Selective encapsulation and extraction of anions by artificial receptors is one of the most far-reaching areas of supramolecular chemistry, with implications in chemical, biological and environmental sciences. The extraction of kosmotropic anions from aqueous media is challenging, due to their large hydration energies. We have recently shown that a class of toroidal copper(II)-hydroxide/pyrazolate complexes (nanojars), with the formula [Cu(�-OH)(�-pz)]n (n = 27-36), totally encapsulate kosmotropic anions with an unprecedented strength. Lined by H-bond donors on the inside and hydrophobic on the outside, these ~2 nm sized assemblies selectively extract kosmotropic anions from mixtures with chaotropic anions. Up to twelve hydrogen bonds from the neutral host assembly wrap around and sequester anions from aqueous solutions, similarly as in their analogs in living organisms, such as the sulfate- and phosphate-binding proteins. Tetrabutylammonium �lids� seal the nanojars and render the encapsulated anion completely buried and inaccessible, so that, for example, sulfate is not precipitated by Ba2+ions. Crystallographic, mass spectrometric, nuclear magnetic resonance, as well as reactivity and selectivity studies of seventeen different anions will be discussed.

Selective encapsulation and extraction of kosmotropic anions by neutral,self-assembled nanojars

248th National Meeting (2014)

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