Synthesis, crystal structures and photoluminescence of Zn–Ln heterometallic polymers based on pyridine-2,3-dicarboxylic acid

Abstract Three new two-dimensional 3d–4f isostructural heterometallic coordination polymers, namely [Ln 2 Zn(2,3-pydc) 4 (H 2 O) 4 ·4H 2 O] n (Ln = Sm ( 1 ), Eu ( 2 ), Gd ( 3 ), 2,3-pydcH 2  = pyridine-2,3-dicarboxylic acid) have been successfully synthesized by the hydrothermal reactions of Ln 2 O 3 , Zn(NO 3 ) 2 ·6H 2 O, H 2 pydc and H 2 O. X-ray diffraction analyses reveal that they possess a 2D heterometallic framework containing 1D lanthanide chains based on dimeric [Ln(2,3-pydc) 2 (H 2 O) 2 ] 2 unit. The Zn(II) ion, which is six-coordinated by four oxygen and two nitrogen atoms from four 2,3-pydc 2− ligands, as a bridge, links the lanthanide chains to make the 1D chains further extend into 2D layer framework. Furthermore, the neighboring layers are assembled into three-dimensional supramolecular network through inter-layer O–H⋯O and C–H⋯O hydrogen-bond interactions. In addition, the solid-state luminescent property of complex 2 was investigated.