Syntheses, structures and luminescence properties of cadmium(II) coordination polymers with in situ formed oxalate and bis(chelating) bridging ligands

Hydrothermal reactions of 2-cyanopyrimidine and CdCl₂ in the absence and presence of sodium azide yielded two coordination polymers, [Cd ₃(ox)₂(pymc)₂]·2H₂O (1) and [Cd₂(pymtz)₂(ox)]·H₂O (2), respectively, where pymc = 2-pyrimidinecarboxylate, pymtz = 5-(2′-pyrimidyl)tetrazolate and ox = oxalate. All the ligands in these compounds were generated in situ by the hydrolysis of 2-cyanopyrimidine (pymCN) or the [2 + 3] cycloaddition of the azide ion to the nitrile. In compound 1, seven-coordinated Cd ions are linked by oxalate bridges into a diamond network based on Cd₂O₂ nodes, and eight-coordinated Cd ions are linked to the network through pymc and oxalate bridges. In compound 2, seven-coordinated Cd ions are bridged by oxalate ions into 1D Cd₂(ox) ribbons, which are further linked by bis(chelating) pymtz to give a 3D framework that exhibits the 5-connected 4 ⁴6⁶ net topology based on Cd₂O₂ nodes. The compounds exhibit intense luminescence in the solid state.