Synthesis and crystal structures of four pH-dependent Pb(II) and Cd(II) phosphonates based on a novel ligand, 3-phosphono-benzoic acid

Four metal phosphonate hybrid compounds, [Pb(Hpbc)] (1), [Pb3(pbc)2(H2O)2] (2), [Cd(H2pbc)2(H2O)2] (3) and [Cd1.5(pbc)(H2O)1.5] · 0.5H2O (4) (H3pbc = 3-phosphono-benzoic acid) were successfully synthesized by the hydrothermal/solvothermal reaction of metal acetate and 3-phosphono-benzoic acid. Compounds 1–4 were pH-dependent products and characterized by elemental analysis, Fourier transform infrared (FT-IR) spectra and single-crystal X-ray diffraction studies. Compound 1 is a two-dimensional (2D) structure constructed by inorganic layer and organic pendant. With the increase of pH value, structure 2 shows 3D inorganic framework with distributing organic moieties in the channels. In 3, the Cd2O10 dimers are linked by alternating terminal and bridging ligands, resulting in 1D chain structure. Compound 4 is a 2D structure where the 1D inorganic chains are connected by the organic moieties of the ligands.

Graphical abstractThe reaction of 3-phosphono-benzoic acid and lead/cadmium salt with different pH value lead to four novel metal phosphonates. Their structures range from one dimension to three dimension, showing structural response on pH value of the reaction clearly.Figure optionsDownload full-size imageDownload as PowerPoint slide