Syntheses, Crystal Structures And Properties Of Metal Diphosphonate Coordination Polymers

In this work, we present six metal diphosphonate coordination polymers, which were synthesized by using N, N’-piperazinebis (methylenephosphonic acid) and1-hydroxy-2-(3-pyridyl)-ethylidene-1,1-diphosphonic acid as ligands. By using oxalate as the second metal linker and direct reaction, six metal phosphonate coordination polymers are hydrothermally synthesized. All compounds were structurally characterized by X-ray single-crystal diffraction together with X-ray powder diffraction, infrared spectroscopy and thermogravimetric analysis. In addition, guest desorption-sorption propertie of compound3has also been studied. The chemical constitution formulas are listed as follow:(1)[La(O3PCH2NH(C2H4)2NHCH2PO3)0.5(C2O4)1.5]·(H3O)·H2O(2)[La(O3PCH2NH(C2H4)2NHCH2PO3)0.5(C2O4)(H2O)]·1.5H2O(3)[Ce(O3PCH2NH(C2H4)2NHCH2PO3)0.5(C2O4)(H2O)]·1.5H2O(4)[Pr(O3PCH2NH(C2H4)2NHCH2PO3)0.5(C2O4)(H2O)]·1.5H2O(5)[Nd(O3PCH2NH(C2H4)2NHCH2PO3)0.5(C2O4)(H2O)]·1.5H2O(6)Ca[(C5H5N)CH2C(OH)(PO3H)2]2·2H2OBy using N, N’-piperazinebis (methylenephosphonic acid) as the phosphonate ligand and by introduction of oxalate as the second metal linker, compounds1-5are synthesized. X-ray diffraction analysis exhibits that compound1features a3D framework structure. Compounds2-5are isomorphousare. Compound5was not obtained single crystals suitable for X-ray structural analysis, however, X-ray powder diffraction analysis indicates that compound5is isomorphous and features a3D framework structure, which is the same as the structure of compounds2-4. By using1-hydroxy-2-(3-pyridyl)-ethylidene-1,1-diphosphonic acid (hpyedpH4) as the phosphonate ligand, compound6is synthesized. X-ray diffraction analysis shows that compound6is one-dimensional structure through hydrogen bonds forming a three-dimensional supramolecular structure.The thermal analysis of these compounds indicates that they form the stabilized framework structure. The guest desorption-sorption properties analyses indicate that the dehydrated solids of compounds2-5may be potential reversible adsorbent materials for water molecules.