Syntheses, Crystal Structures, and Characterizations of a Series of New Layered Lanthanide Carboxylate‐Phosphonates

Hydrothermal reactions of different lanthanide( III ) salts with (H 2 O 3 PCH 2 ) 2 NCH 2 COOH (H 5 L 1 ) led to two new layeredlanthanide( III ) carboxylate‐diphosphonates, namely La(H 2 L 1 )(H 2 O) 2 · H 2 O ( 1 ) and La(H 2 L 1 )(H 2 O) ( 2 ). The structure of compound 1 features a layered architecture in which the nine‐coordinate La 3+ 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 La 3+ ion is eight‐coordinated and the carboxylate group of the ligand is chelated to a La 3+ ion in a bidentate fashion. Hydrothermal reactions of lanthanide( III ) salts with 4‐HOOC–C 6 H 4 –CH 2 N(CH 2 PO 3 H 2 ) 2 (H 5 L 2 ) afforded three new compounds, namely, La(H 4 L 2 )(H 3 L 2 )(H 2 O) · 2H 2 O ( 3 ), Er(H 3 L 2 )(H 4 L 2 ) ( 4 ), and Er(HL 3 )(H 2 L 3 )(H 2 O) ( 5 ) [H 2 L 3 = H 2 O 3 PCH 2 N(CHO)(CH 2 –C 6 H 4 –COOH)]. H 2 L 3 was formed by the in situ oxidation of one P–C bond of the H 5 L 2 ligand. Compound 3 features a (002) lanthanum( III ) phosphonate layer in which the seven‐coordinate La 3+ 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 ErO 6 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 Er 3+ 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.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)