Effect of lanthanide contraction on structures of 3D lanthanide organic frameworks from 5-nitroisophthalic acid and picolinic acid

Two different types of novel lanthanide coordination polymers constructed from 5-nitroisophthalic acid, and picolinic acid as auxiliary ligand, namely, {[Ln 2 (nip) 2 (pic) 2 (H 2 O)]} n (type I, Ln = Pr 1 , Nd 2 , Sm 3 , Eu 4 , and H 2 nip = 5-nitroisophthalic acid, Hpic = picolinic acid), and {[Ln 4 (nip) 5 (pic) 2 (H 2 O) 2 ]·2H 2 O} n (type II, Ln = Tb 5 , Dy 6 , Ho 7 , Er 8 ), have been hydrothermally synthesized and characterized by IR, elemental analysis, thermogravimetric analysis (TGA), single-crystal X-ray diffraction analyses and powder X-ray diffraction (PXRD). Complexes 1 – 4 (type I) are isostructural and the infinite 1D Sm-carboxylate chains are bridged by pia ligands to form 2D sheets, such sheets are further united together to generate a 3D supramolecular structure. Complexes 5 – 8 (type II) are isostructural and the infinite 1D Tb–carboxylate chains are bridged by pia ligands to form 2D sheets, such sheets are further united together to generate a 3D supramolecular structure. Furthermore, the luminescence properties of compounds 4 and 5 have also been studied.