Cucurbit[n]uril−Polyoxoanion Hybrids

Abstract

The first organic-inorganic hybrid complexes between CB[n] and polyoxometalates not only display a surprisingly high structural complementarity, the right pairing also allows their chemical and physical properties to be coupled, as illustrated by two examples.

The Chaotropic Effect as an Assembly Motif in Chemistry

“…It should be noted that indications for the affinity of anions to hydrophobic binding sites existed early in the literature81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100, 101, 102, 103 but were in part attributed to a putative hydrophobic (or lipophilic) property of large anions, implying the hydrophobic effect as driving force. The hydrophobic and chaotropic effect can and need to be conceptually distinguished for the reason stated above and also because the hydrophobic nature of a solute is subject to a conventional definition, which chaotropic ions do not fulfill.…”

“…It is not limited to the interaction with macrocyclic cavities (Figure 3) and the formation of inclusion complexes (Figure 4) but also applies similarly to the interactions with convex surfaces (Figure 6), which accounts for the intrinsic propensity of these large anions to form also exclusion complexes. Indeed, many studies have described their binding to the exterior of macrocycles,41, 64, 84, 86, 87, 88, 90, 91, 92, 93, 94, 154 where the chaotropic effect applies as well. Most of these cases involve macrocyclic hosts with relatively small cavity size, such that inclusion‐type complexes are not possible 41, 64, 94, 154.…”

“…For example, superchaotropic anions, such as POMs and dodecaborate clusters, associate to the hydrophobic exterior of cucurbit[ n ]uril (CB n ) macrocycles (Figure 6). 41, 64, 94, 154 The large size of superchaotropic anions allows them to interact with several macrocycles in a multidentate manner, which can efficiently induce their precipitation, for example, of CB n . This is counterintuitive because conventional chaotropes are otherwise known to increase the solubility of organic solutes (salting‐in Hofmeister effect) 156.…”

A new 3D hybrid architecture containing Keggin-type tungstosilicate and Cu4(EGTA)2 metallamacrocyclic cation

“…Polyoxometalates (POMs), as an outstanding class of metal-oxygen clusters, are garnering increasing attention owing to their unmatched structural variety and diversity in the composition, sizes and shapes [1][2][3][4], which endow them with wide-ranging applications, such as catalysis [5][6][7][8][9], photochemistry [10,11], magnetism [12][13][14], and materials science [15][16][17][18][19][20]. In recent years, a new area of interests in POM chemistry is to immobilize POMs by various transition-metal complexes (TMCs) [21][22][23][24][25][26][27][28][29][30].…”

An intertwined double chain constructed by [SiMo12O40]4− clusters and unusual [Cu2(DF)2H2O] dimers

“…On the other hand, polyoxometalates (POMs) [13][14][15][16][17], as a large family of metal-oxygen clusters, constitute a fascinating class of inorganic systems which is incomparable in structural diversity as well as wide-ranging applications, such as in catalysis [18][19][20], medicine [21], and material science [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38].…”