Synthesis, structures and photoluminescence of three terbium(iii) dicarboxylate coordination polymers

Abstract

Three polymeric terbium(III) complexes of 4,4′-oxybis(benzoic acid) (H₂oba) have been hydrothermally synthesised with different metal∶carboxylate ratios or in the presence of an additional chelate ligand 2,2′-bipyridine (2,2′-bpy) and characterised by single-crystal X-ray diffraction. In [Tb(oba)(Hoba)(H₂O)₂)·H₂O, 1, the metal atoms are bridged by the oba/Hoba carboxylate groups into one-dimensional covalent chains, which are further interconnected by the oba ligands to produce a two-dimensional brick-wall network. In [Tb₂(oba)₃(H₂O]₄], 2, the metal atoms are bridged by the oba/Hoba carboxylate groups into one-dimensional covalent chains different from those in 1, which are further interconnected by the oba ligands to produce a two-dimensional condensed network. In the structure of [Tb₂(oba)₃(2,2′-bpy)₂], 3, there are centrosymmetrical tetrakis(μ-carboxylate)-bridged Tb(III) dimeric structural subunits, which are interlinked by the oba ligands into a three-dimensional framework. The three compounds exhibit interesting photoluminescence at room temperature. The results show that different metal∶carboxylate ratios can influence the polymeric structures and that the presence of 2,2′-bpy ligand alters not only the topology of the framework from two-dimensional to three-dimensional, but also the photoluminescent properties in both intensity and lifetime.