Highly luminescent di-ureasil hybrid doped with a Eu(III) complex including dipicolinate ligands

A short chain di-urea cross-linked poly(oxyethylene) (POE)/siloxane hybrid host (di-ureasil), designated as d-U(600), was doped with the Na3[Eu(dipic)s]·xH2O (where dipic2− is the dipicolinate ion) complex. The resulting material is non-porous, semi-crystalline and thermally stable up to 145 °C. Because of the presence of the bulky dipic2− ligands, the addition of the complex to d-U(600) leads to the partial destruction of the hydrogen-bonded POE/urea aggregates of the hybrid matrix and to the formation of extra urea/urea aggregates. The incorporation of the complex into d-U(600) accounts for an increase of both the 5D0 lifetime and quantum efficiency values (1.950 ± 0.007 ms and 0.50, respectively) with respect to those of the isolated complex (1.7 ms and 0.46, respectively). The addition of the complex also contributes to an enhancement of the absolute emission quantum yield value, whose maximum value (0.66 excited at 280 nm) is the highest value reported for organic–inorganic hybrids modified by lanthanide complexes.