Synthesis, structures and properties of three lead coordination polymers based on ethylenediaminetetraacetate ligand

Three Pb(II)-edta complexes, [Pb3(edta)(H2O)Cl2]n·(H2O)3n (1), [Pb5(edta)2(H2O)2X2]n·(H2O)2n (X = Cl (2), Br (3)) (H4edta = ethylenediaminetetraacetic acid) have been synthesized by the reaction of PbX2 and H4edta under hydrothermal conditions, and were characterized by elemental analysis, thermal analysis, luminescence, powder X-ray diffraction and single-crystal X-ray diffraction. The results of X-ray crystallographic analysis reveal that these complexes are the first bilayer two-dimensional (2D) Pb-edta coordination polymers with 1D channels. The bilayers of complexes 1, 2 and 3 are linked by [Pb2Cl4], [PbCl2] and [PbBr2] clusters with carboxylate groups respectively. They are 3D supramolecular structures which are resulted from different halogenide anions. The emission spectra of 1–3 are dominated by intense and broad emission bands which are resulted from the [PbX2] clusters. Optical absorption spectra indicate that theses complexes have wide optical band-gaps and can be probably used as wide optical band-gap semiconductor materials.