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.