ORIGINAL PAPER Solid phases in the systems glycine–ZnX 2 –H 2 O (X 5 Cl 2 , Br 2 ,I 2 ) at 25 °C Stefka Tepavitcharova 1 • David Havlı ´c ˇek 2 • Irena Matulkova ´ 2 • Diana Rabadjieva 1 • Christo Balarew 1 • Rumjana Gergulova 1 • Ivan Ne ˇmec 2 • Ivana Cı ´sar ˇova ´ 2 • Jir ˇı ´ Plocek 3 Received: 4 July 2017 / Accepted: 3 December 2017 Ó Springer-Verlag GmbH Austria, part of Springer Nature 2017 Abstract The crystallization in the systems glycine– ZnX 2 –H 2 O (X = Cl - , Br - ,I - ) was summarised. Occur- rence of both equilibrium and non-equilibrium crystallization was found for these systems. The systems include complex compounds, from which three anhydrous and four hydrate formula types were obtained. The main building units of their crystal structures were mixed elec- troneutral tetrahedra, isolated in the case of xGlyÁZnX 2 ÁyH 2 O(x = 1, 2, 3; y = 0, 1, 2) compounds, or connected in more complex polymer chains in the cases of GlyÁZnX 2 and 2GlyÁ3ZnI 2 Á4H 2 O. These crystallization processes were explained on the basis of Pearson’s soft- ness–hardness concept and the chemical species existing in the solutions. The study of the system glycine–ZnBr 2 –H 2 O at 25 °C showed the occurrence of equilibrium and non- equilibrium crystallization in it. Three hitherto unknown compounds were obtained, GlyÁZnBr 2 (monoclinic crystal system, space group P2 1 ), 3GlyÁZnBr 2 (orthorhombic crystal system, space group Pna2 1 ) and 2GlyÁZnBr 2 Á2H 2 O (monoclinic crystal system, space group C2/c), and char- acterised by XRD, IR, Raman, and DTA methods. Graphical abstract Keywords Phase diagrams Á X-Ray structure determination Á IR spectroscopy Á Raman spectroscopy Á Equilibrium crystallization Á Non-equilibrium crystallization Introduction The crystallization processes in glycine-metal(II) halo- genide solutions are scarcely studied and are not systematised although the ability of glycine to form a variety of complexes is well known. Not many systems of this type are studied and reported. Most of the data concern the crystal structures of the glycine compounds. Fleck [1] systematized some of these compounds with an attempt to throw light on their crystal structures. Our previous studies elucidated the crystallization process in glycine-metal(II) sulfate solutions and found crystallization of compounds belonging to three formula types—GlyÁMSO 4 Á5H 2 O (Gly = glycine, M = Mg, Mn, Fe, Co, Ni, and Zn), GlyÁCoSO 4 Á3H 2 O and GlyÁMnSO 4 [2] to take place. In memory of Prof. H. Gamsja ¨ger. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s00706-017-2120-8) contains supple- mentary material, which is available to authorized users. & Stefka Tepavitcharova stepav@svr.igic.bas.bg 1 Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., Bl. 11, 1113 Sofia, Bulgaria 2 Department of Inorganic Chemistry, Faculty of Science, Charles University, Hlavova 2030, 128 40 Prague 2, Czech Republic 3 Institute of Inorganic Chemistry of the ASCR, v. v. i., Husinec-R ˇ ez ˇ 1001, 250 68 R ˇ ez ˇ, Czech Republic 123 Monatsh Chem https://doi.org/10.1007/s00706-017-2120-8