Luminescence study of new Ln(III) compounds formed with Anderson’s heteropolyanions Al(OH) 6Mo 6O 183− and Cr(OH) 6Mo 6O 183−

Abstract

Crystalline compounds of trivalent Eu, Tb formed with Al(OH) 6Mo 6O 18 3− and Cr(OH) 6Mo 6O 18 3− anions were prepared from solutions containing lanthanide(III) and (NH 4) 3M(OH) 6Mo 6O 18 (M=Al,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 Tb 3+ in complex with Al(OH) 6Mo 6O 18 3− is surprisingly intense, in spite of a strong quenching effect by energy transfer to the Tb 4+–Mo 5+ charge transfer state which one could expect. The Eu 3+ compound formed with Cr(OH) 6Mo 6O 18 3− represents the system where two different metal ions could emit light and a very effective energy transfer from Eu 3+ to Cr(III) could occur.