Reversible crystal-to-crystal transformation of a 3D–3D coordination polymer by solid state anion-replacement with no change in nano-particle morphology

Abstract

A reversible crystal-to-crystal transformation of a 3D lead(II) coordination polymer with the ligand 1H-1,2,4-triazole-3-carboxylic acid (HL), from [Pb(L)(μ₂-Br)(H₂O)]_n (1) to 3D [Pb(L)(μ_1,1-NCS)(H₂O)]_n (2) by solid state anion-replacement, has been observed. The thermal stabilities of compounds 1 and 2 were studied by thermal gravimetric and differential thermal analyses. Powder X-ray diffraction experiments showed that the structural transformation occurs in the powder samples and leads to monophasic products. Nano-particles of compound 1 were synthesized by a sonochemical process and characterized by scanning electron microscopy (SEM), powder X-ray diffraction, IR spectroscopy, elemental analyses, thermal gravimetric and differential thermal analyses. The SEM images showed that no morphology change occurs during this solid state anion-replacement.