Highly Efficient and Selective Recognition of Dicyanoaurate(I) by a Bambusuril Macrocycle in Water

Abstract

Dicyanoaurate(I) anion, [Au(CN) 2 ] À , plays a central role in the current industrial production of gold, as its extraction from crude ore samples represents the most money-consuming step. Herein, we present the strongest host-guest recognition of dicyanoaurate anion using the bambusuril receptor in water, a highly competitive solvent. The micromolar stability of such a complex facilitated the up to date most efficient supramolecular stripping of dicyanoaurate from activated carbon at ambient temperature. Thermodynamic characteristics of bambusuril binding with [Au(CN) 2 ] À differing from binding of other inorganic chaotropic anions are rationalized, as well as the bambusuril selectivity for [Au(CN) 2 ] À over [Ag(CN) 2 ] À .

Large anion binding in water

“…In 1 H NMR aqueous-solution spectra, the complexation-induced chemical shifts confirmed the formation of inclusion complexes, as indicated by the large downfield shifts of the inner protons of γ-CD. In addition, 77 Se and 125 Te NMR experiments supported the complexation pattern in solution. The binding affinities of the anions to γ-CD were determined using ITC experiments, which showed that the complexation is enthalpically driven, in agreement with the chaotropic effect.…”

“…71 The macrocycle was later intensively investigated for its binding to halides with high affinity and selectivity (see below). 38,39,[72][73][74][75][76][77] Recent developments in large anion binding and mechanistic interpretations (after 2015)…”

“…71 The macrocycle was later intensively investigated for its binding to halides with high affinity and selectivity (see below). 38,39,72–77…”

Synthesis of Enantiomerically Pure Bambus[6]urils Utilizing Orthogonal Protection of Glycolurils

“…27 They function as efficient anion transporters, 27 supramolecular hydrogels, 28 as rotaxane constituents, 29 and in the selective recognition of diacyanoaurate(I). 30 Majority of bambusurils are achiral. 15 However, the synthesis of the first chiral bambusurils was recently reported, and their ability to bind enantiomers of biologically relevant compounds with selectivity exceeding 3 was demonstrated.…”

“…Bambus[6]­urils show high association constants ranging up to 10 11 M –1 in organic solvents . They function as efficient anion transporters, supramolecular hydrogels, as rotaxane constituents, and in the selective recognition of diacyanoaurate­(I) …”