RESUMO
A series of isostructural compounds Na(HL)(CH3COO)Ln(Al(OH)6Mo6O18)(H2O)6·10H2O [L = nicotinate; Ln = Eu (1), Tb (2)] and Na(HL)(CH3COO)EumTbnLa1-m-n(AlMo6(OH)6O18)(H2O)6·10H2O (3-8, L = nicotinate), wherein Anderson-type polyanions AlMo6(OH)6O183- as basic inorganic building blocks are connected by Eu(CH3COO)(HL)(H2O)3]24+ and [Na2(H2O)8]2+ cations, resulting in formation of three-dimensional lanthanide metal-organic open frameworks, were synthesized successfully with AlCl3·6H2O, Na2MoO4·2H2O, nicotinic acid, and lanthanide nitrates as starting materials. The compounds were characterized by UV-vis, IR, elemental analysis, powder XRD, and TG-DTA measurements. The single-crystal structures of compounds 1 and 2 show that the two compounds display three-dimensional open frameworks with 1D channels along the b and c axes. Investigation of the energy transfer mechanism indicated that the organic nicotinate ligand can transfer energy efficiently to Tb3+ rather than Eu3+. The influence of the POM moiety on the fluorescence of the compounds is also studied. Compounds 1-8 exhibit tunable luminescence color, and emitting of white light was realized through adjusting the molar ratio of Eu:Tb:La within the compounds.
RESUMO
Composite films with the general formula (POM/CuTAPc)n derived from water-soluble Keggin-type polyoxometalates (POMs = H5PMo10V2O40, H4SiW12O40, H3PMo12O40 and H3PW12O40) and water-insoluble 4,9,16,23-copper tetraaminophthalocyanine (denoted CuTAPc) are successfully fabricated by a layer-by-layer self-assembly technique and systematically characterized. The structure of the polyoxometalate anions in the multilayers is kept intact; the deposition amounts of POM and CuTAPc remain constant in every adsorption cycle of the composite film assembly process. The nonlinear optical properties of the composite films were studied by a Z-scan technique at a wavelength of 532 nm and a pulse width of 7 ns. The results not only show that the composite films exhibit notable optical nonlinear self-defocusing behavior and a saturated absorption effect with the nonlinear optical absorption co-efficient ß, refractive index n2, and third-order NLO susceptibility χ(3) of the films increasing with the increase in number of layers of the films, but also reveal importantly that the discrepancy of LUMO levels between CuTAPc and POMs is proportional to their third-order NLO response.
