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 extends 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.