Synthesis and spectroscopic studies of chosen heteropolytungstates and their Ln(III) complexes

The heteropolytungstates [(Na)P5W30O110](14-) (I), [(Na)Sb9W21O86](18-) (II ) and [(Na)As4W40O140](27-) (III) and the monovacant Keggin structure of th e general formula [XW11-xMo(x)O(39)](n-) (X-Si, P; n = 7 for P and 8 for Si ) (IV) as well as their europium(III) complexes were studied. The structure s of I-IV as well as the europium(III) encrypted [(Eu)P5W30O110](12-) (VI), [(Eu)Sb9W21O86](16-) (VII), [(Eu)As4W40O140](25-) (VIII) and sandwiched [E u(XW11-xMoxO39)(2)](n-) (n = 11 for P and n = 13 for Si) (V) complexes were synthesized and spectroscopically characterized. The complexes were studie d using UV-Vis absorption and luminescence, as well as the laser-induced eu ropium ion luminescence spectroscopy. Absorption spectra of Nd(III) were us ed to characterize the complexes formed. Excitation and emission spectra of Eu(III) were obtained for solid complexes and their solutions. The relativ e luminescence intensities of the Eu(III) ion, expressed as the ratio of th e two strongest lines at 594 nm and 615 nm, eta = I-615/I-594, which is sen sitive to the environment of the primary coordination sphere about the Eu(I II) ion, was calculated. In the case of the sandwiched [Eu(XW11-xMoxO39)(2) ](n-) complexes a linear dependence of the luminescence quantum yield of Eu (III) ion, phi, (calculated using [Ru(bpy)(3)]Cl-2 as a standard) on the co ntent of Mo (number of atoms, x) in the [Eu(XW11-xMo(x)O(39))(2)](n-) struc ture was observed.