Influence of counter ions on structure, morphology, thermal stability of lanthanide complexes containing dipicolinic acid ligand.

Two kinds of lanthanide coordination polymers formed by dipicolinic acid with lanthanide ions were synthesized by varying the counter ions. And their crystal structures, morphology and thermal stabilities were measured and compared. X-ray single-crystal diffraction analysis reveals that Na3[Ln(DPA)3] (Ln = Tb or Eu) stretches to a rigid network by means of bridging Na+ ion. Moreover, Na3[Ln(DPA)]3 exhibits good thermal stability and luminescent properties, and its optical properties can be remained even after heating at 200 °C more than 3 days. However, when Na+ in Na3[Ln(DPA)3] was replaced with NH4+, i.e., (NH4)3[Ln(DPA)3] with a supramolecular structure based on π-π stacking and other weak interactions, shows relatively poor thermal stability which leads to deterioration of their luminescence properties after heating treatment. This result confirms that the rigid frame structure of Na3[Ln(DPA)]3 plays a crucial role in improving its thermal stability and keeping its highly luminescent quantum efficiency.

A novel nitrogen heterocycle platform-based highly selective and sensitive fluorescence chemosensor for the detection of Al3+ and its application in cell imaging.

In the study, a highly selective and sensitive fluorescence sensor derived from nitrogen heterocycle was synthesized and characterized. By the fluorescence experiments, it was found to show a higher response toward Al3+ than other commonly coexistent metal ions in C2H5OH/H2O media (pH = 7.2). Moreover, the large binding constant (3.44 × 1014 M-1) between Al3+ and the sensor was calculated by fluorescence titration experiment. In addition, the synergistic effect mechanism due to photoinduced electron transfer (PET) and C[double bond, length as m-dash]N isomerization was deduced according to the fluorescence behavior. In addition, the fluorescence imaging in living cells was studied systemically, which exhibited high fluorescence sensing activity toward Al3+.

A heterometallic metal-organic framework based on multi-nuclear clusters exhibiting high stability and selective gas adsorption.

The design and synthesis of porous heterometallic metal-organic frameworks (MOFs) with high thermal and chemical stability is a challenging task at present. In this work, by the heterometallic cooperative crystallization (HCC) approach, an original heterometallic MOF based on a tetra-carboxylic ligand has been solvothermally synthesized [In6O3Tb3O(CBDA)3]·18DMF·3H2O (In/Tb-CBDA) [CBDA = 5,5'-(carbonylbis(azanediyl))-diisophthalic acid, DMF = N,N-dimethylformamide]. The framework of In/Tb-CBDA is cooperatively assembled from the rarely reported tetra-nuclear In4O2(COO)4 and tri-nuclear Tb3O(COO)6 clusters, and an organic ligand. Topological analysis indicates that In/Tb-CBDA exhibits a new (4,4,6)-connected topology with the Schläfli symbol (4·63·82)6(43·69·83)2(62·84)3. Noteworthy, forming multi-nuclear metal clusters prompts the framework to maintain high stability under the conditions of heating to 150 °C, exposure to air, and soaking in acidic and basic aqueous solutions for 12 h. After desolvation, In/Tb-CBDA shows permanent porosity proved by N2 adsorption isotherms. In addition, theoretical ideal adsorption solution theory (IAST) calculation indicates that In/Tb-CBDA displayed high selective adsorption of CO2/CH4, C2H6/CH4 and C3H8/CH4 at room temperature. This work shows a striking example of a porous heterometallic MOF material with high thermal and chemical stability, which exhibits high-efficiency selective gas adsorption behaviour.

Water-soluble Tb(3+) and Eu(3+) complexes based on task-specific ionic liquid ligands and their application in luminescent poly(vinyl alcohol) films.

Novel water-soluble lanthanide complexes (Ln(IMI-DPA)3) have been synthesized using the task-specific ionic liquid consisting of a dipicolinic acid motif as the sensitizer of lanthanide luminescence. In Ln(IMI-DPA)3, Ln(3+) ions are in 9-fold coordination through six carboxylate oxygen atoms and three nitrogen atoms in pyridine units, and the water molecule is excluded from the coordination sphere of the lanthanides. It is found that Ln(IMI-DPA)3 possess bright luminescence, long luminescence lifetime in aqueous solution, high thermal stability and good water solubility. Furthermore, these complexes can be incorporated into water-soluble poly(vinyl alcohol) (PVA) matrixes to obtain highly luminescent, transparent and flexible PVA composite films. The emission colors of the films can be tuned from red, orange, yellow, light green, green to white light by regulating the concentration of the various luminescent components.