Synthesis, crystal structures, and luminescent properties of two types of lanthanide phosphonates

Hydrothermal reactions of different lanthanide(III) salts with an amino-diphosphonate ligand (H 4L=C 6H 5CH 2N(CH 2PO 3H 2) 2) led to two series of lanthanide phosphonates, namely, Ln(H 2L)(H 3L) ( Ln=La, 1; Pr, 2; Nd, 3; Sm, 4; Eu, 5; Gd, 6; Tb, 7). Compounds 1–5 feature a one-dimensional (1D) chain structure in which dimers of two edge-sharing LnO 8 polyhedra are interconnected by bridging phosphonate groups, such 1D arrays are further interlinked via strong hydrogen bonds between non-coordinated phosphonate oxygen atoms into a two-dimensional (2D) layer with the phenyl groups of the ligands orientated toward the interlayer space. Compounds 6 and 7 also show a different 1D array in which the LnO 6 octahedra are bridged by phosphonate groups via corner-sharing, such chains are also further interlinked by hydrogen bonds into a 2D supramolecular layer. Compounds 5 and 7 emit red and green light with a lifetime of 2.1 and 3.7 ms, respectively. Two series of luminescent lanthanide phosphonates have been synthesized and structurally characterized. Their structures feature two different types of 2D sumpramolecular layers based on two types of 1D arrays interlinked via strong hydrogen bonds.