Structures and luminescent properties of Tb(III) and Tb(III)–Ni(II) coordination polymers based on pyridyl dicarboxylate

The N,O ligand, namely 5-(pyridin-4-yl)isophthalic acid (LH2), with carboxylic acid groups and pyridyl group separated, prefers to act as a bridging ligand. Its Tb(III) coordination polymer, [TbL(LH)(H2O)2]∞·xH2O (1), and heterometallic Tb(III)–Ni(II) coordination polymer, [TbNiL2(LH)(H2O)]∞·xH2O (2), have been successfully prepared. Complex 1 exhibits a two-dimensional layered structure with (4,4) network leaving all the pyridyl N-donors uncoordinated, while complex 2 has a three-dimensional structure due to coordination of Ni(II) to part of pyridyl N-donors. Both the complexes were characterized by single-crystal X-ray diffraction, X-ray powder diffraction, FT-IR spectroscopy and thermogravimetry analysis. The ligand is capable of sensitizing the Tb(III) ion, and both the complexes emit characteristic visible green luminescence of Tb(III).