Luminescence and circularly polarized luminescence of macrocyclic Eu(III) and Tb(III) complexes embedded in xerogel and sol–gel SiO2 glasses

Luminescence, time-resolved luminescence, circularly polarized luminescence (CPL) and decay profiles of Ln(III)(15-crownether-5) (Ln=Ce, Sm, Eu, Tb) and Tb(III)-(R),(S)-cyclen derivative complexes doped in xerogel and sol–gel silica glasses are measured at temperatures down to 10 K to characterize luminescence properties and the electronic structure in the excited states. Luminescence spectral profiles and calculation of crystal field parameters (B0(2),B2(2)) in the 5D0→7FJ(J=1,2) transition give evidence of the fact that the pentagonal and planar structure of Eu(III) (15-crownether-5) does hold in xerogel and sol–gel glasses prepared at temperatures below 100°C. As annealing temperatures are increased from 80°C to 750°C, Eu(III) complexes in sol–gel glasses are found to decompose gradually to SiO2:Eu3+. Tb(III)-(R) and (S)-cyclen derivative complexes in xerogel reveal at room temperature and 10 K sharp CPL spectra with luminescence dissymmetry factors glum=−0.1 and 0.1, respectively. These complexes doped in sol–gel glasses represent luminescence characteristics of rare earth ions encapsulated in the nano-porous host.