Fluorescent sensors for Ca(2+) and Pb(2+) based on binaphthyl derivatives.

Two novel binaphthyl compounds have been synthesized for the selective fluorescent recognition of Ca(2+) or Pb(2+). By introducing different terminal groups to the receptor unit, the fluorescence signals of the receptors are significantly changed: 1 is fluorescence enhancement for Ca(2+), 2 is fluorescence quenching for Pb(2+). The binding properties for metal ions were examined by the absorption and fluorescence spectra. The fluorescence intensity enhancement was ascribed to the complex formation between Ca(2+) and 1 which blocked the photo-induced electron transfer process.

Synthesis, structure and spectroscopic properties of rare earth complexes with a new aryl amide 2,2'-bipyridine derivative.

Solid complexes of rare earth nitrates and picrates with a new aryl amide ligand 3.3'-bis(benzylamido)-2,2'-bipyridine (L) were synthesized and characterized by elemental analysis, IR and molar conductivity measurements. The molecular structures of the complex [TbL(2)(NO(3))(3)H(2)O].2H(2)O have been determined by single-crystal X-ray diffraction. The fluorescent properties of the Eu(III) and Tb(III) nitrates and picrates complexes in solid state were also investigated in detail. Under the excitation, these complexes exhibited characteristic emissions of europium and terbium ions. It is worth noting that the nature of the anion has a great effect upon the composition of the complexes as well as emission properties of them.

Synthesis and spectroscopic properties of lanthanide nitrate complexes with a new amide-based quinoxaline-2,3-dione ligand.

Solid complexes of lanthanide nitrate with 1,4-di(N,N-di-n-butyl-acetamido)-quinoxaline-2,3-dione (L), [Ln(N03)3L.H2O] (Ln=La, Nd, Eu, Gd, Tb, Er), have been prepared and characterized by elemental analysis, IR, UV-vis spectra and conductivity measurements. The fluorescence property of the europium complex in solid state and in MeCN, acetone, AcOEt and THF was studied. Under the excitation, the europium complex exhibited characteristic emissions of europium. The result indicates that the triplet state energy level of the ligand matches better to the resonance level of Eu(III) than Tb(III) ion.

Tuning the self-assembly and luminescence properties of lanthanide coordination polymers by ligand design.

Two new structure-related tripodal ligands featuring salicylamide pendant arms, 1,3,5-tris{[(2'-furfurylaminoformyl)phenoxyl]methyl}-2,4,6-trimethylbenzene (L(I)) and 1,1,1-tris{[(2'-furfurylaminoformyl)phenoxyl]methyl}ethane (L(II)) have been designed and synthesized with the ultimate aim of self-assembling lanthanide polymers with interesting luminescent properties. Among two series of Ln(III) nitrate complexes (Ln = Pr, Nd, Sm, Eu, Gd, Tb or Dy) which have been characterized by elemental analyses, XRD, TGA and IR spectra, three new coordination polymers have been determined by X-ray diffraction analysis. The coordination polymer type {[Ln(NO(3))(3)(L(I))].nH(2)O}(n) possesses an unusual ladderlike double chain which can be further connected through pi-pi stacking interactions constructing a three-dimensional supramolecular structure. In contrast, the coordination polymer type {[Ln(NO(3))(3)(L(II))].nCH(3)OH}(n) displays a (3,3)-connected puckered two-dimensional net with 4.8(2) topological notation. The photophysical properties of the Sm, Eu, Tb and Dy complexes at room temperature are investigated. The present work substantiates the claim that the supramolecular structure as well as the luminescent properties of the coordination polymer can be tuned by varying either the backbone group or the terminal group of the organic ligand.

Design of a semirigid molecule as a selective fluorescent chemosensor for recognition of Cd(II).

A new 8-hydroxyquinoline-based chemosensor possessing a semirigid structure was designed, and its fluorescent sensing behavior toward metalions was investigated. A prominent fluorescence enhancement only for Cd(2+) was found in aqueous methanol solution. The results clearly suggest that the specific semirigid structure could selectively accommodate Cd(2+) according to ionic radius, which would effectively suppress the intramolecular radiationless transitions from the n pi* state to enhance the fluorescence response.