Survival of the Fittest Nanojar: Stepwise Breakdown of Polydisperse Cu27−Cu31 Nanojar Mixtures into Monodisperse Cu27(CO3) and Cu31(SO4) Nanojars

Nanojars are emerging as a class of anion sequestration agents of unparalleled efficiency. Dinegative oxoanions (e.g., carbonate, sulfate) template the formation of a series of homologous nanojars [Cu(OH)(pyrazolato)]n (n=27–31). Pyridine selectively transforms less stable, larger CO32− nanojars (n=30, 31) into more stable, smaller ones (n=27, 29), but leaves all SO42− nanojars (n=27–29, 31) intact. Ammonia, in turn, transforms all less stable nanojars into the most stable one and allows the isolation of pure [CO32−⊂{Cu(OH)(pz)}27] and [SO42−⊂{Cu(OH)(pz)}31]. A comprehensive picture of the solution and solid‐state intricacies of nanojars was revealed by a combination of variable temperature NMR spectroscopy, tandem mass spectrometry, and X‐ray crystallography. Homologous nanojars based on a copper–hydroxide–pyrazolate repeating unit self‐assemble around dinegative oxoanion templates and are transformed into one single species by etching with ammonia. Tandem mass spectrometry, paramagnetic NMR, and X‐ray diffraction analyses provide a detailed picture of the solution‐ and solid‐state intricacies of this emerging anion encapsulating agent family of unparalleled binding strength (see figure).