Water cluster supported architecture of lanthanide coordination polymers with pyrazinetricarboxylic acid

Abstract

The first examples of lanthanide coordination polymers with pyrazinetricarboxylic acid, [Ln(PZTA)(H₂O)₄]·2H₂O (Ln = Eu(1), Gd (2), PZTA = pyrazine-2,3,5-tricarboxylate) and [Ln(PZTA)(H₂O)₂]·H₂O (Ln = Er(3), Yb(4)) were synthesized under hydrothermal conditions and characterized by single-crystal X-ray diffraction. Structural analysis shows that complexes 1 and 2 are composed of 1-D lanthanide-pyrazinetricarboxylate (Ln-PZTA) framework and two types of water clusters while complexes 3 and 4 have 3-D Ln-PZTA framework with 1-D channel, at which a 1-D water cluster chain is located. This shows the effect of lanthanide contraction on the construction of the Ln-PZTA framework. The results of TG curves and PXRD display that the uncoordinated and coordinated water molecules are removed, the Ln-PZTA frameworks collapse, which shows that the water clusters play an important role in constructing Ln-PZTA frameworks in the title complexes.