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

Abstract

Herein, we show how the chaotropic effect is able to accelerate significantly supramolecular organizations during the acidification of aqueous solution of reduced molybdate ions. Time-resolved Small Angle X-ray Scattering (SAXS) analysis suggests that molybdenum-blue oligomeric species form huge aggregates in the presence of g-cyclodextrin (g-CD) which results in the fast formation of nanoscopic {Mo154}-based host-guest species, while X-ray diffraction analysis reveals that the ending-point of these dynamic supramolecular organizations involving g-CD results in an unprecedented well-ordered core-shell-like motif. A similar three-component core-shell like arrangement was found by using preformed hexarhenium chalcogenide-type cluster [Re6Te8(CN)6] 4as exogenous guest. This seminal work brings better understanding of the self-assembly processes in general and gives new opportunities for practical applications in the design of complex multicomponent materials via the simplicity of the non-covalent chemistry.Consequently, chaotrope species are identified and then classified according to their ability to increase the CP temperature of C8E4. As shown in Fig. 1b, addition of {Mo154} 14increases markedly the CP temperature, showing

Host‐Guest Complexation Between Cyclodextrins and Hybrid Hexavanadates: What are the Driving Forces?

“…On the other side, purely inorganic POMs with low charge density, including Lindqvist [M 6 O 19 ] 2À , Keggin [XM 12 O 40 ] 3/4À (M = Mo or W, and X = P or Si), Dawson [P 2 W 18 O 62 ] 6À or giant Mo blue wheel {Mo 154 }, showed extremely high ability to form supramolecular aggregates with CDs induced by the "chaotropic effect". [14][15][16][17][18][19][20] These chaotropic POM units act as water-structure breakers, that leads to high energy hydration shell. It is worth to note that the chaotropic binding by CDs is not limited to POMs since this self-assembly process is also observed on other nanosized inorganic ions such as octahedral metal-atom clusters or dodecaborates.…”

Switchable Redox and Thermo‐Responsive Supramolecular Polymers Based on Cyclodextrin‐Polyoxometalate Tandem

“…[9,12,13] Moreover, such an effect in action may even be at the origin of counter-intuitive phenomena such as anionanion recognition processes that overcome the electrostatic repulsions. [14,15] Furthermore, the solvation mode of these chaotropic ions gives rise to clear thermochemical features of the supramolecular processes in water, highlighted both by enthalpy gains and entropy penalties. [10,12,13] This chaotropic effect is now recognized as one of the main driving forces behind supramolecular chemistry.…”