A Highly Selective and Sensitive Fluorescent Chemosensor for Aluminum Ions Based on Schiff Base.

An efficient "off-on" type fluorescent chemosensor, (E)-N'-(4-(diethylamino)-2-hydroxybenzylidene)-2-hydroxybenzohydrazide (H 2 L), based on Schiff base for the determination of Al3+ has been designed, synthesized, and evaluated. Upon treated with Al3+, the fluorescence of H 2 L was enhanced 45-fold due to the chelation-enhanced fluorescence (CHEF) effect based on the formation of a 1:1 complex between the chemosensor and Al3+. Other metal ions, such as Na+, K+, Mg2+, Ca2+, Cu2+, Ga3+, Zn2+, Cr3+, Cd2+, Ag+, Fe3+, In3+, Mn2+, Pb2+, Co2+, and Ni2+ had little effect on the fluorescence. The results demonstrate that the chemosensor H 2 L has stronger affinity with Al3+ than other metal ions. The detection limit of H 2 L for sensing Al3+ is 3.60 × 10-6 M in EtOH-H2O (3:7, v/v) solution. And the recognizing behavior has been investigated both experimentally and computationally.

Self-assembly synthesis, structural features, and photophysical properties of dilanthanide complexes derived from a novel amide type ligand: energy transfer from Tb(III) to Eu(III) in a heterodinuclear derivative.

A novel amide type ligand benzyl-N,N-bis[(2'-furfurylaminoformyl)phenoxyl)ethyl]-amine (L) has been designed and applied for the self-assembly generation of homodinuclear lanthanide coordination compounds [Ln2(µ2-L)2(NO3)6(EtOH)2] [Ln = Eu (1), Tb (2), and Gd (3)] and a heterodinuclear derivative [EuTb(µ2-L)2(NO3)6(EtOH)2] (4). All the complexes have been characterized by the X-ray single-crystal diffraction analyses. They are isostructural, crystallize in a monoclinic space group P21/c, and form [2 + 2] rectangular macrocycle structures. Compound 4 is the first example of a [2 + 2] rectangular macrocycle heterodinuclear EuTb complex assembled from an amide type ligand. In 4, the discrete 0D dimeric [EuTb(µ2-L)2(NO3)6(EtOH)2] units are extended, via the multiple N-H···O hydrogen bonds, into a 2D supramolecular network that has been topologically classified as a uninodal 4-connected underlying net with the sql [Shubnikov tetragonal plane net] topology. The triplet state ((3)ππ*) of L studied by the Gd(III) complex 3 demonstrated that the ligand beautifully populates Tb(III) emission (Φ = 52%), whereas the corresponding Eu(III) derivative 1 shows weak luminescence efficiency (Φ = 0.7%) because the triplet state of L has a poor match with (5)D1 energy level of Eu(III). Furthermore, the photoluminescent properties of heterodinuclear complex 4 have been compared with those of the analogous homodinuclear compounds. The quantum yield and lifetime measurements prove that energy transfer from Tb(III) to Eu(III) is being achieved, namely, that the Tb(III) center is also acting to sensitize the Eu(III) and enhancing Eu(III) emission in 4.