Hydrothermal Syntheses, Crystal Structures and Properties of Two Novel 3‐D Lanthanide(III) Coordination Polymers Constructed with Mixed Heterocyclic Carboxylic Acid

The hydrothermal reactions of Ln 2 O 3 (Ln = Nd and Eu) with pyridine‐2,5‐dicarboxylic acid (H 2 pydc) resulted in the formation of two isomorphic three‐dimensional (3D) polymeric Ln III complexes, [Ln(pydc)(nic)·H 2 O] n (Ln = Nd( 1 ) and Eu( 2 )), in which nic (nicotinate; also named as pyridine‐2‐carboxylic acid) might have been formed from the pydc ligands through the C–C bond cleavage and CO 2 molecules releasing. Pydc ligands bridge lanthanide centers to form the three‐dimensional framework featuring hexagonal channels along the axis a which are occupied by bridging nic anions and mono‐coordinated water molecules. From the topological point of view, two three‐dimensional nets are binodal with six‐ and three‐connected nodes, which display a distorted rutile (4.6 2 ) 2 (4 2 ·6 10 ·8 3 ) topology. Magnetic measurements (2‐300 K) reveal that all polymers possess weak antiferromagnetic property. A strong fluorescence emission spectrum of compound 2 was observed.