Synthesis, crystal structure and photoluminescent properties of four lanthanide 5-nitroisophthalate coordination polymers

Abstract

Four new lanthanide coordination polymers, [Y(Hnip)(nip)(H 2O)]·H 2O ( 1), [ Ln(Hnip)(nip)(H 2O) 2]·2H 2O [ Ln=Eu( 2), Tb( 3)] and [Y(nip) 2]·(H 24,4′-bpy) 0.5 ( 4) [5-nip=5-nitroisophthalate, 4,4′-bpy=4,4′-bipyridine], have been hydrothermally synthesized and structurally characterized. Compound 1 features novel lanthanide–carboxylate groups chains composed of three samehanded helical strands intersecting each other through hinged lanthanide atoms, and these chains are cross-linked by phenylene moieties of carboxylate ligands into a 2D layer structure. Compounds 2 and 3 are isomorphous, and contain 1D catenanelike Ln–O–C–O– Ln chains, which are interconnected by phenylene moieties into 2D layer structures. Compound 4, however, displays a 3D architecture sustained by strong hydrogen bonding interactions between the protonated 4,4′-bpy and the carboxyl oxygen atom from [Y 2(nip) 4] 2− with 2D layer structure, and 4,4′-bpy as the guest molecules exist in bilayer channel. The studies for the thermal stabilities of the four compounds show that compound 4 is more stable than other compounds. Compound 2 emits characteristic red luminescence of Eu 3+ ions at room temperature, and its luminescent lifetime and quantum efficiency has been determined.