Crystallization and characterization of the compounds Gly.MSO4.mH2O (M = Mg2+, Mn2+, Fe2+, Co2+, Ni2+, Zn2+; m = 0, 3, 5, 6)
Abstract
The equilibrium crystallization of complex compounds of the type Gly.MSO4.5H2O with a structure derived from those of the crystallized double salts MSO4.xH2O, where x = 6, 7 was predicted and proven in the systems Gly-MSO4-H2O (M = Mg2+, Mn2+, Fe2+, Co2+, Ni2+ and Zn2+). It was predicted that stable octahedral complexes [M(H2O)6]2+ and trans-[M(H2O)4(O-gly)2]2+, as well as [SO4]2- tetrahedra, which were the main building units of the crystallizing Gly.MSO4.5H2O compounds (triclinic crystal system, space group P MINUS SIGN 1), were predominating in these solutions.
The vibrational spectra and the thermal behavior of the Gly.MSO4.5H2O compounds (M = Mg2+, Co2+, Zn2+) 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 MnSO4.H2O (308 K) crystallizes, the only complex compound is the anhydrous Gly.MnSO4 with a polymeric type structure. A new compound Gly.CoSO4.3H2O was found in the cobalt system under unstable equilibrium conditions.
Gly.CoSO4.3H2O was proven to consist of two types of octahedra, trans-[Co(H2O)4(O-gly)2]2+ and trans-[Co(H2O)2(SO4)2(O-gly)2]2MINUS SIGN , forming a chain structure (monoclinic crystal system, space group P21/c).