The effect of pH on visible and near-infrared luminescent lanthanide coordination compounds based on a conjugated pyridine carboxylate ligand

Abstract Four new lanthanide coordination compounds, [Pr2(bpdc)3(H2O)2]n·2nH2O (1), [Nd2(bpdc)2(H2O)6(NO3)]n·n(NO3) (2), [Eu(bpdc)(NO3)(H2O)3] (3), [Eu8(bpdc)12(H2O)12]·7H2O (4) (H2bpdc= 2,2ʹ-bipyridine-6,6ʹ-dicarboxylic acid) have been synthesized at different pH values under hydrothermal conditions. Compound 1 exhibits a 4-connected 2D layer with the sql topological network. Compound 2 shows a 3-connected 2D layer with the hcb topological net. Compound 3 is a mononuclear structure, which is extended to a 2D supramolecular layer by hydrogen bonding interactions. Compound 4 exhibits an octa-nuclear molecular structure, and further extend to a 2D supramolecular layer through hydrogen bonding interactions. The pH of the reaction system plays an important role in modulating the structure of coordination compounds. In addition, compounds 1−4 show visible and near-infrared luminescence.