Compounds of glycine with halogen or metal halogenides: review and comparison

Abstract

Abstract The large family of glycine halogenides and metal halogenides encompasses a high variety of different crystal structures. The role of the glycine molecule as a structural unit as a mono-, bi- or tridentate ligand, of the halogenide ions as well as the composition and condensation of the cationic polyhedra is discussed. With respect to the connectivity of the building units, five different structure families of glycine halogenides and glycine-metal halogenides can be distinguished. Parameters such as symmetry, ionic radii, electronegativity of cation and anion and their difference, charge, coordination number, hydration states, stoichiometric ratios and connectivity were weighed against each other in order to see if any correlations exist. The data suggest that cations with high electronegativities seem to promote formation of structures with a low grade of connectivity, i.e., isolated units, and vice versa.