Abstract
Three lanthanide compounds have been synthesized, namely, {[Dy2(bpda)3(H2O)3]4·2H2O}(Dy-1), {[Sm(bpda)2·(H2O)]·H2O}n (Sm-2) and {[Tb2(bpda)3(H2O)3]4·2H2O} (Tb-3) (H2bpda = 2,2′-bipyridine-6,6′-dicarboxylic acid). Their structures were determined by single crystal X-ray diffraction and characterized by elemental analysis, infrared spectroscopy and thermogravimetric analysis. Dy-1 and Tb-3 are isostructural with a conjugate bimolecular four-nuclear cluster structure constructed with intramolecular hydrogen bonds and they form a 3D supramolecular structure with intermolecular hydrogen bonding. Sm-2 is a one-dimensional chain structure and is further connected by intricate hydrogen bonds into a three-dimensional supramolecular structure. These three compounds exhibit significant characteristic luminescence from the ligand to the central Ln(iii) ion, which is found by solid-state photoluminescence measurement. Sm-2 exhibits a long luminescence lifetime and high fluorescence quantum yield. A slow relaxation phenomenon is observed for the dysprosium compound by measuring the alternating-current susceptibility at low temperature and the underlying mechanism was further confirmed by theoretical calculations.
Highlights
Through the past decades, lanthanide compounds including europium(III), terbium(III) and samarium(III) compounds have attracted much attention in the elds of biological analysis,[1] magnetism,[2,3] chemosensors,[4,5,6] electroluminescent devices and laser systems.[7,8,9,10,11] lanthanide(III) ions usually have very low optical transition absorption coefficients, which greatly limits their practical applications
The bands at 1545–1667 cmÀ1 could be attribute to the asymmetric stretching vibrations of carboxylate (nas(COOÀ)), and the bands at 1378–1457 cmÀ1 could be ascribed to the symmetric stretching vibrations of carboxylate (ns(COOÀ)) in the complexes.[20]
The main mass loss occurs in the temperature range of 460–544 C with the loss of 54.41%, corresponding to the decomposition of residual organic components of the compound, which is consistent with the crystal structure analysis results
Summary
Lanthanide compounds including europium(III), terbium(III) and samarium(III) compounds have attracted much attention in the elds of biological analysis,[1] magnetism,[2,3] chemosensors,[4,5,6] electroluminescent devices and laser systems.[7,8,9,10,11] lanthanide(III) ions usually have very low optical transition absorption coefficients, which greatly limits their practical applications This disadvantage can be overcome by using highly absorbent ligands to efficiently sensitize lanthanide ions. H2bpda ligand can be coordinate to lanthanide ions in various modes, such as unidentate coordinating, bidentate chelating and bridging coordination since the carboxyl group of the ligand
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