Five novel metal–organic framework constructed by lanthanide metals and 2,2′-bipyridine-6,6′-dicarboxylate: Hydrothermal synthesis, crystal structure, and thermal properties

Five lanthanide coordination compounds, [Ln 3(bpdc) 4(Hbpdc)(H 2O) 2]·12H 2O (Ln Ce(1), Nd(2) and Pr(3)) and [Ln 2(bpdc) 3(H 2O) 3]·3H 2O (Ln Er(4) and Tm(5)) were obtained from 2,2′-bipyridine-6,6′-dicarboxylate acid and corresponding lanthanide salts by hydrothermal synthesis. Single-crystal X-ray diffraction reveals that 1–3 are isomorphous and isostructural, composed of one-dimensional infinite double zigzag chain structure, and further extended to two-dimensional networks via hydrogen bonds and π–π interactions; while isomorphous and isostructural 4–5 are zero-dimensional discrete moieties and further joined into three-dimensional framework by rich intermolecular hydrogen bonds and π–π interactions. The pyridyl nitrogen atoms and the carboxylate oxygen atoms of the bpdc ligand are coordinated to lanthanide ions, resulting into versatile coordination modes. Thermogravimetric analyses of 1–5 display a considerable thermal stability.