Structure tuning of metal phosphonates: Syntheses, structures and characterizations of two new lead (II) trisphosphonates

Two lead (II) trisphosphonates, [Pb3(H3L1)2(H2O)] (1) and [Pb5(HL2)(H3L2)(H4L2)(H2O)2][(H2O)2] (2), have been synthesized from two trisphosphonate ligands and characterized by EA, IR, UV–vis, TGA, powder and single-crystal X-ray diffraction methods. The single-crystal X-ray diffraction analyses reveal that they both feature three-dimensional framework structures. The lead (II) ions are mainly five-coordinated, forming square pyramid coordination geometry. Although the two trisphosphonate ligands are very similar, different coordination modes and conformations are observed for them, suggesting that attachment of methyl groups to the central benzene ring has a major effect on the structure formation. They both absorb below 325 nm and are thermally robust.