Synthesis, Crystal Structure of Zinc(II)–Cysteamine Complex and Improvement of Cysteamine Stability

The principal objective of this study is to evaluate the protective effect of cysteamine (Cym) against oxidation by chelating with metal cations. Cym–Zn complex has been prepared through a simple procedure using Cym ⋅ HCl and ZnSO4. The results have shown that the chelating efficiency of zinc is better when the molar ratio of the reactant Cym · HCl to zinc ions is 1.4–1.5. IR spectra of as-synthesized Cym–Zn complex suggests Cym cross-links with Zn through N and S atoms. X-ray powder diffraction analysis shows that the crystal structure is consisted of a coordination unit [Zn2(SC2H6N)3], a chlorine atom and an H2O molecule. Besides, the cell parameters of the monoclinic crystal are a = 7.9581(5) Å, b = 15.0794(10) Å, c = 12.2910(8) Å and β = 103°. Cym retention rate and thermal decomposition characteristics of Cym–Zn complex are significantly improved, and doping of iron, copper and manganese cations is helpful to suppress Cym oxidization because of the formation of stronger bonds with sulfur atom than zinc cation. The investigation indicates metal ion is an effective inhibitor for Cym oxidation.