Solution and Solid‐State Preparation of 18‐Crown[6] Complexes with M[HSO₄]_n Salts (M = NH₄⁺, K⁺, Sr²⁺ and n = 1, 2) and an Investigation of Solvation/Desolvation Processes and Crystal Polymorphism

Abstract

18-Crown[6] ether has been used to prepare a new class of organic-inorganic complexes of general formula 18-crown[6]M[HSO(4)](n) (where M = NH(4) (+), K(+), Sr(2+) and n = 1, 2) by reacting directly in solution or in the solid state the crown ether 18-crown[6] with inorganic salts such as [NH(4)][HSO(4)], K[HSO(4)], and Sr[HSO(4)](2). The structures of 18-crown[6][NH(4)][HSO(4)]2 H(2)O (12 H(2)O), 18-crown[6][NH(4)][HSO(4)] (1), 18-crown[6]K[HSO(4)]2 H(2)O (22 H(2)O), 18-crown[6]K[HSO(4)] (2), and 18-crown[6]Sr[HSO(4)](2) (3) have been characterized by single-crystal X-ray diffraction. The reversible water loss in compounds 12 H(2)O and 22 H(2)O leads to formation of the corresponding anhydrous phases 18-crown[6][NH(4)][HSO(4)] (1), and 18-crown[6]K[HSO(4)] (2), which undergo, on further heating, enantiotropic solid-solid transitions very likely associated with the on-set of a solid state dynamical process. Similar high-temperature behavior is shown by 18-crown[6]Sr[HSO(4)](2) (3). The dehydration and phase-transition processes have been investigated by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and variable temperature X-ray powder diffraction.

Potassium cation exchange with "crowned" indium(I) trifluoromethanesulfonate

“…Even at −100 • C, the crown ether ligand exhibits significant disorder and was modeled in two different positions, only one of which is depicted in the figure. In contrast to the structure of the indium analogue, the potassium salt has two K-O contacts with the triflate anion with bond distances of 2.877(5) and 2.985(5) Å; the presence of two such contacts and all of the observed metrical parameters are consistent with those reported in the CSD for sulfate and sulfonate salts of [K( [18]crown-6)] + [28]. Depictions of the crystalline packing of the salts [K( [18]crown-6)][OTf] and 1 (Fig.…”

Unusual centrosymmetric structure of [M(18-crown-6)]+(M= Rb, Cs and NH4) complexes stabilized in an environment of hexachloridoantimonate(V) anions

“…These values are significantly smaller than typical values observed previously. For example, in [NH 4 (18-crown-6)] + compounds the essential size mismatch of the components is commonly reflected by pronounced dislocations of the ammonium cation from the ring centroid, such as d = 1.03 Å for the hydrogen sulfate complex (Braga et al, 2007) and d = 0.98 Å for the hydrated bromide complex (Nagano et al, 1978). The forced geometry of the NH 4 + cation exactly inside the 18-crown-6 cavity has only one precedent (Ponomarova & Domasevitch, 2002), while the centrosymmetric structure of the [Cs(18crown-6)] + aggregate is entirely unprecedented.…”

Dealing with Crystal Forms (The Kingdom of Serendip?)

“…[15] These crystals were "engineered" to find alternative proton-conducting solid electrolytes for fuel-cell technologies. [15] These crystals were "engineered" to find alternative proton-conducting solid electrolytes for fuel-cell technologies.…”

“…Another example is provided by the hydration/dehydration behavior of a series of crown ether complexes recently investigated in our group. [15] These crystals were "engineered" to find alternative proton-conducting solid electrolytes for fuel-cell technologies. [16] The hydrate crystal forms of the crown ether salts undergo a series of transformations as water is removed or added.…”