Solvent-regulated assemblies of 1D lanthanide coordination polymers with the tricarboxylate ligand

Abstract

Solvothermal reactions of the tricarboxylic acid ligand, biphenyl-3,3′,5-tricarboxylic acid (H₃bpta), and rare earth nitrate (Ln(NO₃)₃·6H₂O) in the presence of KOH or DMF produced eight 1D linear coordination polymers, namely, [La(bpta)(H₂O)₅·(H₂O)₃]_n (1), [Pr(bpta)(H₂O)₅·(H₂O)_2.5]_n (2), [Nd(bpta)(H₂O)₅·(H₂O)_1.75]_n (3), [Sm(bpta)(H₂O)₅·(H₂O)_0.5]_n (4) and [Ln(bpta)(DMF)(H₂O)₃·(H₂O)]_n [Ln = Eu (5), Gd (6), Tb (7), Dy (8)]. The 1D chain further assembles into a 3D supramolecular network structure through hydrogen bonds and π–π stacking among chains. Complexes 3–5 and 7 display the typical emission spectra for lanthanide-centred luminescence. The optical properties of 5 were analysed in detail and coincide well with the structural properties. The influence of temperature on the luminescence lifetime of 6 has been studied and different non-radiative decay paths have been discussed. The magnetic properties show that 4 and 5 exhibit strong spin–orbit coupling, while weak antiferromagnetic coupling exists in 6.