Synthesis, Structures and Properties of Two Ln(III) Coordination Polymers based on Pyrimidine-2-carboxylic Acid and Sodium Dicyanamide

Assemblies of pyrimidine-2-carboxylic acid (Hpmc) and samarium nitrate or europium nitrate in the presence of sodium dicyanamide (Na-dca) under ambient conditions yielded two new coordination polymers, namely [Ln(pmc)(2)(dca)(H2O)(2)](n) (Ln=Sm (1), Eu (2)). The complexes were characterized by single-crystal X-ray diffraction analysis, elemental analysis, IR and fluorescence spectra. Structure analysis shows two complexes are isostructural with monoclinic (C2/c) symmetry. And each central metal atom is coordinated by three chelate pmc(-), one terminal dca(-) and two water molecules to generate an infinite zigzag chain. Through O-water-H... O-carboxylate, O-water-H...N-pyrimidine hydrogen bonds, the chains are connected to a two-dimensional net, which is furtherly extended to a three-dimensional supramolecular structure by O-water-H... N-cyano hydrogen bonds. Luminescent measurement of complex 2 shows the characteristic fluorescence of Eu3+.