Syntheses, crystal structures, and characterizations of a series of new layered lanthanide carboxylate-phosphonates

Hydrothermal reactions of different lanthanide((III)) salts with (H2O3PCH2)(2)NCH2COOH (H5L1) led to two new layered lanthanide((III)) carboxylate-diphosphonates, namely La-(H2L1)(H2O)(2)center dot H2O (1) and La(H2L1)(H2O) (2). The structure of compound I features a layered architecture in which the nine-coordinate La3+ ions are bridged by phosphonate groups of the ligands. The carboxylate group of the phosphonate ligand remains protonated and is involved in the interlayer hydrogen bonding. Compound 2 features a double layer structure in which the La3+ ion is eight-coordinated and the carboxylate group of the ligand is chelated to a La3+ ion in a bidentate fashion. Hydrothermal reactions of lanthanide((III)) salts with 4-HOOC-C6H4-CH2N(CH2PO3H2)(2) (H5L2) fforded three new compounds, namely, La(H4L2)(H3L2)- (H2O)center dot 2H(2)O (3), Er(H3L2)(H4L2) (4), and Er(HL3) (H2L3) (H2O) (5) [H2L3 = H2O3PCH2N(CHO)(CH2-C6H4-COOH)]. H2L3 was formed by the in situ oxidation of one P-C bond of the H5L2 ligand. Compound 3 features a (002) lanthanum((III)) phosphonate layer in which the seven-coordinate La3+ ions are bridged by diphosphonate moieties of the ligands. The carboxylate group remains protonated and is involved in the interlayer hydrogen bonding. The structure of compound 4 contains a 1D chain along the a axis in which each pair of ErO6 octahedra is bridged by a pair of phosphonate groups. These 1D chains are further interconnected by hydrogen bonds between noncoordinated phosphonate oxygen atoms into a (002) layer with the phenyl carboxylate groups hanging on the interlayer space. The structure of compound 5 is also layered. The interconnection of Er3+ ions by bidentate and tetradentate bridging phosphonate groups resulted in a (002) inorganic layer with the organic groups orientated to the interlayer space. Luminescence properties of compounds 4 and 5 have also been studied. (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006.