Chromate Incarceration by Nanojars and Its Removal from Water by Liquid-Liquid Extraction

Supramolecular Binding of Phosphonate Dianions by Nanojars and Nanojar Clamshells

Despite the widespread use of phosphonates (RPO32-) in various agricultural, industrial, and household applications and the ensuing eutrophication of polluted water bodies, the capture of phosphonate ions by molecular receptors has been scarcely studied. Herein, we describe a novel approach to phosphonate binding using chemically and thermally robust supramolecular coordination assemblies of the formula [RPO3⊂{cis-CuII(μ-OH)(μ-pz)}n]2- (Cun; n = 27-31; pz = pyrazolate ion, C3H3N2-; R = aliphatic or aromatic group). The neutral receptors, termed nanojars, strongly bind phosphonate anions by a multitude of hydrogen bonds within their highly hydrophilic cavities. These nanojars can be synthesized either directly from their constituents or by depolymerization of [trans-CuII(μ-OH)(μ-pz)]∞ induced by phosphonate anions. Electrospray-ionization mass spectrometry, UV-vis and variable-temperature, paramagnetic 1H and 31P NMR spectroscopy, single-crystal X-ray diffraction, along with chemical stability studies toward NH3 and Ba2+ ions, and thermal stability studies in solution are employed to explore the binding of various phosphonate ions by nanojars. Crystallographic studies of 12 different nanojars offer unprecedented structural characterization of host-guest complexes with doubly charged RPO32- ions and reveal a new motif in nanojar chemistry, nanojar clamshells, which consist of phosphonate anion-bridged pairs of nanojars and double the phosphonate-binding capacity of nanojars.

An octa-nuclear nickel(II) pyrazolate cluster with a cubic Ni8 core and its methyl- and n-octyl-functionalized derivatives

The mol-ecular and crystal structure of a discrete [Ni8(μ4-OH)6(μ-4-Rpz)12]2- (R = H; pz = pyrazolate anion, C3H3N2 -) cluster with an unprecedented, perfectly cubic arrangement of its eight Ni centers is reported, along with its lower-symmetry alkyl-functionalized (R = methyl and n-oct-yl) derivatives. Crystals of the latter two were obtained with two identical counter-ions (Bu4N+), whereas the crystal of the complex with the parent pyrazole ligand has one Me4N+ and one Bu4N+ counter-ion. The methyl derivative incorporates 1,2-di-chloro-ethane solvent mol-ecules in its crystal structure, whereas the other two are solvent-free. The compounds are tetra-butyl-aza-nium tetra-methyl-aza-nium hexa-μ4-hydroxido-dodeca-μ2-pyrazolato-hexa-hedro-octa-nickel, (C16H36N)(C4H12N)[Ni8(C3H3N2)12(OH)6] or (Bu4N)(Me4N)[Ni8(μ4-OH)6(μ-pz)12] (1), bis-(tetra-butyl-aza-nium) hexa-μ4-hydroxido-dodeca-μ2-(4-methyl-pyrazolato)-hexa-hedro-octa-nickel 1,2-di-chloro-ethane 7.196-solvate, (C16H36N)2[Ni8(C4H5N2)12(OH)6]·7.196C2H4Cl2 or (Bu4N)2[Ni8(μ4-OH)6(μ-4-Mepz)12]·7.196(ClCH2CH2Cl) (2), and bis-(tetra-butyl-aza-nium) hexa-μ4-hydroxido-dodeca-μ2-(4-octylpyrazolato)-hexa-hedro-octa-nickel, (C16H36N)2[Ni8(C11H19N2)12(OH)6] or (Bu4N)2[Ni8(μ4-OH)6(μ-4-nOctpz)12] (3). All counter-ions are disordered (with the exception of one Bu4N+ in 3). Some of the octyl chains of 3 (the crystal is twinned by non-merohedry) are also disordered. Various structural features are discussed and contrasted with those of other known [Ni8(μ4-OH)6(μ-4-Rpz)12]2- complexes, including extended three-dimensional metal-organic frameworks. In all three structures, the Ni8 units are lined up in columns.