Syntheses, crystal structures and luminescence properties of lanthanide-based coordination polymers constructed from a functionalized terpyridyl carboxylate ligand

Abstract

Six families of new lanthanide coordination polymers, [Ln2(L)6(H2O)2]n·3nH2O (Ln = Nd (1), Sm (2), Eu (3), Gd (4), Tb (5), Dy (6), Ho (7), Er (8), Yb (9)), [Pr2(L)2(ox)2(H2O)4]n·9nH2O (10), [Pr2(L)2(glu)2(H2O)2]n (11), [Er2(L)2(glu)2]n (12), [Nd2(L)2(adip)2]n (13), [Ln2(L)2(1,2-bdc)2(H2O)2]n (Ln = Eu (14), Gd (15), Er (16)), (HL = 4′-(2-carboxyphenyl)-4,2′:6′,4′′-terpyridine, H2ox = oxalic acid, H2glu = glutaric acid, H2adip = adipic acid, H2(1,2-bdc) = benzene-1,2-dicarboxylic acid) were synthesized under hydrothermal conditions and characterized by elemental analysis, IR and single crystal X-ray diffraction. Compounds 1–9 are isomorphic 1D chain structures based on binuclear Ln(III) units. Compound 10 is a 1D chain, where L− ligands dangle on two sides of the Pr-ox zigzag chain. Compounds 11 and 12 exhibit distinct 2D-layer structures consisting of Ln2(COO)4 binuclear units. Compound 13 displays an appealing 3D network structure, where the auxiliary ligand H2adip plays a significant role in the self-assembly process. Compounds 14–16 present a 1D-chain structure which is extended to a 2D-supramolecular framework by means of weak interactions. The diverse structures further verify the potential of HL ligand in the preparation of coordination polymers with new structures and properties. The effects of auxiliary ligands and coordination modes of HL ligand on the crystal architectures are discussed. The solid-state luminescence and thermal stabilities of compounds 1–16 also were studied. Based on the luminescent properties, we have designed and constructed successfully a series of doped-lanthanide MOF by adjusting the co-doping ratio of Eu(III) and Tb(III) into the same framework as that of 1–9. Interestingly, the luminescent colors of the Eu(III)-doped Tb(III) compounds can be tuned with change of excitation wavelength. Moreover, white-light emission was achieved on excitation at 330 nm.