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

18-Crown[6] ether has been used to prepare a new class of organic-inorganic complexes of general formula 18-crown[6]center dot M[HSO4](n) (where M = NH4+, K+, Sr2+ 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 [NH4][HSO4], K[HSO4], and Sr[HSO4](2). The structures of 18-crown[6]center dot[NH4][HSO4]center dot 2H(2)O (1 center dot 2H(2)O), 18-crown[6]center dot[NH4][HSO4] (1), 18-crown[6]center dot K[HSO4]center dot 2 H2O (2 center dot 2H(2)O), 18-crown [6]center dot K[HSO4] (2), and 18-crown [6]center dot Sr[HSO4](2) (3) have been characterized by single-crystal X-ray diffraction. The reversible water loss in compounds 1 center dot 2H(2)O and 2 center dot 2H(2)O leads to formation of the corresponding anhydrous phases 1.8-crown[6]center dot[NH4][HSO4] (1), and 18-crown[6]center dot K[HSO4] (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]center dot Sr[HSO4](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.