Anhydrous Lithium Acetate Polymorphs and Its Hydrates: Three-Dimensional Coordination Polymers

Lithium acetate is a very common salt with many and varied uses. Nevertheless, only two compounds were known apparently, the anhydrous salt and lithium acetate dihydrate, but only the latter was really characterized. In this paper, two polymorphs of anhydrous lithium acetate and three novel hydrates (with lithium acetate/H₂O ratios 4:1, 7:3, and 1:1) are reported for the first time, besides the well-known lithium acetate dihydrate. The five new compounds are three-dimensional (3D) coordination polymers, different from the one-dimensional (1D) structure of lithium acetate dihydrate. The structures and the relative stability of the two anhydrous lithium acetate polymorphs are also compared. The compounds were studied by single crystal X-ray diffraction (SCXRD), powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and infrared spectroscopy (FTIR).