Irreversible Crystal to Crystal Transformation of Nano Lead(II) Coordination Polymer by Solid State Anion-Replacement

Abstract

Irreversible crystal-to-crystal transformation of 3D lead (II) coordination polymer with the ligand 1H-1,2,4-triazole-3-carboxylic acid (HL), [Pb (L)(μ1,1-NCS)(H2O)]n (1) to 3D supramalecular compound [Pb (L)(μ2-I)]n (2) by solid state anion-replacement have been studied. Structural determination of compound 2 reveals the Pb (II) ion is five coordinated with hemidirected geometry, bonded to one nitrogen atom, two oxygen atoms from the Lˉ ligand and two iodide ions. The irreversible solid state structural transformation of compound 1 to compound 2, by anion-replacement processes under mechanochemical reaction have been verified by PXRD measurements. Nanoparticles of compound 1 was synthesized by sonochemical process and characterized by scanning electron microscopy (SEM), powder X-ray diffraction, IR spectroscopy and elemental analyses. The SEM images showed that no morphology change occur during this solid state anion-replacement.