Abstract
Anion binding and extraction from solutions is currently a dynamic research topic in the field of supramolecular chemistry. A particularly challenging task is the extraction of anions with large hydration energies, such as the carbonate ion. Carbonate-binding complexes are also receiving increased interest due to their relevance to atmospheric CO2 fixation. Nanojars are a class of self-assembled, supramolecular coordination complexes that have been shown to bind highly hydrophilic anions and to extract even the most hydrophilic ones, including carbonate, from water into aliphatic solvents. Here we present an expanded nanojar that is able to bind two carbonate ions, thus doubling the previously reported carbonate-binding capacity of nanojars. The new nanojar is characterized by detailed single-crystal X-ray crystallographic studies in the solid state and electrospray ionization mass spectrometric (including tandem MS/MS) studies in solution.
Highlights
Capacity of Nanojars by the Nanojars are a family of supramolecular coordination complexes that form from a solution of Cu2+, OH− and pyrazolate ions in the presence of a hydrophilic anion, such as carbonate [1], sulfate [2], phosphate [3], arsenate [3] or chloride [4]
We have recently shown that nanojars bind the incarcerated oxoanions with unprecedented strength by wrapping a multitude of hydrogen bonds around the anion and totally isolating it from its surrounding medium
We have demonstrated that nanojars are able to transfer these anions, including one of the most hydrophilic ones, carbonate, from water into aliphatic solvents [11]
Summary
Capacity of Nanojars by the Nanojars are a family of supramolecular coordination complexes that form from a solution of Cu2+ , OH− and pyrazolate (pz = C3 H3 N2 − ) ions in the presence of a hydrophilic anion, such as carbonate [1], sulfate [2], phosphate [3], arsenate [3] or chloride [4]. Three (in the case of carbonate, sulfate, phosphate, arsenate) or four (in the case of chloride) of these metallamacrocycles self-assemble around a central anion into nanojars of the formula [anion⊂{CuII (μ-OH)(μ-pz)}n ] (n = 27–33), via inter-metallamacrocycle and anion-metallamacrocycle hydrogen bonding, as well as inter-metallamacrocycle Cu···O interactions. We have recently shown that nanojars bind the incarcerated oxoanions (carbonate, sulfate, phosphate, arsenate) with unprecedented strength by wrapping a multitude of hydrogen bonds around the anion and totally isolating it from its surrounding medium (as in the sulfate [9] and phosphate [10] binding proteins). Nanojars can be used as extraction agents for the removal of such anions from contaminated aqueous media by liquid–liquid extraction [12]
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