Functionalized Lanthanide(III) Complexes Constructed from Azobenzene Derivative and ß-Diketone Ligands: Luminescent, Magnetic, and Reversible Trans-to-Cis Photoisomerization Properties.

The coordination ability of ligands functionalized by azobenzene was manipulated, and two novel chelating ligands, (E)-4-(phenyldiazenyl)-N,N-bis(pyridin-2-ylmethyl) benzohydrazide (C25H22N6O, PBPM) and (E)-4-((4-(dimethylamino)phenyl)diazenyl)-N,N-bis(pyridin-2-ylmethyl) benzohydrazide (C27H27N7O, dmPBPM), were synthesized. The ligands can offer four coordinating atoms (one oxygen and three nitrogens) to act as tetradendate ligands, together with the two ß-diketonates (4,4,4-trifluoro-1-phenylbutane-1,3-dionate, tfd), and the trifluoroacetate anion presented as a ligand and a counterion to form the quaternary units with lanthanide(III) ions (La, Eu, and Gd), [Ln(tfd)2(PBPM)(CF3CO2)] (LnC47H34F9N6O7) and [Ln(tfd)2(dmPBPM)(CF3CO2)] (LnC49H39F9N7O7), where the lanthanide(III) ions are nine coordinated with N3O6 donor sets. All six complexes were structurally characterized, and four crystals were obtained and further analyzed by means of single-crystal X-ray diffraction. They all crystallized in the monoclinic P21/c space group with very similar lattice parameters, forming a monocapped twisted square antiprism. We successfully observed the photoluminescent properties of Eu(III) complexes at a wavelength of 614 nm in both solution and the solid state, as well as the trans-to-cis photoisomerization with the quantum yield (Φt→c = 10-2) of [Eu(tfd)2(PBPM)(CF3CO2)] complex that was comparable to that of PBPM. Moreover, the trans-to-cis photoisomerization rates of complexes [Ln(tfd)2(PBPM)(CF3CO2)] (La, Eu, Gd) (10-3-10-2 s -1) were also at the same level as that of PBPM and much higher than azobenzene itself (10-5-10-4 s-1). With the aid of TD-DFT calculations, the luminescence of Eu(III) complexes was found to originate from the attenuation effect of ß-diketonates. These features provide the foundation for the development of azobenzene-derived ß-diketonates lanthanide(III) complexes with photoisomerization and photoluminescence dual functions.

4-Amino-3-(4-pyrid-yl)-1,2,4-triazole-5(4H)-thione.

In the title mol-ecule, C(7)H(7)N(5)S, the pyridyl and triazole rings form a dihedral angle of 20.07 (6)°. Inter-molecular N-H⋯N hydrogen bonds link the mol-ecules into chains extended in the direction [10]. Further stability is provided by π⋯π stacking inter-actions, indicated by short distances between the centroids of triazole rings [3.480 (5) Å] and pyridyl rings [3.574 (5) Å] of neighbouring mol-ecules.

[Study on the CD and ORD of the crystal NaClO3].

Chiral isotropy material should be obtained in order to manufacture chiral optical waveguide. In the present paper, a chiral crystal of NaClO3 was grown from water solution by standard rocking techniques. Crystal incising and optical polishing were doneand a transparent 10.9 mm x 8.2 mm x 4.7 mm crystal NaClO3 was obtained. Along the six directions perpendicular to the surface of the crystal NaClO3, its circular dichroism and UV spectra were collected, and at the same time its optical rotatory dispersion was measured by a self-fabricated ORD apparatus. It was approved by our experiment that the CD, UV spectrum and the optical rotatory dispersion of the crystal NaClO were isotropic, which is not the same as those of quartz.