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

Abstract

Under hydrothermal conditions, 1,4-naphthalenedicarboxylic acid (H₂NDC) reacts with lanthanide(III) chloride to form the coordination polymers [Ln₂(NDC)₃(H₂O)₂]·nH₂O [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 [Ln₂(NDC)₃(4,4′-bpy)_0.5(H₂O)₃]·(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.