Shaozhe Lu

Hydrothermal synthesis and structural studies of novel 2-D lanthanide coordination polymers with phthalic acid

This paper presents four lanthanide coordination polymers, [Ln2(BDC)3(H2O)]n (Ln = La, 1; Ln = Eu, 2; Ln = Tb, 3; BDC = 1,2-benzenedicarboxylate) and [Yb4(BDC)6(H2O)2]n (4) prepared by the hydrothermal technique. They are all 2-D infinite structures with BDC anions connecting adjacent metal ions. In complex 1, La(III) ions are eight- and nine-coordinated, and all La(III) ions are coplanar in the 2-D structure. In complexes 2 and 3, Eu(III) and Tb(III) ions are also eight- and nine-coordinated, but they are distributed in a wave-like 2-D network. In complex 4, the Yb(III) ions have four different coordination numbers (6, 7, 8 and 9), which are rarely found in one lanthanide complex. Both the coordination numbers and the arrangement of Ln atoms in these coordination polymers show the lanthanide contraction. In the four complexes, all the oxygen atoms of BDC take part in coordination with Ln(III) ions, adopting tetra-, penta- and hexadentate coordination modes for the phthalate anions. The luminescent properties of complex 2 have been investigated and the results for the explanation of the chemical environment of the Eu(III) ion are consistent with the X-ray analysis.

Supramolecular architecture of new lanthanide coordination polymers of 2-aminoterephthalic acid and 1,10-phenanthroline

This paper presents five new lanthanide coordination polymers with 2-aminoterephthalic acid (H2atpt) and 1,10-phenanthroline (phen), [Ln(atpt)1.5(phen)(H2O)]n [Ln = La (1); Eu (2)], [Ln2(atpt)3(phen)2(H2O)]n [Ln = Tb (3); Er (4)] and [Yb2(OH)(atpt)2.5(phen)2]n·1.75nH2O (5), prepared by hydrothermal reactions and structurally characterized. 1 and 2 are isostructural, in which all the Ln3+ ions are eight-coordinated. 3 and 4 are also isostructural and have two types of lanthanides; Ln(1) (Ln = Tb, Er) is seven-coordinated and Ln(2) (Ln = Tb, Er) is eight-coordinated in the asymmetric unit. 1–4 are two-dimensional rhombus-like grids constructed by bridging atpt ligands, and further form 3-D supramolecular architectures via hydrogen bonds and π–π stacks between phen molecules. Complex 5, in which there are two eight-coordinated Yb3+ ions linked by one hydroxyl group and one atpt ligand in the asymmetric unit, exhibits an interpenetrated 3-D network with a brick structure. In 1–4 one atpt ligand is coordinated to three or four Ln3+ ions (Ln = La, Eu, Tb, Er) in bridging modes and in 5 one atpt ligand is coordinated to two or three Yb3+ ions by double chelating or chelating-bridging mode. The high-resolution emission spectrum of 2 shows only one Eu3+ ion site in 2, which is in agreement with the results of the X-ray diffraction. The thermal stabilities of the supramolecular compounds 2, 4 and 5 show that the presence of amino groups induces formation of hydrogen bonds that are responsible for the increase in the thermal stability.

Crystal structure and luminescence of a europium 3-methoxybenzoate complex with 2,2′-bipyridine

The structure of the dimer [Eu(m-MOBA)3·2,2 0 -bipy]2 (m-MOBA: m-methoxybenzoate, 2,2 0 -bipy: 2,2 0 -bipyridine) was determined by single crystal X-ray diffraction. Each europium atom is coordinated with two oxygen atoms of the chelated carboxyl group, four oxygen atoms of the bidentate bridging carboxylate groups and two nitrogen atoms from a 2,2 0 -bipyridine molecule forming a dimeric structure with coordination number 8. The luminescence behaviour of the Eu 31 ion in [Eu(mMOBA)3·2,2 0 -bipy]2 was observed at 77 K. The emission spectra of 5 D1! 7 FJ OJa 1‐3U and 5 D0! 7 FJ OJa 0‐4U transitions were measured. The complex displays intense luminescence and the Eu 31 ions in the dimer occur in slightly different

Crystal structure and luminescence of (4,4 '-dimethyl-2,2 '-bipyridine)-tris(benzoate)europium(III)

Abstract A mixed ligand europium complex, [Eu(BA)3dmbpy]2, has been prepared, where BA = benzoate and dmbpy = 4, 4′-dimethyl-2, 2′-bipyridine. The complex crystallizes in the tri-clinic system, space group P − 1. Its structure has been determined using X-ray diffraction methods. The two europium ions in the molecule are held together by four carboxylate groups of benzoic acid and each europium ion is further bonded to one bidentate carboxylate group and one 4, 4′-dimethyl-2, 2′-bipyridine molecule. Excitation and luminescence spectra observed at 77 K show that the europium site in the crystal has low symmetry and changes of the chemical surroundings of the europium ion in the molecule depend mainly on the flexibility of 4, 4′-dime-thyl-2, 2′-bibyridine.

Crystal Structure and Luminescence of a Europium Nitrate Complex with Furancarboxylic Acid and 2,2′-Bipyridine

Abstract A quaternary mixed ligand europium complex, [Eu(FA)2NO3bipy]2, has been synthesized, where FA = α-furancarboxylic acid anion and bipy=2,2′-bipyridine. The europium complex crystallizes in the triclinic system, space group P1. Its structure was determined by X-ray diffraction methods. The two europium ions in the dimer are held together by four carboxylate groups of furancarboxylic acid and each europium ion is further bonded to one chelated bidentate nitrate and one 2,2′-bipyridine molecule. The coordination modes of the four carboxylate groups are divided into two types, bidentate bridging and tridentate bridging, making a coordination number of 9. Excitation and luminescence spectra observed at 77 K show that the europium ion site in the crystal has low symmetry and emission 5D 1→7 FJ of the Eu3+ ion disappears after 20 μs.