Synthesis, structural characterization, and solution properties of a 1-D Pb(II)-bipyridine coordination polymer

Abstract

A new one-dimensional (1-D) Pb(II) coordination polymer, [Pb(2,2′-bpy)(NO3)2(H2O)]n (1) (2,2′-bpy = 2,2′-bipyridine), has been synthesized and characterized by different spectroscopic techniques and X-ray single-crystal analysis. From the X-ray crystal structure of 1, the Pb2+ can be best described as a highly distorted pentagonal bipyramid with O4 (water) and O6 (nitrate) at apical positions (O4-Pb-O6 of 143.7(1)°). Variability in bond distances reveals that Pb2+ is unsymmetrically surrounded by two nitrates, one 2,2′-bpy and one water. Nitrates bridge between monomers. The molecule crystallizes in the monoclinic P21/n (14) space group. This is the first example of a 1-D Pb(II) polymer in which nitrates show three different coordination motifs (terminal, chelating, and bridging). Solid state as well as solution phase UV-vis spectral analysis and mass spectrometric studies clearly reveal instability with breakdown of Pb(II) polymer in aqueous solution. The arrangement of the 2,2′-bpy, water, and nitrates leaves a coordination gap at the Pb(II) occupied probably by a stereo-active lone pair of electrons.