Nanojars are emerging as a class of anion sequestration and extraction agents of unparalleled efficiency. Dinegative oxoanions (e.g., carbonate, sulfate) template the formation of a series of homologous nanojars, [anion2-{Cu(OH)(pz)}n] (pz = pyrazole; n = 27–31). The different {Cu(OH)(pz)}n rings in nanojars are conveniently probed by variable temperature NMR, which also provides insight into their different distribution of spin density. The self-assembly process was monitored by electrospray ionization mass spectrometry, and a mechanism is proposed based on intermediates either identified by direct observation, or suggested based on circumstantial evidence. 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, 28, 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], respectively. A comprehensive picture of the solution and solid state intricacies of nanojars is provided by a combination of variable temperature paramagnetic NMR spectroscopy, tandem mass spectrometry and single-crystal X-ray crystallography. Highly efficient extraction of toxic anions (arsenate, chromate, selenate) from water using nanojars will also be discussed.

Mechanism of formation, structure, and reactivity of anion-incarcerating nanojars

251st National Meeting (2016)

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