Synthesis and crystal structure of a zinc citrate complex [Zn(H₂cit)(H₂O)]_n

Abstract

A zinc citrate coordination complex, [Zn(H₂cit)(H₂O)] _n (1), was prepared from Zn(NO₃)₂ · 6H₂O and citric acid at pH = 1.5–3.0 in aqueous solution. The complex was characterized by elemental analyses, IR spectroscopy and X-ray crystallography. The Zn(II) ion in complex 1 exists in an octahedral coordination environment. The citrate binds Zn(II) tridentately via its α-hydroxyl, α-carboxylate and one of the β-carboxylate groups. Complex 1 forms a chiral helical chain running along the α axis of the crystal via two bridged oxygens of the α-carboxylate group. The interconversions of different zinc citrate complexes in aqueous solution show their pH-dependent patterns.

Keywords:

• Citric acid
• Crystal structure
• pH-dependent
• Zinc

Acknowledgments

This work is supported by the Guangdong Natural Science Foundation of China (B6060400). We also thank the South China University of Technology for financial support.