Energy transfer in europium and terbium compounds formed with (Cr(OH)6_6 Mo6_6O18_{18})3−^{3-} and (Cr0.1_{0.1}Al0.9_{0.9}(OH)6_6 Mo6_6O18_{18})3−^{3-} heteropolyanions

The new compounds Ln[M(OH)(6)Mo6O18].11H(2)O (Ln=Tb, Eu and M=Al, Cr) were synthesized and their luminescence properties analysed and discussed. Results show that there is a very efficient energy transfer from Eu3+ (Tb3+) to Cr3+ ions in Eu[Cr(OH)(6)Mo6O18].11H(2)O and Tb[Cr(OH)(6)Mo6O18].11H(2)O. The transfer strongly quenches Eu3+ (Tb3+) luminescence and greatly shortens the lifetimes of the radiative levels. By using selective excitation at low temperature, the transfer mechanisms are investigated and models are presented. Based on the above model, a rate of ET k(C) = 1.33x10(6) s(-1) from Tb3+ to Cr3+ ions in Tb[Cr(OH)(6)Mo6O18].11H(2)O at 12 K is obtained

Energy transfer in europium and terbium compounds formed with (Cr(OH)6_6 Mo6_6O18_{18})3−^{3-} and (Cr0.1_{0.1}Al0.9_{0.9}(OH)6_6 Mo6_6O18_{18})3−^{3-} heteropolyanions

The new compounds Ln[M(OH)(6)Mo6O18].11H(2)O (Ln=Tb, Eu and M=Al, Cr) were synthesized and their luminescence properties analysed and discussed. Results show that there is a very efficient energy transfer from Eu3+ (Tb3+) to Cr3+ ions in Eu[Cr(OH)(6)Mo6O18].11H(2)O and Tb[Cr(OH)(6)Mo6O18].11H(2)O. The transfer strongly quenches Eu3+ (Tb3+) luminescence and greatly shortens the lifetimes of the radiative levels. By using selective excitation at low temperature, the transfer mechanisms are investigated and models are presented. Based on the above model, a rate of ET k(C) = 1.33x10(6) s(-1) from Tb3+ to Cr3+ ions in Tb[Cr(OH)(6)Mo6O18].11H(2)O at 12 K is obtained

Luminescence study of new Ln(III) compounds formed with Anderson's heteropolyanions Al(OH)6_6Mo6_6O18_{18}3−^{3-} and Cr(OH)6_6Mo6_6O18_{18}3−^{3-}

Crystalline compounds of trivalent Eu, Tb formed with Al(OH)(6)Mo6O183- and Cr(OH)(6)MoO183- anions were prepared from solutions containing lanthanide(III) and (NH4)(3)M(OH)(6)Mo6O183- (M=AI,Cr). Stoichiometric compounds containing both Eu and Gd were also prepared. The calculated mean value of hydration numbers of lanthanide ions, n=7.6+/-1.4, is consistent with the X-ray diffraction data leading to n=7. Luminescence of Tb3+ in complex with Al(OH)(6)Mo6O183- is surprisingly intense, in spite of a strong quenching effect by energy transfer to the Tb4+-Mo5+ charge transfer state which one could expect. The Eu3+ compound formed with Cr(OH)(6)Mo6O183- represents the system where two different metal ions could emit light and a very effective energy transfer from Eu3+ to Cr(III) could occur