Controlled synthesis, structures and properties of one-, two-, and three-dimensional lanthanide coordination polymers based on (8-quinolyloxy)acetate

Hydrothermal reactions of Ln(NO3)(3) and (8-quinolyloxy) acetic acid (HQOA) with auxiliary ligands resulted in a series of new one-, two-and three-dimensional (1D, 2D and 3D) coordination polymers, namely, [Ln(QOA)(2) (H2O)(2)] center dot NO3 center dot H2O [Ln = Eu (1), Gd (2)], [Ln(2)(QOA)(4)(ox)(H2O)] center dot 3H(2)O [Ln = Pr (3), Er (4)], [Ln(2)(QOA)(4)(BDC) (H2O)] center dot 4H(2)O [Ln = Sm (5)] and [Ln(QOA)(BDC)] [Ln = Sm (6), Eu (7)] [QOA = (8-quinolyloxy) acetate; ox = oxalate; BDC = 1, 4-benzenedicarboxylate], respectively. Compounds 1-2 possess 1D zigzag chains bridged by QOA anions and 3-4 contain 1D folded chains alternately bridged by oxalates and QOA anions. Complex 5 is an ordered (2,4)-connected 2D sheet-like structure. In compounds 6-7, four BDC anions bridge two adjacent metal atoms to form dinuclear lanthanide building blocks and these dinuclear blocks are further connected together to form an 8-connected 3D network. The progressive variation from 1D zigzag chains (1-2) to 1D folded chains (3-4) to a 2D layer network (5) and to 3D frameworks (6-7) is mainly attributed to the change of bridging ligands as well as the different coordination modes of organic carboxylic ligands. Moreover, the thermal stabilities and photoluminescent properties of these compounds show a remarkable difference due to the progressive variation of crystal structures.