Sulfate binding in zinc(II) complexes of a monopyridylurea ligand N-(1-naphthyl)-N′-(3-pyridyl)urea

Two zinc(II) complexes of a urea-functionalized pyridyl ligand, [Zn(SO ₄)L₃]•CH₃OH (1) and {[Zn(μ₂- SO₄)L₂]•0.5CH₃OH}_n (2) (L = N-(1-naphthyl)-N′-(3-pyridyl)urea), have been synthesized by the reaction of L with ZnSO₄•7H₂O under different conditions. Complex 1 is a hydrogen-bonded 2D grid structure in which the sulfate anion not only coordinates to the Zn^II ion as a monodentate ligand but also forms multiple hydrogen bonds with the urea groups of adjacent molecules. In complex 2 the sulfate ion serves as a μ₂-bridging ligand, connecting the Zn^II ions to form an infinite 1D organic-inorganic hybrid framework. Meanwhile, the sulfate anion is also bound by neighboring ligands through hydrogen bonds between urea groups and the non-coordinated oxygen atoms. The solid-state emission spectra of 1 and 2 show a red shift of the fluorescence emission of ligand L.