Showing papers by "Gellert Mezei published in 2022"

Supramolecular Incarceration and Extraction of Tetrafluoroberyllate from Water by Nanojars.

Abstract: The previously unexplored noncovalent binding of the highly toxic tetrafluoroberyllate anion (BeF42-) and its extraction from water into organic solvents are presented. Nanojars resemble anion-binding proteins in that they also possess an inner anion binding pocket lined by a multitude of H-bond donors (OH groups), which wrap around the incarcerated anion and completely isolate it from the surrounding medium. The BeF4-binding propensity of [BeF4⊂{CuII(OH)(pz)}n]2- (pz = pyrazolate; n = 27-32) nanojars of different sizes is investigated using an array of techniques including mass spectrometry, paramagnetic 1H, 9Be, and 19F NMR spectroscopy, and X-ray crystallography, along with thermal stability studies in solution and chemical stability studies toward acidity and Ba2+ ions. The latter is found to be unable to precipitate the insoluble BaBeF4 from nanojar solutions, indicating a very strong binding of the BeF42- anion by nanojars. 9Be and 19F NMR spectroscopy allows for the unprecedented direct probing of the incarcerated anion in a nanojar and, along with 1H NMR studies, reveals the fluxional structure of nanojars and their inner anion-binding pockets. Single-crystal X-ray diffraction provides the crystal and molecular structures of (Bu4N)2[BeF4⊂{Cu(OH)(pz)}32], which contains a novel Cux-ring combination (x = 9 + 14 + 9), (Bu4N)2[BeF4⊂{Cu(OH)(pz)}8+14+9], and (Bu4N)2[BeF4⊂{Cu(OH)(pz)}6+12+10] and offers detailed structural parameters related to the supramolecular binding of BeF42- in these nanojars. The extraction of BeF42- from water into organic solvents, including the highly hydrophobic solvent n-heptane, demonstrates that nanojars are efficient binding and extracting agents not only for oxoanions but also for fluoroanions.

Crystal Structure, Hirshfeld Analysis, and DFT Calculations of Three Trinuclear Cu(II) Polymorphs

Abstract: The crystal structure of the ferromagnetically-coupled CuII3−pyrazolato complex, (Bu4N)2[Cu3(μ3-Cl)2(μ-4-NO2-pz)3Cl3] (1a, pz = pyrazolato anion), was originally determined in the triclinic P-1 space group. By varying the recrystallization solvent and temperature, two additional true polymorphs were crystallized in the monoclinic P21/n (1b) and orthorhombic Pbca (1c) space groups. Comparison of the metric parameters of the three polymorphs revealed only minor variations in their bond lengths and angles but clearly distinguishable packing patterns. The DFT calculations showed that, in vacuum, 1a had the lowest energetic minimum (also the densest of three polymorphs), whereas 1b and 1c lay at 6.9 kcal/mol and 7.8 kcal/mol higher energies. The existence of isolable 1b and 1c is, therefore, attributed to the intermolecular interactions analyzed by the Hirshfeld methods.