Second ligand-directed self-assembly of lanthanide(III) coordination polymers with 1,4-naphthalenedicarboxylate

Under hydrothermal conditions, 1,4-naphthalenedicarboxylic acid ( H2NDC) reacts with lanthanide(III) chloride to form the coordination polymers [Ln(2)(NDC)(3)(H2O)(2)] center dot nH(2)O [n = 2, Ln = Eu ( 1); n = 1.5, Ln = Gd (2)]. If a second ligand, 4,4'-bipyridine (4,4'-bpy), is added to the reaction mixture, the coordination polymers [Ln(2)(NDC)(3)(4,4'-bpy)(0.5)(H2O)(3)] center dot (4,4'-bpy) [Ln = Eu ( 3); Ln = Yb ( 4)] are obtained. 1 and 2 are isostructural and they possess a porous 3D network with the lanthanide( III) ions bridged only by NDC anions. 3 and 4 are unprecedented lanthanide coordination polymers of polycarboxylate with 4,4'-bpy. They possess a 3D porous structure assembled by lanthanide ions with the linkers NDC and 4,4'-bpy, while lattice molecules of 4,4'-bpy are enclathrated in the cavities. The photophysical properties of 3 and the magnetic properties of 2 were investigated, and the thermogravimetric analyses of 1 and 3 were also carried out.