories on nano-ion behavior − ,, in order to prepare well-defined and stable “poly­(nano-ions)”. We synthesized metallacarborane-containing polyelectrolytes, polynorbornene-COSAN (PNC), as sodium and lithium salts (Na*PNC and Li*PNC, respectively) via ROMP.…”

“Host in Host” Supramolecular Core–Shell Type Systems Based on Giant Ring‐Shaped Polyoxometalates

“…Actually, the extremely high stability constants found for such hybrid organic‐inorganic assemblies suggest that the (super)‐chaotropic effect should be considered among the conglomerate of contributors as a generic driving force in supramolecular chemistry [22] . More recently, the chaotropic effect has been pinpointed out within the formation of POM‐based globular assemblies or blackberry‐like structures [23, 24] . Here we report on the aqueous solution behaviour of the giant Mo‐blue ring‐shaped polyoxometalate [Mo 154 O 462 H 14 (H 2 O) 70 ] 14− (abbreviated {Mo 154 } and shown in Figure 1 a) [25, 26] in the presence of γ‐cyclodextrin (noted γ‐CD), a highly popular macrocycle for its remarkable hosting properties and related applications [27, 28] .…”

“…[22] More recently,t he chaotropic effect has been pinpointed out within the formation of POM-based globular assemblies or blackberry-like structures. [23,24] 1a) [25,26] in the presence of gcyclodextrin (noted g-CD), ah ighly popular macrocycle for its remarkable hosting properties and related applications. [27,28] Strikingly,w hen condensation of molybdates occurs under reducing conditions in the presence of g-CD, avery fast growing process of {Mo 154 }was detected by smallangle X-ray scattering (SAXS) analysis.F ormation mechanism of the nanosized {Mo 154 }species appears consistent with ap re-association step of molybdate-based oligomers around the g-CD acting as as upramolecular template.R esulting species have been characterized structurally showing unprecedented nanosized core-shell type arrangement, reminiscent of the postulated host-guest template process.Asaproof-ofconcept, this supramolecular template effect can even be extended deliberately to exogenous guests,s uch as chalcocyano hexarhenium cluster [Re 6 Te 8 (CN) 6 ] 4À ,thus opening the way toward the design of hierarchical functional system.…”