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

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 -hydroxyl, -carboxylate and one of the -carboxylate groups. Complex 1 forms a chiral helical chain running along the axis of the crystal via two bridged oxygens of the -carboxylate group. The interconversions of different zinc citrate complexes in aqueous solution show their pH-dependent patterns.