Synthesis, crystal structure, infrared spectroscopy, thermal analysis and Hirshfeld surface analysis of a new hemihydrate of [Zn (H2O) 6][{(CH2)6N4}ZnCl3]2·0.5H2O. AbstractThe new organic-inorganic hybrid material [Zn(H2O)6][{(CH2)6N4}ZnCl3]2·0.5 H2O, is the second hydrate in this system, the first having been the hexahydrate. The new solid was prepared by slow evaporation of a solution of the reactants at room temperature and was structurally characterized by X-ray crystallography. This compound crystallizes in the trigonal system, space group P-3c1 with a = 9.8303(2)Å, c = 17.5460(2)Å, V = 1468.38(4)Å 3 and with Z = 2. The complex was characterized by FT-IR, thermogravimetric analysis (TGA), differential thermal analysis (DTA) and with a detailed analysis of Hirshfeld surfaces and fingerprint plots. The structural unit of the title compound consists of a [Zn II (H2O)6] 2+ cation, two [Zn II Cl3(hmt)]anions and half of a water molecule, partially occupied and disordered [hmt is hexamethylenetetramine, (CH2)6N4]. Crystal packing is mediated by O-H…N and O-H…Cl hydrogen bonds between the anions and cations, and to a lesser extent by O-H…O contacts, which are present only part of the time as a consequence of the partial occupancy of the isolated water molecules. The relationship between the packing in the new structure and that of the previous hexahydrate is described.

The analysis of a hydro­phobic–hydro­philic ion-pair structure at two temperatures permits the comparative evaluation of the accurate geometric results obtained at low temperature and less accurate results at room temperature using a knowledge-based approach.