Syntheses, Crystal Structures and Photophysical Properties of a Series of Ln III (Ln = Sm, Tb, Pr) Coordination Polymers

Four new lanthanide(Ш) coordination polymers, [Ln( p -aminobenzoate) 2 (DMF)(HCOO) (H 2 O)] n (Ln = Sm 1 , Tb 2 , Pr 3 ) and {[Pr(2,5-dcp)(CH 3 COO)(H 2 O)]·1.5H 2 O} n ( 4 ) (DMF = N , N -dimethylformamide, 2,5-dcp = pyridine-2,5-dicarboxylate), have been synthesized by hydrothermal method. The structures are determined by the single-crystal X-ray diffraction. The four polymers all crystallize in the monoclinic space group P 2 1 /n. Polymers 1 and 2 are isostructural; both Sm III ion of polymer 1 and Tb III ion of polymer 2 are eight-coordinate. Although polymer 3 possesses the same asymmetric unit as polymers 1 and 2 , the three are not isomorphous. The Pr III ions in polymers 3 and 4 are nine-coordinate. In polymers 1 , 2 and 3 the neighboring units are bridged by formyloxy and extend into infinite chains, which are connected by hydrogen bonds to form a hydrogen bond network. However, polymer 4 is bridged by pyridine-2,5-dicarboxylate and acetates to form an infinite 3D network. At room temperature, the IR, UV–Vis–NIR and emission spectra of the four polymers were measured and analyzed. The four polymers emit in the visible or NIR region. The luminescent properties are discussed.