Synthesis and characterization of two isostructural 3 d –4 f coordination compounds based on pyridine‐2,6‐dicarboxylic acid and 4,4′‐bipyridine

The design and synthesis of 3 d –4 f heterometallic coordination polymers have attracted much interest due to the intriguing diversity of their architectures and topologies. Pyridine‐2,6‐dicarboxylic acid (H 2 pydc) has a versatile coordination mode and has been used to construct multinuclear and heterometallic compounds. Two isostructural centrosymmetric 3 d –4 f coordination compounds constructed from pyridine‐2,6‐dicarboxylic acid and 4,4′‐bipyridine (bpy), namely 4,4′‐bipyridine‐1,1′‐diium diaquabis(μ 2 ‐pyridine‐2,6‐dicarboxylato)tetrakis(pyridine‐2,6‐dicarboxylato)bis[4‐(pyridin‐4‐yl)pyridinium]cobalt(II)dieuropium(III) octahydrate, (C 10 H 10 N 2 )[CoEu 2 (C 10 H 9 N 2 ) 2 (C 7 H 3 NO 4 ) 6 (H 2 O) 2 ]·8H 2 O, (I), and 4,4′‐bipyridine‐1,1′‐diium diaquabis(μ 2 ‐pyridine‐2,6‐dicarboxylato)tetrakis(pyridine‐2,6‐dicarboxylato)bis[4‐(pyridin‐4‐yl)pyridinium]cobalt(II)diterbium(III) octahydrate, (C 10 H 10 N 2 )[CoTb 2 (C 10 H 9 N 2 ) 2 (C 7 H 3 NO 4 ) 6 (H 2 O) 2 ]·8H 2 O, (II), were synthesized under hydrothermal conditions and characterized by IR and fluorescence spectroscopy, thermogravimetric analysis and powder X‐ray diffraction. Both compounds crystallize in the triclinic space group P . The Eu III and Tb III cations adopt nine‐coordinated distorted tricapped trigonal–prismatic geometries bridged by three pydc 2− ligands. The Co II cation has a six‐coordination environment formed by two pydc 2− ligands, two bpy ligands and two coordinated water molecules. Adjacent molecules are connected by π–π stacking interactions to form a one‐dimensional chain, which is further extended into a three‐dimensional supramolecular network by multipoint hydrogen bonds.