Western Michigan University, Chemistry, Kalamazoo, MI 49008
Selective recognition and encapsulation of anions by artificial receptors is one of the most far-reaching areas of supramolecular chemistry, with implications in chemical, biological and environmental sciences. We have recently developed a new class of anion-binding agents, based on nano-sized toroidal copper(II)-hydroxide/pyrazolate complexes (“nano-jars”), which possess an unprecedented ability to totally encapsulate anions. Lined by H-bond donors on the inside and hydrophobic on the outside, these assemblies selectively extract kosmotropic anions from mixtures with chaotropic anions. Up to twelve hydrogen bonds from the neutral host assembly wrap around and sequester PO43–, AsO43–, HAsO42–, CO32–, SO42–, CrO42–, Cl–, F–,TeO32–, MoO42–, or WO42– anions, similarly as in their analogs in living organisms, such as the sulfate- and phosphate-binding proteins. Tetrabutylammonium “lids” seal the “nano-jars” and render the encapsulated anion completely buried and inaccessible, so that, for example, sulfate is not precipitated by Ba2+ ions. Details of crystallographic, mass spectrometric, nuclear magnetic resonance and selectivity studies will be presented.
[Abstract (DOCX)]