The equilibrium crystallization of complex compounds of the type Gly·MSO 4 ·5H 2 O with a structure derived from those of the crystallized double salts MSO 4 ·xH 2 O, where x=6, 7 was predicted and proven in the systems Gly–MSO 4 –H 2 O (M=Mg 2+ , Mn 2+ , Fe 2+ , Co 2+ , Ni 2+ and Zn 2+ ). It was predicted that stable octahedral complexes [M(H 2 O) 6 ] 2+ and trans-[M(H 2 O) 4 (O-gly) 2 ] 2+ , as well as [SO 4 ] 2− tetrahedra, which were the main building units of the crystallizing Gly·MSO 4 ·5H 2 O compounds (triclinic crystal system, space group P−1), were predominating in these solutions. The vibrational spectra and the thermal behavior of the Gly·MSO 4 ·5H 2 O compounds (M=Mg 2+ , Co 2+ , Zn 2+ ) are in accord with the refined crystal structures. The cobalt compound displays antiferromagnetic behavior whereas the nickel and manganese compounds are ferromagnetic.In the manganese system where MnSO 4 ·H 2 O (308K) crystallizes, the only complex compound is the anhydrous Gly·MnSO 4 with a polymeric type structure (trans-[Mn(SO4)4(O-gly)2]n2-).A new compound Gly·CoSO 4 ·3H 2 O was found in the cobalt system under unstable equilibrium conditions. Gly·CoSO 4 ·3H 2 O was proven to consist of two types of octahedra, trans-[Co(H 2 O) 4 (O-gly) 2 ] 2+ and trans-[Co(H 2 O) 2 (SO 4 ) 2 (O-gly) 2 ] 2− , forming a chain structure (monoclinic crystal system, space group P2 1 /c).