Synthesis, structures, luminescence and magnetism of nine lanthanide complexes with three-dimensional frameworks constructed from 2-(pyridyl-N-oxide)methylphosphonic acid and oxalic acid

To investigate the coordination nature of the pyridyl-N-oxide phosphonate ligands with rare earth metals, two series of nine lanthanide complexes, namely, {[Ln(HL)((C sub(2)O sub(4)) sub(0.5)) sub(2)(H sub(2)O)].3H sub(2)O} sub()n{Ln = Eu(1), Gd(2), Tb(3), Dy(4) and Ho(5)} and {[Ln sub(2)(L)(C sub(2)O sub(4)) sub(2)(H sub(2)O) sub(3)].H sub(2)O} sub()n{Ln = Er(6), Tm(7), Yb(8) and Lu(9)} {H sub(2)L = 2-(pyridyl-N-oxide)methylphosphonic acid; H sub(2)C sub(2)O sub(4) = oxalic acid }, have been hydrothermally synthesized and characterized by IR spectroscopy, thermogravimetric analysis, and powder and single-crystal X-ray diffraction. Complexes 1-5 are isomorphic, featuring a three-dimensional (3D) porous structure with a diatopological framework, while the isomorphic complexes 6-9 show a 3D 3,4-connected topological framework with a point symbol of {7 super(2).8} sub(2){7 super(3).8 super(3)}. Photoluminescence spectra of complexes 1 and 3 exhibit the strong luminescence characteristic of Eu(iii) and Tb(iii) ions, respectively, suggesting that HL super(-) and L super(2-) anions are able to efficiently sensitize the luminescence of lanthanide ions. The magnetic analyses of complexes 2-5 show the characteristic magnetic susceptibilities of isolated Gd(iii), Tb(iii), Dy(iii) and Ho(iii) ions, respectively.